CHLOROPHYLL FLUORESCENCE AND GAS EXCHANGES IN FLOODED SOYBEAN AND SUNFLOWER PLANTS

Flooding reduced photosynthetic rate and stomatal conductance of water vapour in leaves of sunflower plants whereas in soybean the decline i n photosynthesis was accompanied by an increase in stomatal conductanc e and transpiration rate. Ln this latter species there was also an inc rease in intercellular CO2 concentration. Thus the responses of the tw o species to flooding were different: in sunflower the limitation appe ared to due to stomatal closure and alteration of photosynthetic machi nery; in soybean the mesophyllic activity was the main cause of Amax r eduction.