Single plant cells have amazing capacities for regenerating into entire plants. This property is known as ‘totipotency’ discovered in the 1920s. Linking this with increasing understanding of growth control by plant hormones resulted in the development of the sterile, in vitro, culture. Tiny groups of cells, explants, are cut from the rapidly growing tips of shoots in controlled environments and washed in sterilising agents. These are cultured sterile jars containing a layer of agar supplemented with nutrients and hormones.
Green plantlets growing on sterile agar
The process is known as ‘tissue culture’ or micropropagation. As the cells divide and multiply, they are transferred through a series of sterile conditions which encourage root formation.
Roots growing from newly developing plantlets
Ultimately numerous new whole plants are generated. At that point they are removed from sterile conditions and weaned by planting into clean compost in high humidity environments. High humidity is essential as these transplants lack the protective coating of leaf and stem waxes which prevent desiccation. Ultimately when fully weaned the plants are grown under normal nursery conditions into saleable products.
Why bother with this processes which requires expensive facilities and highly skilled staff? A prime advantage is that micropropagated plants have genotypes very closely similar to those of the original parent, essentially they are clones. As a result vast numbers of progeny can be generated from a few parents preserving their characteristics. That is particularly important as a means of bulking-up newly bred varieties of many ornamental and fruit producing plants which otherwise would be reproduced vegetatively from cuttings or by grafting and budding onto rootstocks. Micropropagation is therefore a means for safeguarding the intellectual property of plant breeding companies.
Explants cut from parent plants before culturing can be heat-treated as a means of removing virus infections. The resultant end-products of rooted plants are therefore disease-free or more accurately disease-tested. These plants are usually more vigorous and produce bigger yields of flowers and fruit. Orchids are one of the crops where the impact of micropropagation is most obvious in florists’ shops and supermarkets.
Orchids have benefitted greatly from micropropagation
Large numbers of highly attractive orchids are now readily available. Previously orchids were very expensive and available in sparse numbers.
The world is not perfect and there are disadvantages with micropropagation. Because the progeny are genetically similar they are uniformly susceptible to pests and pathogens. Crops of clonal plants can be and have been rapidly devasted by existing and new strains of insects and diseases to which they have no resistance.
Elderflowers are in full bloom this month, both in hedgerows as well as gardens across the country. Whether they are the wild Sambucus nigra or a cultivated variety with green or black leaves they are all beautiful and useful plants.
The black leaved cultivar growing in the SCIence Garden has pink blooms, whereas the wild species has white flowers. It was purchased as ‘Black Beauty’, but is also sold as ‘Gerda’.
Sambucus nigra f. porphyrophylla ‘Black Beauty’ growing in the SCIence Garden
This cultivar, along with ‘Black Lace’ (Eva) was developed by Ken Tobutt and Jacqui Prevette at the Horticulture Research International research station at East Malling in Kent and released for sale in the horticulture trade in 2000. The leaves stay a dark purple throughout the year and the flowers have a good fragrance.
The shrub will tolerate hard pruning so is useful for smaller spaces and provides a long season of interest. The plant is also a forager’s delight, both in early summer (for the flowers) and in the autumn (for the berries).
Most commonly one may think of elderflower cordial, or perhaps even elderflower champagne, but an excellent alternative to the rose flavoured traditional “Turkish Delight” can be made - https://www.rivercottage.net/recipes/elderflower-delight. I can highly recommend it!
The chemistry of the elderflower aroma is complex. Analyses such as that in the reference below* have identified many different terpene and terpenoid components including nerol oxide, hotrienol and nonanal.
* Olfactory and Quantitative Analysis of Aroma Compounds in Elder Flower (Sambucus nigra L.) Drink Processed from Five Cultivars. Ulla Jørgensen, Merete Hansen, Lars P. Christensen, Karina Jensen, and Karl Kaack. Journal of Agricultural and Food Chemistry 2000 48 (6), 2376-2383. DOI: 10.1021/jf000005f
One of the most beloved flowers in China (and elsewhere) this small tree was planted here in the SCIence garden to represent the Chinese UK group. It is in bloom from late winter and the bright pink flowers have a strong perfume. It is growing in the centre at the back of the main area of the garden.
There are 309 accepted species in the genus Prunus listed on the Plants of the World Online database (plantsoftheworldonline.org). The genus is distributed mainly across the Northern temperate zones but there are some tropical species.
