Category: botany

Plant blindness

Posted on by andy.winfield

You may or may not of heard of the term ‘plant blindness’; it’s a phrase that we in the Botanic Garden have been hearing much more of in recent years and will continue to throw around in the future. It refers to the slow shutting off of plant knowledge from generation to generation resulting in an inability to acknowledge plants around us. The simple things that were once common knowledge, such as dock leaves used for nettle stings are becoming bred out of a collective instinct and plants are becoming irrelevant and annoying green things to many people.
I can remember when my eyes were truly opened. I noticed trees that I hadn’t before; as I walked along the street I started looking at the borders and the hanging foliage all around me. Before, I’m not sure what I looked out for in the streets, the pavement or the shops, who knows, but plants for sure changed my life and I see them changing the lives around me at the Botanic Garden. I think I could live to be three hundred and still find something in the plant world that fascinated me. This week I learnt about the incredible relationships between some species of orchid and ants. The ants don’t pollinate the orchid flower but hang around the plant living off an ‘extrafloral’ nectar secreted elsewhere; they then do everything to protect their food source and keep the plant safe. Plants and animals have these delicate relationships that allow both to flourish, and it’s fair to say that ours has become less delicate over the years.
Dandelion seed head
This change in the collective instinct of people has come about through successive generations becoming more urbanised with less plant interaction such as blowing a dandelion seed head, throwing a grass seed dart, eating wild blackberries or sticking cleavers to jumpers; children still do this but there are many who don’t and lose a connection with the plant world. The result of this is that education reduces the amount of plant learning, and in biology courses there is a main focus on the animal kingdom; there is a perceived lack of interest in the plant world. Things have become so bad that the Oxford Junior Dictionary removed words like ‘acorn’ and ‘buttercup’ preferring instead ‘broadband’ and ‘cut and paste’; they were seen as no longer relevant to a child’s life.
University of Bristol Botanic Garden
There is however, a great appetite among young people to be green, to recycle and mend the excesses of the generations that went before them; often students tell me it’s the biggest issue for them and they’d like to make a difference. How is a difference made? I think we can all make a simple difference by introducing plants to friends and relatives, opening eyes to the trees and weeds and the force of life going on around us and under our feet. It could be argued that many of the world’s problems can be solved with plants; forests, food, habitats are all areas that need experts, and while there are many graduates of zoology degrees there are few from plant sciences. This is changing with Universities now offering full plant science degrees; there are many jobs in plant sciences as governments and companies are beginning to see how important it is. Bristol University is launching a plant science degree starting in September 2019 based in the magnificent Life Sciences building with a group of world experts in the field of plant science. Of course, undergraduates will use the Botanic Garden as a second home and have access to all our knowledge and experience, we’re really looking forward to it. If you, a relative, son or daughter are interested click here to view the degree.
We all have a role to play in protecting our relationship with the natural world which can be played by simply talking about the plants we see to people. I’m always disposed to optimism and today’s

young people seem to be committed to green ways; this problem arose through successive generations and perhaps it can be cured in the same way, the passing down of knowledge as we go.

By Andy Winfield

Mycoheterotrophs: the sly swindlers of the plant world

Posted on by andy.winfield

By Helen Roberts

New plant species are discovered all the time. But it is not typical for plants to be discovered in areas that have been meticulously surveyed. Last year, however, a thoroughly unusual species was found on an island in the Kagoshima prefecture, Japan [1].

Gastrodia kuroshimensis is a mycoheterotroph
discovered last year in Japan.
Photo credit:Kenji Suetsugu/Kobe University


Gastrodia kuroshimensis neither photosynthesises nor flowers. Certainly by no means an ornamental showstopper, it is undoubtedly odd looking with fleshy tubers, the absence of leaves and no flowers. In essence, it resembles a pathetic looking fungal protuberance. Strangely enough, it is not a fungus, but a vascular plant. The fact that it does not photosynthesise means it belongs to a peculiar group of plants that are called mycoheterotrophs, which get all or some of their nutrients from a host fungi attached to a vascular plant. The newly found species, Gastrodia kuroshimensis, is what is termed ‘fully’ mycoheterotrophic in that it depends entirely on its association with the fungus throughout its lifecycle. The relationship between it and the host fungi is not mutualistic – it takes all it needs while offering nothing in return. In other words, it’s a big fat cheat.

Mycoheterotrophs parasitise fungi, which are in turn getting their nutrients from a host plant. The fungi that are preyed upon by these cheaters are usually mychorrizal fungi, with mycoheterotrophs often parasitizing a specific arbuscular mycorrhiza (arbuscular mycorrhiza are those that penetrate the cortical cells of plant roots). In this sense, they are dissimilar to parasitic plants like dodder, which obtain their nutrients by directly taking what they need from the vascular tissue using an adapted root.

Who wants flowers?

The second interesting thing about Gastrodia kuroshimensis is that it is entirely cleistogamous, producing flowers that never blossom. Most plants also produce chasmogamous (cross-pollinating) flowers; it is extremely rare to find plants that are entirely cleistogamous. The term cleistogamy means ‘closed marriage’ and the plant produces flowers that are self-fertilised within closed buds. It is essentially a way of ensuring reproduction [2].

The evolutionary reasons are still a puzzle, but it is considered a way of safeguarding fertilisation if suitable pollinators are not around or they have somehow missed the plant or if environmental conditions are not conducive. It can also aid plants in adapting to local habitats, where both sets of maternal genes are passed onto the progeny, thereby removing harmful gene variants. Being cleistogamous also use fewer resources; flowers that are chasmogamous require more energy to produce. However, in most cases chasmogamous flowers are beneficial as they help to provide variability necessary for adaptation, hybrid vigour and negate the effects of deleterious mutations. The reasons for complete cleistogamy remain unresolved but the discovery of Gastrodia kuroshimensis may well help to answer some of these questions.

