We investigated the photosynthesis and leaf development of cherry tomato seedlings grown under five different combinations of red and blue light provided by light-emitting diodes (LEDs). Fresh biomass increased significantly under treatments with blue light percentages of 50, 60, and 75%, with 50% blue-light-grown seedlings accumulating significantly more dry mass. The 25% blue-light-grown seedlings were obviously weaker than those from the other LED treatments. An increase in net photosynthetic rate upon blue light exposure (25-60%) was associated with increases in leaf mass per unit leaf area, leaf area, leaf density, stomatal number, chloroplast and mesophyll cell development, and chlorophyll contents. Our results imply that photosynthesis and leaf development in cherry tomato seedlings are associated with both the proportion and quantity of blue light., X. Y. Liu, X. L. Jiao, T. T. Chang, S. R. Guo, Z. G. Xu., 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
Nicosulfuron is a post-emergence herbicide used for weed control in fields of maize (Zea mays L.). We used a pair of nearly isogenic inbred lines, SN509-R (nicosulfuron-resistant) and SN509-S (nicosulfuron-sensitive), to study the effect of nicosulfuron on waxy maize seedling. After the nicosulfuron treatment, net photosynthetic rate, stomatal conductance, transpiration rate, leaf maximum photochemical efficiency of PSII, photochemical quenching of chlorophyll fluorescence, and the actual photochemical efficiency of PSII were significantly lower in SN509-S than those of SN509-R, contrary to intercellular CO2 concentration, stomatal limitation, and nonphotochemical quenching. Compared to SN509-R, antioxidant enzyme activities in SN509-S decreased significantly in response to the nicosulfuron treatment, while SN509-S exhibited an increased malondialdehyde content, which was associated with lower antioxidant enzyme activities. These results collectively suggest that the nicosulfuron-resistance mechanism was associated with photosynthetic rate, reactive oxygen species metabolism, and protective mechanisms., J. Wang, X. M. Zhong, X. L. Lv, Z. S. Shi, F. H. Li., and Obsahuje bibliografii
Photosynthesis has walked into the path of evolution for over millions of years. Organisms relying directly on photosynthesis, when subjected to adverse environments for a long duration, experience retardation in their growth and development. Salinity stress is perceived as one of the major threats to agriculture as it can cause an irreversible damage to the photosynthetic apparatus at any developmental stage of the plant. However, halophytes, a special category of plants, carry out all life processes, including photosynthesis, without showing any compromise even under high saline environments. The fascinating mechanism for Na+ exclusion from cytosol besides retaining photosynthetic efficiency in halophytes can provide a valuable genetic resource for improving salt stress tolerance in glycophytes. Understanding how plants stabilize their photosynthetic machinery and maintain the carbon balance under saline conditions can be extremely useful in designing crops for saline and dry lands., S. Wungrampha, R. Joshi, S. L. Singla-Pareek, A. Pareek., and Obsahuje bibliografické odkazy
The microstructure of leaves and ultrastructure of chloroplasts were examined in tomato (Lycopersicon esculentum L.) plants treated with elevated temperature. Plants were exposed to 35°C for 30 d after florescence. The plants grown continuously under 25°C served as controls. Compared with the controls, the net photosynthetic rate (PN) in stressed plants decreased significantly. Stomatal conductance, intercellular CO2 concentrations, the rate of transpiration, and the limitation of stomatal conductance showed that the decrease in PN was caused mainly by nonstomatal restrictions. Meanwhile, stomata density increased significantly in the stressed plants. The stomata status of opening and closing became disorganized with a prolonged 35°C exposure. The damage of chloroplast membrane occurred earlier and was more serious in the plants under elevated temperature. At the same time, the thylakoids were loosely distributed with lesser grana, but the number of lipid droplets increased in chloroplasts. The number of starch grains in chloroplasts increased first and then decreased. In addition, the length of the main nerve in leaves increased and the main vein showed distortion in the plants stressed by 35°C. An increase was observed in the number of cells on the abaxial side of the main vein and these cells were overly congregated. The thickness of a vertical section became thinner in the stressed leaves. The cells of the upper epidermis thinned, and the ratio of palisade tissue to spongy tissue decreased. Generally, the photosynthetic apparatus of tomato changed significantly and the changed chloroplast ultrastructure might be one of the important reasons that caused the decrease of PN under 35°C., J. Zhang, X. D. Jiang, T. L. Li, X. J. Cao., and Obsahuje bibliografii
To evaluate utility of different salt-tolerant lines, three soybean lines with different resistance to salt were planted in the field under control and salt-stress conditions for two years. The results showed that net photosynthetic rate (PN) was significantly different among lines at the anthesis stage and decreased on average by 13.6-34.1% under conditions of salt stress. The stomatal conductance was a primary limiting factor for the reduction of PN under salt stress. Meanwhile, the grain yield (GY) decreased on average by 14.0-35.3% among lines under salt stress. The salt-tolerant lines S111-9 and S113-6 showed higher PN and GY under salt stress in comparison with the salt-sensitive cultivar Melrose. Regression analysis indicated that there was extremely significantly positive correlation between GY and PN under field conditions. Therefore, PN might be used as a physiological index for field resistance of soybean to salt stress., Y. He, Y. Chen, C. L. Yu, K. X. Lu, Q. S. Jiang, J. L. Fu, G. M. Wang, D. A. Jiang., and Obsahuje bibliografii
