Elucidation of Weed Seed Dormancy Mechanism and Application of Calcium Cyanamide Fertilizer, a Dormancy-breaking Agent for Ecological Control of Weeds

通过生理和分子生物学分析，阐明了稗草种子休眠的机理，并进行了氰氨化钙肥料的生态防除试验。研究结果表明：1.种子休眠机制休眠因子存在于颖果或颖果的外壳中，其中该因子在去除外壳后容易扩散或降解。水稻稗种子休眠的遗传控制由两对等位基因组成，一对为休眠基因，另一对为保持休眠基因。这两种杂草和栽培形式的种子休眠和无休眠，分别有两个等位基因编码1-半胱氨酸过氧化物酶，已被报道为一个休眠特异性抗氧化剂在许多物种。但栽培形式的种子在吸胀时不表达这些基因，而杂草形式的种子表达这些基因。氰氨化钙生态防除稻田杂草三年田间试验结果表明，稻后处理，即使在秋季，氰氨化钙也能刺激稗草出苗，但出苗的幼苗会被随后冬季的低温杀死。春季处理也刺激出苗，并且通过划水实践杀死所得植物。氨腈肥料对埋在土壤中的杂草种子也有一定的杀种作用。

We conducted physiological and molecular biological analyses to elucidate mechanism of seed dormancy in Echinochloa oryzicola, and tested calcium cyanamide fertilizer, a potent dormancy-breaking agent to ecologically control weeds in flooded rice. The followings were suggested from results obtained:1. Seed dormancy mechanisma. A dormancy-imposing factor is present either in outer covers of the caryopsis or caryopsis in which the factor readily diffuses out or degraded upon the removal of the outer covers. Two pairs of alleles, one for dormancy-imposing and the other for its maintenance genetically control of seed dormancy in Echinochloa oryzicola.b. Both weedy and cultivated forms of this species, with seed dormancy and without dormancy, respectively, have two alleles coding 1-Cys peroxiredoxin that has been reported as a dormancy specific antioxidant in many species. But seeds of the cultivated form do not express the genes upon imbibition, while those of weedy form express.2. Ecological weed control with calcium cyanamide fertilizerThree year's field experiment revealed that with the post-rice harvesting treatment the fertilizer stimulates emergence of Echinochloa oryzicola even in autumn and the young plants emerging were killed by low temperatures of the succeeding winter. The spring treatment also stimulates the emergence and resultant plants were killed by paddling practice. The cyanamide fertilizer also had seedcidal activity against weeds seeds buried in soil.