The physiological basis of seed dormancy in Avena fatua. VIII. Action of malonic acid

Abstract

Adkins, S. W., Symons, S. J. and Simpson, G. M. 1988. The physiological basis of seed dormancy in Avena fatua. VIII. Action of malonic acid ‐ Physiol. Plant, 72: 477–482.A low concentration of malonic acid (50 mM) induced germination in four genetically pure dormant lines of Avena fatua L. Sensitivity to this treatment was poor immediately after harvest but increased markedly during after‐ripening, indicating that the mode of action of malonic acid (50 mM) was similar to that of another organic acid, citric acid. Over the concentration range (10–50 mM) where malonic acid promoted germination, oxygen uptake was also stimulated, and this was before the first visible signs of germination. At higher concentrations (100–300 mM) where there was no promotion of germination, malonic acid strongly inhibited oxygen uptake. These results show that malonic acid has a dual effect on oxygen uptake and subsequent germination. Low concentrations (10–50 mM) act by stimulating the Krebs cycle and germination through an acidification reaction like citric acid, and high concentrations (100–300 mM) act by inhibiting germination through enzymatic restraint of the Krebs cycle.The stimulation of both oxygen uptake and germination by three established germination promoters (sodium nitrate, citric acid and ethanol) was inhibited by a high concentration of malonic acid (200 mM) but unaffected by a low concentration (50 mM). These results show that oxygen uptake, and hence the activity of the Krebs cycle, are important processes involved in the dormancy breaking mechanism of these three promotors.