Early Growth of the Developing Ear of Spring Barley

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Abstract
The change in fresh weight of the developing ear and of groups of spikelets of Maris Mink spring barley was measured for plants grown under three different conditions. Growth was closely described by a third order polynomial equation. Instantaneous values of relative growth rate derived from these equations showed a decline to a minimum value, which was dependent on the growing conditions and on position along the spike, followed by a rapid rise. The minimum value was reached about 5 d before spikelet initiation ceased and the subsequent rise in relative growth rate coincided with the period of rapid elongation of the rachis. Within the car there was a tendency for younger spikelets to have a slightly higher relative growth rate than those initiated earlier. Possible reasons for these growth changes are discussed in relation to spikelet differentiation, vascularization of the ear and nutrient availability.