Abstract:

【Objective】 The present study was carried out to characterize the distribution and development of starch granules during grain filling in two wheat cultivars differing in gluten. 【Method】 Two wheat cultivars, Lumai 21 (weak gluten winter wheat) and Jinan 17 (strong gluten winter wheat) were used as materials to investigate the distribution of starch granule size with laser-diffraction particle-size analyzer during endosperm development at Tai’an of Shandong Province in 2004-2006 growing season.【Result】 At different days after anthesis (DAA), the percent number distribution of starch granules in wheat endosperm exhibited single peak curves with peaks at 0.5~1.1 μm. The starch granules initiated before 7 DAA and increased in size to maximum diameter of 20 μm at 7 DAA. These early synthesized granules (A-type) continued to enlarge to their maximum diameter of 30 μm at 10 DAA. By 14 DAA, a burst of synthesis created a new population of small starch granules (B-type), which reduced the number proportion of big starch granules. A third group (C-type) of small granules was initiated at 21 DAA. From 24 to 28 DAA, the percent number of ＜0.6 μm starch granules increased and those of ＞9.8 ?m starch granules decreased continuously, indicating that new granules were still synthesized, however, the magnitude of increase reduced. These small granules continued to enlarge in diameter by 35 DAA. The percent number of ＜0.6 μm starch granules and that of ＞0.6 ?m in Lumai 21 was lower and higher, respectively, than in Jinan 17 at 7-14 DAA. However, there were opposite changes at 17-28 DAA. 【Conclusion】 It is concluded that Lumai 21 has higher starch granule accumulation rate and stronger capacity of new starch granule synthesization than Jinan 17, respectively, at early and late grain filling stage. At maturity, the percentages of volume and surface area of B-type starch granules in Jinan 17 are higher than those in Lumai 21, but on the contrary in the percentages of A-type starch granules.

Key words: wheat (Triticum aestivum L.), starch, granule size, particle distribution