COMPARISON OF SINK-SOURCE RELATIONSHIP OF SOYBEAN AND CANOLA CULTIVARSEsmaeil Yasari, Saedeh Mozafari and Einali Shafiee
In order to evaluate and compare responses of soybean (Glycine max (L.) Merrill) and canola (Brassica napus L.) cultivars to elimination of parts of sinks and sources on seed yield and yield components at different dates of sowing two sets of split plot factorial designs based on completely randomized block were carried out during cropping seasons 2006-2007 and 2007-2008 in Dasht-e-Naz Sari of northern Iran. There were four soybean cultivars and three canola cultivars and five levels of leaf and flower elimination. The result indicated that two weeks delay from optimum date of sowing resulted in 9.26 % and 7.63 % decrease in soybean and canola seed yield, respectively. Source limitation, i.e. leaf elimination of one-third length of upper part of the plant resulted in minimum seed yield in soybean (7.45 g. plant) showing 50 % decrease comparing to control (15.16 g. plant) whereas in canola, leaf elimination of one-third length of upper part of the plant resulted (13.5 g. plant) having 18 % decrease in seed yield comparing to control (16.5 g. plant). It could be postulated that the leaves at the upper part of canopy in soybean played more important role compared with canola in portioning photosynthesis assimilates. Leaf elimination of middle part of the plant (8.93 g. plant) resulted in 41 % decrease in soybean seed yield comparing to control (15.16 g. plant), but in canola (12.1 g. plant) resulted in 26.6 % decrease to control (16.5 g. plant). It showed that leaf from middle part of the canopy in soybean also played more important role in photosynthesis assimilates comparing to canola plant. Least effects were observed for the leaf of lower part of the plant in both the crops, i.e. 12.7 % decrease in soybean and 11% decrease in canola comparing to control. In soybean plant it was shown that the treatment of elimination of one-third flowers at flowering stage resulted in 11.34 g. plant seed yield which means 25% decrease from control treatment (15.16 g. plant) interestingly, the exact amount of decrease in canola seed yield from control.
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