ISHS Acta Horticulturae 171: I International Symposium on Water Relations in Fruit Crops
RELATIONSHIPS BETWEEN TRANSPIRATION AND PHOTOSYNTHESIS DURING A WATER STRESS. |
| Authors: | J.F. BOIS, Ph. COUCHAT, G. LASCEVE |
| Abstract:
Rice plants were grown in a controlled environment and transpiration and photosynthesis observed during a drying and rewatering sequence. The response of different upland rice and lowland rice were compared during vegetative growth. Plants were grown in soil containers in a sealed growth chamber inserted in an open circuit air flow controlled for temperature and humidity. Water and CO2 concentrations were measured by infra-red analyser in order to calculate H2O and CO2 exchanges between the aerial part of plant and the atmosphere. The water stress was obtained by sopping irrigation. Soil matric potential was measured with tensiometers connected to pressure cells. Plant water deficits led to a decrease in gas exchanges, due to stomatal closure and leaf rolling. The stomatal response progressively took place at a soil water potential threshold, lower for upland rice varieties (about -700 mbar) than irrigated ones (about -450 mbar). Transpiration was more influenced than photosynthesis at the beginning of drying period. Irrigation induced a rapid resumption of transpiration and photosynthesis, simultaneously with the leaf unrolling and progressive stomatal opening. The relationship between photosynthesis and transpiration showed hysteresis from drying to rewatering for some rice varieties. The hysteresis subsists when the plant suffers other water stresses. | |
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