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

Aug 29, 2014: Themeda triandra

Taisha completes the series on South African plants and biomes with this entry. It is also her last official day as a work-learn student with Botany Photo of the Day, though there are about a half-dozen other entries she has written that will be posted while the new students learn the ropes. Thank you, Taisha. She writes:

Today we feature the grasslands biome of South Africa with photographs of Themeda triandra, which is known as rooigrass in Afrikaans ("red grass"). These images (image 1| image 2) were uploaded to the Botany Photo of the Day Flickr Pool by Marie Viljoen@Flickr. The first image was originally posted on Marie's blog, where she later posted a poem about Themeda triandra by South African poet, Antjie Krog. Thanks again, Marie!

The grasslands, also known locally as Grassveld, is the largest biome within South Africa. It is found mainly on the high central plateau of South Africa as well as the inland areas of the Eastern Cape. This biome neighbours the savanna, thicket, and Nama Karoo biomes. This region is relatively flat, though it can vary between sea level and 2850m elevation. The semi-arid to arid grasslands have varying temperatures, with frost being common. Precipitation ranges between 600-1000 mm, with rainfall decreasing westward. The grassland occurs on a variety of soils from humic clays to poorly structured sands.

A single vegetative layer of grasses dominates the grasslands, although other species such as bulbs occur. There are two categories of grassland: sweet veld and sour veld. Sweet grasses occur on the semi-arid regions of the Eastern Cape in eutrophic soils, while the sour grasses can be found in the higher rainfall regions of Drakensberg on acidic soils.

Themeda triandra is a tufted C4-photosynthesis perennial grass occurring widely across parts of Africa, Australia, and Asia. In South Africa, Themeda can occur in the savanna biome, but is primarily found in the grassland biome in regions with rainfall between 500-950 mm and at elevations of sea level-1800m. When young, this grass is a green to blue-green colour tinged pink. It then turns red with age. Rooigrass at higher altitudes tends to be shorter and darker compared to plants at lower elevations. The spikes flower from October to July. Flowers may or may not long black or white hairs. The awned spikelets hang from clusters and are surrounded by reddish brown leaf-like spathes or bracts. Rooigrass does not vegetatively spread long distances, so it is instead an obligate seeder. The long hygroscopic awns twirl when wet, driving the barbed seeds into the ground. There, they will germinate if there is a layer of litter or pioneer plants. This species is noted to be resistant to fire, with resistance increasing if the site is not overgrazed and burnt at regular intervals to allow for regeneration.

Aug 28, 2014: Welwitschia mirabilis

The second-last in the plants and biomes of South Africa series is featured today. Taisha writes:

Today, we take a slight detour from South Africa, as this species is not present in the country. Welwitschia is found only in the Namib Desert of Namibia. However, the Namib Desert slightly extends into South Africa where it forms the country's sole area of desert biome. The Namib Desert is one of the smallest and oldest deserts in the world. I chose Welwitschia as it has not been featured on Botany Photo of the Day before and it was not easy to find a plant species in the Botany Photo of the Day Flickr Pool to represent this biome. Still, this species is an interesting representative for the desert. Daniel contributed these photographs of Welwitschia mirabilis from Huntington Botanical Garden.

As implied above, the desert biome occurs in only a small part of northwestern South Africa, primarily the Springbokvlakte area of the Richtersveld. The altitude is between 600 and 1600 m, which results in a slightly cooler climate than other true deserts (though it remains more climatically extreme than the succulent Karoo and the Nama-Karoo biomes). Temperatures can be hot, up to 45°C. Similarly extreme, temperatures can drop over 20°C from day to night. Winter temperatures can be as low as -12°C. Fog from the nearby Atlantic Ocean accounts for much of the precipitation, although there is some variable summer rainfall (~10-80mm annually). True deserts are largely sandy with low organic material in their soils.

The vegetation within the desert biome is typically annual grasses and other plants. After a season with rarely abundant rains, short annual grasses may grow, whereas in most years the annual plants persist as seeds. Some perennials may survive, particularly in areas associated with local concentrations of water.

Welwitschia mirabilis is a monotypic species of the Welwitschiaceae under the plant Division Gnetophyta--a small group of seed plants that have intermediate characteristics between gymnosperms and angiosperms. The oldest specimens of Welwitschia in the Namib Desert are thought to be more than 1500 years old, and recent fossil evidence suggest that Welwitschia was present during the Cretaceous (~112 million years ago). Some photos of the plant in habitat are available via Wikimedia Commons: the biggest known plant and a couple plants in the landscape.

