Influence of potassium nutrition and water stress on the content of abscisic acid in grains and flag leaves of wheat during grain development

Increasing the potassium (K) supply to wheat plants grown in pots extended the period of grain filling and increased the rate of grain growth, thus increasing the single grain weight. In all K treatments abscisic acid (ABA) content in the grain reached a maximum and this occurred when the growth rate of the grain declined and full ripening commenced. Increasing the K supply delayed the occurrence of the ABA maximum and reduced its absolute value. It seems that an extension of the grain filling period by better K nutrition might not only be due to a longer production of assimilates, but also due to a retarded and lower production of ABA in the grain. This result is supported by the finding that withholding of water supply for 1‐week periods during grain development increased ABA content in the grain and reduced single grain weight.