Finch-Savage W E, Phelps K, Steckel J R, Whalley W R, Rowse H R
Horticulture Research International, Wellesbourne, Warwick CV35 9EF, UK.
J Exp Bot. 2001 Nov;52(364):2187-97. doi: 10.1093/jexbot/52.364.2187.
Both temperature and soil moisture vary greatly in the surface layers of the soil through which seedlings grow following germination. The work presented studied the impact of these environmental variables on post-germination carrot growth to nominal seedling emergence. The rapid pre-crook downward growth of both the hypocotyl and root was consistent with their requirement for establishment in soil drying from the surface. At all temperatures, both hypocotyl and root growth rates decreased as water stress increased and there was a very distinct temperature optimum that tended to occur at lower temperatures as water stress increased. A model based on the thermodynamics of reversible protein denaturation was adapted to include the effects of water potential in order to describe these growth rate responses. In general, the percentage of seedlings that reached the crook stage (start of upward hypocotyl growth) decreased at the extremes of the temperature range used and was progressively reduced by increasing water stress. A model was developed to describe this response based on the idea that each seedling within a population has lower and upper temperature thresholds and a water potential threshold which define the conditions within which it is able to grow. This threshold modelling approach which applies growth rates within a distribution of temperature and water potential thresholds could be used to simulate seedling growth by dividing time into suitable units.
种子萌发后，幼苗生长所经过的土壤表层，温度和土壤湿度变化都很大。本文的研究探讨了这些环境变量对胡萝卜种子萌发后直至幼苗出土阶段生长的影响。下胚轴和根在弯钩形成前迅速向下生长，这与它们在表层土壤变干时扎根的需求是一致的。在所有温度条件下，随着水分胁迫加剧，下胚轴和根的生长速率均下降，并且存在一个非常明显的最适温度，随着水分胁迫增加，该最适温度往往出现在较低温度下。基于可逆蛋白质变性的热力学原理建立了一个模型，并纳入水势的影响，以描述这些生长速率响应。总体而言，在所使用的温度范围两端，达到弯钩阶段（下胚轴开始向上生长）的幼苗百分比下降，并且随着水分胁迫加剧而逐渐降低。基于种群中每株幼苗都有较低和较高温度阈值以及一个水势阈值来定义其能够生长的条件这一理念，开发了一个模型来描述这种响应。这种阈值建模方法通过将时间划分为合适的单位，应用温度和水势阈值分布内的生长速率，可用于模拟幼苗生长。
