Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis in the field conditions under both ambient and higher temperature. Six diverse cotton cultivars were grown in the field at Stoneville, MS under both an ambient and a high temperature regime during the 2006-2008 growing seasons. Mid-season leaf net photosynthetic rates (PN) and dark-adapted chlorophyll fluorescence variable to maximal ratios (Fv/Fm) were determined on two leaves per plot. Temperature regimes did not have a significant effect on either PN or Fv/Fm. In 2006, however, there was a significant cultivar × temperature interaction for PN caused by PeeDee 3 having a lower PN under the high temperature regime. Other cultivars' PN were not affected by temperature. FM 800BR cultivar consistently had a higher PN across the years of the study. Despite demonstrating a higher leaf Fv/Fm, ST 5599BR exhibited a lower PN than the other cultivars. Although genetic variability was detected in photosynthesis and heat tolerance, the differences found were probably too small and inconsistent to be useful for a breeding program., W. T. Pettigrew., and Obsahuje bibliografii
The objective of this study was to investigate a response to low-light environments in hybrids and commercial cultivars of Boehmeria nivea L. Two hybrids (Chuanzhu 11 and Chuanzhu 8) and two commercial cultivars (Chuanzhu 12 and Chuanzhu 6) of ramie were subjected to a shade treatment for 6, 12, and 18 days. The shade treatment led to a significant decrease in some plant traits and fiber yield in four ramie cultivars, whereas their leaf area and plant height increased. In addition, net photosynthesis and stomatal conductance significantly declined in response to shade, while transpiration rate and intercellular CO2 did not significantly change. Moreover, chlorophyll (Chl) and carotenoid (Car) concentration, Chl/Car, and Chl (a+b) per leaf dry mass significantly increased in the response to shade, while the Chl a/b ratio decreased. Furthermore, Chuanzhu 6 and Chuanzhu 11 were more tolerant to shade than Chuanzhu 12 and Chuanzhu 8, thus, they could be potentially used for management practices and breeding programs., C.-J. Huang, G. Wei, Y.-C. Jie, J.-J. Xu, S. A. Anjum, M. Tanveer., and Seznam literatury
The effects of calcium chloride solution (10 mmol L-1) on mesophyll cell ultrastructure, gas exchange, chlorophyll and carotenoid content, and PSII in tobacco leaf were studied by simulating water deficit conditions via treatment with 25% PEG-6000 for 24 h. The results showed that under drought stress, the mesophyll cell structure and morphology were destroyed, photosynthesis and gas-exchange processes changed, photosynthetic pigment content decreased, and the electron transfer efficiency in PSII reduced. However, compared with the control treatment, under drought conditions, the addition of exogenous calcium could stabilize the structure and function of the chloroplasts, mitochondria, and endomembrane system in the mesophyll cells, maintain normal leaf net photosynthetic rate and gas exchange, alleviate the degree of photosynthetic pigment degradation, and increase the electron transfer energy in the leaves in PSII. As a means of ensuring normal photosynthesis under drought stress, we discovered that the application of exogenous calcium was more important for stabilization of the structure of the organelles, regulation of the osmotic balance, and increase of the photosynthetic pigment content, and proved to be less important for regulation of stomatal opening and closing., W. Hu, S. B. Tian, Q. Di, S. H. Duan, K. Dai., and Obsahuje bibliografii
The effects of exogenous sodium nitroprusside (SNP), as nitric oxide donor, and spermidine (Spd) on growth and photosynthetic characteristics of Bakraii seedlings (Citrus reticulata x Citrus limetta) were studied under NaCl stress. In citrus plants, SNP- and Spd-induced growth improvement was found to be associated with reduced electrolyte leakage, malondialdehyde, hydrogen peroxide content, and leaf Na+ and Cl- concentration. However, we found increased leaf Ca2+, Mg2+, and K+ concentrations, relative water content, chlorophyll fluorescence parameters, antioxidant enzyme activities, such as ascorbate peroxidase, catalase, superoxide dismutase and peroxidase, as well as higher photosynthetic rate, intercellular CO2 concentration, stomatal conductance, and transpiration rate under saline regime. Foliar application of SNP and Spd alone mitigated the adverse effect of salinity, while the combined application proved to be even more effective., D. Khoshbakht, M. R. Asghari, M. Haghighi., and Obsahuje bibliografii
The effects of soil and water contamination by lead (Pb) and the consequences on plant growth and yield are of great concern worldwide. Limits of the Pb concentration in water have been established by governmental institutions but these differ from each other. In this study, Lactuca sativa (var. Reine de Mai) plants were exposed to low Pb(NO3)2 doses (0.05-20 mg L-1), including the recommended limit values for irrigation water by the Food and Agriculture Organization (FAO). After 28 d of exposure, lettuce plants did not present visible morphological alterations or growth impairment, but CO2 assimilation rate (PN), photochemical quenching, and effective quantum efficiency of PSII were negatively affected, while intercellular CO2 concentration, stomatal conductance, or transpiration rate were not influenced. Our results suggested that limitations on photosynthesis occurred from different reasons than due to the decrease of internal CO2 availability, alterations of photophosphorylation, and/or electron transport rate. Thus, this lettuce cultivar showed photosynthetic susceptibility to low doses of Pb, even at lower concentrations than those maximal allowed for irrigation water by FAO. Furthermore, PN seemed to be the most sensitive biomarker for evaluation of Pb susceptibility., S. Silva, G. Pinto, C. Santos., and Obsahuje bibliografii
