大穗型小麦品种强、弱势籽粒淀粉积累和相关酶活性的比较

Starch Accumulation and Related Enzyme Activities in Superior and Inferior Grains of Large Spike Wheat

在大田条件下，以两个大穗型小麦品种山农12和PH01-35为材料，对籽粒发育过程中强、弱势籽粒淀粉积累及其相关酶活性变化进行了比较研究。结果表明，两品种强势粒直链淀粉积累量和支链淀粉积累量均高于弱势粒。Logistic方程模拟淀粉积累过程，强势粒淀粉积累起始势（Co）高，活跃持续期长，平均积累速率（Rmean）高，最终淀粉积累量高。籽粒蔗糖合酶（SS）、ADPG焦磷酸化酶（AGPase）、UDPG焦磷酸化酶（UGPase）、可溶性淀粉合酶（SSS）和束缚态淀粉合酶（GBSS）活性均呈单峰曲线变化，强势粒上述酶活性均高于弱势粒。花后7-21d，弱势粒蔗糖含量明显高于强势粒，表明弱势粒淀粉积累量低，并不以其淀粉合成底物的供给为限制因子，而主要与淀粉合成能力低有关，同时与籽粒灌浆前期胚乳细胞的数量关系密切。

Starch, the major component of grain, consists of amylose and amylopectin. It is synthesized and accumulated during grain filling in wheat （Triticum aestivum L.）, and regulated by many enzymes including sucrose synthase （SS）, adenosine diphos- phorate glucose pyrophosphorylase （AGPase）, uridine diphosphorate glucose pyrophosphorylase （UGPase）, soluble starch synthase （SSS）, granule-bound starch synthase （GBSS）, starch branching enzyme （SBE） and so on. According to recent studies, AG- Pase, starch synthase, and SBE are the key enzymes controlling starch synthesis. Previous researches have revealed that the allocation of carbohydrate, grain weight, and the transformation of sucrose to starch were significantly different between superior and inferior grains of wheat. But to date, there are few reports about the differences of starch accumulation and the relationship between starch accumulation and related enzyme activities in superior and inferior grains. Therefore, a field experiment was carried out, and two large-spike type cultivars, SN 12 and PH01-35 were used to investigate the mechanism of starch accumulation and the relationship with related enzyme activities in superior and inferior grains. Forty spikes was sampled at 7, 14, 21, 28, and 35 d after anthesis, and partitioned into two groups, superior grain （the 1st and 2nd grains from the basal part of a spikelet） and inferior grain （the 3rd and 4th grains from the basal part of a spikelet）. Half grains of each group were used to determine the enzyme activities, and the other half for starch content measurement. The result showed that the accumulation of amylose and amylopectin in superior grain were significantly higher than those in inferior grain. The simulation with Logistic equation showed that the accumulation rate and initial potential were higher, the accumulation duration was longer, so the starch final amount was higher in superior grain. The activities of SS, AGPase, UGPase, SSS, and GBSS changed in the pattern of a single-peak curve during grain filling. The related enzyme activities in superior grain, which had higher starch accumulation, were higher than those in inferior grain. The sucrose content in inferior grain was much higher than that in superior grain at 7-14 d after anthesis, indicating that the substrate of starch synthesis should not be the limiting factor for starch accumulation in inferior grain, which related to starch synthesis efficiency, also the number of endosperm cells at early grain filling stage.