Effects of Light and Temperature During Plant Growth on Subsequent Leaf Co2 Assimilation Rates Under Standard Conditions

Abstract

The rate of photosynthetic C02 assimilation and transpiration as measured under standard conditions was determined for Zea maY8, Amaranthus palmeri, Helianthus annuus, Triticum ae8tivum, G088ypium hir8utum, and Phaseolus vulgare after culture at a range of temperatures (15/10 to 36/31°C day/night temperatures) and natural (seasonal) or artificial light conditions. In general, the relative classi· fication of the six species as to rate of C02 uptake was the same for plants grown under a wide range of conditions. C02 assimilation was depressed at the lower temperature limits for growth in Z. maY8 and G. hirsutum where plants were chlorotic. C02 assimilation shifted from one class of rates to another in H. annuus and G. hir8utum as seasonal radiation increased from winter to summer. Some of this change was caused by a factor inside the leaf, after seasonal variations in transpiration were accounted for. Much of the variation in CO2 assimilation within and between H. annUU8, T. ae8tivum, G. hir8utum, and P. vulgare was associated with differences in transpiration or the conductance for diffusion of CO2 into the leaf.