RICE SCIENCE

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Changes in Enzyme Activities Involved in Starch Synthesis and Hormone Concentrations in Superior and Inferior Spikelets and Their Association with Grain Filling of Super Rice

  1. Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Yangzhou University, Yangzhou 225009, China
  • Online:2013-03-28 Published:2013-01-30
  • Contact: YANG Jian-chang
  • Supported by:

    This work was supported by the grants from the National Natural Science Foundation of China (NSFC-IRRI Joint Research Project 31061140457), General Project (Grant Nos. 31071360 and 31271641), the National Basic Research Program (Grant No. 2009CB118603), the National Key Technology Support Program of China (Grant Nos. 2011BAD16B14 and 2012BAD04B08), the Basic Scientific Research Special Operation Cost of the Central Research Institutions in 2011 (Grant No. 201103003).

Abstract:

The changes in activities of key enzymes involved in sucrose-to-starch conversion and concentrations of hormones in superior and inferior spikelets of super rice were investigated and their association with grain filling was analyzed. Four super rice cultivars, Liangyoupeijiu, IIyou 084, Huaidao 9 and Wujing 15, and two high-yielding and elite check cultivars, Shanyou 63 and Yangfujing 8, were used. The activities of sucrose synthase (SuSase), adenosine diphosphoglucose pyrophosphorylase (AGPase), starch synthase (StSase) and starch branching enzyme (SBE), and the concentrations of zeatin + zeatin riboside (Z + ZR), indole-3-acetic acid (IAA) and abscisic acid (ABA) in superior and inferior spikelets were determined during the grain filling period and their relationships with grain filling rate were analyzed. Maximum grain filling rate, the time reaching the maximum grain-filling rate, mean grain filling rate and brown rice weight for superior spikelets showed a slight difference between the super and check rice cultivars, but were significantly lower in the super rice than in the check rice for inferior spikelets. Changes of enzyme activities and hormone concentrations in grains exhibited single peak curves during the grain filling period. The peak values and the mean activities of SuSase, AGPase, StSase and SBE were lower in inferior spikelets than in superior ones, as well as the peak values and the mean concentrations of Z + ZR and IAA. However, the peak value and the mean concentration of ABA were significantly higher in inferior spikelets than in superior ones and greater in the super rice than in the check rice. The grain filling rate was positively and significantly correlated with the activities of SuSase, AGPase and StSase and the concentrations of Z + ZR and IAA. The results suggested that the low activities of SuSase, AGPase and StSase and the low concentrations of Z + ZR and IAA might be important physiological reasons for the slow grain filling rate and light grain weight of inferior spikelets in super rice.

Key words: super rice, superior spikelet, inferior spikelet, enzyme activity, hormone concentration, grain filling