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Botany Photo of the Day
In science, beauty. In beauty, science. Daily.

Nov 21, 2014: Apium graveolens var. rapaceum 'Ibis'

A short entry by work-learn student Tamara Bonnemaison today. She was also the photographer.

Last week I woke up to the first frost of the year, and decided it was the perfect time for a morning stroll through UBC Botanical Garden. Walking through the Food Garden, I was reminded of the feeling of surveying my small farm after a frost, feeling at once relieved that the busy season was over, and disappointed at the loss of income that a frost represented. Now that I am a student, I can walk through a garden and focus instead on the pattern of ice crystals kissing the edges of leaves, and wonder at the biology that allows some plants to withstand freezing while others succumb at the slightest dip in temperature. This celeriac, Apium graveolens var. rapaceum 'Ibis', looked like it was only gently touched by the frost, and the knobby stem will remain delicious for many cold months.

Celeriac, also called knob celery, is a type of celery grown primarily for its flavourful knobby hypocotyl (stem below seed leaves), leaves, and roots. It is cultivated in temperate vegetable gardens and farms around the world, but is most popular in Europe. Celeriac requires a long growing season, and the taste of its gnarly-looking stem sweetens after a frost, making it perfect for wintery dishes such as these recipes for remoulade and soup. I haven't yet tried these, but they look particularly delicious.

Celeriac has a number of the qualities that allow it to survive and stay tasty in cold weather. A report by the FAO discusses frost physiology in common vegetables, and Apium gravoeolens var. rapaceum exhibits a number of the traits that the FAO lists as ways that plant species tolerate cold temperatures. For example, the large, fleshy stem has a high heat capacity, preserving the day's heat well into the night. Also, the entire plant is able to gradually "harden" by increasing concentrations of solutes such as sugar to lower the freezing temperature of its tissues. All that is to say that it is very convenient that starchy root vegetables such as celeriac achieve their peak late in the season, just in time for the thick soups and comfort foods that feel so good to eat in the winter.

Nov 18, 2014: Dicranum scoparium

Dicranum scoparium

...and another entry by Tamara Bonnemaison today:

Thank you to to Robert Klips (aka aka Orthotrichum@Flickr) for posting a lovely shot of broom moss in the snow (with a little fern moss, Thuidium delicatulum, also making in appearance). Robert took this photo last February in Delaware County, Ohio, USA. For a close-up image of Dicranum scoparium with sporophytes at different stages of maturity, see this image by Phil Pullen.

The widely-distributed Dicranum scoparium is found on moist and sunny rocks, cliff edges and logs across North America, Europe, Asia, Australia and New Zealand. The 2-8cm tall stems form soft turfs. The hair-like leaves have a "swept" appearance, giving this species its common name.

Robin Wall Kimmerer inspired me to write about this species. Kimmerer has written a very entertaining book, Gathering Moss, A Natural and Cultural History of Mosses. Moss reproduction is a fascinating subject in general (well, at least if you are a plant geek like me - but as you are reading this, I suspect you are!) and I found the way that Kimmerer describes Dicranum reproduction particularly colourful. Moss reproduction is often hit and miss, and in the case of Dicranum scoparium, the female of the genus has taken control of the process in order to ensure a higher chance of success. Broom moss spores have no gender, and the ultimate sex depends on where the spore lands in relation to other female members of its species. If the spore lands away from the nearest turf of broom moss, it will develop into a female. Those spores that land on an established female develop into something called a "dwarf male".

Dwarf males grow to only a few millimeters, and to the visible eye appear as nothing more than a miniscule cluster of leaves, growing as an epiphyte on a full-sized female. There are many advantages to this arrangement. By commanding the least amount of space and resources possible, dwarf males do not compete with the females, who need moisture, sunlight, and nutrition in order to support the growth of their sporophytes. Even more importantly, dwarf males are placed as close to the female gametophyte as possible, greatly reducing the amount of ground that a swimming sperm needs to cover in order to be successful. This reproductive tactic is quite effective, with higher rates of fertilization occurring on the females hosting the largest numbers of dwarf males.