This dioecious (male and female individual plants; male and female cones are shown above) evergreen species has a woody unbranched stem that is shaped like an inverted cone. The stem is surrounded by a bi-lobed crown of green photosynthetic tissue. There are only two opposite, persistent, ribbon-like leaves that grow continuously from a basal meristem and die off at their tips over time. Unique among all extant plant species, after the first two leaves form, the terminal bud dies and the apical meristematic activity is transferred to the periphery and base of the leaves. In other words, it has ever-growing persistent leaves, with the leaf ends being the oldest part of the leaf.

Aug 25, 2014: Bauhinia galpinii

Bauhinia galpinii

Here is entry number six in Taisha's South African plants and biomes series. She writes:

Bauhinia galpinii, known as Pride of the Cape or Pride of De Kaap, is featured today as part of the savanna biome. Even though the name may suggest it is from the Cape (de kaap= cape), it is actually named after the De Kaap valley in the northeastern region of South Africa. This 2007 photo was taken by frequent BPotD contributor, Bart Wursten (aka zimbart@Flickr), in Manica, Mozambique. In addition to South Africa and Mozambique, the species is also present in Zimbabwe. Thanks for sharing, Bart!

The savanna biome spans a large area over the lowveld and Kalahari regions of South Africa. Elevation ranges between sea-level and 2000 m. Summers are very hot and rainy in this region, with temperatures anywhere between 12 and 39°C. This is followed by a cooler dry season where temperatures range from 0-32°C. Annual rainfall varies from 235mm-1000mm in the biome, and some parts of it may be frost-free while others can have up to 120 days of frost/year. Many of the major soil types (PDF) are represented in the region, though soils are usually porous, quick-draining, and with a thin layer of humus.

The savanna has a distinguishable grass-dominated ground layer accompanied by the different densities of woody shrubs and trees (shrubs may be the most prolific plants in overgrazed areas). C4 grasses form much of the grass layer where there is a hot growing season (C4 photosynthesis is best-suited for heat), while C3 grasses tend to be in the majority in cooler, wetter parts of the biome. Many plant species are adapted to survive fires, and most will resprout from stem bases even after severe burning.

Bauhinia galpinii is a fabaceous shrub with two-lobed leaves and bright red-orange flowers. This species is traditionally used medicinally by the Venda (or vhaVenda) people of the Limpopo province. In Mahwasane et al.'s survey of indigenous knowledge on medicinal plants used by the traditional healers of Limpopo's Lwamondo area, the roots of Bauhinia galpinii are boiled and the mixture drunk to treat stomach worms or to improve sexual performance. They also add that the concoction can be used to make a soft porridge for stomach pains. The researchers further mention that other studies have claimed that this species is used for treating diarrhea and infertility (bark and leaves), for infertility using the roots, or for amenorrhea (seeds). Traditional healers (herbalists) of the vhaVenda use up to 16 species of herbs, trees, or shrubs within seven families for medicinal purposes. Those from the Fabaceae are used most frequently; other families represented were Annonaceae, Asteraceae, Ebenaceae, Orobanchaceae, Oxalidaceae, and Verbenaceae. Different plant parts are collected from the medicinal species, most often the roots (also the leaves, bark, flowers, or whole plant), and diversely prepared for treating the above illnesses as well as others, including stomach ailments, dysmenorrhoea and oedema (see: Mahwasane, S., L. Middleton, and N. Baoduo. (2013). An ethnobotanical survey of indigenous knowledge on medicinal plants used by the traditional healers of the Lwamondo area, Limpopo province, South Africa. South African Journal of Botany. 88:69-75).

Aug 22, 2014: Crassula ovata

Crassula ovata

Number five in the series on South African plants and biomes series from Taisha, who writes:

The informally-recognized thicket biome of South Africa is featured today with an accompanying photograph of Crassula ovata. This image is another shared via the Botany Photo of the Day Flickr Pool, and photographed by Sean Rangel@Flickr. Thanks for sharing, Sean!

The Albany thicket occurs along the Fish, Sundays, and Gamtoos river valleys in the eastern Cape, and moves west along the intermontane valleys of inland Fold Mountains and east into Maputaland-Pondoland Bushland and thicket. Annual temperatures range from 0°C to 40°C, with it being more extreme inland, and more moderate toward the coast. Annual rainfall is between 300-550mm per year, varying between inland and coastal areas, and valley mists are common on the coast. Soils are deep, lime-rich, sandy loams that are well drained and often have low moisture levels for extended periods of time.

