Photosynthesis and Plant Water Status of Irrigated and Dryland Cultivars of Groundnut

Groundnut cultivars grown in drylands are generally different from those grown in irrigated areas. In a field study during two rainy seasons, three cultivars (JL - 24, TMV - 2 and Kadiri - 3) were grown under irrigated and dryland conditions, with the objective of finding out whether cultivars for irrigated (JL- 24) and dryland (TMV -2 and Kadiri -3) areas differed in their assimilation and plant water status, when drought occurred at any stage of growth. Seasonal photosynthesis rate decreased by 22 per cent but the transpiration rate decreased only by 9 per cent in dry lands in one season resulting in lower transpiration efficiency. No significant difference was observed between the two kinds of cultivars in photosynthesis rate, transpiration rate, stomatal conductance and leaf water potential when drought occurred but canopy temperature measurements showed that JL -24 suffered water stress at peak flowering relatively more than the two dryland cultivars. The results indicate that measurements of integrated physiological processes, rather than of instantaneous rates of assimilation and water loss, are likely to reveal basis for cultivar differences in groundnut in water limited environment.