| Twenty two cultivars were employed to study the seed vivipary characteristics of dwarf bean (Phaseolus vulgaris var. humilis Alef.) during 2002 and 2003, both in greenhouse and open field. The frequency of vivipary seed was investigated, and the distribution of vivipary seed in pod and plant was calculated as well. The main results were summarized as follows:The frequency of vivipary seed varied significantly among cultivars. Some cultivars never germinated on plant, others did germinate on plant, and the percentage of vivipary seed was more than 20%. The frequency of vivipary seed was affected with seed development conditions. Generally, the frequency of vivipary seed planted in greenhouse was lower than that in open field. Seed did not germinate on the plant until 35 days after flower, if the cultivar had such a character of vivipary and under a suitable condition. The distribution of vivipary seeds was regularly in pod or on plant, i.e., vivipary seeds were mainly distributed in the tip of pod, and more than 60 percent of vivipary seeds happened in the lower part of plant. Color-grained cultivars such as 'Provider' 'Wujin Caidou 'P48' are generally resistant to sprouting, on the contrast, white-grained ones such as 'SG259 '97-34 '250' are easy to sprouting. These six cultivars are suitable to study the vivipary hi Phaseolus vulgaris var. humilis Alef. according to their characteristics.At the end of maturity stage, all cultivars start dehydration. Seed moisture content in cultivars that were lower in percentage of preharvest sprouting, such as 'Provider' 'Wujin Caidou' and 'P48' decreased less than 30%, on the contrast, seed moisture content of 'SG259 '97-34' and '250', which were higher in percentage of preharvest sprouting, were still more than 35%.The result showed that positive correlation existed between percentage of preharvest sprouting and water uptake rate, and coat-color. Similar electric conductivity was detected among various cultivars both in seed and pod, and no correlation between electric conductivity and percentage of preharvest sprouting was found.During the various development stages, the difference of the peroxidase (POD) activity between various cultivars was obviously. According to the POD activity, cultivars used in this experiment could be grouped into two categories: one included 'Provider' 'Wujin Caidou' and 'P48', and the other included 'SG259' '97-34' and '250'. The peroxidase activity of the former group which was tolerant to precocious germination declined steadily during the whole development stages. On the contrary, the peroxidase activity of the latter group which was susceptible to preharvest sprouting increased sharply at the end of maturity stage. Characteristic of low peroxidase activity could be used as the indirect identification of high tolerance to precocious germination at the end of maturity stage.amylase activity of seed was very high before germination. However, it decreased at the end of germination. The same conclusion can be made from amylase isozyme bands. On the other hand, the level of a-amylase activity of seed was very low until germination. There were no a-amylase bands until 37 hours after germination.During the various development stages, the difference of -amylase activity between various cultivars was significantly, especially in the maturity stage. P -amylase activity of varieties which were tolerant to precocious germination, such as '86259' and '97-34', was increased. However, amylase activity of cultivars which were susceptible to preharvest germination, such as 'Wujin Caidou' and 'P48' was decreased sharply. On the other hand, the level of a-amylase activity of all cultivars increased steadily during the whole development. No relationship existed between the preharvest germination and a-amylase activity. While the low-level amylase activity in seed could be the indirect identification of high tolerance to precocious germination.
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