The influence of plant temperature on photosynthesis and translocation rates in bean and soybean

Abstract

Phaseolus vulgaris cv. Black Valentine and Glycine max cv. Maple Arrow and cv. Evans were grown at 20 °C. They were pruned to a simple source – sink system and placed in a steady-state 14 C-labeling system, where their photosynthesis and translocation rates were determined at the growth temperature. The temperature of each plant was then raised or lowered and the rates were measured again. All three varieties showed net photosynthetic optima near the growth temperature. Translocation rates increased sigmoidally from 5 to 35 °C in Phaseolus, giving a decreasing Q 10 value, but exponentially from 5 to 40 °C in Glycine, giving a Q 10 of about 2.0. Rates were suboptimal at the highest temperatures used. Plants grown at 30 °C and exposed to higher or lower temperatures responded in parallel to the 20 °C grown plants. When grown at 12.5 °C and exposed to higher temperatures, the plants responded in parallel to the 20 °C grown ones, but at lower temperatures translocation was higher than predicted for cv. Maple Arrow.