The genus Prunus is generally defined based on a combination of characteristics which include: a solitary carpel (the structure enclosing the ovules – a combination of the ovary, style and stigma) with a terminal style, a fleshy drupe (fruit), five sepals and five petals and solid branch pith. The drupe contains a single, relatively large, hard coated seed (stone) – familiar to us in cherries, apricots, nectarines, peaches etc
This particular species, Prunus mume, originates from southern China in the area around the Yangtze River. The ‘Beni-chidori’ cultivar has been given an Award of Garden Merit by the Royal Horticultural Society.
Over 300 different cultivars of this species have been recorded in China, perhaps not surprisingly for a plant that has been domesticated for thousands of years due to its floral beauty. A recent study on the genetic architecture of floral traits across the cultivars of this species was published in Nature Communications.1
Prunus mume was introduced from China into Japan, Korea, Taiwan and Vietnam and it is now fully integrated into the cuisines of all these countries. In addition to its uses in many foodstuffs and drinks, extracts from the fruit are also widely used in traditional Chinese medicine and in the traditional medicines in Korea and Japan. Anti-bacterial, anti-oxidative, anti-inflammatory and anti-cancer properties have all been ascribed to the extract which has been used to treat tiredness, headaches, constipation and stomach disorders amongst other things. A recent review published in the Journal of Ethnopharmacology2 gathers together information from literature reports on the anti-cancer activity of Prunus mume fruit extract.
One standardised extract in particular (MK615) has shown antitumour activity against most common cancer types.
The anti-cancer activity has not been ascribed to a particular component. Compounds isolated from the extract include ursolic acid, amygdalin, prunasin, chlorogenic acid, mumefural and syringaresinol.
Like all the plants in the SCIence garden – there’s a lot more to this one than just its ornamental beauty.
1. Zhang, Q., Zhang, H., Sun, L. et al. The genetic architecture of floral traits in the woody plant Prunus mume. Nat Commun 9, 1702 (2018). https://doi.org/10.1038/s41467-018-04093-z
2. Bailly, C. Anti-cancer properties of Prunus mume extracts. J Ethnopharmacology 246, 2020, 112215. https://doi.org/10.1016/j.jep.2019.112215
Aldrin, Armstrong and Collins, Apollo 11’s brave astronauts were the first humans with the privilege of viewing Earth from another celestial body. These men uniquely wondered “what makes Earth special?” Certainly, within our Solar System, planet Earth is very special. Its environment has permitted the evolution of a panoply of life.
Green plants containing the pigment, chlorophyll either in the oceans as algae or on land as a multitude of trees, shrubs and herbs harvest energy from sunshine. Using a series of chemical reactions, known as photosynthesis, light energy is harvested and attached onto compounds containing phosphorus.
Captured energy then drives a series of reactions in which atmospheric carbon dioxide and water are combined forming simple sugars while releasing oxygen. These sugars are used further by plants in the manufacture of larger carbohydrates, amino acids and proteins, oils and fats.
The release of oxygen during photosynthesis forms the basis of life’s second vital process, respiration. Almost all plants and animals utilise oxygen in this energy releasing process during which sugars are broken down.
Released energy then drives all subsequent growth, development and reproduction. These body-building processes in plants are reliant on the transfer of the products of photosynthesis from a point of manufacture, the source, to the place of use, a sink.
Leaves and shoots are the principle sources of energy harvesting while flowers and fruits are major sinks with high levels of respiration.
Figure 1: Photosynthesis vs respiration, drawn by James Hadley
Transfer between sources and sinks occurs in a central system of pipes, the vascular system, using water as the carrier. Water is obtained by land plants from the soils in which they grow. Without water there would be no transfer and subsequent growth. Earth’s environment is built around a ‘water-cycle’ supplying the land and oceans with rain or snow and recycles water back into the atmosphere in a sustainable manner.
Early in Earth’s evolution, very primitive marine organisms initiated photosynthetic processes, capturing sunlight’s energy. As a result, in our atmosphere oxygen became a major component. That encouraged the development of the vast array of land plants which utilise rain water as the key element in their transport systems.
Subsequently, plants formed the diets of all animals either by direct consumption as herbivores or at second-hand as carnivores. As a result, evolution produced balanced ecosystems and humanity has inherited what those astronauts saw, “the Green Planet”.
Earth will only retain this status if humanity individually and collectively defeats our biggest challenge – climate change. Burning rain forests in South America, Africa and Arctic tundra will disbalance these ecosystems and quicken climate change.
Controlling when and how vigorously plants flower is a major discovery in horticultural science. Its use has spawned vast industries worldwide supplying flowers and potted plants out-of-season. The control mechanism was uncovered by two American physiologists in the 1920s. Temperate plants inhabit zones where seasonal daylength varies between extending light periods in spring and decreasing ones in autumn.
