Ground concentration of ozone (O3) causes serious threat to plants. In order to protect sensitive plants from O3 pollution, many kinds of antioxidants were assessed in previous studies. In this study, effects of O3 fumigation (a single spike of 120 ± 20 nmol mol-1 for four hours) on an ornamental species (Coleus blumei) was examined in open-top chambers. Before the O3 treatment, plants were sprayed respectively either with a solution of three different antioxidants [Na-ascorbate (NaAsA), kinetin (KIN), and spermidine (Spd)] or with distilled water to compare their protective effects to plants. Our results revealed that O3 fumigation impaired the plasma membrane, decreased chlorophyll (Chl) content, inhibited photosynthesis, induced photoinhibition and photodamage, and caused visible injury. Spraying with KIN, NaAsA or Spd ameliorated the decrease of the Chl content and photosynthetic capability, the impairment of membrane, and visible injury under O3 fumigation. The plants treated with KIN showed the best ability to mitigate the injury caused by O3., L. Zhang, L. L. Jia, J. X. Sui, M. X. Wen, Y. J. Chen., and Obsahuje bibliografii
Waterlogging is one of the critical factors controlling the distribution, regeneration, and survival of vegetation in wetlands. Here, we tested the hypothesis that Mitragyna parvifolia (Roxb.) Korth. and Syzygium cumini Keels, inhabiting the Keoladeo National Park, a Ramsar wetland (Bharatpur, India), are tolerant to waterlogging. The morphological and photosynthetic variables of four-month-old seedlings subjected to waterlogging, along with the concentrations of macroand micronutrients, were examined. After 35 days, treatment was halted due to high mortality of S. cumini seedlings in contrast to that of M. parvifolia seedlings. Significant declines in most of the studied variables were observed in both species when compared with their respective controls. In addition, M. parvifolia seedlings developed adventitious roots and lenticels and showed an increased root biomass. Based on the results, we concluded that adaptive traits displayed by M. parvifolia seedlings facilitate its tolerance to waterlogging in contrast to S. cumini seedlings., A. Bidalia, Z. Okram, M. Hanief, K. S. Rao., and Obsahuje bibliografii
A hydroponic experiment was conducted to investigate bioaccumulation and photosynthetic activity response to Cd in sweet sorghum seedlings. The seedlings were treated with 0, 50, and 100 μM Cd for 15 d. Our results showed that morphological characteristics of sweet sorghum were significantly affected by Cd treatments. The Cd concentrations in roots and shoots increased with increasing Cd concentrations in the nutrition solution; higher Cd accumulation was observed in the roots. Meanwhile, the photosynthetic activity decreased significantly and a shape of chlorophyll (Chl) a fluorescence transient in leaves was altered by Cd treatments. The Chl contents in the leaves decreased significantly, which was demonstrated by a change of spectral reflectance. Our data indicated that the higher Cd concentration reduced Chl contents and inhibited electron transport in the leaves, leading to the decrease of photosynthetic activity., Z. C. Xue, J. H. Li, D. S. Li, S. Z. Li, C. D. Jiang, L. A. Liu, S. Y. Wang, W. J. Kang., and Obsahuje bibliografii
The effects of phosphate concentration on plant growth and photosynthetic performance were examined in leaves of Zizania latifolia. Plants were grown for four weeks in a solution containing 0, 0.16, 0.64, and 2.56 mM orthophosphate. The results showed that the highest net photosynthetic rate (P N) was achieved at 0.64 mM orthophosphate, which corresponded to the maximum content of organic phosphorus in leaves. Low phosphorus (low-P) content in the culture solution inhibited plant growth, affecting plant height, leaf length, leaf number, tiller number, and fresh mass of leaf, sheath, culm, root, and total plant. In addition, we observed that low-P (0.16 mM) did not hinder the growth of roots but increased the root:shoot ratio, and significantly decreased the chlorophyll content, P N, stomatal conductance, and transpiration rate, but increased the intercellular CO2 concentration. Additionally, low-P significantly decreased the maximum carboxylation rate of Rubisco, the maximum rate of ribulose-1,5-bisphosphate regeneration, the effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and electron transport rate, but increased the nonphotochemical quenching. However, the maximal quantum yield of PSII photochemistry was not significantly affected by low-P. High phosphorus (2.56 mM) caused only a slight decrease in gas-exchange parameters. Therefore, the decrease in growth of P-deficient Z. latifolia plants could be attributed to the lowered photosynthetic rate., N. Yan, Y.-L. Zhang, H.-M. Xue, X.-H. Zhang, Z.-D. Wang, L.-Y. Shi, D.-P. Guo., and Obsahuje seznam literatury
Tomato (Lycopersicon esculentum Mill. cv. Pearson) plants were grown in growth chambers for 25 days with cadmium (Cd) and then exposed briefly to ozone (O3). Gas exchange, chlorophyll a fluorescence, and pigment composition were analysed in leaves at the end of the treatment to assess the effects of a single pollutant and their combination on photosynthesis. The CO2 assimilation rate was dramatically reduced in plants subjected to the combined treatment, while the single effect of Cd appeared less severe than that of O3. The decline of CO2 photoassimilation found in all
O3-exposed plants was attributed to both stomatal and nonstomatal limitations. Tomato plants seemed to detoxify Cd to a great extent, but this resulted in growth suppression. In response to O3 exposure, the plants protected their photosystems by heat dissipation of excess energy via the xanthophyll cycle. Cd combined with O3 affected adversely this cycle resulting in an increase in photosynthetic performance under the same experimental light conditions., E. Degl’Innocenti, A. Castagna, A. Ranieri, L. Guidi., and Obsahuje bibliografii