Other fungi tricksters

Other plants that fall under the mycoheterotrophic category are orchids, monotropes (a subfamily of Ericaceae), members of the Gentian family, certain liverworts and the gametophyte stages of ferns and clubmosses. Some are quite attractive if you like the look of fungal fleshy looking vascular plants with varying hues of red, white and cream. Some are even striped red and white and so commonly known as candystick. Whatever their appearance though, they are unquestionably interesting. But because or their size and rarity they often go unnoticed, lingering in the background like villainous free-loaders.

Mycoheterotrophs at the University of Bristol Botanic Garden

The inflorescences of toothwort in the pollinator display
this week at the Botanic Garden.
Photo credit: Andy Winfield

A wonderful example of a mycoheterotroph at the Botanic Garden is toothwort (Lathraea squamaria L.). It spends most of its time below ground, but in April it sends up aerial inflorescences about 20-25 cm tall. These were in their full glory in the garden a couple of weeks ago, but can still be seen (see photo) in both the pollinator display on the left as you walk in the main gate, or at the east gate.

Unlike Gastrodia kuroshimensis, toothwort flowers are bisexual and pollinated by bumble-bees.

Stop in over the weekend if you get a chance and have a look at this interesting plant.

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.


Sources:

[1] Kobe University. (2016). Plant discovered that neither photosynthesizes nor blooms.
< https://www.sciencedaily.com/releases/2016/10/161014092115.htm>

[2] Allaby, M. (2016). Plant Love: The scandalous truth about the sex life of plants. Filbert Press, pp. 98-103.

Floral visits to the western Mediterranean

Posted on by andy.winfield

By Helen Roberts

A floral excursion to the western Mediterranean at this time of year appeals to many of us. The anticipation of warm weather, beautiful landscapes and a dizzyingly diverse range of exquisite wild flowers and I want to pack my bags in a flash. I certainly felt that way when I saw some of the images of the region’s wild flowers in a recent Friends‘ talk given by botanist Dr Chris Thorogood.
However, if you cannot escape overseas, then the Mediterranean collection at the University of Bristol Botanic Garden will give you a taste of some of the Mediterranean Basin species although you will have to wait till later in the year to see some of the flowers in bloom. 
If you do have a trip in mind though, here are a few of Chris Thorogood’s favourite spots to see the wild flowers of the western Mediterranean:
Cape St Vincent, Portugal. Photo courtesy of Peter Broster via
Flickr [CC license]

The Algarve, Portugal:

This area has a diverse flora due to varied geology and weather with numerous endemic species and beautiful wild flower meadows. Cape St Vincent, the most south-westerly point in the area and a vast nature reserve, has a spectacular display of flowers in the spring and early summer (January through to the end of May). There are many unique species of thyme and endemic rarities like the tiny diamond flower (Ionopsidium acaule).

Almeria, Spain:

This province is located in the southeast of the Iberian Peninsula and has a wealth of species adapted to cope with extremely dry conditions. Many plants are salt tolerant including sea lavenders like Limoniuminsigne and the rare low growing lily, Androcymbium europaeum whose flowers emerge on sand dunes in mid winter. An area called Cabo de Gata, an impressive tract of volcanic cliffs, is host to numerous unusual species. Many of these are freakishly odd looking from the succulent Caralluma europaea with its purple and yellow striped flowers to the phallic form of the parasitic Cynomorium coccineum.

Cap de Formentor, Mallorca:

This peninsula in the northeast of the island has many unique sea lavenders and orchids. Endemics are closely dotted only metres apart. Much of the landscape is fairly inaccessible due to its rocky and precipitous nature so one needs to be fairly adventurous to spot some species. Notable endemic species include Arum pictum, an arum that smells of rotten meat to attract its fly pollinators and a species of St John’s Wort unique to Mallorca, Hypericum balearicum.

Maremma, Southern Tuscany, Italy:

The Maremma region is rich in wild flowers and contains 25% of all Italian flora. It has a unique geology and extremely varied landscapes including the protected coast, swathes of pine forest and abandoned agricultural plains. The giant fennel, Ferula communis, is one such distinctive plant with its towering inflorescences that can take many years to develop.

Gargano National Park, Puglia, Italy:

The yellow bee orchid (Ophrys lutea) is one of the orchid
species found in Gargano National Park.
Photo credit: Alastair Rae [via Flickr, CC license]
This park has a unique flora and are highly specialised for growing in certain conditions many being endemic. The park covers a vast area and as a result the landscapes are varied from rich beech forests, steep cliffs, karstic plateaus and scrubby maquis. There are many orchid species here (over 65) including some unique bee orchids.

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.

Keeping your head above water: plants coping with waterlogging

Posted on by andy.winfield

By Helen Roberts

Flooding on the Somerset Levels.
Photo credit: Nigel Mykura [CC BY-SA 2.0],
via Wikimedia Commons

Britain has had its fair share of flooding over the last couple of years. In 2014, the Somerset Levels was under water for weeks and 2015 saw some truly devastating flooding occurring in the northwest of England. Flooding can have detrimental effects on our own lives, but also on plant communities.

Waterlogging of plants can cause chlorosis (loss of the normal green colour) of the leaves, root rot and eventually death. It’s a common problem that many gardeners face every day and there are different techniques to cope with this ever persistent problem on our shores. Precautions are even taken at the University of Bristol Botanic Garden during this wet weather.

“As far as the garden borders go, we’re very careful about never walking on them when there’s been heavy rain,” explained Andy Winfield, horticultural technician at the Botanic Garden. “If we have to get on a border for any reason, we use a board and then fork over where it was to prevent compaction and a pan forming. When a pan forms, then water is more likely to sit on the surface and create problems.”