This study compared the relationship between chlorophyll (Chl) content, gas exchange, Chl fluorescence characteristics, and leaf color, using paired near-isogenic lines (NILs) of a medium-green leaf inbred line SN12 and a yellow-green leaf mutant SN62 to explore the photosynthesis of the yellow-green mutant. The SN62 was found in a female parent, Xianyu 335, which grew normally, although there were small yellow spots on the leaves at the seedling stage and yellow-green leaves appeared from the seedling to the maturation stage. The results indicated that Chl a (b), quantum efficiency of PSII, and maximal quantum yield of PSII photochemistry of SN62 were significantly lower than those of SN12, but there were almost no differences in the net photosynthetic rate (P N). There was no significant correlation between Chl a (b) and P N of inbred lines with different leaf colors. In the reproductive stage, photochemical quenching, effective quantum yield of PSII photochemistry, and the electron transport rate of SN62 increased obviously, and all parameter values exceeded the values of SN12. It explained that increasing the openness of the PSII reaction center was able to compensate for the lower Chl content, which was beneficial for harvesting more light energy for photochemical reactions. It also ensured that P N was not reduced., X. M. Zhong, S. F. Sun, F. H. Li, J. Wang, Z. S. Shi., and Obsahuje seznam literatury
Physiological responses from sensitive (S156) and resistant (R123) genotypes of ozone bioindicator, snap bean, were investigated after exposing the plants to cumulative, phytotoxic ozone amounts. Daily course of gas-exchange parameters showed delayed stomatal response in S156 leaves to environmental changes comparing to the response of R123 leaves. Potential photosynthetic quantum conversion, Stern-Volmer nonphotochemical quenching (NPQ), and maximum photochemical efficiency of PSII (Fv/Fm) values changed differently in the two genotypes between the first and last measuring days. We concluded that the higher ozone sensitivity originated at least partly from inferior regenerating and/or antioxidant capacity. Experimental protocol proved to be determinant on chlorophyll fluorescence parameters: Fv/Fm and NPQ declined at midday, and only the sensitive leaves showed a slight increase in NPQ between 12 h and 16 h. We explained these results by moderately high temperatures and shade-adapted state of our experimental plants under substantial ozone stress. On the base of temperature dependence of minimal fluorescence yield (F0), critical temperature proved to be higher than 32.7°C for Phaseolus vulgaris under these conditions. We found a strong linear correlation between NPQ and nonphotochemical quenching of F0, indicating that NPQ was determined mostly by energy-dependent quenching (qE). The qE is the light-harvesting complex located component of NPQ and depends on the amount of zeaxanthin molecules bound in PSII proteins. Thus, difference between daily courses of NPQ in the two genotypes was probably due to different ways of utilization of the zeaxanthin pool under the interactive effect of ozone and moderate heat stress., V. Villányi, Z. Ürmös, B. Turk, F. Batič, Z. Csintalan., and Obsahuje bibliografii
While photosynthesis of soybean has been enhanced by breeding, it remains to be clarified whether the improvement of root function could bring a further increase of photosynthetic capacity for the development of soybean cultivars. The objective of this grafting experiment was to determine the influence of record-yield soybean cultivars, Liaodou14 (L14) and Zhonghuang35 (Z35), as rootstocks on photosynthetic traits of cultivars released in different decades. Grafting of various soybean cultivars onto L14 or Z35 rootstocks showed a higher root physiological activity, which resulted in significant increases in some photosynthetic traits at the late grain-filling stage compared with the non-grafted and self-grafted plants. The genetic gain for some photosynthetic traits of cultivars released from 1966 to 2006 increased by using L14 and Z35 as rootstocks. It suggested that the photosynthetic traits of the recently released cultivars could increase more if their root functions are improved., S. Y. Li, F. Teng, D. M. Rao, H. J. Zhang, H. Y. Wang, X. D. Yao, C. M. Yu, C. H. Li, M. Z. Zhao, S. K. St. Martin, F. T. Xie., and Obsahuje seznam literatury
Predicting the effects of increased ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion on temperate desert ecosystems requires better knowledge of the ecophysiological response of common moss species. The aim of the current work was to determine whether elevated UV-B radiation affected photosynthetic performance and chloroplast ultrastructure of two moss crusts and whether response differences were observed between the crusts. In laboratory experiments, Bryum argenteum and Didymodon vinealis, which show microdistributions and are dominant in soil crusts at the Tengger Desert, Northern China, were subjected to four levels of UV-B radiation of 2.75 (control), 3.08, 3.25, and 3.41 W m-2 for 10 days, simulating 0, 6, 9, and 12% of stratospheric ozone at the latitude of Shapotou, respectively. The results showed that chlorophyll a fluorescence parameters (i.e., the maximal quantum yield of PSII photochemistry, the effective quantum yield of PSII photochemistry, and photochemical quenching coefficient), pigment contents, soluble protein contents, and the ultrastructure were negatively influenced by elevated UV-B radiation and the degree of detrimental effects significantly increased with the intensity of UV-B radiation. Moreover, results indicated that B. argenteum was probably more sensitive to supplementary UV-B radiation than D. vinealis. Therefore, we propose the use of B. argenteum crusts as a bioindicator of responses to elevated UV-B radiation., R. Hui, X. R. Li, R. L. Jia, L. C. Liu, R. M. Zhao, X. Zhao, Y. P. Wei., and Obsahuje bibliografii