Anastatica hierochuntica is an annual desert plant, which was recently shown to have unusually low nonphotochemical quenching (NPQ) and a high PSII electron transport rate (ETR). In the current study, we examined how these unusual characteristics are related to a lack of CO2 and inhibition of net photosynthetic rate (P N). We compared the photosynthetic and photoprotective response of A. hierochuntica and sunflower (Helianthus annuus), under conditions of photosynthetic inhibition, with either low CO2 or drought. We found that under nonsteady state conditions of low CO2 availability, A. hierochuntica exhibited about half of the NPQ values and almost twice of the ETR values of H. annuus. However, the long-term inhibition of P N under drought caused a similar increase in NPQ and a decrease in ETR in both A. hierochuntica and H. annuus. These results suggest that the unusually low NPQ and high ETR in A. hierochuntica are not directly related to a response to drought conditions., A. Eppel, S. Rachmilevitch., and Obsahuje seznam literatury
Alterations in photosynthetic performance of lutein-deficient mutant lut2 and wild type (wt) of Arabidopsis thaliana were followed after treatment with low temperature and high light for 6 d. The obtained results indicated lower electrolyte leakage, lower excitation pressure, and higher actual photochemical efficiency of PSII in lut2 plants exposed to combined stress compared to wt plants. This implies that lut2 is less susceptible to the applied stress conditions. The observed lower values of quantum efficiency of nonphotochemical quenching and energy-dependent component of nonphotochemical quenching in lut2 suggest that nonphotochemical quenching mechanism(s) localized within LHCII could not be involved in the acquisition of higher stress tolerance of lut2 and alternatives to nonphotochemical quenching mechanisms are involved for dissipation of excess absorbed light. We suggest that the observed enhanced capacity for cyclic electron flow and the higher oxidation state of P700 (P700+), which suggests PSI-dependent energy quenching in lut2 plants may serve as efficient photoprotective mechanisms, thus explaining the lower susceptibility of lut2 to the combined stress treatments.
The sustainable production of upland cotton, an economically important fiber crop, is threatened by changing environmental factors including high temperatures and low-soil water content. Both high heat and low-soil water can reduce net photosynthesis resulting in low fiber yields or poor fiber quality. Leaf chlorophyll content has a direct relationship with photosynthetic rate. Understanding how high heat and low-soil water affect chlorophyll content can identify opportunities for breeding improvement that will lead to sustainable fiber yields. A two-year field trial located in Maricopa Arizona measured leaf chlorophyll content, available soil water, ambient air temperatures, and cotton growth measurements collected by a high-clearance tractor equipped with proximal sensors. The results showed that low-soil water significantly increased leaf chlorophyll content, while high temperatures significantly reduced content. Structured equation modeling revealed that cotton may divert available resources to leaf area and chlorophyll content for the production of photosynthates during periods of high temperatures.
Ramie (Boehmeria nivea L.) is an important crop that serves as fine fiber material, high protein feedstuff, and valuable herbal medicine in China. However, increasing salinity in soil limits the productivity. We investigated in a greenhouse experiment responses to salinity in two ramie cultivars, Chuanzhu-12 (salt-tolerant cultivar, ST) and Xiangzhu-2 (salt-sensitive cultivar, SS), to elucidate the salt tolerance mechanism of this species. Salinity stress substantially reduced both chlorophyll and carotenoid contents. In addition, net photosynthesis, transpiration rate, stomatal conductance, intercellular CO2 concentration, and the ratio of intercellular CO2 to ambient CO2 were affected, less in ST. Nevertheless, salinity stress markedly improved water use efficiency and intrinsic water use efficiency in both species. Moreover, relative water contents, soluble proteins, and catalase activity were substantially impaired, while proline accumulation and superoxide dismutase activity were enhanced substantially, more in ST. Furthermore, noteworthy increase in peroxidase activity and decrease in malondialdehyde content was recorded in ST, whereas, in SS, these attributes changed conversely. Overall, the cultivar ST exhibited salt tolerance due to its higher photosynthetic capacity, chlorophyll content, antioxidative enzyme activity, and nonenzymatic antioxidants, as well as reduced lipid peroxidation and maintenance of the tissue water content. This revealed the salt tolerance mechanism of ramie plants for adaptation to salt affected soil., C.-J. Huang, G. Wei, Y.-C. Jie , J.-J. Xu, S.-Y. Zhao, L.-C. Wang, S. A. Anjum., and Obsahuje seznam literatury
This study investigated whether gas exchange and the present content of antioxidant compounds can contribute to the survival of Euterpe oleracea plants in environments of frequent waterlogging. A factorial randomised, experimental design included two distinct water conditions (waterlogging and control) and five evaluation times (0, 6, 12, 18, and 24 d). Gasexchange parameters, leaf temperature, electrolyte leakage, and contents of antioxidant compounds were measured. Waterlogging did not promote significant alterations in net photosynthetic rate and transpiration, and stomatal conductance was reduced only after 18 d. Malondialdehyde and glutathione contents did not significantly change during waterlogging. Additionally, electrolyte leakage was significant only after 18 d of waterlogging. Thus, this study revealed that maintenance in gas exchange and antioxidant compounds might contribute to the survival of E. oleracea plants in environments exposed to waterlogging., T. S. Pereira, A. K. S. Lobato, G.A.R. Alves, R.N. Ferreira, O.N. Silva, A. P. Martins Filho, E.S. Pereira, L.S. Sampaio., and Obsahuje bibliografii