赤霉素与脱落酸对番茄种子萌发中细胞周期的调控

利用细胞流检仪检测番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．） ＧＡ－缺陷型、ＡＢＡ－缺陷型和相应的正常品种（野生型）成熟种子胚根尖细胞倍性水平时发现：ＧＡ－缺陷型和野生型种子绝大多数细胞ＤＮＡ 水平为２Ｃ，而ＡＢＡ－缺陷型种子则含有较多的４Ｃ细胞。在标准发芽条件下，ＡＢＡ－缺陷型和野生型种子浸种１ ｄ 后胚根尖细胞ＤＮＡ 开始复制，随后胚根突破种皮而发芽。然而ＧＡ－缺陷型种子除非加入外源ＧＡ，否则既不发生细胞ＤＮＡ 复制，也不发芽。这说明内源ＧＡ 是启动番茄种子胚根尖细胞ＤＮＡ 复制的关键因素，同时也说明番茄根尖细胞ＤＮＡ 复制是种子发芽的必要条件。实验证明：ＡＢＡ 不抑制细胞ＤＮＡ 合成，但阻止Ｇ２ 细胞进入到Ｍ 期。外源ＡＢＡ处理野生型种子与渗控处理结果相似，可以大幅度提高胚根尖４Ｃ／２Ｃ细胞的比例，但抑制种子的最终发芽

GA AND ABA REGULATION ON THE CELL CYCLE IN GERMINATION OF TOMATO SEEDS

Flow cytometric determination of ploidy levels in embryos of GA deficient, ABA deficient mutant and isogenic wild type tomato (Lycopersicon esculentum Mill. cv. Moneymaker) seeds revealed that, large amount of 2C DNA signals existed both in wild type and GA deficient mutant seeds, showing that most cells had arrested in the cell cycle at presynthesis G1, whereas a relative amount of 4C proportion which is a sign of seed germination was found in ABA deficient mutant seeds, indicating that endogenous ABA play a role in regulating the switch from development to germination in seeds. DNA replication was stimulated 1 d after the seed was imbibed in water and a visible germination occurred subsequently either in wild type GA deficient mutant seeds. But it was not the case for ABA deficient mutant seeds unless an exogenous GA was supplemented. This demonstrated that DNA replication in embryo root tips cells was subjected to be a compulsory factor for seed germination, whereas endogenous GA triggered DNA synthesis. It was evident that exogenous ABA could inhibit seed germination not by suppressing DNA synthesis but by bloking the route leading to mitosis since a great amount of 4C proportion was found in the germinating wild type and GA deficient mutant seeds in the ABA solution when visible germination did not occur. Finally a simple mode of hormonal regulation on cell cycle in high plants was hypothesized.