Improvement of water-use efficiency of crops using symbiotic microorganisms: A potential sustainable approach to water management in cropping systems

Hyungmin Rho；Sharon Lafferty Doty；Soo-Hyung Kim

Plant-endophyte symbiosis ； Water relations ； Photosynthesis ； Respiration ； Water-use efficiency

臺中區農業改良場特刊

151號（2023 / 10 / 01）

86 - 122

英文

This study focuses on a collection of endophytes comprising plant-living bacteria and yeast isolated from native Salicaceae trees in Washington State of the United States. The article demonstrates the agricultural potential of these endophyte isolates through laboratory and greenhouse experiments conducted under abiotic stress conditions, highlighting their capacity for biological nitrogen fixation (BNF) and other growth-promoting traits. Among the various benefits observed, this article discusses explicitly the enhanced water use efficiency (WUE) observed in host plants that could be utilized in agricultural water management in cropping systems. Elite endophyte strains were carefully selected based on their growth-promoting characteristics, BNF capacity, and in vitro phytohormone production profiling, confirming their ability to synthesize ABA and other hormones. Furthermore, a consortium of these endophytes successfully colonized rice plants and significantly increased biomass under N-limited conditions. In a subsequent study on leaf physiology, rice leaves inoculated with the endophytes exhibited reduced stomatal conductance during the daytime and decreased stomatal density. These responses were likely attributed to increased ABA content in the inoculated plants, resulting in reduced transpiration and improved WUE without compromising photosynthetic capacity. Even with less opening stomata the inoculated rice plants were able to maintain photosynthetic capacity. This may due to re-assimilation of respiratory CO2 from the endophytes. Additionally, the endophytes facilitated electron transfer and CO2 diffusion in rice leaves, particularly under elevated CO2 conditions. These findings suggest that the enhanced WUE conferred by endophytes is closely related to stomatal responses in the host plant. The effects were particularly pronounced under N-limited, drought stress, and elevated CO2 conditions. However, the specific contribution of increased ABA synthesis, CO2 re-assimilation, or both remains unclear, necessitating further mechanistic investigation.