Location: Water Management and Systems Research
Project Number: 3012-13000-010-17-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2020
End Date: Aug 31, 2021
The long-term goals of this cooperative research project are: 1) Determine what internal (xylem conduit) and external (branching, venation patterns) water transport traits allow plants to operate at lower water potential and/or improve water transport efficiency. 2) Determine the optimal coordination of xylem, stomata, and leaf traits that will maximize either seasonally-integrated water use efficiency, or soil water extraction, which are the cornerstone traits of drought tolerance and drought avoidance. 3) Determine the physiological costs and risks (i.e., tradeoffs) that arise when xylem, stomata, and leaf traits are manipulated to improve water use efficiency or soil water extraction.
The Cooperator and USDA-ARS scientists will work closely together to design experiments (field, greenhouse, growth chamber), build and evaluate computer models, and develop theory to advance our understanding how crop plants should be modified to improve their performance under water limited conditions. - Objective 1 approach. Existing hydraulic network models will be used to assess the impact of manipulating (via breeding and gene editing) the conduit properties of plant xylem (e.g., conduit size, length, connectivity) on the efficiency of water transport (supply of water to photosynthesis) and the safety of the water transport system when exposed to drought (low apoplast pressure). - Objective 2 approach. Continue to improve and use the TREES model (whole-plant growth) to make predictions about how plant traits should be manipulated to improve performance under a range of soil and climate conditions that are experience by farmers. The model will be used to manipulate (in silico) key physiological traits (photosynthesis, roots, xylem, stomata), and the connections between these traits, to recommend breeding and gene editing targets that are likely to result in improved performance. Phenotypic data will also be collected from existing plant breeding populations to compare model predictions with trait variation across existing genotypes. The aim of this research will be to identify key traits of the vascular system that can be manipulated to improve performance under specific conditions. - Objective 3 approach. Although modeling efforts can inform us about the benefits of specific trait networks on performance, the costs and risks associated with modifying plant traits (e.g., hydraulic efficiency) are poorly understood and require experimentation on real plants. Our approach to this question will involve measuring respiratory costs and risks (e.g., conduit embolization) that are associated with specific trait manipulations, including but not limited to 1) increasing xylem conduit size, 2) whole-xylem conductivity, 3) conduit wall thickness, and 4) poor alignment between stomatal functioning and water supply (via roots and xylem). These experiments will be carried out in greenhouse, growth chamber and field settings.