在大田条件下，以豫麦49 (Tritictun aestivurn cv. Yumai 49)为试材，研究了开花期外施0、0.1、1.0、10.0 µg/L表油菜素内酯(epi-BR)对小麦籽粒灌浆过程中腺苷二磷酸葡萄糖焦磷酸化酶(ADPGPPase)、可溶性淀粉合成酶(SSS)、颗粒束缚型淀粉合成酶(GBSS)和淀粉分支酶(SBE)活性，以及淀粉积累速率的影响，同时对收获籽粒的淀粉成分和淀粉特性进行了测定。结果表明，开花期外施epi-BR提高了小麦籽粒中ADPGPPase、SSS和SBE活性，epi-BR 0.1和1.0 µg/L 处理可降低GBSS活性，10.0 µg/L处理可提高 GBSS活性，从而改变小麦籽粒灌浆期间的淀粉积累速率，改善小麦籽粒淀粉成分与特性，提高淀粉品质。在本试验条件下，以epi-BR 1.0 µg/L处理对籽粒淀粉的调控效果最好，使小麦籽粒中总淀粉含量、淀粉的支/直比、高峰黏度值和崩解值分别提高8.88% (α＜0.01 ）、34% (α＜0.01）、32.4 BU (α＜0.05）和13.7 BU (α＜0.05)。
It has been found that the application of epi-brassionolide (epi-BR) at anthesis results in improving photosynthetic character, postponing senescence, and increasing wheat grain weight. However, the physiological effects of epi-BR application at anthesis on starch accumulation and starch quality of grains were poorly understood. The present study reports the effect of epi-BR application on the activities of some key enzymes involved in starch synthesis at grain filling stage. The experiment was carried out on the farm of Henan Agricultural University in the growing season of 2003–2004 with winter wheat cultivar Yumai 49. Four different concentrations (0, 0.1, 1.0 and 10.0 µg/L) of epi-BR were used. Epi-BR was sprayed at a rate of 75 mL/m2 on the leaves and spikes on 3 days after anthesis (DAA). The activities of key starch-synthesizing enzymes in grains, i.e. adenosine diphosphorate glucosepyrophorylase (ADPGPPase), soluble starch synthase (SSS), granule-bound starch synthase (GBSS) and starch branching enzyme (SBE), as well as the total starch content, amylopectin and amylose accumulation rate during grain filling were measured. The total starch content, amylopectin and amylose content of grains, and grain starch quality were also examined at maturing stage. The results indicated that changes in activities of ADPGPPase (Fig.1-A), SSS (Fig.1-B) and SBE (Fig.1-D) were consistent with those in total starch content and the accumulation of amylopectin. Activity of GBSS (Fig.1-C) was consistent with the accumulation of amylose. The activities of ADPGPPase, SSS and SBE were increased in the treatment of 1.0 µg/L epi-BR, thereby the total starch (Fig.2-A) and amylopectin accumulation rate accelerated (Fig.2-B). The activity of GBSS was decreased, thereby the rate of amylose accumulation slowed down by epi-BR treatment (Fig.3). Consequently, contents both of total starch and amylopectin were significantly increased (α＜0.01） compared with those of the control, respectively. Amylose content was significantly decreased (α＜0.05）, and the ratio of amylopectin to amylose increased significantly (α＜0.01 ） by epi-BR application (Table 1). The peak value and breakdown of epi-BR application treatments were 32.4 BU and 13.7 BU, significantly higher (α＜0.01） than those of control, respectively (Table 2). Epi-BR at 10.0 µg/L had similar effects, but the high value duration of the indexes were shorter. Consequently, content of total starch, amylopectin, and amylose was significantly increased (α＜0.05 ）, respectively. However the ratio of amylopectin to amylose was not significantly different with that of control. Compared with control, the peak value and swelling power were significantly higher, respectively, while the setback was significantly lower (α＜0.05）. At 0.1 µg/L, the effects of epi-BR were similar to those at 1.0 µg/L, but weaker than those at either 1.0 or 10.0 µg/L, therefore, the total starch content and starch quality were not significantly different with those of control. The results indicated that epi-BR plays an important role in starch accumulation and starch quality, probably through affecting the activities of ADPGPPase, SSS, SBE and GBSS. Under the experimental condition, epi-BR at 1.0 µg/L had the best regulative effects on total starch content, ratio of amylopectin to amylose, starch pasting properties and starch quality.
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