Leaf Gas Exchange Rates as a Function of Temperature

D.R. Krieg


 
ABSTRACT

Temperature is one of the primary ecological variables determining the distribution of plants. In addition, any given plant within a prescribed habitat is subject to rather large diurnal and seasonal fluctuations in temperature. Temperature variation across the cotton belt is quite large with seasonal variation exceeding 20 C and diurnal variation approaching 20 C. Depending upon location, the temperature variation during any given growth stage can range from cool to warm to hot.

Photosynthesis, like all growth processes, is strongly affected by temperature (1). In most plants, the change in photosynthetic rate in response to temperature is reversible over a range from 10 to 35 C. However, temperatures above or below this range cause irreversible injury to the photosynthetic system. It is fairly clear that plants occupying thermally contrasting environments generally exhibit photosynthetic temperature responses that reflect an adaptation to the temperature regimes of their respective habitats (2). Plants native to and grown in cool environments generally exhibit higher photosynthetic rates at low temperatures but are extremely sensitive to high temperatures as compared with plants adapted to and grown in warm-to-hot habitats.

Photosynthetic temperature adaptations have major significance in evaluation of new germplasm for agronomic performance. The growth environment must reflect the natural habitat, to a large extent, if we expect maximum genetic expression.



Reprinted from Proceedings: 1989 Beltwide Cotton Research Conferences pp. 49 - 52
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998