Influence of potassium nutrition on germinability, abscisic acid content and sensitivity of the embryo to abscisic acid in developing seeds of Sorghum bicolor (L.) Moench

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Abstract
Summary: Pre‐harvest sprouting in maturing seeds of Sorghum bicolor (L.) Moench is a major problem in the cultivation of this crop plant. The influence of potassium nutrition on germinability, abscisic acid (ABA) content and embryo ABA sensitivity in its developing seeds was investigated. Plants were grown in sand culture under three different potassium treatments: K1 (control), K2 (one third of the control potassium supply), and K3 (one ninth of the control potassium supply). Reduced potassium increased the germinability of developing seeds during the late stages of maturation (31 and 36 days after pollination, DAP), particularly in K2 grains. These changes in seed germinability were paralleled by a reduced ABA content in the seed and by a lower embryonic sensitivity to ABA. The ABA content of K2 intact grains peaked at 25 DAP and then decreased sharply, being 30–50% lower than that in the controls at 31 and 36 DAP. ABA content in the control gains peaked later in the developmental period (at 31 DAP). By contrast K3 grains had a remarkably constant ABA content during most of the developmental period (20–36 DAP). Sensitivity to ABA was markedly reduced in the embryos from both the low potassium treatments, particularly when tested at an ABA concentration of 5μM. The data indicate that potassium supply influences germinability, ABA concentrations and embryo ABA sensitivity in developing seeds in this species.