ISHS Acta Horticulturae 537: III International Symposium on Irrigation of Horticultural Crops
MICROCLIMATE EFFECTS ON TRANSPIRATION AND PHOTOSYNTHESIS OF CHERRY SAPLINGS GROWING UNDER A SHADING NET |
| Authors: | A. Massaci, F. Pietrini, M. Centritto, F. Loreto |
| Keywords: | Diurnal trend, temperature, radiation. |
| Abstract:
Cherry saplings were grown outdoors in pots under full photosynthetic photon flux density (PPFD) (control) and a under a white fibreglass net with the PPFD reduced up to 30% (shade). A daily course of leaf gas exchange was measured by a portable infrared gas analyser system by the end of August. Transpiration was almost always higher in plants grown in full than in reduced PPFD. In contrast, photosynthesis was not significantly different. Both control and shaded plants had maximum rates of transpiration and photosynthesis around mid hours and early in the morning, respectively. A midday depression of photosynthesis occurred in the hottest hours in both treatments. The dependence of photosynthesis and transpiration on environmental factors were investigated by varying one at a time leaf-air vapour pressure (VP) gradient, PPFD and leaf temperature (Lt). Increases of VP gradient, when PPFD was maintained either at 785 or 1160 µmol m-2s-1 and temperature at either 29 or 33.7°C, increased leaf transpiration but did not significantly affect photosynthesis. Increases of PPFD at a temperature of either 29 or 33.7°C and at a constant VP gradient of 21 mbar bar-1 similarly increased transpiration and photosynthesis. On the other hand, an increase of temperature from 29 to 33.7°C when PPFD and VP gradient were kept constant significantly reduced net photosynthesis but not transpiration. Implications on irrigation scheduling of transpiration and photosynthesis dependencies on environmental factors are considered. | |
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