How does waterlogging affect soils and plants?

The profile of a soil will greatly affect its interaction with water. Soils are composed of solid material with spaces filled with water, gases, roots and other living organisms – these attributes impact water retention and drainage. For example, clay soils have small pore spaces and so retain more water compared with sandy loams.

Subsoils can also influence soil structure and its interaction with water. Waterlogged soils are not only affected by the amount of water coming into the system, but by the soil’s ability to disperse and absorb that water.

When soils are waterlogged, the air spaces between the particles are filled with water and the movement of gases within the soils is inhibited preventing the roots from respiring properly. Gases such as ethylene and carbon dioxide begin to accumulate, which leads to further negative impacts on root growth. Anaerobic processes begin to changes the soil biochemistry, which leads to plant death through the build up of toxins within soils.

What is happening to plants at a cellular level when faced with anoxic or hypoxic conditions? 

When plants are waterlogged, they are not getting enough oxygen via the roots for cellular respiration and energy production. Because the plants cannot obtain oxygen via the roots, plants turn on their own energy reserves. This is much like when we use our muscles during strenuous exercise and we can’t get sufficient oxygen to the hard working cells – the cells undergo anaerobic respiration, which produces lactic acid. Plants can also undergo anaerobic respiration, but it is not sustainable and eventually, the plant dies as the demand for energy exceeds the supply.

Until recently little was known about how some plants cope with the stress of waterlogging. However, researchers from the Max Planck Institute of Molecular Plant Physiology, with colleagues from Italy and the Netherlands, have discovered a protein that triggers the activation of stress response genes when oxygen levels drop due to waterlogging. This protein is attached to the cell membrane under normal aerobic conditions, but when levels drop it detaches from the membrane and relocates to the nucleus where it switches on the stress genes. When oxygen levels return to normal, the protein degrades and the stress response genes switch off again.

How some plants have evolved to cope with anoxic and hypoxic conditions

When out walking as a child on Exmoor, I would often pick the stems of the soft rush, Juncus effusus, and peel back the green outer coating to reveal the soft, husky white pith inside. I was amazed when an adult told me this material was once used for making rush lights. The pith would be extracted from the rush leaves and combined with fat or grease to provide a source of artificial light. This pithy material is interesting though in this context as it contains a tissue called aerenchyma, which is usually found in the roots and stems of many hydrophytes (plants adapted for living in water). The tissue has large interconnected intercellular gas spaces that help to oxygenate the roots and increase buoyancy.

Other plants adapted to soggy conditions will produce fine surface roots called adventitious roots. These roots scavenge oxygen from the surface where there is a thin aerobic layer. Many of the Melaleuca species, mostly from Australia, use this way of coping with water hypoxia.

Some plants are adapted to rise above it all; they elongate their shoots to get above the water, as is the case with some floodplain Rumex species (docks and sorrels). Nymphaea species (the water lilies) – which you can see in the Botanic Garden glasshouses –  have a hugely elongated petiole, often more that two metres long, to keep their leaves and flowers at the water surface.

Arial roots (pneumatophores) of the grey mangrove
(Avicennia marina var resinifera) from South Australia.
Photo Credit: Peripitus (Own work) [GFDL, CC-BY-SA-3.0 )
or CC BY-SA 2.5-2.0-1.0 ], via Wikimedia Commons

Large tree species have also adapted their roots to cope with swamp-like conditions. These strange looking roots are known as pneumatophores – woody extensions that grow vertically upwards from the underground root system to reach above water and capture that much needed oxygen. The bald cypress, Taxodium distichum, which is found in the southern USA in lowland river floodplains and swamps, forms these roots that look like knees sticking up out of the water. The actual surface of the root is pockmarked with many lenticels, which are small stomata-like pores found in the bark that allow gaseous exchange. Other swamp and mangrove species have variations of these root adaptations to cope with low oxygen levels including pencil and cone roots (which belong to the pneumatophore group) and other types of aerial roots like knee, stilt, peg and plank roots. These roots differ in both their morphology and function, but are ultimately adapted to cope with waterlogging and often saline conditions.

The importance of wetlands as carbon sinks

Waterlogged lands are not all doom and gloom, in fact, bogginess is vitally important in terms of the Earth’s climate. Peatlands fall into that category. They act as important carbon sinks and currently cover about four per cent of the Earth’s land surface. Drainage of these areas of peatlands and wetlands for agricultural use leads to increases in greenhouse gas emissions. Researchers are actively trying to understand the effects of climate change on peatlands globally and there have been pushes to effectively  conserve and manage these precious ecosystems.

Sources:

Guillermina M. Mendiondo, Daniel J. Gibbs, Miriam Szurman-Zubrzycka, Arnd Korn, Julietta Marquez, Iwona Szarejko, Miroslaw Maluszynski, John King, Barry Axcell, Katherine Smart, Francoise Corbineau, Michael J. Holdsworth. Enhanced waterlogging tolerance in barley by manipulation of expression of the N-end rule pathway E3 ligasePROTEOLYSIS6. Plant Biotechnology Journal, 2015; DOI: 10.1111/pbi.12334

Francesco Licausi, Monika Kosmacz, Daan A. Weits, Beatrice Giuntoli, Federico M. Giorgi, Laurentius A. C. J. Voesenek, Pierdomenico Perata, Joost T. van Dongen. Oxygen sensing in plants is mediated by an N-end rule pathway for protein destabilization. Nature, 2011; DOI: 10.1038/nature10536

