Performance and Metabolic Alterations in Sesamum indicum L. under Different Intensities of Water Stress

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Abstract
Effects of mild (ψplant −0·7 MPa), moderate (−1·6 MPa) and severe ( −2·2 MPa) water stress on diverse plant processes were compared with the control (−0·2 MPa) at the critical stage of onset of flowering of Sesamum indicum L., an indeterminate oil-seed crop, under pot-culture conditions. Measurements were taken of different aspects of growth, development and yield, uptake and concentration of N and P in the shoot and also the oil, protein and carbohydrate composition of seeds at harvest maturity. Changes in the levels of leaf metabolites (free proline, free amino acids, starch, reducing sugar and total chlorophyll) and the activities of leaf enzymes (nitrate reductase, peroxidase, acid and alkaline pyrophosphatases) were estimated just before the end of drought periods of different intensities. The effects of water stress on the various parameters measured generally increased with the increase in stress intensity, but a discernible change, large or small, occurred in all cases under mild stress. The synchrony of the effects of mild stress on diverse parameters of plant performance and metabolism suggested that water stress might be perceived simultaneously by all the plant processes. The results are discussed in the light of current concepts.