试验以 sh2 胚乳突变体（超甜玉米）为材料，以普通杂交玉米（掖单12）为对照，比较了两者于6℃和10℃和25℃条件下吸胀的生理生化变化。试验结果表明，经6℃和10℃吸胀处理的超甜玉米种子发芽率、发芽指数和活力指数显著降低，而6℃低温吸胀对掖单12玉米种子影响甚微。低温吸胀均引起两种玉米种子吸胀速率、电解质渗出速率和核苷酸渗漏量的显著下降，可溶性糖渗漏量在浸泡一段时间以后出现增加。低温吸胀提高两种玉米种子的脱氢酶活性，显著降低掖单12玉米种子的过氧化物酶活性，但显著提高超甜3号种子的过氧化物酶活性，两种玉米种子的ɑ-淀粉酶和β-淀粉酶活性也因低温吸胀而降低。

Studies were conducted on specific core collections constructed on the basis of different traits and sample size by the method of stepwise cluster with three sampling strategies based on genotypic values of cot-ton. A total of 21 traits (11 agronomy traits, 5 fiber traits and 5 seed traits) were used to construct main core collections. Specific core collections, as representative of the initial collection, were constructed by agrono-my, fiber or seed trait, respectively. As compared with the main core collection, specific core collections tended to have similar property for maintaining genetic diversity of agronomy, seed or fiber traits. Core collections developed by about sample size of 17% (P2=0.17) and 24% (P1=0.24) with three sampling strategies could be quite representative of the initial collection.

A genetic model with genotyp