The Albany thicket can be divided into three regions, each with unique vegetation patterns. The dry, inland areas of the Fish, Sundays, and Gamtoos Rivers are rather sparse, and have been classified as Valley Bushveld. This region contains both leaf and stem-succulent shrubs and a few characteristic woody species. Coastal area of these river valleys, known as Kaffarian succulent thicket, are extremely dense with ~90% canopy cover. These thickets are rich with species of spinescent shrubs, woody vines and succulents. Lastly, the intermontane valleys, know as Spekboomveld or Spekboom succulent thickets, are a dense shrubland dominated by Spekboom (Portulacaria afra) with other succulents, herbs, and grasses also occurring.

Crassula ovata is one of the most common crassulas occurring in South Africa. This well-branched succulent shrub occurs naturally on rocky hillsides from Willomore to East London, and north to Queenstown and KwaZulu-Natal. From a picture of the foliage, you may recognize that this as the commonly cultivated plant known as the jade plant or money tree. Many people grow these as container plants, both in and outdoors.

Like most Crassula species, Crassula ovata reduces water loss from its leaves by utilizing Crassulacean Acid Metabolism, or CAM. Part of the CAM biological process is that stomata are closed during the day to prevent water from evaporating, and instead opened at night to collect carbon dioxide (this is the reverse of how most plant species exchange gases, with stomata open during the day instead). The carbon dioxide is stored overnight in the form of crassulacean acids, which are then broken down during the day. This releases the CO2 for the photosynthesis process during the day. During extremely dry periods, Crassula species may undergo CAM-idling, where stomata are not opened during the day or night. Instead, the plants will recycle the CO2 within the cells. This leaves them unable to grow or develop new tissue, but the plants are able to survive the lack of water by losing very little of it during this time.

Aug 21, 2014: Cunonia capensis

Taisha continues with the South African plants and biomes series. She writes:

The forest biome of South Africa is up next. To accompany this entry, we have two photographs (image 1 | image 2) of Cunonia capensis (also known as the butterspoon tree, rooiels in Afrikaans, and umLulama in Zulu) from University of California Botanical Garden at Berkeley. These were uploaded to the Botany Photo of the Day Flickr Pool by James Gaither (aka J.G. in S.F.@Flickr), who has since passed away.

The smallest biome in South Africa, the forest biome covers less than .25% of the country. Still, it is divided into two regions: Knysna forest along the southern Cape coastline, and the Amatole further east inland. The Knysna-Amatole forests are part of the afromontane archipelago--discontinuous regions analogous to sky islands. Knysna occurs on gentle slopes between 5-1220m, while the Amatole Mountains lie between 700-1250 m. Rainfall and temperatures vary between ~500-1220 mm and ~10-25°C respectively with the Amatole Mountains being both wetter and cooler than Knysna. The soils of these forests are generally acidic and nutrient-poor.

The floristically diverse forests have some 636 and 649 vascular plant species recorded respectively. Evergreen trees primarily form a continuous canopy, covering layers of vegetation that include (but aren't limited to) lianas, herbaceous species such as ferns, and epiphytes. Because of the dense shade from the layers above, the ground layer is almost absent.

A species that can be found in this biome is Cunonia capensis, the tree featured in today's photographs. Cunonia capensis, of the Cunoniaceae, is a tree found along the coast and adjacent inland areas of South Africa. In the forest it may reach up to 10m in height, and about half that height in the open. The showy, scented flowers appear in February and continue through March. They are collected in cream-coloured spikes, as shown in the first photograph. The fruits are brown two-horned capsules that release fine, sticky seeds. Seeds are either wind-dispersed or may also stick to visiting birds that fly off with them attached to their feathers, legs, or bills. One of the more prominent characteristics of Cunonia capensis is the pair of stipules that enclose the growing tip of developing branches. They are large and are pressed together and look much like a spoon--hence one of the common names, butterspoon tree. The second photo shows this phenomenon, as well as additional images via the Fernkloof Nature Reserve site: Cunonia capensis.

Aug 20, 2014: Mimetes cucullatus

Here is Taisha again, with the third entry on South African plants and biomes. She writes:

Today we feature two photographs of Mimetes cucullatus, known as the common mimetes or pagoda or the red mimetes or pagoda. In Afrikaans, this species is known as rooistompie, or simply stompie. Rooi means "red", and stompie means "little stump". Retired UBC Botanical Garden staff member, David Tarrant, sent these images from his visit to Cape Town's Kirstenbosch National Botanical Garden last November. Thank you kindly, David!

