Effects of paclobutrazol on growth and development, yield and seed quality in indeterminate and determinate soybean [Glycine max (L.) Merrill]
1996
Danai Hussem
Effects of paclobutrazol on growth and development, yield and seed quality in indeterminate (SJ.1) and determinate (NW.1) soybean were studied. The first experiment was conducted during dry season using a 2*3*3 factorial in randomized complete block design with four replications. The first factor was soybean cultivar, the second factor was stage of application (R1, R3 and R5 growth stage) and the third factor was rate of application (0, 500 and 750 grams ai. per hectare). The second experiment was carried out in wet season in both cultivars employing a 2*3 factorial in randomized complete block design with four replications. The first factor was rate of application (0 and 500 grams ai. per hectare) and the second factor was stage of application (R1, R3 and R5 growth stage). In dry season, it was found that application of paclobutrazol at R5 stage increased soybean yield only in SJ.1 cultivar but had no effect on yield in NW.1. In the rainy season, application of paclobutrazol at growth stages R3 and R5 increased yield in both cultivars. These yield increases were due to the increase in pod number per plant. Pacolobutrazol reduced intraplant competition by retarding internode elongation resulting in reduced plant height, and promoted reproductive growth by diverting assimilates to flower, pod and seed. Moreover, paclobutrazol increased leaf number per plant, leaf area index (LAI) and leaf dry weight measuring at 65-75 days after planting, providing higher source strength during pod growth, seed set, and seed development, yielding maximum seed set and dry weight accumulation in seed. However, paclobutrazol applied at growth stage R1 had no effect on seed yield. The adversed effect from applying paclobutrazol at R1 stage was found through the reduction of pod number per plant. Paclobutrazol slightly reduced seed quality when applied at growth stage R1 but had little or no effect when applied at growth stages R3 and R5.
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