Effect of Water on Morphological Development in Seedlings of Three Range Grasses: Root Branching Patterns

Abstract

Root morphology is important for successful seedling establishment and survival on semiarid rangelands. This study was conducted to determine the response of early seedling root morphological development of 'Hycrest' [Agropyron desertorum (Fisch. ex Link) Schult. X A. cristatum (L.) Gaert.], 'Whitmar' [Pseudoroegneria spicata (Pursh) Loeve], and cheatgrass (Bromus tectorum L.) to water. A greenhouse line-source sprinkler system provided a gradient of water application (77, 66, 37, and 5 ml/day). Root morphology was examined at 15, 30, and 45 days after seedling emergence. Order of branching of roots associated with the first foliar node was greater in cheatgrass than in Hycrest or Whitmar at all water applications and dates. Length of the primary root, length of the second group of seminal roots, and length of the first group of adventitious roots were similar in cheatgrass and Hycrest. Root branching for the 3 species decreased as less water was applied, except for cheatgrass irrigated with 5 ml/day. The ability of cheatgrass seedlings to grow with little water was related to their greater order of branching of seminal roots, branching density on the main axis, and length of lateral roots and external-external links. The greater root branching densities, lateral root lengths, and external-external link lengths enabled Hycrest seedlings to grow better than Whitmar seedlings with little water. These root morphological characteristics may prove useful in improving seedling establishment of perennial range grasses.