Laboratory Report

Too Much of a Good Thing

Sundew plants (Drosera) occupy an interesting ecological niche. The evolutionary success of so-called “carnivorous” plants is attributed to their ability to thrive in nitrogen-scarce habitats. What happens, though, when nitrogen in the form of industrial pollution is free, and there is no selective pressure for carnivorous plants to work for nitrogen acquisition? Researchers in Sweden analyzed the nitrogen isotopes in sundew plants to determine what proportion of nitrogen is acquired from either soil or insects. In areas where nitrogen pollution was more available in soil, the sundew plants used the soil nitrogen and scaled back the expensive strategy of luring and trapping insects. Plants in these areas were larger and were less red, perhaps because they did not need to attract as many insects. Although this might seem to be a good thing for the sundew, in the long run, they are still carnivorous plants by design, and may not be able to compete well enough with the other nearby plants.

New Phytologist, 195, Vol 1, 182-188

Stretching to Cool Off

Mouse-ear cress (Arabidopsis) is the lab rat of the plant world. Scientists growing these plants at higher-than-optimum temperatures observed a marked stretching of the stems. Although it has been shown in prior work what caused the stems to stretch, it was not known why this occurred—until recently. The recent study examined water use strategy. Despite the production of fewer stomata when grown at high temperatures, increased water loss and enhanced evaporative cooling was associated with this change in architecture.

Current Biology, 22: Issue 10, 396-397

Van Gogh Sunflowers – Mutants Still Popular

The evolution of floral structure interests plant biologists, due to its implication in plant-pollinator interactions. The development of bilaterally symmetric flowers is believed to increase pollinator specificity, contribute to reproductive isolation, and lead to speciation. The plant family Asteraceae has been particularly interesting to study, due to the existence of both radially symmetric disc florets and bilaterally symmetric ray florets on the same flower head. Research at the University of Georgia presents evidence that bilateral flower symmetry has evolved more than once during the diversification of the composites, and several different genes have been employed to accomplish the task. The flower head of a common, wild-type sunflower is arranged with a single whorl of ray florets surrounding multiple whorls of disc florets. Van Gogh captured a mutant sunflower form in his painting that is one of today’s popular sunflower types, the so-called double flower, where the center disc flowers are elongated and show bilateral symmetry similar to the ray florets. Analysis of this flower type identified a specific gene, that when expressed improperly due to one type of mutation, caused the double flower type portrayed by Van Gogh. When this gene suffers a different type of mutation, causing it not to function at all, the ray florets lose their bilateral symmetry and become radially symmetric tubular florets.

Public Library of Science – Genetics, March 2012

Pot Size Matters

Aficionados of bonsai know that plants growing in small containers will remain smaller than the same plant grown in a large container. In studies of different types of plants, doubling the pot size resulted in plants growing 43 percent larger. MRI imaging of root systems in containers demonstrated that roots quickly grow out to the edge of a pot, as most of us observe. In some way that is not yet understood, roots are able to communicate to the plant how much soil volume there is. Plants respond to this information by regulating their photosynthetic rate, not necessarily the number or size of leaves. This data warns plant researchers to be certain to choose appropriately sized containers for their experiments to ensure that no abiotic stress factors  nullify results.

Functional Plant Biology, published online, June 2012