RUI: Contractile Roots: Their Role in Anchorage and Resource Acquisition in the Agavaceae

这项研究的目的是研究根收缩(纵向缩短)如何帮助植物根系发挥两个主要功能：锚定和获取资源。以前的研究表明，收缩根是一种将植物拉到更有利的土壤深度或帮助在与其母植物相距一定距离的地方建立分支的手段。虽然已经对一些物种的收缩过程进行了研究，但相关的解剖修饰对根系水分吸收的影响还没有被研究过。收缩根以前被描述为龙舌兰属的一种成员，似乎在龙舌兰科中广泛存在，该科包括美国西南部和墨西哥的几个具有生态重要性的物种。这项研究的指导假设是，收缩根不仅可以促进季节性干旱生境中幼苗的建立和无性系繁殖，而且还可以在降雨稀少和有限的地区增加水分吸收。这一假设将通过比较龙舌兰科植物中不同物种对收缩根的结构和功能来检验，这些物种在栖息地(例如，草原和沙漠)、生长习性(例如，肉质和非肉质、莲座状和树状)和繁殖方法(例如，经常是营养的和严格的有性繁殖)上存在差异。将在实验室和普通花园中对不同条件下的根收缩和地上部移位量进行量化，并将部分挖掘南加州本土物种龙舌兰和丝兰的根系，以确定田间根收缩的程度。收缩根与非收缩根的水分吸收以及微管取向、细胞形状和大小、细胞活力和细胞壁修饰等解剖特征将被研究，特别是当它们影响水分吸收和运输时。这项研究将包括几个尺度(从细胞器到植物科)，并使用来自几个领域(解剖学、生态学和生理学)的技术，为本科生的学习和未来研究的准备提供多种但综合的选择。由于西方学院作为致力于多样性的机构的声誉，以及它位于洛杉矶东北部的位置，代表不足的学生参与研究的机会很大。此外，这项研究承诺阐明收缩根在生态和经济上具有重要意义的植物群体中的功能意义，并首次研究收缩对根获得和运输水分的能力的影响。

The purpose of this study is to investigate how root contraction (longitudinal shortening) can help plant root systems perform two primary functions: anchorage and resource acquisition. Contractile roots have been studied previously as a means of pulling a plant to a more favorable soil depth or helping establish an offshoot at some distance from its parent plant. Although the process of contraction has been investigated for a number of species, the effects of the associated anatomical modifications on root water uptake have not been examined. Contractile roots, which have been described previously for one member of the genus Agave, appear to be widespread in the family Agavaceae, which includes several species of ecological importance in the southwestern U.S. and Mexico. The guiding hypothesis of this study is that contractile roots not only improve seedling establishment and clonal propagation in seasonally dry habitats but also enhance water uptake in regions of infrequent and limited rainfall. The hypothesis will be tested by comparing the structure and function of contractile roots for paired species in the Agavaceae that differ in habitat (e.g., grassland vs. desert), growth habit (e.g., succulent vs. non-succulent, rosette vs. tree-like), and method of reproduction (e.g., frequently vegetative vs. strictly sexual). The amount of root contraction and shoot displacement will be quantified under various conditions in the laboratory and in a common garden, and root systems of native species of agave and yucca in southern California will be partially excavated to determine the extent of root contraction in the field. Water uptake by contractile versus non-contractile roots will be investigated along with anatomical features such as microtubule orientation, cell shape and size, cell vitality, and cell wall modifications, particularly as they affect water absorption and transport. The study will encompass several scales (organelle to plant family) and employ techniques from several fields (anatomy, ecology, and physiology), providing multiple yet integrated options for undergraduate learning and preparation for future research. Due to the reputation of Occidental College as an institution committed to diversity and its location in northeast Los Angeles, the opportunity for under-represented students to become involved in the research is great. In addition, the study promises to illuminate the functional significance of contractile roots in an ecologically and economically important group of plants and to examine for the first time the effects of contraction on the ability of roots to acquire and transport water.