Root Length and Its Relationship to Root Plasticity and Root Life-Span

根长与根干重的比率(比根长SRL)在不同植物之间差异很大。由于水分和养分吸收更多地受到根长而不是质量的影响，高SRL的树种可能比低SRL的树种更有效地投资其根生物量。然而，更完整的成本分析必须包括根部的寿命。形成细根的树种(高SRL)可能倾向于在适宜的土壤体积中繁殖根，而在不利的土壤体积中更容易脱落根，而不是粗根的物种(低SRL)。因此，高SRL根系的短期效率可能会被与较高的根系周转率相关的较高成本所抵消。这项建议通过在田间埋在地下的透明管中插入微型摄像机来测试SRL与根系可塑性和根系寿命的关系。一个柑橘砧木试验，将遗传多样化的根系嫁接到遗传相同的新梢上，将作为模式植物系统。这项研究将提供影响根系死亡和周转的因素的信息，并深入了解根部特征的种间差异如何影响养分和水分的获取、根系周转，并最终影响植物生产力。在植物育种中，根据特定的根性状进行选择的情况很少。虽然柑橘砧木试验是检验根系特征和根系周转率之间基本关系的一个很好的模式系统，但所获得的信息也具有直接的实际应用，因为研究中的砧木都具有重要的经济意义。此外，这些信息对用于帮助估计全球气候变化的生态系统模型将是有价值的，因为根周转是二氧化碳排放到大气中的主要来源。

The ratio of root length to root dry weight (specific root length SRL) varies widely among plant species. Since water and nutrient uptake is influenced more by root length than mass, species of high SRL may appear to invest their root biomass more efficiently than species of low SRL. A more complete cost-analysis, however, must include the life-span of the root. Species that construct fine roots (high SRL) may tend to proliferate roots in favorable volumes of soil and shed roots in unfavorable soil volumes more readily than species with coarse roots (low SRL). Thus, the short-term efficiency of high SRL roots may be offset by higher costs associated with higher root turnover rates. This proposal tests the relationship of SRL to root plasticity and root life- span by using a microvideo camera inserted into transparent tubes buried in the ground in the field. A citrus rootstock trial, with genetically diverse root systems grafted to genetically identical shoots, will serve as the model plant system. This study will provide information on factors that influence root death and turnover as well as insights into how interspecific differences in root characteristics may influence nutrient and water acquisition, root turnover, and, ultimately, plant productivity. In plant breeding, selection based on specific root traits is seldom undertaken. While the citrus rootstock trial serves as an excellent model system with which to examine basic relationships between root characteristics and root turnover rates, the information gained also has direct practical applications, since the rootstocks in the study are all of economic importance. Additionally, this information will be valuable for ecosystem models that are being used to help estimate global climate change, since root turnover is a major source of carbon dioxide efflux into the atmosphere.