Effect of Planting Density and Chlormequat Chloride on Morphological and Physiological Characteristics of Winter Barley (Hordeum vulgare L.) Cultivar "Valfajr"

In a field experiment the effect of five planting densities (100, 175. 250, 325 and 400
plants in"2 ) with or without foliar application of chlormequat chloride (2-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 32).
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 25(1 plants in"2 increased the grain yield, however, from 250 to 400 plants m"2 there
was no significant change in grain yield. It appeared that the higher planting
densities, i.e. 250 to 400 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.