Activities of the enzymes involved in starch synthesis and starch accumulation in grains of wheat cultivars GC8901 and SN1391

中国人. 选用藁城8901（强筋）和山农1391（弱筋）两个小麦品种，比较研究了其小麦蔗糖代谢、淀粉合成相关酶活性的变化及淀粉组分的积累特征。结果表明，蔗糖合成酶（SS）、磷酸蔗糖合成酶（SPS）、腺苷二磷酸葡萄糖焦磷酸化酶（ADPGPPase）、可溶性淀粉合成酶（SSS）活性以及蔗糖积累量的高低均存在明显的基因型差异，淀粉积累量较高的弱筋品种山农1391显著高于淀粉积累量较低的强筋品种藁城8901。而结合态淀粉合成酶（GBSS）活性与两品种籽粒直链淀粉积累量的变化情况相吻合，小麦籽粒灌浆中后期的GBSS活性对直链淀粉终积累量的调节作用大于籽粒灌浆前期。用Richards方程模拟籽粒直链淀粉和支链淀粉的积累过程发现，直链淀粉和支链淀粉终积累量的高低取决于其积累启动时间的早晚和前期积累速率的高低，而不是积累持续期的长短。通过比较两品种蔗糖转化量、淀粉积累速率与蔗糖和淀粉代谢相关酶活性的变化趋势可以看出，蔗糖转化量与SSS和GBSS的变化趋势一致；淀粉积累速率与ADPGPPase活性和SS/SPS活性比率的变化趋势一致，而与SS 、SPS、SSS或GBSS活性的变化并不吻合，说明籽粒中淀粉积累速率及其组分积累量的高低与SS、SPS、SSS和GBSS单个酶活性的高低并不存在必然联系，而与ADPGPPase活性和籽粒中蔗糖合成与降解的平衡密切相关。

英语. Two wheat cultivars, GC8901 (hard winter wheat) and SN1391 (soft winter wheat), were used for investigating the changes of enzyme activities for sucrose metabolism and starch biosynthesis and the accumulation characters of starch composition. Result showed that, the activities of sucrose (SS), sucrose-phosphate synthase (SPS), adenosine diphosphorate glucose pyrophrylase (ADPGPPase) and soluble starch syntheses (SSS) of SN 1391, which has more starch, were significantly higher than GS 8901, that with low starch content. But the changes of granule-bound starch synthase (GBSS) activity were consistent with the amylose content which indicated that amylose contents in grain were determined by GBSS activity, especially the activity at later grain filling stages. Simulating with Richards Equation showed that it was initiating time and accumulation rate, but not accumulation duration that determined the content of starch composition. Furthermore, the changes of sucrose transport capacity were consistent with SSS and GBSS activities, starch accumulation rate was accordant to ADPGPPase and SS/SPS ration, not SS, SPS, SSS or GBSS activities. The results suggested that there is no inevitable relation of starch accumulation rate and starch composition contents with the activity of single enzyme such as SS, SPS, SSS or GBSS, but closely related to ADPGPPase activity and SS/SPS ratio, and it was SPS and ADPGPPase have played a vital role in the biosynthetic pathway. Later polymerization reactions catalyzed by SSS and GBSS do not seem to control the rate of starch accumulation, but do affect starch structure.