Y. Emam - Department of Agronomy, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
G. R. Moaied - Agricultural Research Center, Darab, Islamic Republic of Iran.

In a field experiment the effect of five planting densities (۱۰۰, ۱۷۵. ۲۵۰, ۳۲۵ and ۴۰۰ plants in"۲ ) with or without foliar application of chlormequat chloride (۲-till o methyltrimethyl uminonion chloride, CCC) on growth, development and grain yield of winter barley (cv Valfajr) was studied. The results indicated that Increasing plant density hastened the rate of apical development and stem elongation. This pattern continued up to the beginning of rapid stem elongation phase (Zadoks growth stage ۳۲). However, during the rapid stem elongation and ear growth, the pattern was reversed i.e. it had become slightly in favor of the lower densities. Increasing plant density up to ۲۵(۱ plants in"۲ increased the grain yield, however, from ۲۵۰ to ۴۰۰ plants m"۲ there was no significant change in grain yield. It appeared that the higher planting densities, i.e. ۲۵۰ to ۴۰۰ plants m~- were in a range around the supposed "optimum" density. Foliar application of CCC slowed down the rate of apical development and stein elongation in all plant densities, hut without any significant effect on its spikelet initiation rate. Such retardation of development in CCC-treatecl plants was initially associated with lower dry weight accumulation. However, this trend was reversed before anthesis, as the CCC- treated plants had accumulated more dry matter by anthesis, and gave a higher grain yield. The interactive effect of CCC and plant density is worthy of further exploration.

Yield components, Planting density, Growth regulation, Plant development