Quantitative limitations to photosynthesis in K deficient sunflower and their implications on water-use efficiency

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• 作者：Bá ; lint Já ; kli^a ; ^{balint.jakli@yahoo.com} ; Ershad Tavakol^a ; Merle Trä ; nkner^a ; Mehmet Senbayram^a ; ¹ ; Klaus Dittert^a ; ^b
• 关键词：AN ; net assimilation ; Cc ; CO2 concentration in chloroplasts ; Ci ; intercellular CO2 concentration ; Fv/Fm ; maximum quantum yield of photosystem II ; gm ; mesophyll conductance ; gs ; stomatal conductance ; gtot ; total conductance ; Lb ; biochemical limitation ; Lm ; mesophyll limitation ; Ls ; stomatal limitation ; NPQ ; non-photochemical quenching ; PEG ; polyethylene glycol 6000 ; Vc ; max ; maximum carboxylation velocity of RubisCo ; WUEL ; leaf water-use efficiency ; WUEP ; plant water-use efficiency ; ΦII ; effective
• 刊名：Journal of Plant Physiology
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：209
• 期：Complete
• 页码：20-30
• 全文大小：1978 K
• 卷排序：209

文摘

Potassium (K) is crucial for crop growth and is strongly related to stress tolerance and water-use efficiency (WUE). A major physiological effect of K deficiency is the inhibition of net CO2 assimilation (AN) during photosynthesis. Whether this reduction originates from limitations either to photochemical energy conversion or biochemical CO2 fixation or from a limitation to CO2 diffusion through stomata and the leaf mesophyll is debated. In this study, limitations to photosynthetic carbon gain of sunflower (Helianthus annuus L.) under K deficiency and PEG- induced water deficit were quantified and their implications on plant- and leaf-scale WUE (WUEP, WUEL) were evaluated. Results show that neither maximum quantum use efficiency (Fv/Fm) nor in-vivo RubisCo activity were directly affected by K deficiency and that the observed impairment of AN was primarily due to decreased CO2 mesophyll conductance (gm). K deficiency additionally impaired leaf area development which, together with reduced AN, resulted in inhibition of plant growth and a reduction of WUEP. Contrastingly, WUEL was not affected by K supply which indicated no inhibition of stomatal control. PEG-stress further impeded AN by stomatal closure and resulted in enhanced WUEL and high oxidative stress. It can be concluded from this study that reduction of gm is a major response of leaves to K deficiency, possibly due to changes in leaf anatomy, which negatively affects AN and contributes to the typical symptoms like oxidative stress, growth inhibition and reduced WUEP.