Day time fluctuations in photosynthetic parameters and water relations in juvenile coconut palms grown under rainfed and irrigated conditions
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Date
2007-02-08
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Abstract
Day time (7 h to 18 h) fluctuations in photosynthetic parameters (net photosynthetic rate, Pn; stomatal conductance, gs; internal CO2 concentration, Ci); water relations (leaflet water potential, Yiear; transpiration rate, E) and weather parameters (photosynthetically active radiation, PAR; leaflet temperature, Tleaff; air vapor pressure deficit, VPD) were estimated in juvenile palms of coconut grown under rainfed and irrigated conditions. Variations in values and day time fluctuations in photosynthetic parameters and water relations were observed between palms grown under rainfed and irrigated conditions, Pn, E and gs were maximum between 09:00 and 11:30 and 15:00 and 16:00 h. Ci and ψie,r were least during mid-day. Mid-day slump in Pn and gs was observed. Tleaf, PAR and VPD were maximum between 09:00 and 16:00 h. E and VPD were positively correlated. Rainfed palms had higher Tleaf, Ci, CilCa and leaf to ambient temperature difference (∆T) and lower Pn, ψr and E compared to the irrigated palms. Instantaneous and intrinsic water use efficiency increased under mild water-deficit conditions. It is apparent that under rainfed conditions the carbon assimilation efficiency was low compared to irrigated condition. VPD and Ar influenced gs and water relations during day time which predominantly determined the variations in photosynthetic efficiency of coconut under irrigated and rainfed conditions.
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Keywords
Diurnal course, VPD, transpiration, photosynthesis, drought, WUE, stomatal conductance, water relations, gas exchange parameters
Citation
Journal of plant biology 2000 v-27 i-1 p-27-32