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

May 28, 2015: Trifolium repens

Trifolium repens

I am very familiar with Trifolium repens, or white clover, but I did not recognize it in Bruce Brethauer's (aka Glichidman@Flickr) close-up of Trifolium repens florets (a floret is a small flower in a composite of flowers). Thanks Bruce, for making me see a familiar plant species from an entirely different perspective.

There is a good chance that you have seen a Trifolium repens plant today. Originally from Europe, northern Africa,and Asia, white clover (also called Dutch clover) is widely naturalized in most parts of the world. It is commonly found in lawns, parks, gardens, roadsides, rangelands, and in most types of disturbed sites. As far as weeds go, it is a rather useful one. Trifolium repens (pdf) fixes nitrogen, and is highly-resistant to trampling, making it suitable for high-traffic areas such as lawns and also on farm lanes, where it prevents soil compaction from farm equipment. It is an excellent, high-protein forage crop for livestock, and can also be boiled lightly to make it digestible to humans. Trifolium repens is considered one of the best honey plants by apiarists - you have probably tasted clover honey, which has a mild, floral flavour.

As a child, it is likely that you spent time crawling through grass, searching for four-leaved clovers, but according to the science writer David Bradley, four-leaved clovers are only considered lucky if you find them by accident (actually, Bradley quite adamantly asserts that there is no luck involved, only a random mutation that occurs about once in every 10,000 specimens). So, 99.99% of the time, Trifolium repens leaves are trifoliate (have three leaflets). They are alternately arranged and borne on long, curving stalks. The individual leaflets are oval, egg-shaped, or heart-shaped and are 10-55 mm long by 6-30 mm wide. The adaxial (upper) surface of each leaf has a white chevron (upside-down 'v') marking that is quite distinctive.

The white clover inflorescence is a globose (spherical) head borne on a long stem. Each head has 20-100 white to pinkish florets, borne on a short stalk (pedicel). Bruce's photo shows that each of those florets resembles a typical pea flower - a feature I had not noticed, but which makes a lot of sense, since Trifolium is in the pea family, the Fabaceae. When fertilized, the florets produce tiny pods (4-6 mm long), each containing 3-4 seeds that remain hidden inside the old flower parts. The seeds are dispersed by livestock, earthworms, and birds, but are also dispersed by humans.

May 27, 2015: Preissia quadrata

Preissia quadrata

Todays photo features a complex thallose liverwort, Preissia quadrata. This photo was taken by Robert Klips (aka Orthotrichum@Flickr) in Adams County, Ohio, U.S.A. Thanks, Robert!

If you are like me, you have no idea what a complex thallose liverwort is. Thankfully, there are many sources available to us as we embark on a crash-course on liverwort morphology. Liverworts are the most ancient group of land plants, and are non-vascular and spore-producing. They do not have flowers. The UBC Bryology course website provides a helpful introduction to liverworts, and explains that there are two types: the leafy liverworts (which look leafy), and the thallose liverworts (which look like flat green pancakes). The thallose liverworts do not have stems or leaves: they have a thallus, which is the undifferentiated vegetative tissue that forms the entire body of the liverwort. Of the thallose liverworts, some are simple, and some are complex. The Friends of the Australian National Botanic Gardens have published a very helpful information page about thallose liverworts, which explains that complex thallose liverworts have a thallus that is "many cells thick and the cells in different layers within the thallus have different functions". The simple thallose liverworts, on the other hand, have a thallus that lacks such differentiation.

Preissia quadrata has flat, branched, leathery thalli (the plural of thallus) up to 1 cm wide. It is found growing in mats in the cracks of alkaline rocks in the Arctic, Subarctic, or at high altitudes in the Northern Hemisphere. The upper surface of the Preissia quadrata thallus is dark green and covered by conspicuous, raised air pores. I could write an entire entry about the reproduction of Preissia quadrata, but today I encourage anyone interested in the subject to read this article on "Liverwort Reproductive Structures," published by Field Bryology. When he submitted today's photo, Robert Klips pointed out that the specimen photographed was "beginning to release spores. The black sporophytes are produced on the undersides of the umbrella-like archegoniophore. They look fuzzy because of thread-like twisted elaters which help push out the spores."

May 25, 2015: Tradescantia occidentalis

Tradescantia occidentalis

Thank you Jim Nelson (aka Vegas Nelson@Flickr), for this beautiful photo of Tradescantia occidentalis taken in Zion National Park in Utah, U.S.A.

Tradescantia occidentalis, or prairie spiderwort, is a perennial monocot found in central North America. Although it has a fairly wide-spread distribution, there are only four known populations of this species in Canada, where it is listed as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Prairie spiderwort grows in grasslands and on partially-stabilized sand dunes. In Canada, suitable habitat occurs only in the southern parts of the prairie provinces: Alberta, Saskatchewan, and Manitoba.

