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
The effects of various concentrations of bensulfuron-methyl residues (BSM, 0-500 μg kg-1) on the growth and photosynthesis of soybean and peanut were studied. Shoot length, root length, root-to-shoot ratio, and biomass of soybean and peanut seedlings declined with the increase of BSM residue concentrations. As the concentration of BSM increased, SPAD value, net photosynthetic rate, stomatal limitation, stomatal conductance, and transpiration rate also declined with varying extent, but dark respiration rate and intercellular CO2 concentration increased gradually. PSII maximum quantum yield, actual quantum yield, and electron transport rate were significantly reduced by the BSM residues in soil, and the reduction was mostly attributed to the decrease in photochemical quenching coefficient. The results showed that photosynthesis in both crops was limited by nonstomatal factors. The residues of BSM caused reversible damage in PSII reaction centers and decrease the proportion of available excitation energy used for photochemistry., W. C. Su, L. L. Sun, Y. H. Ge, R. H. Wu, H. L. Xu, C. T. Lu., and Obsahuje bibliografii