Effects of vertically heterogeneous soil salinity on tomato photosynthesis and related physiological parameters
Sheng ChenZhenchang WangXiangping GuoGhulam RasoolJian ZhangYi XieAlhaj Hamoud YousefGuangcheng Shao
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Keywords:
Stomatal Conductance
DNS root zone
Soil horizon
The effects of different concentrations of cadmium(0,25,50,100,200 μmol/L) on the photosynthesis and chlorophyll fluorescence characteristics of cucumber seedlings were studied with a solution culture.The results showed that net photosynthetic rate(Pn),stomatal conductance(Gs) and transpiration rate(Tr) greatly decreased but intercellular CO2 concentration(Ci) showed no change at the 4th day of cadmium stress,relative chlorophyll content only decreased at 200 μmol/L cadmium treatment,while major PSII florescence parameters(the maximal photochemical efficiency of PSII Fv/Fm,the actual photochemical efficiency of PSII in the light Yield and electron transport rate ETR) did not change,indicating a stronger stomatal limitation in the decline of photosynthesis for those treatments with cadmium lower than 200 μmol/L.On the 8th day of cadmium,net photosynthetic rate,stomatal conductance and transpiration decreased more sharply with the increase of intercellular CO2 concentration(Ci),relative chlorophyll content and major fluorescence parameters except NPQ also decreased,implying a stronger nonstomatal limitation such as decreased chlorophyll content and destroyed PSII primary reaction.The lower value of main fluorescence parameters except NPQ at 50 μmol/L cadmium treatment on the 8th day might be related with serious Fe deficiency caused by cadmium stress.
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Muskmelon seedlings,cv.Huanghemi and Baishami,were employed to study the effect of NaCl stress on photosynthesis,chlorophyll contents and chlorophyll fluorescence parameters.The results indicated that net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),maximum photochemical efficiency of PSⅡ(Fv/Fm),potential activity of PSⅡ(Fv/Fo),quantum efficiency of non-cyclic electron transport of PSⅡ(ΦPSⅡ) and photochemical quenching(qP) decreased,while non-photochemical quenching(qN) increased under NaCl stress,especially under high concentrations in both varieties.When NaCl concentration was ≤50 mmol·L-1,intercellular CO2 concentration(Ci) decreased,while stomatal limitation value(Ls) increased.In contrast,Ci increased but Ls decreased when NaCl concentration was ≥100 mmol·L-1.The results indicated that photosynthesis of muskmelon was limited by stomatal factor under slight NaCl stress,but mainly by non-stomatal factors under severe NaCl stress.
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Taking the seedlings of Salvia miltiorrhiza cv. Sativa (SA) and S. miltiorrhiza cv. Silcestris (SI) as test materials, this paper studied the effects of drought stress on their leaf gas exchange and chlorophyll fluorescence parameters. After 15 days of drought stress, the net photosynthetic rate (P(n)) and the maximal photochemical efficiency of PS II (F(v)/F(m)) of SA were decreased by 66.42% and 10.98%, whereas those of SI were decreased by 29.32% and 5.47%, respectively, compared with the control, suggesting that drought stress had more obvious effects on the P(n) and F(v)/F(m) of SA than of SI. For SI, the reduction of P, under drought stress was mainly due to stomatal limitation; while for SA, it was mainly due to non-stomatal limitation. Drought led to a decrease of leaf stomatal conductance (G(s)), but induced the increase of water use efficiency (WUE), non-photochemical quenching coefficient (q(N)), and the ratio of photorespiration rate to net photosynthetic rate (P(r)/P(n)), resulting in the enhancement of drought resistance. The increment of WUE, q(N), and P(r)/P(n) was larger for SI than for SA, indicating that SI had a higher drought resistance capacity than SA.
Salvia miltiorrhiza
Photorespiration
Stomatal Conductance
Water Use Efficiency
Drought stress
Drought Resistance
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An image instrumentation system capable of quantitative analysis of chlorophyll (Chl) fluorescence images and thermal images was developed. Using this system, measurements of Chl fluorescence images and thermal images were performed on attached Cucumis sativus L. leaves during 10-3 M abscisic acid (ABA) treatment. Images of quenching parameters, such as qP, qN, NPQ and Yield were calculated from Chl fluorescence images obtained by the saturation pulse method. Images of stomatal conductance were computed by a method developed by Omasa et al. (1981) from leaf temperature images. Stomatal conductance immediately decreased by ABA treatment. However, the quenching parameters did not change during 75 min after the treatment, showing that ABA primarily induced a decrease in stomatal conductance and did not affect intercellular CO2 mole fraction (Ci). Following the 75 min period, the quenching parameters changed gradually. For example, photochemical efficiency of photosystem II decreased because of the declining CO2 supply to the site and the decrease in Ci in conjunction with the decrease in stomatal conductance. Consequently, it was shown that simultaneous use of Chl fluorescence image analysis and thermal image analysis was effective for analyzing the heterogeneous response and patchy distribution of stomatal aperture and photosynthesis.
