Comparative Gas Exchange of Ulmus crassifolia (Cedar Elm, Ulmaceae) and Ungnadia speciosa (Mexican Buckey, Sapindaceae) at Ambient and Elevated Levels of Light, CO₂ and Temperature  

作　　者：Matthew B. Grunstra Oscar W. Van Auken Matthew B. Grunstra;Oscar W. Van Auken(Department of Integrative Biology, University of Texas at San Antonio, San Antonio, TX, USA)

机构地区：[1]Department of Integrative Biology, University of Texas at San Antonio, San Antonio, TX, USA

出　　处：《American Journal of Plant Sciences》2023年第6期691-709,共19页美国植物学期刊（英文）

摘　　要：Ulmus crassifolia Nutt. (Cedar elm, Ulmaceae) is a tree found in central and east Texas, northern Mexico, east to Florida, and north to southern Missouri and Oklahoma. Ungnadia speciosa Endl. (Mexican-buckeye, Sapindaceae) is a shrub or small tree found in woodlands and savannas of central and western Texas, southern New Mexico and northern Mexico. In central Texas, both species are found in Juniperus ashei/Quercus virginiana woodlands or savannas or also at low density in inter-canopy grassland gaps or patches. Environmental conditions in this area are stressful because of shallow soils, high summer temperatures, and inconsistent low rainfall. Currently, both species have a low density in these areas, and Ulmus crassifolia is usually a tree, while Ungnadia speciosa is a woody understory shrub. This study suggests U. crassifolia and U. speciosa are tolerant or intermediate species, with juveniles starting in shade. Maximum photosynthetic rate (A_max), dark respiration (R_d), intercellular CO₂, light saturation (L_sp) and water use efficiency significantly increased when light levels and CO₂ concentrations were elevated for both species, but not when temperatures were elevated. Stomatal conductance decreased when the CO₂ concentration doubled, but there were few effects from elevated temperature. These findings suggest that U. speciosa and U. crassifolia should be more common and imply that they will have a higher density in a future high CO₂ environment.Ulmus crassifolia Nutt. (Cedar elm, Ulmaceae) is a tree found in central and east Texas, northern Mexico, east to Florida, and north to southern Missouri and Oklahoma. Ungnadia speciosa Endl. (Mexican-buckeye, Sapindaceae) is a shrub or small tree found in woodlands and savannas of central and western Texas, southern New Mexico and northern Mexico. In central Texas, both species are found in Juniperus ashei/Quercus virginiana woodlands or savannas or also at low density in inter-canopy grassland gaps or patches. Environmental conditions in this area are stressful because of shallow soils, high summer temperatures, and inconsistent low rainfall. Currently, both species have a low density in these areas, and Ulmus crassifolia is usually a tree, while Ungnadia speciosa is a woody understory shrub. This study suggests U. crassifolia and U. speciosa are tolerant or intermediate species, with juveniles starting in shade. Maximum photosynthetic rate (A_max), dark respiration (R_d), intercellular CO₂, light saturation (L_sp) and water use efficiency significantly increased when light levels and CO₂ concentrations were elevated for both species, but not when temperatures were elevated. Stomatal conductance decreased when the CO₂ concentration doubled, but there were few effects from elevated temperature. These findings suggest that U. speciosa and U. crassifolia should be more common and imply that they will have a higher density in a future high CO₂ environment.

关 键 词：Light Response Gas Exchange Photosynthesis Respiration Water Use Efficiency 

分 类 号：S71[农业科学—林学]