The effect of a day at low irradiance of a maize crop. II. Photosynthesis, transpiration and respiration

The kinetics of daily photosynthesis, transpiration and dark respiration of shoots of maize plants ( Zea mays L.) were studied in a growth chamber. After one or two days of reduced light intensity, the photosynthesis and the transpiration returned immediately to a level higher than expected. Respiration, which was reduced by at least 50%, returned slowly for over 2 days towards the initial level. These results suggest the existence of reserves of assimilation products which are used up while maintaining the growth of the aerial part in spite of the lack of assimilation. The prolonged reduction of the respiration shows that it is not strongly correlated to photosyntheis or to growth but rather to the amount of available reserves of assimilate.