ISHS Acta Horticulturae 171: I International Symposium on Water Relations in Fruit Crops
CO2 ASSIMILATION AND WATER USE EFFICIENCY OF YOUNG EXPANDING CITRUS LEAVES |
| Author: | J.P. Syvertsen |
| Abstract:
Net gas exchange characteristics of young grapefruit seedlings growing in the greenhouse were studied to determine the effect of leaf age on CO2 and H2O vapor exchange. Conductance of H2O vapor through the cuticle of young leaves not yet fully expanded was initially high but reached minimum values about 10 days before leaves were fully expanded. Stomatal conductance and CO2 assimilation rate reached maximum levels by the time leaves were fully expanded, about 28 days after initiation. Water use efficiency (= mmo1 CO2/mo1 H2O) was also highest when leaves were 28 days old but decreased along with CO2 assimilation rates as leaves matured. This was partially due to the CO2 compensation points reaching minima and mesophyll conductances reaching maxima at about day 28. Changes in CO2 assimilation rate were generally more strongly correlated with mesophyll conductance than with stomatal conductance and water use efficiency followed the same pattern as mesophyll conductance during leaf expansion and maturation. Since evergreen citrus leaves can live for several seasons and new growth flush leaves can replace old leaves at virtually any time of the year, physiological characteristics that change as leaves age can play an important role in citrus trees. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
