Effects of soil drought stress on photosynthetic gas exchange traits and chlorophyll fluorescence in Forsythia suspensa

• Published in: Journal of forestry research Vol. 29; no. 1; pp. 45 - 53
• Main Authors: Lang, Ying, Wang, Ming, Xia, Jiangbao, Zhao, Qiankun
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2018; Springer; Springer Nature B.V; Shandong Provincial Key Laboratory of Water and Soil Conservation and Environmental Protection/College of Agriculture and Forestry Science, Linyi University,Linyi 276000, People's Republic of China%State Key Laboratory of Earth Surface Processes and Resource Ecology/Academy of Disaster Reduction and Emergency Management, Beijing Normal University,Beijing 100875, People's Republic of China%Shandong Provincial Key Laboratory of Eco-Environmental Science for Yellow River Delta, Binzhou University,Binzhou 256603, People's Republic of China%Linyi Agricultural Comprehensive Development Office, Linyi 276000, People's Republic of China
• Subjects: Analysis; Biomedical and Life Sciences; Carbon dioxide; Chlorophyll; Conductance; Dark adaptation; Drought; Droughts; energy; Fluorescence; Forestry; Forsythia suspensa; Gas exchange; heat; Heat exchange; Life Sciences; Moisture content; Original Paper; Photochemicals; Photochemistry; Photosynthesis; Photosynthetic apparatus; Photosystem II; Reduction; Resistance; seedling growth; Seedlings; Soil conditions; Soil management; Soil moisture; Soil stresses; Soil water; soil water content; Stomata; Stomatal conductance; Water content; Water deficit; Water management; water stress; Water use; water use efficiency; 叶绿素荧光;光合作用;土壤干旱;连翘属;植物;应力;PSII;气体; Chlorophyll fluorescence; Stomatal mechanism; Photosynthetic rate; Soil water deficit; Gas exchange; Water-use efficiency; Photosynthetic rate Soil water deficit
• ISSN: 1007-662X; 1993-0607
• DOI: 10.1007/s11676-017-0420-9

To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.