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The effect of drought stress on the photosynthetic gas exchange parameters of twenty cocoa genotypes (Theobroma cacao L.) was examined under glasshouse conditions. Photosynthesis, chlorophyll fluorescence and stomatal conductance evaluated in 100% and 50% of the field capacity revealed significant differences between non-stressed and stressed plants and different genotypes. Among the genotypes, the percentage reduction in terms of photosynthetic rate (29.22 and 27.68% respectively), chlorophyll fluorescence (4.2 and 4.01% respectively) was low in VTLCH 3 and VTLCH 4 while the highest reduction in stomatal conductance (48.70 and 50%) and transpiration rate (57.81 and 56.80%) under stress regimes was also recorded in the same genotypes. Therefore, VTLCH 3 and VTLCH 4 were grouped as water stress tolerant genotypes based on the dynamics of gas exchange parameters. Thus, these two genotypes could be utilized for cultivation in Tamil Nadu condition and in further breeding programs.
Theobroma
Stomatal Conductance
Water Use Efficiency
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Stomatal Conductance
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Effects of Glutathione(GSH) with different concentrations on chlorophyll content(Chl),photosynthetic parameters and chlorophyll fluorescence parameters in leaves of pepper were investigated,using pepper varieties of 'Longjiao No.5' and 'Qicunhong' under autotoxicity.Results showed that Chl,net photosynthetic rate(Pn),stomatal conductance(Gs) and transpiration rate(Tr) declined sharply,but intercellular CO2 concentration(Ci) increased significantly after treated with leaf aqueous extracts of 50g·L-1.The contents of Chl,Pn,Gs and Tr increased,while Ci increased at first then decreased rapidly after treated with exogenous GSH,which suggested that Pn reduction was mainly due to non-stomatal factors.Maximum photochemical efficiency of PSII(Fv/Fm),maximal efficiency at open centers in the presence of NPQ(Fv′/Fm′) and actual quantum yield of PSⅡelectron transport(ФPSII) declined,but origin fluorescence(Fo) increased under autotoxicity.The peppers treated with GSH had higher Fv/Fm,Fv′/Fm′ and ФPSII,while Fo decreased significantly under different concentrations of GSH compared with those treated by water or leach liquor only.It was illustrated that exogenous GSH regulated the changes of leaf gas exchange and chlorophyll fluorescence parameters,especially,by preventing the accumulation of CO2 in the leaves which was associated with an improvement in the non-stomatal factors,then alleviated the barrier of continuous pepper cropping caused by autotoxicity.There were certain alleviate effects of exogenous GSH on the two varieties of peppers under autotoxicity,among the glutathione concentrations used,50 and 30 mg·L-1 were the optimum concentrations for 'Longjiao No.5' and 'Qicunhong',respectively.
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This experiment aimed to evaluate the leaf chlorophyll fluorescence and gas exchange response to drought conditions of young rubber plants with different scions. Buds from four genotypes of a progeny derived from crossed clones of RRIM600 x RRII105 from Nongkhai Rubber Research Center, T187, T186, T149 and T172, were grafted to RRIM 600 rootstocks. Eight-month old plants with two flushes were used in this study. Two levels of water treatment were used, drought condition (W 1 ) and well-watered as control (W 0 ). Leaf chlorophyll fluorescence, stomatal conductance (g s ) and net photosynthesis rate (Pn) were investigated in three phases: before drought, during drought and after re-watering. Leaf gas exchange parameters were measured using Li-6400 (LiCor Inc.). Leaf chlorophyll fluorescence was measured using FluorPen FP 100 (Photon Systems Instruments). Before drought, genotype T186 had the greatest net photosynthesis rates followed by T172, T187 and T149; there was no difference in maximum quantum yield of photosystem II (F v /F m ) and performance index on absorption basis (PI ABS ). Drought conditions caused reduction in stomatal conductance, net photosynthesis rates, and leaf chlorophyll fluorescence in all genotypes. In re-watering conditions, genotype T186 and T172 experienced quick recovery while the others showed partial recovery but the values of all parameters did not reach previous levels before treatment.
Stomatal Conductance
Water Use Efficiency
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