University of Bristol Botanic Garden
Lose yourself in the world of plants…
This week we attempted a live tour of the Garden on our Facebook page with Curator Nick Wray. Of course, despite the driest spring and early summer we can remember, the rain fell down and the thunder and lightening raged. The show went on however, and for those who missed it, here it is in all it’s glory; enjoy!
f
The one animal that springs to most people’s mind for eating honey is bears. Especially a particularly round individual who gets his hand stuck in the honey pot numerous times. However, many animals around the world, including raccoons, skunks, opossums and honey badgers, feast on honey. They brave the fury of the hive to not only get at the sweet sticky stuff, but for the protein obtained from eating the bees and larvae themselves. We humans are fussier and prefer to stick to just the honey, though some people will eat honey on the comb.
For centuries, honey has been recognised not only for its culinary uses but its medicinal uses, due to its antimicrobial properties. The potential scope of honey in medicine is vast and still developing despite its use since ancient times; the ancient Egyptians and Greeks commonly used honey to treat wounds. Research into the medicinal properties of honey is ongoing and not only restricted to its use in promoting wound healing, but also its potential as an anti-inflammatory, anti-fungal, treatment for burns, aid in the treatment of chronic rhinosinusitis and combatant against the bacterial biofilms that can form in urinary catheters.
 |
| Manuka flowers (Leptospermum scoparium). Photo credit: FlowerGirl on Flickr [CC BY-ND 2.0] |
Manuka honey (MH) is a monofloral honey produced in New Zealand and is made exclusively by European honey bees from the flowers of the Manuka bush, Leptospermum scorparium. MH is also produced in other countries, such as Australia and even in the UK, although it could be argued that this is not the ‘real deal’, having not come from New Zealand. In fact, there is currently an acrimonious disagreement between Australian and New Zealand honey producers over the right to market MH. New Zealand producers want exclusive trademarks on MH and Australian apiarists are fighting this, arguing that MH has been used in Australia since 1831, 8 years before New Zealand even got European honey bees. The bitter battle ensues.
The unique antibacterial properties of MH are attributable to the organic compound called methylglyoxal (MGO), which comes from the conversion of dihydroxyacetone (DHA) – a simple carbohydrate that is found in the nectar of Manuka flowers. DHA is one of the markers used to grade MH on a scale known as the UMF, or Unique Manuka Factor. Manuka honey needs a minimum rating 10 UMF to be labelled as Manuka.
Microbiologist Dr Rowena Jenkins, Lecturer at Cardiff Metropolitan University, and her research team have discovered numerous health benefits of using MH, which has been supported by clinical trials. This is an opportune moment for research into non-antibiotic agents as more antibiotic resistant pathogens emerge. Jenkins and her team are particularly interested in how MH might help battle the most challenging infectious agents…the ‘superbugs’.
Meticillin-resistant Staphylococcus aureus (MRSA) is the ‘superbug’ many of us associate with health care facilities. Jenkins’ team is exploring how MH wipes out MRSA that have infected wounds sites by preventing the bacteria from dividing. In addition, Jenkins highlighted the potential for MH to be used in combination with antibiotics to stop the growth of MRSA.
If you’re interested in learning more about the ongoing research into honey, on the 24th of August, Dr Rowena Jenkins will be a guest speaker at the University of Bristol Botanic Garden Science Picnic. Visitors can relax in the garden and engage with Rowena in an informal discussion about her ongoing research into the health benefits of honey. It’s a rare opportunity to mingle with the scientists working on the edge of cutting research. You can book your place at the University of Bristol’s online shop.
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.
Adams, C.J., Manley-Harris, M. and Molan, P.C. 2009. The origin of methylglyoxal in New Zealand Manuka (Leptospermum scoparium) honey. Carbohydrate Research, 344(8):1050-1053.
Jenkins, R., Burton, N. and Cooper, R. 2011. Manuka honey inhibits cell division in methicillin-resistant Staphylococcus aureus. Journal of Antimicrobial Chemotherapy, 66(11): 2536-2542.
Roberts, A.E.L., Brown, H.L., Jenkins, R.E. 2015. On the antibacterial effects of Manuka honey: mechanistic insights. Research and Reports in Biology, (6): 215-224.
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.
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 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.
 |
| 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.
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.