Tradescantia occidentalis has semi-succulent stems, and narrow-bladed leaves. The 3-petaled flowers grow in a raceme of up to 10 flowers, which can be pink, white, violet, or most commonly, dark blue as shown in today's photo. The bright yellow anthers contrast beautifully with the deep blue of the petals and filaments, which are decorated with blue hairs. Some sources claim that the spider-like appearance of these hairy filaments give spiderwort its common name, while others attribute the name to cobweb-like strands that form from a sticky fluid when the leaves or stem are broken.

The habitat required by Tradescantia occidentalis (pdf) is quite specific. Sand dunes must be fairly stable, yet also must have some bare patches where seedlings can become established, as prairie spiderwort only reproduces by seed. Historically, regular fires and disturbance by ungulates routinely created patches of bare sand for Tradescantia occidentalis to colonize. Now, Canadian management plans call for rangeland management practices and prescribed fire to create the levels of disturbance needed by this species.

You may be wondering, if population levels of Tradescantia occidentalis are healthy through most of its range, why worry about a few small populations in Canada? A report by David Fraser, titled Species at the Edge: The Case for Listing of 'Peripheral' Species, does a good job of explaining some of the principles that guide ecologist's concern for peripheral populations. One of the numerous arguments presented by Fraser is that individuals growing in marginal habitats are exposed to higher selective pressures, and are usually genetically distinct from core populations. This genetic diversity may prove to be an important factor in the long-term survival of a species.

May 23, 2015: Rubus spectabilis

Rubus spectabilis

Do you eat the red ones last? I've often wondered why some Rubus spectabilis berries are red and some are yellow, so I thought I would write an entry that answers the question. I found this wonderful photo of salmonberries taken by Richard Droker (aka Wonderflechten@Flickr)in the Alpine Lakes Wilderness, Washington, U.S.A. Thanks Richard -- I hope those berries were as delicious as they look.

Rubus spectabilis is a polymorphic species. That is, there are multiple phenotypes, or visible genetic traits, that occur within the same population, and members with different phenotypes (red or yellow berries) are able to breed freely. This characteristic is similar to the variability in hair colour found in people of European descent. In fact, polymorphism is very common in the natural world: sexual dimorphism, or the differences between males and females of a species, is an example we can all relate to.

Polymorphism arises when a genetic mutation occurs within an individual (or individuals), and is spread through a population. In the case of Rubus spectabilis, we do not know which morph was the original and which was the mutation. It is also unclear which factors allowed both morphs to become fairly evenly represented through the species' western North American range.

In order to better understand why Rubus spectabilis displays fruit-colour polymorphism, I turned to an article written by Anna Traveset and Mary Willson, titled Ecology of the Fruit-Colour Polymorphism in Rubus spectabilis. The two ecologists examined the effects of fructivore preference, seed dispersers, soil type, and seed predation on the yellow and red morphs. They found that a greater number of fruit-eating birds preferred red berries to yellow, but that overall this preference was minor and unlikely to exert a strong selective pressure. Seed dispersers and seed predation had no effect, but soil type was a key factor in determining the germination, and therefore the range for each morph. Overall, soil type (likely coupled with other, unstudied factors) determines whether an area is likely to have more red or yellow-berried Rubus spectabilis plants.

To answer the question I first posed -- I do eat the red ones last. I find that along my heavily-used urban trail, the red salmonberries are picked much more frequently than the yellow ones. Whether my fellow trail-walkers prefer the red ones or just don't realize the yellow berries are ready, I am not sure, but I am quite happy to eat my fill of juicy, golden berries while everyone else searches high and low for the red ones.

For those of you on the west coast of North America, salmonberry season is upon us! Let me know if you manage to try out this recipe for salmonberry pie.

May 22, 2015: Shepherdia canadensis

Shepherdia canadensis

Today's photo features the inflorescence of Shepherdia canadensis, a common berry-producing shrub of western North America. Anne Elliott (aka annkelliott@Flickr) took this macro in South Glenmore Park, Calgary, Alberta. Thanks Anne!

Shepherdia canadensis, also known as soopalallie or buffaloberry, is an incredibly important species for grizzly bears (Ursus arctos). The online field guide, MountainNature, advises hikers in the Canadian Rockies to become familiar with this species, and to avoid late-summer hiking on trails where it grows plentifully. According to the field guide, an adult grizzly will eat upwards of 20,000 soopalallie berries in August and September. David Hamer, in his article "Buffaloberry fruit production in fire-successional bear feeding sites", points out that soopalallie is the primary food source for bears during the 'hyperphagic' period, or the period in late summer when bears must 'fatten-up' for winter hibernation. Hamer also remarks that human-bear conflicts increase in years of poor berry production, and that the success of Shepherdia canadensis, and hence that of grizzly bears, relies on a regular fire regime that maintains open areas within the landscape.

