通过测定旗叶和籽粒中磷酸蔗糖合成酶(SPS)、蔗糖合成酶(SS)、AGP焦磷酸化酶(AGPase)、UGP焦磷酸化酶(UPGase)、可溶性淀粉合成酶(SSS)和束缚态淀粉合成酶(GBSS)的活性，以及蔗糖含量，研究了播种期对藁城8901蔗糖代谢和淀粉合成相关酶活性变化及淀粉组分积累的影响。结果表明，早播和晚播均可降低籽粒直链淀粉积累量，但其支链淀粉积累量随播期的推迟逐渐升高；直链淀粉和支链淀粉积累的最适平均日照时数分别为9.06和11.07 h；支链淀粉积累的最佳日均气温为22.75℃，而直链淀粉积累对温度的适应范围较宽，日均气温在17~25℃之间时，直链淀粉含量与日均气温呈正相关关系。推迟播期使旗叶SPS和SS活性升高，而旗叶蔗糖积累量、籽粒SS、SPS活性和蔗糖积累量均显著降低；籽粒AGPase、SSS活性和支链淀粉积累量明显升高；而UGPase、花后14 d的GBSS活性和直链淀粉积累量显著降低。表明在小麦植株体内存在淀粉积累对蔗糖代谢的反馈调节作用，它主要是通过降低籽粒SPS活性而不是SS活性来实现的。由SS催化的蔗糖降解不是提供小麦籽粒淀粉积累所需底物的惟一途径。在小麦籽粒淀粉合成过程中，AGPase、SSS、UGPase和GBSS均起着重要的调节作用。植株本身可通过反馈抑制籽粒UGPase和某一时期的GBSS活性来调节籽粒中蔗糖向淀粉的转化以及淀粉组分的积累，以维持体内合理的直/支比例。
Grain starch is synthesized from sucrose of leaves, and regulated by a series of enzymes in wheat (Triticum aestivum L.). Previous researches have revealed that sowing date affects wheat quality by changing protein content, wet gluten content, sedimentation value, dough development time and stability time. Grain quality also relates to starch content, especially the component of starch. In order to understand the regulation mechanism of sowing date to the accumulation and component of grain starch, a wheat coultivar, Gaocheng 8901, was employed with different sowing dates. The starch (amylose and amylopectin) content in grain, and the activities of sucrose-phosphate synthase (SPS), sucrose synthase (SS), adenosine diphosphorate glucose pyrophrylase (AGPase), uridine diphosphorate glucose pyrophrylase (UGPase), soluble starch synthase (SSS) and granule-bound starch synthase (GBSS), as well as sucrose content in flag leaf and grain were determined during grain filling. The results showed that the accumulation of amylose was decreased under both early and late sowing treatments, but that of amylopectin increased significantly (P<0.01) (Fig.1). The optimum daily sunlight hour (ASH) for amylose and amylopectin accumulation were 9.06 and 11.07 hours, respectively (Table 1). The amylopectin content was maximal when the average daily air temperature (ATD) was 22.75℃, while amylose content showed a positive correlation with ATD from 17℃ to 25℃. Under late sowing treatment, the activities of SS and SPS increased in flag leaf, but decreased in grain significantly (P<0.05) 14 days after anthesis, while the sucrose accumulation in flag leaf and grain both reduced (Fig.3–6). Late sowing also resulted in the increase of AGPase activity, SSS activity and amylopectin accumulation, but the decrease of UGPase and GBSS activities in grain at mid to late period of grain filling (Fig.7, 8). The above results suggest a feedback system of sucrose metabolism by starch accumulation in wheat, which takes function through reducing the activity of SPS instead of SS in grain. The approach of sucrose decomposition catalyzed by SS is not the unique one for starch synthesis in grain. AGPase, SSS, UGPase and GBSS all play important roles in starch synthesis, of which UGPase and GBSS activities are restrained at certain stages to regulate the transformation of sucrose to starch and the accumulation of starch component, so that a reasonable ratio of amylose to amylopectin can be kept.
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