Daniel J. Gibbs, Seung Cho Lee, Nurulhikma Md Isa, Silvia Gramuglia, Takeshi Fukao, George W. Bassel, Cristina Sousa Correia, Françoise Corbineau, Frederica L. Theodoulou, Julia Bailey-Serres, Michael J. Holdsworth. Homeostatic response to hypoxia is regulated by the N-end rule pathway in plants. Nature, 2011; DOI: 10.1038/nature10534

To grow or not to grow: plant propagation at the Botanic Garden

Posted on by andy.winfield

By Helen Roberts

At the start of December, I met up with Penny Harms, Glasshouse Co-ordinator at the University of Bristol Botanic Garden, to discuss the plants that are propagated at the Garden and how this valuable work is carried out. Over the course of the year, I will be investigating the different forms of propagation techniques used in the Garden to maintain and enhance their existing stock of plants. I will cover briefly how these techniques are carried out (bearing in mind that there are a plethora of books available on plant propagation), but I’ll also examine what is happening at the cellular level and examine the ‘why’ behind certain propagating techniques.

As Penny and I examined some seedling plants, she explained to me why propagation is so important at the Botanic Garden. “If we lose some plants outdoors in a cold wet winter, we have a back up of new plants. Some are not simply insurance plants, but are taken as cuttings as a necessity every year as they survive in our climate as annuals, particularly those plants from the South African collection. Others, such as the Mediterranean plants, do not survive as long here in Bristol as it’s generally much wetter and therefore they need to be replaced fairly frequently. Most plants we take from cuttings are mainly tender perennials and frost tender plants.”

Propagation in the Garden won’t likely restart until the spring depending on weather conditions.

In the glasshouses, Penny showed me many of the plants that have been propagated from cuttings, including some beautiful decorative Aeonium species (commonly known as tree houseleek), as well as Pelargonium (geranium), Clematis, Salvia and Passiflora (passion vines) species. Some plants raised from cuttings  are placed in a unit that is misted with water regularly and the bottom is heated to a temperature of 25°C in order to encourage roots to form. The plants all looked wonderfully healthy, not at all like my puny looking specimens that I had taken cuttings of back in September at home. However, the plants that really caught my eye were some small fern plants potted up, which Penny called “fernlets”.

Ferntastic ferns

Ferns belong to the plant division of pteridophytes (spore-producing vascular plants) and are extremely diverse in habitat, form and reproductive methods. Most ferns grow in moist warm conditions and very few tolerate dry cold places. Although they aren’t flowering plants, the frond shapes and colours can be exquisite. Closer inspection of the undersides of the leaves reveal beautiful patterns of sporangia – the vessels containing the spores.

Fern reproduction 101

Fern lifecycle
Image credit: Carl Axel Magnus Lindman
[CC BY-SA 3.0], via Wikimedia Commons

Like other plants, ferns have alternating haploid (single set of chromosomes) and diploid (two sets of chromosomes – one from each parent) generations; the haploid gametophyte produces the cells for sexual reproduction while the diploid sporophyte produces spores that produce the gametophyte. Unlike flowering plants where the gametophyte is reduced to the pollen and embryo sac, fern gametophytes are free-living. (Although they are admittedly less conspicuous than the sporophyte we generally identify as ferns.)

In brief, the sporophyte produces spores, which are shed and grow into gametophytes (also often called the prothallium). In some species, individual gametophytes will be either male or female, while in others an individual gametophyte will function as both sexes. When the conditions are right, the gametophyte releases mature sperm from the antheridium, which swim to the egg-producing part called the archegonia under the gametophyte’s underside. Fertilisation produces a zygote, which develops into an embryo and eventually outgrows the gametophyte to become the sporophyte.

The plantlet sailboats on the fronds of Woodwardia prolifera.
Photo credit: Andy Winfield.

Like many other plants, ferns can also reproduce asexually through branching of the underground root stem or rhizome. Some species will even produce leaf proliferations known as plantlets or offsets, such as the beautiful Woodwardia prolifera, which comes from Asia and grows in coastal regions. It’s small plantlets (or “sailboats” as Penny calls them) drop off the plant and fall to the ground, securing themselves quickly with their roots.

Fern propagation at the Botanic Garden

Fern spores are carefully collected when the ferns are sporolating by cutting fronds and letting spores fall into paper bags. Spores are only collected when they are ripe; usually the sporangia will swell and will turn brown, black, blue or orange depending on the species.

“As far as when to collect the spores,” said Penny, “it is really a case of watching and waiting. The beautiful orange [sporangia] on the Phlebodium aureum var glaucum go a slightly darker brown when they are ready, which makes it easier to know when to collect. And if you lightly tap the frond over some white paper you can watch to see if the spores are being released.”

The underside of a frond from Phelbodium aureum var. glaucum,
showing the sporangia. Photo: Andy Winfield.

Penny added that she often collects additional spores by simply placing a fern frond onto a tray containing already wetted peat-neutral compost with bark mulch to allow spores to drop onto the substrate. Penny had great success growing new plants from spores harvested from a miniature tree fern species called Blechnum gibbum. This plant was looking in a sorry state before the move to The Holmes at Stoke Bishop and so Penny collected spores just in case it didn’t survive the move. However, research revealed that this fern was behaving like a deciduous plant -it had died back, but wasn’t dead. Thanks to Penny’s careful propagation, the glasshouse now holds a number of specimens from this species – all grown from spores of the original plant.

The tree huggers

Some the glasshouse ferns are also epiphytic and will reproduce effectively from spores. One such example is Stenochlaena tenufolia, a South African fern that will grow up trees. Its climbing rhizome can reach up to 20m in length and 15mm in diameter. As young plants, they start off on the ground, but soon start to ascend trees, trading in their connection with the soil for life in the trees. Often plants don’t produce fertile fronds until the rhizome has climbed sufficiently to expose the apical region of the plant to sufficient light. These ferns are grown both from spores and vegetatively at the Botanic Garden.

