RESPONSE OF YIELD, YIELD ATTRIBUTES AND GRAIN QUALITY OF THREE CORNCULTIVARS TO DEFOLIATION

Any kind of decrease or inefficiency of corn leaves caused by factors such as pests, diseases, mechanical damages and hail, leads to decrease photo-assimilate translocation to the kernels and yield decrease. In order to investigate the role of each part of maize canopy leaves on yield and yield component, and grain quality, an experiment was conducted in a factorial experiment using randomized complete block design (RCBD) with three replications at the Research Farm of faculty of agriculture, Tabriz University, Tabriz, Iran, during year 2007. maize cultivars were single cross 647, 604, 504 and defoliation treatments contain leaf removal in 1/3 of upper, 1/3 of median, 1/3 of lower part of canopy and control (without defoliation) that imposed at tasseling. The results indicated that while defoliation had significant effects on yield components (except number of row per cob and 100 grain weight ), grain yield per unit area, as well as ear length and leaf area index (LAI), quality of produced grains at defoliation levels including protein percent and oil percent did not differ considerably. The maximum LAI belonged to control and the least to the defoliation of the 1/3 in middle part of the canopy. In this study cultivars affected grain yield and mean 100 grain weight. Since the defoliation treatments had no significant impact on stem dry weight so it is concluded that maize leaves and especially median leaves have crucial role on photosynthesis and yield.