EFFECT OF WATER-DEFICIT STRESS AND GENOTYPES ON PINITOL OCCURRENCE INSOYBEAN PLANTS

Pinitol (3-O-methyl-D-chiro-inositol) has been found to accumulate sig nificantly in a number of plant species under water-deficit stress, bu t its importance in soybean (Glycine max L. Merr.) stress tolerance is not known. It has been hypothesized that an increased pinitol level i n the plant may be associated with improved stress tolerance. The obje ctives of this experiment were to determine the effect of water-defici t stress on pinitol content in soybean plants, and the relationship be tween pinitol accumulation and plant tolerance to water deficit. Field and controlled environment studies were conducted under well watered and water-stressed conditions with different soybean genotypes. Pinito l content in the plant material was determined using high-performance liquid chromatography. Water-deficit stress significantly increased pi nitol content in soybean leaves and stems in some genotypes. Increase in the pinitol content in response to water deficit differed among soy bean genotypes, and those more tolerant to water deficit tended to acc umulate more pinitol. The pinitol:sucrose ratio increased with water d eficit, indicating that pinitol was preferentially accumulated in resp onse to the stressor. The plant growth regulators, Atonik, PHCA and PG R-IV, did not affect pinitol content in the plant. It was concluded th at pinitol was an important stress metabolite in soybean plants, and i ts accumulation may be related to plant tolerance to water-deficit str ess. (C) 1997 Elsevier Science B.V.