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Pakistan Journal of Biological Sciences

Year: 2001 | Volume: 4 | Issue: 3 | Page No.: 301-308
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Authors

Begum Samsun Nahar

Takeshi Ikeda

Keywords

Research Article

Effect of Different Soil Water Levels on Production and Abscission of Reproductive Organs of Soybean under High Temperature

Begum Samsun Nahar and Takeshi Ikeda
An experiment was conducted during summer 1999 in and out sides of a glasshouse to evaluate the effect of different soil water levels on growth, physiological aspects and, production and abscission of flowers and pods of soybean. Three stress treatments were imposed by 40, 60 and 80% reduced water from flower initiation to maturity in the glasshouse. Two well-watered unstressed controls were also included for comparison of performances in and out sides of the glasshouse. Fluctuation in air temperature was 30 to 40°C in the glasshouse during reproductive period and the inside air temperature was 3 to 4°C higher than outside of the glasshouse. Leaf temperature, stomatal conductance, leaf transpiration, photosynthesis and leaf water potential decreased with increase in water stress which influenced the production and abscission of flowers and pods. Water stresses reduced pod number due to both increased flower and pod abscission and fewer flowers per plant with low photosynthesis, decreased leaf water potential and high leaf temperature. In case of well watered soybean, pod number decreased in the glasshouse (T1) than the outside (T0) treatment due to a little increase in abscission of flowers and pods or low photosynthesis due to high air temperature inside the glasshouse. The flower production was significant between T0, T1 and T2 treatments, while pod number and seed number were found to decrease in T1 and T2 treatments due to increase in abscission percent of flowers and pods with the variation of photosynthesis and its parameters. The data indicated that environmentally induced variation in pod numbers in soybean was the result of both changes in flower and pod abscission and the number of reduced flower production. With the variation of high air temperature in the glasshouse, pod and seed number were reduced in T1 than in T0 treatment. Nitrogen accumulation of leaf declined drastically in T1 treatment at R6 stage which was limiting factor for photosynthesis and finally total dry matter as well as seed yield decreased in T1 compare to T0 treatment. The stress treatments reduced all growth parameters, dry matter production and nitrogen accumulation thus seed yield decreased in T2, T3 and T4 treatments, respectively. The differences in different soil water levels and temperature were reflected in lower production of total dry matter and seed yield.
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