Shepherdia canadensis is a spreading, deciduous shrub that grows to 1-2 meters in height. The branches are grey-brown, and covered with rusty spots when young. The inflorescence of soopalallie is described as inconspicuous, but this macro photo makes it look downright strange. Ann's photo clearly shows the 4 yellowish-brown sepals and 8 stamens that make up the male flower. Shepherdia canadensis is dioecious, and the female flowers have the same oddly-coloured sepals and lack of petals as the male flower, but rather than stamens, they have one pistil. When pollinated, the female flowers form a red berry that is 4-6 mm across, edible, but very sour.

These tart berries are the crucial ingredient in sxusem, or 'indian ice cream', eaten traditionally by many North American First Nations peoples. In order to make sxusem, Shepherdia canadensis berries are collected by whacking the shrub with a stick so that the ripe berries fall onto a mat. The berries are then placed into a container (it cannot be plastic or oily, as this will prevent the berries from frothing), crushed, and whipped with water until foamy. Other berries are often added to sweeten the 'ice cream', and contemporary recipes usually include sugar or some other form of sweetener. A chemical compound found in the berries, saponin, is responsible for the soap-like foam that is produced.

May 20, 2015: Pycnostachys urticifolia

Today I am inspired by this lovely photo of Pycnostachys urticifolia, taken by Christopher Young (aka c.young@Flickr).This entry is also complemented by another excellent photo showing the leaves and stem of this species, taken by Vojtěch Zavadil (aka vojtechzavadil@Flickr). Thank you for posting, Christopher and Vojtěch!

Pycnostachys urticifolia is a beautiful plant, with a mouthful of a name. While trying to find a more melodious way of referring to this species, I came across a number of equally-difficult common names; you may also call this species dark blue pycnostachys, groot ystervarksalie, or unkungwini. Thankfully, it is also known by some as hedgehog sage, so I will stick with that one, as I never was very good at tongue twisters.

Hedgehog sage is an aromatic perennial herb in the mint family. It grows ubiquitously in South Africa but even though it is a common plant (and in the mint family, at that), it does not appear to be used as food or medicine. It does have potential as an ornamental species, and also appears to have wildlife value, with the Plantz Africa website listing it as a nectar source for butterflies and bees, as well as food for grasshoppers. The book Chewa Medical Botany mentions that hedgehog sage is used as a fly repellent in Chitipa, Malawi.

Hedgehog sage grows to a height of 1-2.5 meters, and has petiolate leaves that are similar to those found in nettles (Urtica species), hence the species name urticifolia, which means 'nettle-like leaves'. The bright blue inflorescence is the part of the plant most likely to excite a gardener; dense terminal spikes burst forth from this shrub in great number late in the fall. After flowering, the calyx (the sepals, collectively) becomes sharply spiny; all of the sources that I found describe the sepals as reddish-purple, but Vojtěch Zavadil's photo clearly shows them as light green, with only a purple tinge at the very tips. I find it interesting that the sepals are able to protect the un-opened flowers, and then protect the maturing seeds by converting into spiky herbivore-deterrents. How efficient!

May 19, 2015: Thespesia populneoides

Thank you Andreas Lambrianides (aka Andreas Lambrianides@Flickr) for these two images of Thespesia populneoides blooms. Surprisingly, both flowers are of the same species, and perhaps even from the same tree; Thespesia populneoides flowers are yellow with a touch of red toward the base when in full bloom, and turn red or pink following anthesis (full bloom).

Thespesia populneoides has been considered a synonym of Thespesia populnea by many botanists. However, a case has been made that Thespesia populneoides should be considered a distinct species. Sultanul Abedin et. al. point out that the two taxa have different ranges, and that Thespesia populneoides has many distinct characteristics from Thespesia populnea, including having harder fruit, young growth that is coppery and densely peltate hairy (as opposed to green and sparsely peltate hairy), and deeply cordate (as opposed to truncate) leaves. The two species hybridize frequently.

Thespesia populneoides, also known as pacific rosewood or milo, grows on low elevation beach forests and gallery forests in Australia, the Indian Ocean islands, southeast Asia, and Malesia. It is highly saline-tolerant and wind-resistant, making it a wonderful species for seaside plantings. The attractive flowers bloom intermittently year-round in equatorial climates, and the richly-coloured, dark wood is highly-valued for crafting into beautiful objects such as carvings, platters, and musical instruments. The beautiful wood of Thespesia populnea (and likely also Thespesia populneoides, as these are not always seen as distinct species)was used to carve sacred objects in Polynesian cultures, and groves of milo were planted around Tahitian places of worship. The botanist Daniel Solander, while a member of Captain Cook's first voyage, gave milo the genus name Thespesia, meaning 'divinely decreed', after seeing the species growing in sacred areas.

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