Plants of Oreocereus celsianus growing in the altiplano of northern Argentina at an altitude of 4000 m. These cacti have dimorphic wood. While young and small they produce a soft spongy wood and the body is supported by turgor. When older, taller, and heavier they produce a fibrous wood strong wnough to support the body.
Arillate seeds of Cabralea canjerana (Meliaceae) are primarily disperesed by birds in the Atlantic forest of Brazil. However, hundereds of naturally fallen or partially eaten diaspores may be found on the forest floor with bits of aril attached. The red lipid-rich aril is highly attractive to ants, such as the large Odontomachus chelifer (size ~ 2cm). Aril removal by ants greatly facilitates seed germination.
A stoma from the scale of a female cone of Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca). Magnification = 6800x. Photosynthesis and respiration of male and female cones of Douglas-fir may have significant effects on whole-tree physiology.
Sixteen photographs of a single shoot of the vine Lonicera japonica are superimposed to create a time-lapse image of its clockwise rotation. The photographs were taken over a 2-h period and represent the plant movement known as circumnutation.
A site on Stepping Stones Island along the west coast of the Antarctic Peninsula where plants were collected for field and environmental chamber experiments examining the influence of temperature on the growth of flowering plants.
The nonphotosynthetic plant Sarcodes sanguinea (Monotropoideae, Ericaceae) receives all its carbon from the ectomycorrhizal basidiomycete Rhizopogon ellenae(Boletales) that proliferates in its immediate surroundings.
Scaling relationships among photosynthetic rate, foliar nutrient concentration,
and leaf mass per unit area (LMA) have been observed for a broad range of plants.
Leaf traits of the carnivorous pitcher plant Darlingtonia californica,
endemic to southern Oregon and northern California, USA, differ substantially
from the predictions of these general scaling relationships; net photosynthetic
rates of Darlingtonia are much lower than predicted by general scaling
relationships given observed foliar nitrogen (N) and phosphorus (P) concentrations
and LMA. At five sites in the center of its range, leaf traits of Darlingtonia
were strongly correlated with elevation and differed with soil calcium availability
and bedrock type. The mean foliar N : P of 25.2
A glossophagine bat (Anoura geoffroyi, Phyllostomidae) visiting Burmeistera
sodiroana (Campanulaceae) in a flight cage set up in the Bellavista Cloud
Forest Reserve, Pichincha Province, Ecuador. The flower morphology fits the
bat's head closely, allowing precise and consistent pollen placement on the
crown (note the spot of pollen from a previous visit). The well-exposed flowers
of this species and eight other Ecuadorian species of Burmeistera are
dull-colored and emit strong odors and were found to be highly specialized for
bat pollination; although bats and hummingbirds visited their flowers, only
bats effectively transferred pollen. Flowers of a tenth species, B. rubrosepala,
are bright red and yellow with narrow corolla apertures and no odor and were
exclusively hummingbird pollinated.
Light micrograph of a cucumber root tip releasing border cells after immersion
in water. Recent concern about global warming and the underlying anthropogenic
increase in atmospheric CO2 has led to intense interest in carbon
cycles. One component of the carbon cycle is soil sequestration of carbon, which
is ecologically important. Much of the underground cycling of carbon occurs
in rhizospheres, small layers of soil surrounding and influenced by the roots
of higher plants. Throughout its lifetime, a plant root releases organic carbon
to its rhizosphere. Carbon-containing exudates have been found to be particularly
abundant at root tips and at points of initiation of branch roots. The root
tips, including root caps, meristems, and elongation zones, are particularly
active in secreting sugars, organic acids, and specialized compounds such as
phytosiderophores. Mucilage, containing high molecular weight polysaccharides
(particularly polyuronic acids), is produced copiously by root caps and cortical
cells. These carbon sources sustain the rich microflora of the rhizosphere.
Another source of carbon is provided by border cells, a subset of peripheral
root cap cells. These cells are formed as part of the root cap and released
from the exterior of the cap to live freely in the soil for a time. Border cells
are known to exert antibiotic effects, protecting plants from certain pathogenic
microbial infections, and stimulating the growth of other microbes. While examining
the importance of border cell release to carbon cycling in soils, we made the
unexpected discovery that the number of cells released is strongly dependent
on the developmental stage of the root. In four species that were examined,
young, short seedling roots released thousands, while roots longer than 4 cm
released only tens to hundreds of border cells. This developmental program is
hypothesized to protect the plant during the critical period of radicle penetration
of the soil following germination and during seedling establishment.
Buds of yellow buckeye (Aesculus flava, Sapindaceae) showing expanding
new leaves under an open canopy in early spring (ca. 15 March) Great Smoky Mountains
National Park, Tennessee, USA. Yellow buckeye is the earliest tree species to
produce a flush of new leaves in the southern Appalachians. Early leaf emergence
increases light capture before canopy closure and may provide a substantial
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