PLANT SCIENCE: Less and More

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Science  02 Jan 2004:
Vol. 303, Issue 5654, pp. 16c
DOI: 10.1126/science.303.5654.16c

Is it better to grow efficiently within a limited range of conditions or safely across a broader range? Factors that influence this choice are illustrated by comparing water-conducting tissues (xylem) in plants. Wide and long vessels support low-resistance flow of water, but are susceptible to catastrophic failure provoked by a few untoward bubbles. Narrower, shorter xylem vessels struggle to carry as much water, but are a more robust conduit for facing the vagaries of life. Because transpiration and photosynthesis go hand in hand, the amount of water delivered to the leaves determines the amount of photosynthesis that can be supported.

Kocacinar and Sage, examining xylem structure in relation to metabolism and environment, find that some species favor a secure water supply and others favor a maximized water supply that supports more leaf area. An increased leaf canopy is a competitive solution in resource-rich habitats, whereas reliability of water supply is the solution favored for species growing in drought-prone habitats. In either case, C4 photosynthetic plants, which use water more efficiently than do C3 photosynthetic plants, have the advantage of being able to go further with a given amount of xylem tissue. Thus, the advantages of C4 metabolism include not only metabolic efficiency, but also doing more with less in plant infrastructure. — PJH

Plant Cell Environ. 26, 2015 (2003).

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