The fynbos is a biome located in southwestern South Africa. It consists of two distinct vegetation groupings, the fynbos and the renosterveld. These regions together form over 45000 km2 of land, all above 300 meters in elevation. Renosterveld typically has fertile, fine-grained soils of silts and clays whereas fynbos has poorer nutrient quality. Rainfall occurs throughout the year and accumulates anywhere from 300-2000 mm annually. Fire is an important influence on fynbos community processes, and the region must burn every 6 to 45 years to sustain many plant species.

Mimetes cucullatus is an example of a plant that relies on fire for regeneration. This is the only species of Mimetes that is a resprouter (as opposed to only being a reseeder). After fire, plants regenerate from a large, woody, underground rootstock, whereas most others are killed by fire (unless they have a thick, corky bark and survive). Seedlings will also sprout post-fire when conditions are suitable.

Common mimetes is a widespread species. It is easy to distinguish from other members of the Proteaceae with its unusual tubular and wool-like flowers grouped in four perianth segments. In bud, the segments touch each other, but do not overlap. They then separate as the flower opens to expose the style equipped with a sticky pollen presenter. Stigmas on these perfect flowers are not receptive at anthesis, thus preventing self-pollination. Within each of the white tuft-like perianth segments rests a single anther. Colourful leaves surround each floret like a hood. After pollination by sunbirds or sugarbirds, a nut-like fruit develops. The seeds within the fruit have elaiosomes (grey-white oily protuberances) at either end. These eliaosomes attract ants, who collect the seeds to carry back to their underground nests. There, they eat the elaiosomes, but do no damage to the seeds. Seeds deposited in ant nests can remain viable for many years.

Aug 19, 2014: Pachypodium namaquanum

Pachypodium namaquanum

Second in the series on South African biomes and plants, again written by Taisha:

Pachypodium namaquanum is commonly known as halfmens (Afrikaans for "semi-human"), elephant's trunk, or elephant plant. This species is found in the Succulent Karoo. Drew Avery@Flickr took this photo back in 2009 at the Denver Botanic Gardens and shared it via the Botany Photo of the Day Flickr Pool. Thanks, Drew!

The Succulent Karoo biome extends down the western coast of Namibia and further inland and comprises two domains--the Namaqualand-Namib domain along coastal plain, and the Southern Karoo domain to its east. The altitude of this region is mostly below 800 meters, but may reach up to 1500 m. The temperature in the Succulent Karoo ranges from -4°C in the coldest month and can reach over 40°C at other times. Annual rainfall ranges from 20-400 mm and falls mainly in the winter months (summers are arid), with heavy fog supplementing the precipitation. Berg winds may also occur throughout the year. Soils of the succulent Karoo are much like the Nama Karoo--lime-rich, weakly developed soils on rock.

The vegetation in the Succulent Karoo is, as you may have deduced, dominated by succulents (particularly dwarf shrubby species)! There are many leaf succulents present in the Succulent Karoo, and annual displays of asters occur in the spring. Endemism is extremely high, with around 67 genera and over 1,900 species occurring nowhere else. Included amongst these endemics is Pachypodium namquanum, the species in today's photograph.

Pachypodium namquanum is a stem-succulent species of the Apocynaceae that can live up to 300 years or more. This species grows slowly and regularly, eventually attaining a tree-like appearance when mature at 1.5 to 2.5 m in height (see photos linked from the Wikipedia page: Pachypodium namaquanam). The stems are also covered in tubercles, from which spines protrude. The leaves are borne in rosettes and are distinctively wavy. Yellow-green flowers with red interiors appear from July through September and later develop into horn-like, dehiscent capsules enclosing wind-dispersed seeds.

The unusual appearance of the halfmens has made it one of the most famous and sough-after succulents in the world. One of the most intriguing characteristics is the bowing of the stem to the north. There are folklore interpretations of this phenomenon, however researchers attribute this nodding of ~45-65° to the low solar zenith angle during the winter months. They explain that during the winter, where conditions are more favourable for growth over summer, the low solar zenith angle may pose a potential limiting factor on plant growth. The 55° north incline, they explain, would maximize the solar irradiance on the plane of whorled leaves, of which most are also on an inclination to maximize irradiance. The researchers suggest that the slant northward may benefit the species by increasing net primary production, as well as increase tissue temperatures midwinter when the flowers and later fruits are developing thus minimizing the effects of late-season drought on reproductive output (see: Rundel, P., et al. (1995). Winter growth phenology and leaf orientation in Pachypodium namquanum (Apocynaceae) in the Succulent Karoo of the Richtersveld, South Africa. Oecolgia. 10(4):472-477).

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