Kimmerer wrote that a hormone emitted by female Dicranum scoparium causes the males of the species to grow as dwarves, but a literature review by Pichonet and Gradstein (2012) (9 years after Kimmerer's book was published) did not find conclusive evidence that dwarf males were caused by chemical factors. Instead, Pichonet and Gradstein conclude that "genetic factors, environmental factors, and unfavourable nutrient conditions" can all result in dwarf males.

Nov 13, 2014: Mucuna holtonii

Tamara Bonnemaison wrote today's entry:

Today I have selected two photos taken by Reinaldo Aguilar (aka Reinaldo Aguilar@Flickr), one of the authors of the Vascular Plants of the Osa Peninsula, Costa Rica. Reinaldo's images show an otherworldly Mucuna holtonii taken at Charcos, Puntarenas, Costa Rica (other image and complete Mucuna album). I am really excited to write about this species; thank you Reinaldo for providing the photos!

I was inspired to learn more about Mucuna holtonii after reading a National Geographic article about plants that "speak" to bats. This beautifully-written article, "Call of the Bloom", follows the work of Dr. Ralph Simon through his discovery that many bat-pollinated tropical plants have special features that reflect sonar in particular ways, allowing bats to quickly find them in the dark and over large distances. Mucuna holtonii was one of the first species examined for its capacity to guide echo-locating bats to its nectar-rich flowers. This neotropical vine grows high in jungle canopies of central America, and dangles its flower clusters on long stems, isolating the night-blooming flowers from surrounding vegetation. This on its own provides ideal conditions for bats to locate the flower and access its nectar, but the species makes this process even easier through an adaptation that bounces back the bat's sonar at a high amplitude.

Like many other members of the pea family, the flowers of Mucuna holtonii have a banner, keel, and wings formed by 5 irregular petals. In Mucuna holtonii, the banner (also called the vexillum or standard) is waxy, concave and is raised like a flag (or should I say a satellite dish) as the flower bud opens. Today's photo shows this quite clearly, and it is easy to imagine sound bouncing off of the banner's surface in a clear and concentrated manner. The researchers Dagmar and Otto von Helversen found that the presence of these banners made a remarkable difference in bat visitation rates. In their study, 88% of virgin flowers were visited by bats, but when the researchers removed the banners, that number dropped to only 21%. Mucuna holtonii is but one of many plant species that makes itself more visible to echolocating pollinators. In an effort to find other plants with acoustic capabilities, Dr. Ralph Simon has started the Flower Echo Project, and has so far tested the echoes of over 65 flower species.

Flower-bat communication is only one of the many interesting features of Mucuna holtonii. Although I did not come across any common names for this species, the seeds of many Macuna species are referred to as "sea beans" because they often float down rivers and into the ocean (they are also called hamburger beans for their appearance). Washed up on far-away shores, the beautiful black seeds are often polished and strung to form necklaces and bracelets. Kew Garden's Economic Botany Collection is home to one such bracelet, made of a combination of Mucuna holtonii seeds and the smaller seeds of three other species.

Nov 11, 2014: Acer palmatum Amoenum Group

Acer palmatum Amoenum Group

A walkabout last Tuesday in the David C. Lam Asian Garden revealed that not all maples had yet lost their leaves. Photographed from below, it was an attempt at using the bright cloudy sky for background effect. Usually I avoid incorporating cloud-filled skies in my photographs, but that tends to limit photo opportunities during the winter locally. Better to learn how to work with it than not attempt anything at all, perhaps.

