Hilhorst H W
Department of Plant Physiology, Agricultural University, Arboretumlaan 4, NL-6703 BD Wageningen, The Netherlands.
Plant Physiol. 1990 Nov;94(3):1096-102. doi: 10.1104/pp.94.3.1096.
The role of nitrate as a promoter of germination of Sisymbrium officinale seeds was examined in optimal light conditions. It was shown that the requirement for nitrate was absolute. This was true for all seed lots used. The probit of germination in water was log-linearly related to the level of endogenous nitrate. Preincubation at 15 degrees C resulted in an immediate decrease in germination, whereas in 25 millimolar KNO(3) the decrease was delayed. The decline of germination in water was strongly correlated with the rate at which nitrate leached from the seeds. The germination response to a range of KNO(3) concentrations was followed during preincubation at 24-hour intervals. During the entire 264-hour preincubation period increasingly higher nitrate concentrations were required to maintain a response. This resulted in a right-hand shift of the dose-response curve parallel to the x axis. After 120 hours the high maximum germination level started to decline. The dose-response curves could be simulated by an equation from the receptor-occupancy theory. It is proposed that induction of secondary dormancy is a result of a decrease of the number of nitrate receptors. After 24 and 48 hours of preincubation, the nitrate-response curves were biphasic. The biphasic character could be related to the level of endogenous nitrate and to a differential requirement for nitrate of two fractions of the seed population. Similarities with the behavior of fluence-response curves after prolonged dark incubation led to the hypothesis that phytochrome and nitrate share the same site of action.
在最佳光照条件下研究了硝酸盐作为药用大蒜种子萌发促进剂的作用。结果表明，对硝酸盐的需求是绝对的。所用的所有种子批次均是如此。在水中的发芽概率与内源硝酸盐水平呈对数线性关系。在15摄氏度下预培养导致发芽立即下降，而在25毫摩尔硝酸钾中下降则延迟。在水中发芽率的下降与硝酸盐从种子中浸出的速率密切相关。在24小时间隔的预培养期间，跟踪了对一系列硝酸钾浓度的发芽反应。在整个264小时的预培养期间，需要越来越高的硝酸盐浓度来维持反应。这导致剂量反应曲线平行于x轴向右移动。120小时后，高发芽率开始下降。剂量反应曲线可以用受体占据理论的一个方程来模拟。有人提出，二次休眠的诱导是硝酸盐受体数量减少的结果。预培养24小时和48小时后，硝酸盐反应曲线呈双相。双相特征可能与内源硝酸盐水平以及种子群体两部分对硝酸盐的不同需求有关。与长时间黑暗培养后的光通量反应曲线行为的相似性导致了这样的假设，即光敏色素和硝酸盐具有相同的作用位点。