The runners

Other species require a different approach. Diplazium proliferum, a fern that is widespread in the tropics and subtropics, produces little rooting plantlets along its fronds that can be developed into new plants. The frond is simply cut and laid onto bark mulch, pegged with wire and then half buried with the substrate.

The chain fern, Woodwardia radicans (from the Macaronesian region but also found on other Mediterranean islands) also produces bulbils but these are usually located at the ends of the fronds as a hard nodule. The roots start to develop in the air but when they touch the ground will root into the substrate and form new plants.

Penny explained, “We got these plants from Tresco where they grow as huge sprawling mounds. The small bulbils eventually form quite large plants, but are still connected to the original. This gives this fern its very relevant name. New plants can simply have the connection cut and be dug up and transplanted elsewhere.”

A brief step-by-step lesson on how to propagate ferns

At the Botanic Garden ferns are being propagated very successfully, but there is no reason why horticulturists at home should not be able to have the same degree of success. Penny offers her expert advice in propagating ferns by spores below:

Ferns can be propagated vegetatively, by division, or similar to sowing seed from flowering plants, by spores, which are found on the underside of the fern fronds. Some fern species are very difficult to propagate from spores, however Adiantum, Pteris and many Blechnum species are reliable.

Here are the main points for the propagation of cool glasshouse ferns from spores:

  1. The spores should be collected when ripe. The sporangia found on the underside of the frond, will (in most cases) change in colour from a light to dark brown to indicate the spores are ripe. To check, lightly tap the frond to see whether the tiny brown spore cases (sori) are released. If so, the fronds can be cut and gently placed into paper bags in order to collect the fine sori ready for sowing (see point 2) or the frond can be cut and placed directly onto the surface of a pre-prepared tray of compost, allowing the spores to fall naturally as the frond dies away. 
  2. Sow the fern spores. Collect the spores from the bottom of the paper bag and sow immediately. Fresh spores will germinate far more successfully than ones that have been kept for some time and dried out. Use clean, shallow, pots and/or trays with drainage holes. Place a fine layer of gravel on the bottom. Add a layer of peat-free, fine grade compost and gently firm down. Stand the pots and/or trays in water to allow the compost to absorb the water. When the compost is wet, lightly and evenly sow the spores over the surface of the compost. The spores are very fine and on no account should they be covered with more compost, as this will prevent them from germinating.
  3. Keep moist. The trays and/or pots should be covered either with a propagator lid or glass and stood in a shallow tray of water. It is important that the compost does not dry out. 
  4. Position in a semi shaded spot ideally at temperature of 16 – 20°C.
  5. Once the spores start to germinate, the young fern plants (prothalli) should become visible within a couple of weeks. Allow the prothalli to establish themselves for a little while before moving on to the next stage, that of pricking out the delicate new plants.

 Moisture is the most important element for the successful propagation of ferns. 

The fascination of plants

Posted on by andy.winfield

By Helen Roberts

For the past three years, the University of Bristol Botanic Garden has hosted Fascination of Plants Day. The event is part of a much larger initiative launched under the umbrella of the European Plant Science Organisation (EPSO). The goal of the day is to get people interested in plants and share the significance of plant science in both the social and environmental arenas.

In 2013, the inaugural year of the event, a total of 689 institutions in 54 countries opened their doors to the public and talked about the wonder of plants. The activities carried out by each institution were extremely varied, but they were united in their celebration of plants. Here at the University of Bristol Botanic Garden, there was a focus on plant classification. In Russia, huge numbers of people attended guided tours on Siberian flora. In Nigeria, focus groups discussed possible partnerships between farmers, processors and scientists. In Norway, workshops were held for children to teach them how to grow their own vegetable gardens.

This year, Fascination of Plants Day was held on Sunday, 17th May. Students at the University of Bristol were in the garden discussing plant classification and research in the plants sciences. I met two final-year undergraduate students, Joshua Valverde and Will Perry, who were on hand discussing different topics within the plant sciences and fielding questions from the public.

What’s in a name?

Many queries related to binomial nomenclature or plant naming. In biology, the name of a plant (and indeed all living things) is divided into two parts; the first name – the genus –  defines a group that comes from a common ancestor and have some common features and the second part – the species – groups together organisms that can interbreed and produce fertile offspring. Together, the genus and species forms the Latin name. Poster information compiled by Joshua explained the history of plant classification.

Joshua explained how plant classification changed over the centuries.

“To begin with, Theophrastus, a Greek philosopher, was one of the first to document and characterise plants by their morphological features. After that, plants were classified according to their medicinal use. And then long and unwieldy Latin names were used based on the morphology of the particular plant. It wasn’t until the mid-1700s that Carl Linnaeus introduced the binominal system.”

Of course, taxonomists don’t always agree on which groupings some species belong to, nor on where groups should be placed in the broader contexts of plant evolution. Classification of plants originally relied on finding similarities in form and structure (morphology) between plants. “This was subject to error though because unrelated species may evolve similar structures as a result of living in similar habitats or in response to some other adaptive need. This is called convergent evolution,” explained Joshua.

However, molecular methods have helped resolve some of these disputes.

Gnetum gnemon, a member of the order Gnetales.
Photo courtesy of gbohne on Flickr CC.

“Morphological data suggested that the order Gnetales [what we now consider a group of ‘advanced’ conifers] was the closest living relative to the first flowering plant,” explained Joshua. “After molecular analyses of various genes, however, it is now thought that Amborella trichopoda [a shrub native to New Caledonia] is the closest living relative to the first flowering plant. Water lilies also seem to be quite an ancient lineage.”

