INFLUENCE OF MOISTURE STRESS, RELATIVE HUMIDITY AND OXYGEN DIFFUSION RATE ON SEED SET AND YIELD OF WHEAT

Abstract

The influence of oxygen diffusion rate (ODR) and relative humidity (RH) on seed set and yield of wheat was investigated in two growth chamber studies. In one study, plants grown at 80% RH were compared with those grown at 60%. In the other, plants grown in pots without supplemental aeration were compared with plants grown in aerated pots.Wheat grown at low soil moisture stress (between 25 and 16%) produced significantly poorer seed set and grain yield than those grown at higher stress (between 25 and 10%). Seed set was less severely reduced in Manitou than in Chinook. Plants grown at low moisture stress and 60% RH gave better seed set than those grown at 80%. However, even at 60% RH, seed set was less than 65%.The oxygen diffusion rates in unaerated pots were 28 × 10−8, 100 × 10−8 and 200 × 10−8 g cm−2min−1 at 25%, 16% and 10% soil moisture (by weight). In aerated pots, ODR at 25% and 16% soil moisture were 82 × 10−8 and 180 × 10−8 g cm−2min−1, respectively.Seed set and grain yields of Chinook wheat grown at low moisture stress were increased from 54 to 82% and from 11.5 to 26.7 g/pot by improving the soil aeration.The anthers, especially the pollen, were the main reproductive components damaged by poor aeration. This was demonstrated by morphological examination and by hand-pollination experiments. Poor seed set was confined primarily to the top two-thirds of the head.