Growth, photosynthesis and transpiration in Psophocarpus tetragonolobus (L.) DC cultivar 'UPS 99'.
Two methods (whole-plant growth analysis and gas exchange) were used to measure the response of Psophocarpus tetragonolobus (L.) DC cultivar 'UPS 99' to the environment. This plant had an optimal temperature for root growth of 25°C, its rate of acetylene reduction (when inoculated with Rhizobium, strain 'RRIM 56') was maximal at 30°C and it required an atmospheric temperature of about 35°C for optimal shoot growth. Maximum water-use efficiency was ca. 33 mg CO2·g H2O(-1). The rate of photosynthesis reached a plateau at 900 vpm CO2-this condition also gave the lowest rate of transpiration. Under normal conditions, the light compensation point was at 1.7 klx, while that for CO2 was 60 vpm. Photorespiration diminished gross photosynthesis of P. tetragonolobus by forty percent. Water stress (as measured by sensitivity to slightly increased CO2 levels) caused rapid closure of stomata, and the response was 'remembered' for up to five days.
Institut für Obstbau und Gemüsebau der Universität Bonn, 53, Bonn 1, BRD.
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F
Lenz
W J
WJ
Broughton