Will informed me that visitors were particularly interested in how DNA sequencing over the last decade has advanced our understanding of the evolution of plants. He explained that a lot of this work has been carried out by the Angiosperm Phylogeny Group (APG) – an informal group of systematic botanists from around the world who are trying to reach a consensus on the taxonomic groupings of flowering plants. In fact, one of the phylogenetic trees produced by the APG is displayed on a visitor information board in the Botanic Garden.

The roots of a prestigious society

Additional information on plant classification included details about the Linnean Society of London. This society was founded in 1778 and named after the famous Swedish scientist Carl Linnaeus (1707-1778). The aims of the society are to “inspire and inform the public in all areas of natural history through its broad range of events and publications”.

The society maintains the vast animal and plant collections of Carl Linnaeus (the Linnean Herbarium holds some 14,300 specimens alone), looks after his personal library as well as having its own extensive research library. The society has a hugely prestigious past and it was at a society meeting in 1858 that Charles Darwin and Alfred Russel Wallace presented papers relating to the theory of evolution by natural selection! The society today continues to report on scientific advances and holds a number of events (including a student lecture series) throughout the year ranging from the genetic diversity of farmed animals to the future of plant conservation.

Opportunities for hands-on learning

Daisy pollen in oil under a light microscope. Image courtesy
of  microscopy-uk.org.uk/

For those members of the general public that enjoy hands-on learning, the Botanic Garden had some dissecting and light microscopes available to look at various plant structures. Under one microscope there was some daisy pollen, which I heard one member of the general public describe as resembling “those spiky looking naval mines”.

Fascination of Plants Day is held each May, so be sure to join us in the Garden for this worthwhile event next year! And don’t forget to come down to the Festival of Nature this weekend (13th-14th June) learn about pitcher plant research, soil and so much more!

Branching out on your choice of Christmas tree

Posted on by andy.winfield

By Helen Roberts

Nothing quite captures the Christmas mood more than seeing a beautifully decorated Christmas tree. Whether you choose to adorn one yourself or not, the Christmas tree is decorated and celebrated in many different countries and different nations have their own favourite species. 

The foliage of the Balsam Fir.
Photo by Robert H. Mohlenbrock @ USDA-NRCS 

I am particularly picky about the species of tree our family have and the overall shape of the tree. This fussiness stems from spending time living in Canada; high standards were set when our first Christmas tree was a wonderfully large and fragrant Balsam Fir (Abies balsamea), with its dark green, long lasting foliage. This tree is a very popular species used in North America for Christmas, and on our return to England I tried to find a nursery to buy a Balsam Fir for Christmas without luck. I did some research and eventually found a similar species, but also found out some interesting information about our celebrated Christmas tree.

Where does the tradition of the Christmas tree come from?

A Christmas tree. Photo by Malene Thyssen.
Licensed under CC BY-SA 3.0 via Wikimedia Commons – 

Most people know that in 1840 Queen Victoria’s husband, Prince Albert, brought a Christmas tree over from Germany and put it in Windsor Castle. The decorated tree, surrounded by the royal family, appeared in newspaper illustrations and from then on the tradition of the Christmas tree began in Great Britain. The Victorian tree was decorated with toys, gifts, candles, sweets and cakes hung by ribbons.

Queen Charlotte, the wife of King George III in 1800, however, introduced decorated trees to Great Britain even earlier. She decided to use a Christmas tree (a potted up yew tree) instead of a yew bough to be adorned with baubles, fruit, candles and presents. The tree was, therefore, not an unknown tradition in 1840, but became a common practice among the general public after the media publicity with Queen Victoria.  By 1860 the custom was firmly grounded in England.
The history of the Christmas tree goes back much further. The ancient Egyptians, Chinese and Hebrews used evergreen trees, wreaths and garlands in ceremony as they believed evergreens symbolised eternal life. European pagans celebrated the use of evergreens to ward off the devil, celebrate the winter solstice and provide a tree for birds during Christmas time. This tradition survived Christianity and in Germany the Yule tree was placed at the entrance to a building or in the house during the midwinter holidays.
A Christmas pyramid from approximately
1830. Picture by Klaaschwotzer,
via Wikimedia Commons.

The modern Christmas tree originated in Germany where the tree was decorated with apples to represent the Garden of Eden on December 24th (the religious feast day of Adam and Eve). It was also decorated with wafers (to symbolise the host) but later became cookies and candles, to represent Christ. The Christmas pyramid, a structure made from pieces of wood and decorated with figurines, evergreens and candles was also used in addition to the Christmas tree. It was the merging of these two structures in the 16th century that lead to the tradition of the modern Christmas tree.

It is rumoured that the religious reformer Martin Luther invented the Christmas tree. Apparently, one night in 1536 he was walking through a pine forest and was amazed by the beauty of the stars amongst the branches of the pine trees. It inspired him to set up lights on his Christmas tree to remind his children of the starry skies. The custom was widespread within German Lutheran communities by the 18th century and was a well-established tradition by the next century.

What are the most common species of Christmas tree in the UK?

