title: Effects of potassium supply on limitations of photosynthesis by mesophyll diffusion conductance in Carya cathayensis.
abstract: Potassium (K) influences the photosynthesis process in a number of ways; however, the mechanisms underlying the photosynthetic response to differences in K supply are not well understood. Concurrent measurements of gas exchange and chlorophyll fluorescence were made to investigate the effect of K nutrition on photosynthetic efficiency and mesophyll conductance (g(m)) in hickory seedlings (Carya cathayensis Sarg.) in a greenhouse. The results show that leaf K concentrations < 0.7-0.8% appeared to limit the leaf net CO2 assimilation rate (A), and that the relative limitation of photosynthesis due to g(m) and stomatal conductance (g(s)) decreased with increasing supplies of K. However, a sensitivity analysis indicated that A was most sensitive to the maximum carboxylation rate of Rubisco (V(c,max)) and the maximum rate of electron transport (J(max)). These results indicate that the photosynthetic rate is primarily limited by the biochemical processes of photosynthesis (V(c,max) and J(max)), rather than by g(m) and g(s) in K-deficient plants. Additionally, g(m) was closely correlated with g(s) and the leaf dry mass per unit area (M(A)) in hickory seedlings, which indicates that decreased g(m) and g(s) may be a consequence of leaf anatomical adaptation.
authors: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A & F University, Lin'an 311300, China. shjin@zafu.edu.cn
authors: Song Heng
authors: SH
authors: Jin
authors: Jian Qin
authors: JQ
authors: Huang
authors: Xue Qin
authors: XQ
authors: Li
authors: Bing Song
authors: BS
authors: Zheng
authors: Jia Sen
authors: JS
authors: Wu
authors: Zheng Jia
authors: ZJ
authors: Wang
authors: Gen Hua
authors: GH
authors: Liu
authors: Miao
authors: M
authors: Chen
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D031325:Carya / Q000378:metabolism*; D058503:Mesophyll Cells / Q000502:physiology; D010788:Photosynthesis; D011188:Potassium / Q000378:metabolism*; D036226:Seedlings / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D011188:Potassium