There are a number of Japanese maple Groups, with a good summary available on page 3 in Harold Greer's presentation (converted to PDF) on The Wonderful World of Maples (Harold's nursery web site: Greer Gardens). The word "Group" is capitalized as it is a "a formal category for assembling cultivars, individual plants or assemblages of plants on the basis of defined similarity." The Amoenum Group of Acer palmatum, for example, is distinguished by having shallowly to moderately lobed leaves, up to two-thirds the distance to the leaf base. The particular plant in today's photograph may be a named cultivar. If that was the case, and we knew the identify, we could call it Acer palmatum 'CultivarName' Amoenum Group. However, I don't think we have attempted to identify it to cultivar name, in part because we lack the history that is so often useful in determining cultivars. This is an old accession that was received from the campus' horticultural operations over thirty-five years ago. Still, due to its age and beauty, it is retained in our Asian Garden despite the emphasis we have on documented wild-collected accessions.

Nov 6, 2014: Penicillium chrysogenum

Today's entry was written and photographed by Cora den Hartigh. She writes:

Mould isn't often considered beautiful, but I think there is a haunting quality to the gentle blues and soft yellows of this Penicillium chrysogenum. This fungus was cultured on agar medium in the laboratory. Rapid growth hastened a process called guttation, that produced gem-like water droplets suspended on the fuzz of this mould's body. Guttation is common in fungi with some conks oozing blood red or viscous black substances, but it is perhaps most appreciated as a sometimes-contributor to the morning dew on herbaceous plants. If you aren't yet convinced of the beauty of this mould, perhaps the elegance of Penicillium's conidia strung in beads from draping conidiophores under a microscope will prove convincing. If flowers had skeletons, maybe they would look like this!

Aesthetics aside, Penicillium is the famous fungal genus that contributed to the discovery of penicillin, the antibiotic whose discovery opened up a new field of medical treatments. As fungal hyphae stretch into substrates in search of food, they release enzymes to break nutrient sources down for ease of absorption (somewhat akin to having an external stomach). The catch is, they must then protect their processed foods from competitors! Penicillin is just that, an antibacterial that Penicillium uses to protect its plate at dinnertime. It is worth mentioning that Penicillium chrysogenum was discovered on a cantaloupe in Illinois and is not the same as Alexander Fleming's Penicillium notatum, which produces significantly less penicillin. However, it was Penicillium chrysogenum that contributed to the mass-production of penicillin. Resistance to antibiotics is becoming an increasing concern globally; it is a bolstering thought that there remains a vast diversity of fungi yet undiscovered that may have similar potential.

Daniel adds: Tom Volk's always excellent Fungi site has a detailed article on Penicillium chrysogenum, with additional details about the discovery and history of penicillin.

Nov 5, 2014: Celastrus scandens

Celastrus scandens

Botany Photo of the Day Work-Learn student Tamara Bonnemaison contributes both the photography and the written entry today. She scribes:

At this time of year, the winter rains begin to hit Vancouver, and our local world recedes into tones of grey and misty green. Unless, of course, one happens to be strolling through UBC Botanical Garden's Carolinian Forest. Here, the rich yellows and reds one expects to see in eastern North America instead brighten our soggy, West Coast souls. This Celastrus scandens caught my attention with its bright fruit, and I am pleased to finally have taken a photo worthy of sharing with you, the fine readers of Botany Photo of the Day.

Celastrus scandens is a fast-growing woody vine native to central and eastern North America. It was given the common name of American bittersweet by European colonists who thought it resembled the unrelated bittersweet of their homeland, Solanum dulcamara. American bittersweet can be found in many habitats, including dune thickets, roadsides, and forests, and will grow to over 10 meters when given access to a climbing structure. In the garden, it can be used as a sprawling shrub to quickly cover hillsides or unsightly rip-rap, or can be grown on a trellis or fence. The plant photographed was wisely planted along a chain-link fence at the far edge of the Botanical Garden<, where it will soon hide this necessary but uninspiring structure.