The names fir and spruce are liberally applied to anything that looks vaguely like a Christmas tree. Those of us that are botanically minded are aware that the name “fir” is applied to members of the genus Abies (spruces are Picea).
I do not generally pick the common species of Christmas tree. For a while, my husband and I used to bring in a potted up Korean Fir (Abies koreana). It was small, but perfect in shape and form, and at a young age produces very pretty cones that are violet purple in colour and stand upright on the branches. However, we moved overseas and gave our tree a new home in my parent’s garden where it promptly withered and died after being contained in a pot for about 5 years!
Over the years we decided to go bigger as our decorations got more numerous after having children. We now settle on Abies fraseri (the Fraser Fir), a north American species very similar to Abies balsamea in its form and fragrance. These species are popular in North America (the firs are firm favourites) and in England the popular fir species is the Nordman Fir (Abies nordmanniana). This tree is originally from Russia and is known for its ability to retain its soft, dark green needles. Its conical shape and gaps between the branches allow optimal decoration hanging. The other popular fir in this country is the Noble Fir (Abies nobilis or Abies procera), which is glaucous green in colour with an upswept open conical shape.
Blue spruce foliage.
Photo by Nickolas Titkov from Moscow, Russian Federation

It is the Norway Spruce (Picea abies), however, that most people in England consider to be the traditional Christmas tree (it is the one I always relate with my childhood Christmases’). It has a lovely forest smell, though it loses its needles more readily than the firs. Other common spruce species include Blue Spruce (Picea pungens glauca), with its vibrant blue tinge and strong citrus scent (although it is very prickly), and the Serbian Spruce (Picea omorika), which is very popular in central Europe. It has a graceful conical shape with dark green colouring, soft needles and a pleasant fragrance.

For my family, the Fraser Fir reminds us of our time living in Canada and evokes fond memories of past Christmases’ with our children. In a few years, we will probably opt for a pot grown tree, which we can then plant out – hopefully with more success than the Korean Fir!

Green roofs part II: lofty havens for wildlife

Posted on by andy.winfield

By Helen Roberts

The green roof industry has been aided over the past few years by an unlikely character. The black redstart (Phoenicurus ochruros), a robin-sized bird of strange habits, has not only helped draw attention to the green roof industry, it has advanced development of green roof design.
The black redstart is unusual in its call, looks and ecological preferences. Its song starts with a hurried warble followed by a sound similar to that of scrunching of a bag of marbles. Males have a fiery red tail and the species has a propensity to hang out in industrial places.
Within the urban environment, brownfield sites can be rich in biodiversity and can be lost when they are developed. The story of the black redstart is inextricably linked to that of humans and urban centres. Black redstart population numbers have fluctuated in the urban environment due to human activity, and this is where the story of the black redstart has impacted the green roof industry in a positive way.
During and after the Second World War the black redstart population soared because bombsites provided a habitat that closely replicated their preferred habitat found on the scree slopes of the Alps. With redevelopment of areas of London, however, populations declined. Other cities also saw a drop in numbers as a result of development.

Laban Dance Centre in London.
Credit: rucativava,
CC-BY-SA-2.0, via Wikimedia Commons

Deptford Creek in London, an area that was earmarked for development, was important for its populations of black redstarts. The developers were pushed by wildlife groups to provide suitable habitat for the birds through the implementation of green roofs. This truly innovative solution to mitigate the decline in black restart populations led to the development of green roofs designed specifically for black redstarts. The rubbleroof of the Laban Dance Centre in London, installed in 2000, was the first of these in the UK. Rubble roofs, such as the Laban Dance Centre’s, replicate the features of a brownfield site and often incorporate materials from the original site. They have a mix of aggregate materials such as crushed brick and concrete, stones and boulders. The Laban Dance Centre roof also incorporates features such as logs and sand boxes in order to study nesting bees. It has been monitored since 2002 and a number of rare invertebrates have been recordedusing the habitat.
Numerous studies have shown that green roofs help support several Red Data book invertebrates and UK Biodiversity Action Plan species such as the brown-banded carder bee (Bombus humilis) and the nationally scarce Bombardier beetle (Brachinus crepitans) and that these green roof conditions can be replicated at other sites.

The right plants for the right roof

Incorporating the right plant species in to the design of a green roof is important for achieving biodiversity objectives. Simple sedum matting has been shown to have little ecological benefit for invertebrates, though they do provide sources of food for foraging bees in summer.
A truly exemplar green roof that is rich in plant species is the Moos Filtration Plant in Zurich, which cleans all the water for the inhabitants of Zurich. Yet, this green roof came about by chance as there was no original intention to create a green roof as part of the building design. When the filtration plant was built, the multiple roofs were covered in exposed waterproofing which subsequently caused the water below the roof deck to become polluted with bacteria due to high temperatures during the first summer. In order to moderate the temperature of the roofs, a 5cm sand and gravel layer was laid down followed by a layer 15-20cm deep of local meadow topsoil. This soil was teeming with flower and grass seed and it became a flourishing 30,000m2 meadow. Today these expansive roofs provide habitat for 175 species of plants, many of which are rare and endangered at a local and national level, including 14 species of orchid. The roofs now have special protection under Swiss nature conservation laws. 

Due to the pressures of habitat loss through urbanisation, it is becoming increasingly important for biodiversity to be retained. If land is lost at the ground level through building, then green roofs help provide stepping stones above for wildlife and can provide valuable habitat for flora and fauna that would not ever be found on a conventional roof. 

Botanists disperse some ‘big data’

Posted on by andy.winfield
Recently, Botanists at Trinity College Dublin launched a database with information that documents significant ‘life events’ for nearly 600 plant species across the globe. The database is the result of contributions from individuals working across five different continents, who compiled information on plant life histories for a near 50-year span, and is an example of big data.

What is ‘big data’?

Black pine (Pinus nigra), one of the species whose life
history data is part of the database, is seen against a
stunning backdrop of New Zealand. Credit: Yvonne Buckley.

