CAREER: Water movement in leaves and roots of C3 and C4 grasses: mechanisms, coordination and impact on whole plant growth during soil and atmospheric drought

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Two major challenges in plant sciences are to understand the mechanisms leading to the decline in plant growth during drought and pinpoint traits that enable some plants to be more drought resistant than others. Identifying these traits can help inform crop breeders in the development of drought tolerant crops. Research addressing these challenges is needed for grasses, which dominate about 40% of terrestrial surfaces and include some of the most important crops, such as cereals and forage grasses. Grasses are particularly interesting as they exhibit unique diversity in their photosynthetic machinery, and it remains unclear how this diversity relates to differences in plant water movement during soil and atmospheric drought. The goal of this research is to unravel the specific mechanisms which lead photosynthetically diverse crop grasses to decline in growth during drought and how they recover upon re-watering. This work will focus on disentangling the root and leaf responses of diverse grasses during soil and atmospheric drought using cutting-edge imaging techniques, new physiological approaches and modelling. The project will integrate a plan of research and education at a minority-serving undergraduate institution in East Los Angeles— one of the largest concentrations of ethnic minority groups in the nation. Research-like modules integrated throughout the undergraduate curriculum will expose 240 students/year to experimental design and critical thinking in plant sciences. Outreach activities led by undergraduate students will help inspire students at underserved schools of East Los Angeles into higher education and plant sciences.This project seeks to rigorously test mechanisms underlying the coordination in leaf and root hydraulic conductance of C3 and C4 grasses during soil and atmospheric drought and subsequent recovery. Three specific objectives will be carried out: (1) Determine the coordination in leaf and root hydraulic decline with stomatal conductance during dehydration and the underlying mechanisms leading to their decline; (2) Quantify the effects of grass vein anatomy and biochemistry on leaf and root hydraulic conductance during dehydration and rehydration using rice mutants; (3) Achieve a new integrated understanding of the effects of soil and atmospheric drought on leaf and root hydraulic conductance and their impact on plant growth. To carry out these objectives, a large suite of physiological and anatomical traits including leaf and root hydraulics and gas exchange and cutting-edge imaging techniques will be performed on 12 diverse C3 and C4 grasses, and 11 rice aquaporin and vein mutants and their wild type growing in a greenhouse under different soil and atmospheric drought conditions. Simulations using spatially-explicit and whole plant modelling will be employed to test the causality behind specific hypotheses. This work will create new concepts and essential data to help improve predictive models of plant growth and responses to climate change. The educational plan will help transform the experience of students at CSULA, a minority serving institution, through research-infused lectures, a Course Undergraduate Research Experience and student-led outreach activities at local underserved schools.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.