The fruit of this species are particularly interesting. The three-valved capsules enclose a fleshy aril (an outgrowth from the funiculus, or attachment point of the seed), and burst open when the seed is ripe. I look forward to seeing this in action as the autumn progresses, but for now I had to make do with the many photos of this phenomenon available online, including one at the University of Michigan's "Climbers" web site. The bright red aril covers the seeds, and serves as further enticement for the birds who aid dispersal. The fruit is toxic to humans, and was used by the Cherokee to make poison.

The other visually-arresting aspect of this species is its stem. Having no tendrils, American bittersweet relies on twining of the stem apex for its ability to climb. I was not able to take a satisfactory photo of the twining woody stems, but I found them to be quite beautiful. Illustrative photos of the twining stems are available from Prairie Moon Nursery. The stem usually twines dextrally (left to right), and before photographing this plant, I had never considered that plants might have an equivalent to human left and right-handedness. In an attempt to understand why plants twine in one direction over the other, Edwards, Moles and Franks (2007) carried out a study that concluded that twining direction could not be explained by plants tracking the sun across the sky. The same study also concluded that the Coriolis effect was also not responsible for twining direction (on a completely unrelated side-note, the Coriolis effect also does not explain the direction that water drains in your sink). Edwards et. al's full paper, "The Global Trend in Plant Twining Direction", is available online. Now that we have an idea about what doesn't determine a plant's chirality, are there any sources that can explain what does? The best that I could find was the 2011 publication of Burnham and Revilla-Minaya, Phylogenetic Influence on Twining Chirality in Lianas from Amazonian Peru. This article gives the somewhat unsatisfying answer that "genetic, developmental, and physiologic perspectives" are required to understand why a plant may twist to the left or to the right.

Oct 31, 2014: Pontederia cordata

Tamara Bonnemaison writes today's entry, which features a representative of a family never previously highlighted on Botany Photo of the Day, the Pontederiaceae:

Today, regular BPotD contributor 3Point141 (3Point141@Flickr) shares his striking photo of Pontederia cordata, taken on the shoreline of Turkey Lake, Orlando, Florida, USA. Rusty Clark ((Rusty Clark@Flickr) also contributed her image of the species in flower. Thank you to both contributors!

Pontederia cordata, or pickerelweed, is a rhizomatous, emergent perennial that grows in wetlands from Argentina north to eastern Canada. It typically has lance-shaped leaves with rounded lobes, but the leaf shape in particular is quite variable and has led to the naming of several now-synonymized varieties. From June through November in eastern North America, pickerelweed sends up a large spike displaying hundreds of light blue flowers. This species grows prolifically and forms dense stands that, when blooming, are stunning in the wild and in garden ponds. To get an idea of how impressive a stand of pickerelweed in bloom can be, have a look at the fourth image shown on Dr. Spencer Barret's lab's site on floral displays.

Pickerelweed is common, is adapted to a wide range of wetland conditions, and grows rapidly and aggressively - traits that make the species useful in constructed wetlands in North America. Collins, Sharitz and Coughlin's (2005) study, titled "Elemental Composition of Native Wetland Plants in Constructed Mesocosm Treatment Wetlands" examines the beneficial role that Pontederia cordata can play in treating runoff from coal-fired power plants. Power plant runoff is both high in heavy metals and acidity, and the species selected for constructed wetlands treating this runoff must be able to survive such difficult conditions. Collins et al. found that Pontederia coradata was able to establish in shallow wetlands receiving acidic and polluted runoff, and was successful in taking up a moderate amount of heavy metals. Pickerelweed and the rush species, Juncus effusus, were particularly effective in accumulating iron and aluminum. Constructed wetlands can be used to treat water contaminated by many sources, and Pontederia cordata is being examined as one of an assemblage of plants that can be used to remove organic solvents, phosphorus, and other contaminants.

The characteristics that make pickerelweed useful in North American wetlands urge caution in other parts of the world. The species' aggressive nature has allowed it to become invasive in some countries, including Kenya. It has naturalized, though is not recognized as invasive, in areas of Europe, Australia and western North America.

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