Although the beneficial role of Fe, Zn, and Mn on many physiological and biochemical processes is well established, effects of each of these elements on chlorophyll (Chl) a fluorescence and photosynthetic pigment contents is not well studied. The objective of this study was to evaluate effects of Fe, Zn, and Mn deficiency in two lettuce cultivars. The parameters investigated could serve also as physiological and biochemical markers in order to identify stress-tolerant cultivars. Our results indicated that microelement shortage significantly decreased contents of photosynthetic pigments in both lettuce cultivars. Chl a fluorescence parameters including maximal quantum yield of PSII photochemistry and performance index decreased under micronutrient deficiency, while relative variable fluorescence at J-step and minimal fluorescence yield of the dark-adapted state increased under such conditions in both cultivars. Micronutrient deficiency also reduced all parameters of quantum yield and specific energy fluxes excluding quantum yield of energy dissipation, quantum yield of reduction of end electron acceptors at the PSI, and total performance index for the photochemical activity. Osmoregulators, such as proline, soluble sugar, and total phenols were enhanced in plants grown under micronutrient deficiency. Fe, Zn, and Mn deficiency led to a lesser production of dry mass. The Fe deficiency was more destructive than that of Zn and Mn on the efficiency of PSII in both lettuce cultivars. Our results suggest that the leaf lettuce, which showed a higher efficiency of PSII, electron transport, quantum yield, specific energy fluxes, and osmoregulators under micronutrient deficiency, was more tolerant to stress conditions than crisphead lettuce., H. R. Roosta, A. Estaji, F. Niknam., and Obsahuje bibliografii
The aim of this study was to evaluate the photochemistry of Luffa cylindrica (L.) Roem in fungal biocontrol interacting treatments. Healthy plants were infected with Pythium aphanidermatum before the biocontrol application. Biocontrol agents were selected in preliminary Petri-plate experiment evaluation against causative agent P. aphanidermatum. Photosynthetic performance traits were studied. We found that P. aphanidermatum infection caused significant reduction in photosynthetic performance, pigments, and in maximum quantum yield of primary photochemistry, photochemical quenching, and electron transport rate with increase in nonphotochemical quenching as compared with non-infected control. However, application of biocontrol agents substantially improved maximum quantum yield of PSII, performance index, and total content of photosynthetic pigments in infected plants. The fluorescence intensity was used for quantifying the antagonist effect of biocontrol agents on infected plant leaves., H. Amrina, S. Shahzad, Z. S. Siddiqui., and Obsahuje bibliografii
Salicylic acid (SA) and nitric oxide (NO) form a new group of plant growth substances that cooperatively interact to promote plant growth and productivity. Water deficit (WD) stress is a major limiting factor for photosynthesis, which in turn limits crop yield. However, the mechanism of SA and NO in stimulating photosynthesis has not yet been elucidated. Therefore, in this study, we investigated the SA- and NO-mediated photosynthetic adaptability of maize seedlings to WD in terms of photosynthetic parameters, activities and mRNA levels of CO2 assimilation enzymes. Our results showed that SA alleviated the WD-induced reduction of photosynthetic performance. The activities of Rubisco and Rubisco activase enzymes increased significantly due to SA pretreatment. Moreover, higher transcription rates of Rbc L, ZmRCAα and ZmRCAβ mRNA further confirmed the effects of SA on CO2 assimilation. WD or SA-induced decreases or increases of CO2 assimilation ability were further decreased after c-PTIO addition., R. X. Shao, L. F. Xin, J. M. Guo, H. F. Zheng, J. Mao, X.P. Han, L. Jia, S. J. Jia, C. G. Du, R. Song, Q. H. Yang, R. W. Elmore., and Obsahuje bibliografii