Photosynthesis,leaf conductance,and water relations of cowpea under saline conditions |
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| Authors: | D W West G J Hoffman M J Fisher |
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| Institution: | (1) Department of Agriculture, Irrigation Research Institute, Private Bag, 3616 Tatura, Victoria, Australia;(2) Water Management Research Laboratory, USDA-ARS, 2021 S. Peach Ave., 93727 Fresno, CA, USA;(3) Division of Tropical Crops and Pastures, C.S.I.R.O., 306 Carmody Road, 4067 St Lucia, Queensland, Australia |
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| Abstract: | Summary Cowpea (Vigna unguiculata L.), grown widely under both irrigated and dryland conditions, is well adapted to drought and high temperature and is moderately salt tolerant. Data on photosynthetic response and regulation of water relations in cowpea under salinity stress is lacking. Therefore, in conjunction with a field plot experiment to establish the leaching requirement of cowpea, measurements were made of carbon dioxide assimilation rates (A) by 14CO2 uptake, leaf conductances to H2O (g1) by tritum uptake, and to CO2 (g ), and leaf total water potential ( t
1) and osmotic potential (
1).Cowpeas, grown in field plots containing Pachappa fine sandy loam (mixed, thermic, Mollic Haploxeraff), were irrigated daily with saline water (1,350 mg 1–1 total salt concentration) to achieve leaching fractions of 0.17, 0.13, 0.09, 0.07, and 0.02. Cowpea maintained high leaf water potentials, high rates of CO2 assimilation and high leaf conductances under moderately saline conditions (high leaching). Values of t
1 and
1 for high leaching were consistently 50 to 200 J kg–1 higher than for low leaching throughout the day. Calculating
1 at full leaf turgor eliminated diurnal variation in
1. As leaching decreased, however, A, g1, and g, decreased significantly. About 45% of the 1°C assimilated by the leaf was incorporated rapidly into ethanol insoluble compounds. The relationship between A and g1 for cowpea was similar to that reported for other crops.Contribution from the US Salinity Laboratory, USDA-ARS, 4500 Glenwood Dr., Riverside, CA. 92501, USA |
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