اثر حذف برگ و تراكم بوته بر عملكرد و انتقال مجدد دو رقم گندم نان (Triticum aestivum)

The Effect of Leaf Removal and Plant Density on Yield and Remobilization in Two Wheat Cultivars Differing in Potential Yield

Recent investigations on source - sink relations in wheat imply that yield is sink rattier than source limited and hence, leaf defoliation, at least at late stages of growth, should have no negative effect on yield. Thus, one should be able to increase wheat yield and water use efficiency through increasing the density of plants with reduced leaf area at reproductive stage. For a test of this hypothesis, a field experiment was conducted at Research Farm of Karaj Agricultural College, University of Tehran, in 2005. A 3-replicate split factorial based on RCBD was carried out, where Sardari (with low potential yield) and Qods (with high potential yield) cultivars were sown in two densities of 350 and 500 plants per m2. Leaf area was modified by removing all leaves and/or removing all leaves except the flag leaf two weeks after anthesis. Defoliation had no significant effect on grain yield and protein content, probably, implying sink limitation situation in the cultivars and the environmental conditions under consideration. Dry matter remobilization from either of peduncle or penultimate increased in response to leaf removal; the response being more evident where defoliation intensity was higher. Cultivar and cultivar* defoliation effects were not shown to be significant in this experiment. In general, yield increased due to low leaf area accompanied by higher plant density of 6 and 15 % in Qods and Sardari, respectively. There were significant differences observed between the two cultivars in yield, grain weight and grain number, as Qods carried a more grain number but less grain weight than Sardari. Since, final grain weight did not respond noticeably to the reduction of leaf area, it could be concluded that competition among grains for assimilate accumulation is not responsible for small grains even in Qods with lower grain weight