title: Aquaporins are major determinants of water use efficiency of rice plants in the field.
abstract: This study aimed at specifying the reasons of unbalanced water relations of rice in the field at midday which results in slowing down photosynthesis and reducing water use efficiency (WUE) in japonica and indica rice under well-watered and droughted conditions. Leaf relative water content (RWC) decreased in the well-watered plants at midday in the field, but more dramatically in the droughted indica (75.6 and 71.4%) than japonica cultivars (85.5 and 80.8%). Gas exchange was measured at three points during the day (9:00, 13:00 and 17:00). Leaf internal CO2 (Ci) was not depleted when midday stomatal depression was highest indicating that Ci was not limiting to photosynthesis. Most aquaporins were predominantly expressed in leaves suggesting higher water permeability in leaves than in roots. The expression of leaf aquaporins was further induced by drought at 9:00 without comparable responses in roots. The data suggest that aquaporin expression in the root endodermis was limiting to water uptake. Upon removal of the radial barriers to water flow in roots, transpiration increased instantly and photosynthesis increased after 4h resulting in increasing WUE after 4h, demonstrating that WUE in rice is largely limited by the inadequate aquaporin expression profiles in roots.
authors.affiliation: Department of Botany, Faculty of Science, Damietta University, New Damietta 34517, Egypt.
authors.forename: Reham M
authors.initials: RM
authors.lastname: Nada
authors.affiliation: Department of Botany, Faculty of Science, Damietta University, New Damietta 34517, Egypt. Electronic address: g.abogadallah@du.edu.eg.
authors.forename: Gaber M
authors.initials: GM
authors.lastname: Abogadallah
mesh_terms: D000222:Adaptation, Physiological; D020346:Aquaporins / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D055864:Droughts; D012275:Oryza / Q000145:classification / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D054046:Plant Stomata; D018526:Plant Transpiration; D013045:Species Specificity; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D014867:Water; D002245:Carbon Dioxide
keywords: Aquaporin expression; Gas exchange; Relative water content; Rice; Root clipping; Water use efficiency