Effect of water-deficit stress and genotypes on pinitol occurrence in soybean plants

Pinitol (3-O-methyl-D-chiro-inositol) has been found to accumulate significantly in a number of plant species under water-deficit stress, but its importance in soybean (Glycine max L. Merr.) stress tolerance is not known. It has been hypothesized that an increased pinitol level in the plant may be associated with improved stress tolerance. The objectives of this experiment were to determine the effect of water-deficit stress on pinitol content in soybean plants, and the relationship between 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. Pinitol content in the plant material was determined using high-performance liquid chromatography. Water-deficit stress significantly increased pinitol content in soybean leaves and stems in some genotypes. Increase in the pinitol content in response to water deficit differed among soybean genotypes, and those more tolerant to water deficit tended to accumulate more pinitol. The pinitol:sucrose ratio increased with water deficit, indicating that pinitol was preferentially accumulated in response to the stressor. The plant growth regulators, Atonik, PHCA and PGR-IV, did not affect pinitol content in the plant. It was concluded that pinitol was an important stress metabolite in soybean plants, and its accumulation may be related to plant tolerance to water-deficit stress. (C) 1997 Elsevier Science B.V.