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，阐明了米紫藻种子休眠机理，并对生态防治水稻田杂草的有效破休眠剂氰酰胺钙肥料进行了试验。根据所得结果，提出了以下建议：种子休眠机制。施加休眠的因子要么存在于颖果的外盖中，要么存在于颖果的外盖中，在除去外盖后，该因子很容易扩散出去或降解。两对强制休眠等位基因和维持休眠等位基因对紫锥藻种子休眠的遗传控制。该物种的杂草和栽培形式，分别具有种子休眠和不休眠，都有两个编码1-Cys过氧化物还蛋白的等位基因，该等位基因已被报道为许多物种的休眠特异性抗氧化剂。但栽培型种子不表达吸胀基因，而杂草型种子表达吸胀基因。3年的田间试验表明，在水稻收获后施用氰酰胺钙肥，即使在秋季，也会刺激米紫藻的出苗，而随后冬季的低温会杀死正在出苗的幼株。春天的处理也刺激了出苗，由此产生的植物被划水练习杀死。氰胺肥对埋在土壤中的杂草种子也有杀种作用。

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.