Diffusional conductance to CO₂ is the key limitation to photosynthesis in salt-stressed leaves of rice (Oryza sativa)

Abstract

Salinity significantly limits leaf photosynthesis but the photosynthetic limiting factors in salt- stressed leaves remain unclear. In the present work, photosynthetic and biochemical traits were investigated in four rice genotypes under two NaCl (0 and 150 mM) concentration to assess the stomatal, mesophyll and biochemical contributions to reduced photosynthetic rate (A) in salt stressed leaves. Our results indicated that salinity led to a decrease in A, leaf osmotic potential, electron transport rate and CO2 concentrations in the chloroplasts (Cc) of rice leaves. Decreased A in salt-stressed leaves was mainly attributable to low Cc, which was determined by stomatal and mesophyll conductance. The increased stomatal limitation was mainly related to the low leaf osmotic potential caused by soil salinity. However, the increased mesophyll limitation in salt stressed leaves was related to both osmotic stress and ion stress. These findings highlight the importance of considering mesophyll conductance when developing salinity-tolerant rice cultivars.AbbreviationsAphotosynthetic rateCc, CO2concentration at carboxylation sitesCEapparent Rubisco activityChltotal chlorophyll contentCiintercellular CO2 concentrationETRelectron transport rateF0initial fluorescence of photosystem II in darknessFmmaximum fluorescence of photosystem IIFvmaximum variable fluorescence of photosystem IIFv/Fmmaximum quantum efficiency of photosystem IIgmmesophyll conductiongsstomatal conductionJmaxmaximum electron transport rateKleaf K contentLMAleaf mass per areaNleaf N contentPleaf P contentOPosmotic potentialProteinleaf total soluble protein contentqNnon-chemical quenching efficiencyRdday respirationRdarkdark respirationRubiscoRubisco contentVcmaxmaximum carboxylation rateαleaf light absorptance efficiencyβthe distribution of electrons between PSI and PSIIΓ*CO2 compensation point in the absence of respirationΦPSIIquantum efficiency of photosystem II.

Fast photosynthesis measurements for phenotyping photosynthetic capacity of rice

“…where, Φ PSII is the actual photochemical efficiency of photosystem II, α is the leaf absorptivity and β is the partitioning of absorbed quanta between photosystems II and I. In the current study, the αβ value of 0.44 was used based on the previous studies [38,41].…”

“…where A is the photosynthetic rate at PPFD of 1500 μmol m −2 s −1 , C i is the CO 2 mol fraction in the intercellular air space, Γ * represents the CO 2 compensation point in the absence of mitochondrial respiration and R d is the daytime respiration rate. Typical values of 40 μmol mol −1 and 1 μmol m −2 s −1 were used for Γ * and R d , respectively [38]. For each data point generated, we checked whether it met the criterion (10 > dC c /dA > 50) [14].…”

Mesophyll conductance in land surface models: effects on photosynthesis and transpiration

“…The effects of C i and light on g m in a LSM have so far only been tested once by adding empirical response functions to Equation (6) (Figure d,e; Knauer et al , ). Other factors such as salt stress (Delfine et al , ; Wang et al , ) and ozone (Xu et al , ) have been reported to negatively affect g m instantaneously, but these stressors are not always considered in LSMs and have not yet been investigated with respect to g m . On longer time scales (weeks to years) g m is affected by nutrient availability (Jin et al , ; Yamori et al , ) and leaf age (Warren, ; Yin et al , ).…”

The interactive responses of fertigation levels under buried straw layer on growth, physiological traits and fruit yield in tomato plant

“…Photosynthesis is the key physiological process of plants and can provide 90% of plant biomass (Wang et al 2018). Leaves are the main contributors to the crop productivity (Ashraf and Bashir 2003), and their photosynthetic activities are crucial significantly for harvestable fruit yield.…”