A Water Relations Model for the Regulation of Seed Germination

种子萌发是作物在田间生根的关键阶段，也是野生一年生植物生命周期的关键阶段。种子的整体质量与种子在浇水后发芽所需的时间或发芽率密切相关。当温度降低、供水受限或种子在储存过程中变质时，发芽速度就会减慢。物种和变种在其固有的种子发芽率上也可能不同。本课题的目的是研究不同物种或种子批次在不同环境或生理因素下发芽率差异的生理基础。我们修改了植物组织生长的一般模型，使之适应于种子发芽率的描述。它是基于植物细胞生长的水分吸收，因为胚胎组织必须生长才能发芽。通过验证该模型并将其应用于种子，种子内的胚胎和胚乳和种皮等周围组织相互作用，以确定何时或是否发生发芽。这个模型应该允许我们确定外部（环境）因素影响特定组织内部（生理）参数以加速或延迟发芽的机制。这个模型将作为一个框架或指南，引导我们更好地理解种子萌发的复杂过程是如何被调控的。从实际应用的角度来看，研究结果将对优质农用种子的生产和销售具有实用价值。在许多作物中，特别是在蔬菜中，土壤中发芽和出苗的均匀性和时间是作物整体盈利能力的关键因素。通过对种子发芽如何被调控的定量理解，可以开发技术来提高种子在特定环境条件下的性能。这种改良种子已经在一些作物中上市，但迄今为止所使用的程序是通过反复试验而开发的，而不是通过应用对种子发芽如何调节的基本理解。此外，种、变种在种子品质特征上也存在差异。了解这些差异的生理基础，可以确定在育种计划中使用的特定可选择性状，甚至可以通过生物技术方法转移特定基因，以提高种子质量。该项目产生的基本信息将很容易被种业吸收，并纳入他们的计划，以提高农民可获得的种子质量。

Seed germination is a critical phase in the establishment of crop plants in the field, or in the life cycles of wild annual plants. The overall quality of seed is closely related to the time taken for the seed to germinate after it is supplied with water, or the germination rate. The rate of germination slows as the temperature is lowered, as the water supply is restricted, or as the seeds deteriorate during storage. Species and varieties can also differ in their inherent rates of seed germination. The purpose of this project is to study the physiological basis for the differences in germination rates among species or seed lots in response to various environmental or physiological factors. We have modified a general model for the growth of plant tissues to adapt it to the description of seed germination rates. It is based upon water uptake in relation to plant cell growth, since the embryonic tissues must grow in order for germination to occur. By verifying this model and then applying it to seeds both the embryo inside the seed and the surrounding tissues such as the endosperm and seedcoat interact to determine when, or whether, germination occurs. This model should allow us to identify the mechanism(s) by which external (environmental) factors influence internal (physiological) parameters in specific tissues to either accelerate or delay germination. This model will serve as a framework or guide to lead to a better understanding of how the complex process of seed germination is regulated. From the practical viewpoint, the results will have utility in the production and marketing of higher quality seed for agricultural purposes. In many crops, particularly in the vegetables, the uniformity and timing of germination and seedling emergence through the soil are critical factors in the overall profitability of the crop. Through a quantitative understanding of how seed germination is regulated, techniques can be developed to enhance the performance of seeds under specific environmental conditions. Such enhanced seed are already being marketed in some crops, but the procedures used thus far have been developed by trial and error, rather than by application of a fundamental understanding of how seed germination is regulated. In addition, species and varieties differ in their seed quality characteristics. Knowledge of the physiological basis of such differences could identify specific selectable traits to use in breeding programs, or even specific genes to be transferred by biotechnical approaches, in order to improve seed quality. The fundamental information generated by this project will be readily absorbed by the seed industry and incorporated into their programs to improve the quality of seed available to farmers.