Effect of Tiller Removal and Shading on Spikelet Development and Yield Components of the Main Shoot of Wheat and on the Sugar Concentration of the Ear and Flag Leaf

Abstract

Continuous removal of tillers from wheat plants (cv. Gamenya) in an irrigated field crop resulted in an 86% increase in grain yield of the ear on the main shoot due, principally, to more kernels per fertile spikelet. On detillered plants 99% of spikelets were fertile with an average of 3.8 kernels per fertile spikelet compared with 91% and 2.4 for the control. Tiller removal increased spikelet numbers by 1 to a mean of 21.4 but did not affect the rate of production of spikelet primordia. The concentration of sugars (glucose, fructose, sucrose) in leaf bases at terminal spikelet formation and in leaf bases and ears just before ear emergence were the same in control and detillered plants. It was considered unlikely that tillers compete with the main shoot for carbohydrates thus limiting ear development and grain yields of the main shoot; instead, competition for reduced nitrogen may be involved.

Shading plants to 20% of full sunlight, especially during floret development, reduced grain yields per ear by 50% due to fewer kernels per fertile spikelet (2.2) plus a 32% decline in kernel weight. Tiller numbers and shoot size were reduced by shading while spikelet numbers were reduced by two compared with controls due to a reduced rate of production of spikelet primordia. Shading also reduced sugar concentrations relative to controls in leaf bases at terminal spikelet formation and in ears just prior to emergence. The supply of carbohydrates under shading was limited, affecting growth and grain yields.