Grant: Discovery Launch Supplement

Carbon dioxide (CO2) concentration in the atmosphere is predicted to reach 550 ppm by 2050. However, yield increase in plants under long-term exposure to high CO2 (HC) is far below expectations. This poses a major challenge for global food production. The less-than-predicted yield increase is generally attributed to inhibition of photosynthesis at HC. However, I found that overall plant growth is more sensitive to changes in leaf growth than to changes in photosynthesis. While plant growth depends on carbon (C) derived from photosynthesis, the degree to which a plant can grow depends on the amount of carbon partitioned towards leaf expansion (area growth) versus "thickening" (leaf mass per unit area or LMA). An increase in leaf area over LMA results in a lower number of cells per unit area and reduced respiratory costs. Larger leaf area also increases light interception, whole plant C gain, and C available for growth and reproduction. I hypothesize that HC induces opposite trends and reduces C available for growth as plants grown under HC produce smaller and thicker leaves. The HC-induced signaling pathway that alters leaf growth is not known. I propose that limitations to the genetic potential for leaf area growth is a key factor in determining plant growth and productivity under HC. Identifying the signaling pathways and cell wall-modifying enzymes (CWMEs) that modulate leaf growth under HC will provide tools to optimize leaf area growth and maximize plant growth and yield under future climates. The long-term goal of my research program is to discover strategies to enhance plant growth, productivity and resilience to stress under future climate conditions. In the next five years, I will focus on three short-term objectives: Objective 1: Characterizing the effects of HC on leaf area growth and its consequences on plant growth and reproduction. Objective 2: Determining the underlying signaling mechanism(s) through which HC affects leaf growth, and the CWMEs involved in this process. Objective 3: Investigating whether enhanced genetic potential for leaf area growth provides a strategy to (a) increase whole plant C gain, C available for growth and overall plant growth and productivity under long-term exposure to HC, and (b) minimize feed-back inhibition of photosynthesis under short-term and long-term exposure to HC. My research program will discover HC-induced signaling pathways that alter leaf area growth, and how enhancing the genetic potential for leaf area growth can be used as a strategy to improve whole plant C gain, overall plant growth and productivity under future climate conditions. CWMEs characterized during this research will serve as tools to optimize leaf growth and yield in important crops such as canola and soybean; this can have a profound positive impact on Canada's agriculture and food production. The proposed program will directly support training of three graduate students and five undergraduates at Bishop's University.