The Simultaneous Measurement of Apparent Photosynthesis and Transpiration of Citrus Seedlings at Different Soil Moisture Levels1

Abstract

Abstract Diurnal rates of photosynthesis and transpiration of sour orange and sweet lime seedlings were measured continuously and simultaneously under 4 different soil moisture regimes, using an infra-red gas analyzer and hygrosensors. Photosynthesis and transpiration rates were found to decrease gradually as the soil moisture dropped from 17% to 9% (equivalent to tensions of 0.2 to 3 atm). A sharp reduction in both processes was observed for both rootstocks when the soil moisture was in the wilting range. At the high moisture content, photosynthesis and transpiration rates of sweet lime were higher than those for sour orange plants. Conversely, at the low moisture content (in the wilting range), the rates were greater for the sour orange seedlings. The high soil moisture tensions had a relatively greater effect on photosynthesis than on transpiration.