Abstract:

For the purpose of recognizing the physiological effects of phytic acid (PA) on rice plumpness and grain weight, rice cultivar XQZ and its low PA mutant (os-lpa1) were applied to compare the difference in the changing patterns of PA, sucrose content and starch accumulation at filling stage, translocation of carbohydrates in different organs (flag leaf, culm, and sheath) and the activities of some key enzymes involved in grain starch synthesis metabolism. The results showed that os-lpa1 had higher contents of sucrose and total soluble sugar, and more starch accumulation in the flag leaf, culm and sheath, but lower starch synthesis in grains at filling stage compared to XQZ. The relatively lower activities of ADPG-Ppase and SPase in filling grains were probably responsible for poor plumpness and low starch accumulation in os-lpa1. Additionally, compared with XQZ, os-lpa1 exhibited lower activities of SPS and FBPase in sheath at filling stage, resulting in excessive accumulation of starch and blocked flows of assimilates, which could be one of the reasons for the descending yield of os-lpa1.

Key words: Rice (Oryza sativa L.), PA (phytic acid) mutant, Grain starch accumulation, Enzymes