|Arredondo, J -|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 13, 2011
Publication Date: August 25, 2011
Citation: Arredondo, J.T., Johnson, D.A. 2011. Allometry of root branching and its relationship to root morphological and functional traits in three range grasses. Journal of Experimental Botany. 62:5581-5594. Interpretive Summary: Root branching patterns in plants and their relationship to nutrient uptake are not clearly understood. To better understand root branching responses in three important range grasses, seedlings of bluebunch wheatgrass (Pseudoroegneria spicata), crested wheatgrass (Agropyron desertorum x A. cristatum), and cheatgrass (Bromus tectorum] were exposed to four nutrient treatments in a greenhouse. Root branch spacing on the main root and other root branches was determined along with eight other root morphological and biomass allocation characteristics. A root model was used to calculate root exploitation efficiency and root exploitation potential. Results showed a negative relationship between interbranch distances on the main root axis and other lateral root branches, but only for bluebunch wheatgraass. Important relationships also were found between interbranch distances on the mainroot (number of roots, root length) and root allocation charateristics (specific root length, root mass to volume ratio). Interbranch distance on the main root was related to nutrient exploitation potential and efficiency in secondary roots. Bluebunch wheatgrass relies on a relatively fixed pattern of root development compared to crested wheatgrass and cheatgrass, which are opportunistic and rapidly produce roots for soil nutrient uptake. Results from these studies will help in the development of computer models for root growth, which can be used to predict establishment success of these grasses.
Technical Abstract: Several studies have documented the existence of correlative mechanisms that control lateral root emergence in plants. To better understand root branching responses to nutrients, root growth in three range grasses [Whitmar cultivar of bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Love), Hycrest cultivar of crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult. x A. cristatum (L.) Gaert.), and cheatgrass (Bromus tectorum L.)] was examined using a greenhouse split-root pot system with four nutrient treatments. Root branch spacing on the main root axis and first order roots and eight other root morphological and allocation traits were determined. A model of nutrient diffusivity was used to estimate root functional properties (exploitation efficiency and exploitation potential). Results showed a significant negative allometrid relationship between interbranch distances on the main roof axis and 1st order lateral roots (P<0.05), but only for bluebunch wheatgrass. Allometric relationships were found between main root axis interbranch distance and several root morphological traits (number of roots, root length, etc.) and root allocation traits (specific root length, root mass to volume ratio). Main axis interbranch distance was allometrically related to both exploitation efficiency and exploitation potential for first and second order roots, respectively. Results suggested that the degree to which the growth rules were followed depended on the particular root response strategies for soil nutrient acquisition in the three grasses. Thus, species such as bluebunch wheatgrass, which relies on a relatively fixed patern of root development rather than opportunistic root proliferation and rapid growth, exhibited coordinated allometry between root morphological and functional traits. Elucidation of these branching patterns under diverse environmental conditions will help facilitate more accurate simulation modeling of root growth.