Abstract: A wheat (Triticum aestivum L.) cultivar, Yumai 49 was used in a pool experiment to investigate the activities of key enzymes involved in sucrose metabolism in leaf, sheath, stem, and grain during grain filling in clay-loam, mid-loam, and sand-loam soils. The changes of sucrose phosphate synthase (SPS) and sucrose synthase (SS) activities in different organs during grain filling in three types of soil showed a single-peak curve. In the sand-loam soil, SPS activities were the highest in different organs expect grains. In the mid-loam soil, the SPS activity in grains at the early filling stage and the SS activity at the medium-to-late filling stages were significantly higher than those in the clay-loam soil. The 1000-grain weight and starch content in the mid-loam soil and sand-loam soil were significantly highter than those in the clay-loam soil, but those were not significantly different between mid-loam soil and sand-loam soil. This showed that the mid-loam soil and sand-loam soil could affect the sucrose synthesis and degradation in Yumai 49. The sand-loam soil was available for sucrose synthesis in the vegetative organs of wheat, but the mid-loam soil was available for sucrose synthesis in grains of wheat. The SPS and SS activities all correlated significantly or very significantly with grain filling rate, amylopectin and starch accumulation rates in grains in the mid-loam soil and sand-loam soil, but the correlation between the enzymes activities, expect SPS activities in grains, and starch accumulation rate was not significant. It is more important for the sucrose synthesis catalyzed by SPS in the vegetative organs and the sucrose degradation catalyzed by SS in grains to accumulate the starch and amylopectin in grains of wheat in the mid-loam soil and sand-loam soil.

Key words: Wheat, Soil texture, Sucrose metabolism, Starch accumulation, Key enzyme