Those environmental changes result in plants which flower in long-days and those which flower in short-days. ‘Photoperiodism’ was coined as the term describing these events. Extensive subsequent research demonstrated that it is the period of darkness which is crucially important. Short-day plants flower when darkness exceeds a crucial minimum, usually about 12 hours which is typical of autumn. Long-day plants flower when the dark period is shorter than the crucial minimum.
Irises are long day flowers. Image: Geoffery R Dixon
A third group of plants usually coming from tropical zones are day-neutral; flowering is unaffected by day-length. Long-day plants include clover, hollyhock, iris, lettuce, spinach and radish. Gardeners will be familiar with the way lettuce and radish “bolt” in early summer. Short-day plants include: chrysanthemum, goldenrod, poinsettia, soybean and many annual weed species. Day-neutral types include peas, runner and green beans, sweet corn (maize) and sunflower.
Immense research efforts identified a plant pigment, phytochrome as the trigger molecule. This exists in two states, active and inactive and they are converted by receiving red or far-red wavelengths of light.
Sunflowers are day neutral flowers. Image: Geoffery R Dixon
In short-day plants, for example, the active form suppresses flowering but decays into the inactive form with increasing periods of darkness. But a brief flash of light restores the active form and stops flowering. That knowledge underpins businesses supplying cut-flowered chrysanthemums and potted-plants and supplies of poinsettias for Christmas markets. Identifying precise demands of individual cultivars of these crops means that growers can schedule production volumes gearing very precisely for peak markets.
Providing the appropriate photoperiods requires very substantial capital investment. Consequently, there has been a century-long quest for the ‘Holy Grail of Flowering’, a molecule which when sprayed onto crops initiates the flowering process.
Chrysanthemums are short day flowers. Image: Geoffery R Dixon
In 2006 the hormone, florigen, was finally identified and characterised. Biochemists and molecular biologists are now working furiously looking for pathways by which it can be used effectively and provide more efficient flower production in a wider range of species.
At the SCI HQ in Belgrave Square, London, we have curated a beautiful garden filled with plants that represent our technical and regional interest groups. Each of these plants has a scientific significance. On World Wildlife Day, we take a look at how some of our plants are doing in March.
Cyclamen hederifolium - the ivy-leaved cyclamen. Image: SCI
Cyclamen hederifolium is included in the SCIence garden to represent the horticulture group. This beautiful pink flower has a mutualistic relationship with ants, in which the ants carry the seeds far away, ensuring no competition between young plants and the original.
Dichroa febrifuga - a hydrangea with anti-malarial properties. Image: SCI
Not yet flowering, D. febrifuga is a traditional Chinese herbal medicine that is used for treatment of malaria. It contains the alkaloids febrifugine and isofebrifugine which are thought to be responsible for it’s anti-malaria properties.
Fatsia japonica - the paper plant. Image: SCI
F. japonica is also known as the glossy-leaved paper plant and is native to Japan, southern Korea and Taiwan. This plant represents our materials group.
Rosmarinus officinalis aka rosemary - a herb with many uses from culinary to chemical. Image: SCI
Rosemary is a common herb that originates in the Mediterranean. It has many uses, including as a herb for cooking and fragrance. One of it’s more scientific uses is as a supply of lucrative useful phytochemicals such as camphor and rosemarinic acid.
Prunus mume ‘Beni-chidori’ - a Chinese ornamental flower. Image: SCI
The Prunus mume tree is a beautiful ornamental tree that has significance in East Asian culture. It has a wide variety of applications, from medicinal to beverages, and can been seen in many pieces of art. This plant is in the SCIence garden to represent our Chinese Group UK.
Pieris japonica - the Dwarf-Lilly-of-the-Valley-Shrub. Image: SCI
The Pieris japonica ree has Asian origins, and represents our Agrisciences group. The leaves contain diterpenoids which inhibit the activity of feeding pests, such as insects.
Pulmonaria ‘Blue Ensign’ - lungwort. Image: SCI
The lungwort has been used since the Middle Ages as a medicinal herb to treat chest or lung diseases. It is an example of the use of the doctrine of signatures - where doctors believed that if a plant resembled a body, it could be used to treat illness in that body part.
Euphorbia amygdaloides - the wood spruce. Image:SCI
Euphorbia amygdaloides is planted to represent our Materials Chemistry group. It has a waxy feel, and has potential to be used as an alternative to latex.
Erysimum ‘Bowles Mauve’ - a flowering plant in the cabbage family. Image: SCI
The Erysimum ‘Bowles Mauve’ is a member of the cabbage family (Brassicaceae). This plant was used to make the first synthetic dye, Mauvine, when SCI founding member William Perkin discovered in in 1858.