title: Effects of competition on induction of crassulacean acid metabolism in a facultative CAM plant.
abstract: Abiotic drivers of environmental stress have been found to induce CAM expression (nocturnal carboxylation) in facultative CAM species such as Mesembryanthemum crystallinum. The role played by biotic factors such as competition with non-CAM species in affecting CAM expression, however, remains largely understudied. This research investigated the effects of salt and water conditions on the competition between M. crystallinum and the C3grass Bromus mollis with which it is found to coexist in California's coastal grasslands. We also investigated the extent to which CAM expression in M. crystallinum was affected by the intensity of the competition with B. mollis. We found that M. crystallinum had a competitive advantage over B. mollis in drought and saline conditions, while B. mollis exerted strong competitive effects on M. crystallinum in access to light and soil nutrients in high water conditions. This strong competitive effect even outweighed the favorable effects of salt or water additions in increasing the biomass and productivity of M. crystallinum in mixture. Regardless of salt conditions, M. crystallinum did not switch to CAM photosynthesis in response to this strong competitive effect from B. mollis. Disturbance (i.e., grass cutting) reduced the competitive pressure by B. mollis and allowed for CAM expression in M. crystallinum when it was grown mixed with B. mollis. We suggest that moderate competition with other functional groups can enhance CAM expression in M. crystallinum, thereby affecting its plasticity and ability to cope with biological stress.
authors.affiliation: Department of Environmental Sciences, University of Virginia, Charlottesville, VA, 22904, USA. ky9hc@virginia.edu.
authors.forename: Kailiang
authors.initials: K
authors.lastname: Yu
authors.affiliation: Department of Environmental Sciences, University of Virginia, Charlottesville, VA, 22904, USA.
authors.forename: Paolo
authors.initials: P
authors.lastname: D'Odorico
authors.affiliation: Department of Environmental Sciences, University of Virginia, Charlottesville, VA, 22904, USA.|State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A and F University, Yangling, 712100, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Environmental Sciences, University of Virginia, Charlottesville, VA, 22904, USA.|Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou, 730000, China.
authors.forename: Yongli
authors.initials: Y
authors.lastname: He
mesh_terms: D002140:California; D035723:Mesembryanthemum / Q000378:metabolism*; D010788:Photosynthesis; D010944:Plants; D012965:Sodium Chloride; D013312:Stress, Physiological
chemical_list: D012965:Sodium Chloride
keywords: Bromus mollis; California’s coastal grasslands; Competition; Crassulacean acid metabolism; Drought; Grass cutting; Mesembryanthemum crystallinum; Soil salinity