Salicaceae endophyte inoculation alters stomatal patterning and improves the intrinsic water-use efficiency ofPopulus trichocarpaafter a water-deficit

Abstract

ABSTRACTMicroorganisms may enhance plant resilience to water stress by influencing their hosts’ physiology and anatomy at the leaf-level. Bacterial and yeast endophytes, isolated from wild poplar and willow, can improve the intrinsic water-use efficiency (iWUE) of cultivated poplar (Populus) under water-deficits by lowering stomatal conductance (gsw). However, the relevance of stomatal anatomy underlying this reduction remains unclear. We hypothesized endophyte inoculation could change host stomatal anatomy, and this would relate to decreases ingsw. We subjected Salicaceae endophyte-inoculated and uninoculatedPopulus trichocarpato well-watered and water-deficit treatments in greenhouse studies. We examined the changes of individual stomatal traits and related the composition of these parameters, termed stomatal patterning, to leaf gas-exchange under light saturation. After a water-deficit, inoculation improvediWUEat light saturation from preserving carbon assimilation (Anet) and loweringgsw, but these changes were independent of soil-moisture status. Drops ingswcorresponded to underlying shifts in stomatal patterning. Inoculated plants had smaller, more compact stomata and greater anatomical maximum stomatal conductance (gsmax) relative to the control. Salicaceae endophytes may alter stomatal density and size, loweringgswand increasingiWUE. Future efforts may quantify endophyte colonization of the host to draw direct relationships between microbes and stomatal traits.HIGHLIGHTPoplars inoculated with specific bacteria had leaves containing many, tiny pores relative to the trees without the microbes; these plants with the small, dense pores related to greater intrinsic water-use efficiency.