Pedosphere 9(2): 105--112, 1999
ISSN 1002-0160/CN 32-1315/P
©1999 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Tomato leaf photosynthetic responses to humidity and temperature under salinity and water deficit |
| H. L. XU1, R. WANG1, L. GAUTHIER2 and A. GOSSELIN2 |
1 International Nature Farming Research Center, Hata, Nagano 390-1401 (Japan);
2 Horticulture Research Center, Laval University, Ste-Foy, Quebec G1K 7P4 (Canada) |
| ABSTRACT |
| Greenhouse tomato plants (Lycopersicon esculentum Mill cv. Capello) were grown on peat-based substrate and treated with high (4.5 mS cm-1) and low (2.3 mS cm-1) nutrient solution electric conductivity (EC) under high and low substrate water contents. Four weeks after the beginning of the treatments, photosynthesis (PN) was measured under different humidity and temperatures to examine the interactive effects with rhizosphere salinity and water deficit. A rectangular hyperbolic model fitted the light-photosynthesis curve. Photosynthetic capacity (PC) was decreased but quantum yield (YQ) was increased by rhizosphere salinity caused by high EC. PN was decreased by low humidity only in high EC- and/or water-stressed plants. Under high photosynthetic photon flux (PPF), low humidity induced PC decline in water-stressed plants and PN oscillation in high-EC-treated plants. PN increased steadily as the leaf temperature changed from 18 ℃ to 23 ℃ and then decreased steadily from 23 ℃ to 38 ℃. At 34 ℃, PN decreased significantly in water-stressed plants. Dark respiration (RD) increased in an exponential manner as the leaf temperature changed from 18 ℃ to 38 ℃ to an extent about ten times higher under 38 ℃ than under 18 ℃. Our data suggested that PN decrease under high temperature was attributed, at least in part, to the increased RD. RD in high EC- and/or water-stressed plants was higher than that in the plants of control under lower temperature but lower than that in the plants of control under high temperature. The analysis of stomatal and mesophyll conductance showed that low humidity effect was mainly through stomatal response while temperature effect was mainly through biochemical functions. The result showed that environmental stresses affected PN in an additive or synergistic manner. |
| Key Words: humidity, photosynthesis, rhizosphere salinity, temperature, water stress |
| Citation: Xu, H. L., Wang, R., Gauthier, L. and Gosselin, A. 1999. Tomato leaf photosynthetic responses to humidity and temperature under salinity and water deficit. Pedosphere. 9(2): 105-112. |
|
View Full Text
|
|
|
|