In academic circles, the buzz-term across all disciplines seems to be ‘big data’, and it means exactly what it sounds like – a whole lot of information. More formally, of course, big data refers to data sets that are so large and complex that traditional methods of processing the information contained within them simply aren’t adequate. Big data draw upon many sources of information and represent a body of work that far exceeds what a single researcher, or indeed an entire research group, could gather in their careers.
While there are many challenges of working with big data – storing it, analysing, visualising it and ensuring its integrity to name a few – the benefits of working with such large data sets may make overcoming these challenges worthwhile. Repositories of such vast amounts of information can not only help foster collaborations, but they can be used to answer questions surrounding some of the most complex and pressing issues society currently faces, including climate change, food security, and mass species extinctions.
Of course, what is considered to be big data today will not be big data tomorrow as our management systems and computing capacity improve. This is the inevitable path of technological advancement; the Human Genome Project took over ten years (1990-2003) to sequence the human genome and now it can be done in a day for a fraction of the cost.

The importance of sharing knowledge

Plantago lanceolata at Howth Head, Dublin, Ireland – one of
the near 600 plant species that researchers have gathered
extensive life history data on. Credit: Anna Csergo.

The researchers at Trinity have made their database, called COMPADRE, freely available in the hope that other scientists access the information to advance their research. The size of the database means it can be used to help answer an infinite number of questions – such as how plant communities may respond to climate change or physiological processes that might provide insights into our own aging and health.
“Making the database freely available is our 21stCentury revamp of the similarly inspired investments in living plant collections that were made to botanic gardens through the centuries;” said Yvonne Buckley, Professor of Zoology at Trinity’s School of Natural Sciences, “these were also set up to bring economic, medicinal and agricultural advantages of plants to people all over the world. Our database is moving this gift into the digital age of ‘Big Data’.”
The approach of free knowledge sharing is becoming more common and is a critical step toward resolving some of our biggest challenges. The University of Bristol’s Cereal Genomics Group has made the wheat genome along with hundreds of thousands of molecular markers freely available through their searchable database CerealsDB. These data can be used in wheat breeding programmes to develop new varieties of wheat that are more resistant to disease or droughts or produce higher yields.

Our best chance of overcoming some of the global challenges of the 21st Century is to work together. Sharing knowledge through databases, such as COMPADRE and CerealsDB, will ensure every scientific contribution counts towards this united effort.

Beans and bacteria – a complex story of communication

Posted on by andy.winfield
The symbiotic relationship between legumes and soil bacteria has been known for well over a century. The intimate details of this relationship, however, are only recently being revealed. It is a very active area of research as understanding this symbiotic relationship could lead to strategies that help reduce the environmental impacts of food production. 
Rhizobia nodules on the roots of cowpea
(Vigna unguiculata). By Stdout
[GFDL (http://www.gnu.org/copyleft/fdl.html),
via Wikimedia Commons.
Special soil bacteria – known as rhizobia – reside within the nodules of legumes, such as peas, lentils, beans, alfalfa and clover, which are found along the roots of these plants. The bacteria take nitrogen from the air and convert it into ammonia, which the plant is able to use – a process known as nitrogen “fixing”.
This allows legumes to grow well in nitrogen-poor soils. This nitrogen is taken up in the plant material, which can then be worked back into the soil as a natural fertiliser for subsequent crops.
While this all might sound very straight forward – there are details about this relationship that remain unclear. How do the bacteria get into the nodules? Are there signals that the plant uses to stimulate the bacteria to produce nitrogen?

An answer to a century-old debate

In 2011, researchers from the John Innes Centre in Norwich answered the mystery of how nitrogen-fixing bacteria crossed the cell walls into the nodules of legumes. 
It had been a century-old debate as to whether bacteria produced the enzymes to break down the cell walls or whether the plant did. The researchers showed that it was the plant which supplied the enzymes to break down its cell walls in order to give the bacteria access.

How legumes communicate with their symbiotic bacteria

In 2010, Stanfordresearchers discovered the gene in plants that triggered the chemical signal required for the bacteria to fix nitrogen. They found that the rhizobia bacteria would just sit around in the legume nodules if the plant failed to produce the protein that’s required to spur the bacteria into nitrogen fixing mode. This was only part of the communication story.
It is energetically costly for the plant to produce and maintain the root nodules in which the bacteria live; usually the benefit of having a supply of nitrogen outweighs this cost. If there is sufficient useable nitrogen in the soil, however, the plant is able to reduce the number of nodules on its roots.
Communication between the shoots of the plant and the roots of the plant help regulate the number of nodules. The leaves transmit a signal to the roots to either develop more or get rid of rood nodules, depending on circumstances. The roots communicate back up to the leaves using molecules known as peptides.
Research published recently has now discovered that the plant shoots use plant hormones, known as cytokinins, which travel down the phloem into the roots to help regulate nodule development.

The environmental benefits of understanding legumes

Understanding the symbiotic relationship between legumes and soil bacteria is not simply a matter of scientific curiosity. The ability for legumes to produce natural nitrogen fertilisers is a trait that US researchers would like to potentially transfer to non-legume crops as a way of reducing the environmental impact of agriculture.
Manufacturing nitrogen fertilisers for non-legumes is extremely resource intensive. It has been estimated that to produce 68 kg (150 lbs) of nitrogen fertiliser – enough for one acre of corn – would be the equivalent of driving a car 1,046 km (650 miles).
Beyond that, nitrogen fertilisers release the powerful greenhouse gas, nitrous oxide, after they’ve been applied. Excess fertilisers also runoff agricultural land into rivers and lakes and eventually out into the ocean. This influx of nitrogen can provoke algal blooms and create oxygen deplete dead zones.

Therefore, there is great incentive to fully understand this relationship legumes have with soil bacteria. The environmental impact of agriculture could be significantly reduced by utilising legumes with their natural nitrogen fertiliser more by using them in more marginal land and using traditional breeding programs to select for drought resistance or temperature tolerance. In some countries, genetic engineering might even be used to introduce nitrogen-fixing abilities into non-legume species. Genetic modification, however, can be an inflammatory issue with considerable debate as to its pros and cons, particularly with respect to its use in food products.