Water availability is an important factor for plant growth in arid environments. In recent decades, vermicompost (VC) fertilizer has been used in agriculture as a safe and effective fertilizer with high water-holding capacity. The aim of the present study was to characterize effects of VC fertilizer on photosynthetic activity of chickpea (Cicer arietinum L. cv. Karaj) under drought conditions at three different growth stages. Tests were carried out with four volumetric ratios of VC to soil, i.e., 0:100, 10:90, 20:80, and 30:70, and three levels of drought stress, i.e., no stress (NS), moderate drought (MS), and severe drought (SS) (100, 75, and 25% of field capacity, respectively). Evaluations were performed at the seedling, flowering, and podding stage. We found that the VC treatment under NS conditions significantly increased total chlorophyll content [Chl (a+b)], intercellular CO2 concentration (C i), net photosynthetic rate (P N), transpiration rate (E), and maximal quantum yield of PSII photochemistry (Fv/Fm) at all three stages. The VC addition of 10 and 20% significantly enhanced the Chl content and Fv/Fm under MS and Fv/Fm, C i, and P N under SS at the flowering stage. In conclusion, our results proved a positive effect of the VC fertilizer on photosynthesis of chickpea under NS conditions, but it was not found under MS and SS., S. R. Hosseinzadeh, H. Amiri, A. Ismaili., and Obsahuje 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
Photoprotection mechanisms protect photosynthetic organisms, especially under stress conditions, against photodamage that may inhibit photosynthesis. We investigated the effects of short-term immersion in hypo- and hypersalinity sea water on the photosynthesis and xanthophyll cycle in Sargassum fusiforme (Harvey) Setchell. The results indicated that under moderate light [110 μmol(photon) m-2 s-1], the effective quantum yield of PSII was not reduced in S. fusiforme fronds after 1 h in hyposalinity conditions, even in fresh water, but it was significantly affected by extreme hypersalinity treatment (90‰ sea water). Under high light [HL, 800 μmol(photon) m-2 s-1], photoprotective mechanisms operated efficiently in fronds immersed in fresh water as indicated by high reversible nonphotochemical quenching of chlorophyll fluorescence (NPQ) and de-epoxidation state; the quantum yield of PSII recovered during the subsequent relaxation period. In contrast, fronds immersed in 90‰ sea water did not withstand HL, barely developed reversible NPQ, and accumulated little antheraxanthin and zeaxanthin during HL, while recovery of the quantum yield of PSII was severely inhibited during the subsequent relaxation period. The data provided concrete evidence supporting the
short-term tolerance of S. fusiforme to immersion in fresh water compared to hypersalinity conditions. The potential practical implications of these results were also discussed., X. J. Xie, X. L. Wang, L. D. Lin, L. W. He, W. H. Gu, S. Gao, X. F. Yan, G. H. Pan, M. J. Wu, G. C. Wang., and Obsahuje seznam literatury
Guadua amplexifolia and Guadua angustifolia are the most promising timber substitutes amongst American bamboos due to their outstanding dimensions and structural properties. Despite the commercial potential of these species, there are few studies on the survival and adaptability of juveniles in plantations. The present study dealt with survival, growth, and ecophysiological response of juvenile clonal plants of these species, cultivated in abandoned pastures in Mérida, Venezuela. Survivorship, growth (height and culm diameter), and ecophysiological parameters were monitored the first year during wet and dry seasons. Survival rates were high in both species (95% in G. amplexifolia and 89% in G. angustifolia). Midday leaf water potentials decreased in both species during dry months (-1.28 to-2.72 MPa in G. amplexifolia and-1.67 to-2.37 MPa in G. angustifolia, respectively). Net photosynthetic rates measured during wet [16.57 ± 1.40 and 13.68 ± 2.40 μmol(CO2) m-2 s-1, respectively] and dry seasons [12.19 ± 2.82 and 8.12 ± 1.81 μmol(CO2) m-2 s-1, respectively], demonstrated that G. amplexifolia maintained consistently higher photosynthetic rates compared to G. angustifolia, which could explain the higher growth rates of the former. Similar trends were observed for stomatal conductance, transpiration, water-use efficiency, electron transport rate, and photochemical quenching of PSII. G. angustifolia maintained higher nonphotochemical quenching as well as a higher consumption of electrons per molecule of CO2 fixed, indicating a lower photosynthetic efficiency. The maximal photochemical efficiency of PSII (0.73-0.76) suggested that neither of these species suffered from photoinhibition, despite persistently high radiation and air temperatures at the study site., F. Ely, O. Araque, R. Jaimez., and Obsahuje bibliografii
Intercropping, a traditional and worldwide cropping practice, has been considered as a paradigm of sustainable agriculture based on complementary mechanisms among different crop species. Soybean (Glycine max) is widely relay intercropped about 60 days before maize (Zea mays) harvest in Southwest China. However, shade caused by tall maize plants may be a limiting factor for soybean growth at a seedling stage. In field research, we studied the ecophysiological responses of two widely cultivated soybean varieties [Gongqiudou494-1 (GQD) and Gongxuan 1 (GX)] to maize shading in a relay intercropping system (RI) compared with monocropped soybean plants (M). Our results showed that soybean seedlings intercropped with maize exhibited significantly downregulated net photosynthetic rate (PN) (-38.3%), transpiration rate (-42.7%), and stomatal conductance (-55.4%) due to low available light. The insignificant changes in intercellular CO2 concentration and the maximum efficiency of PSII photochemistry suggested that the maize shading-induced depressions in PN were probably caused by the deficiency of energy for carbon assimilation. The significantly increased total chlorophyll (Chl) content (+27.4%) and Chl b content (+52.2%), with lowered Chl a/b ratios (-20.5%) indicated soybean plants adjusted their light-harvesting efficiency under maize shading condition. Biomass and leaf area index (LAI) of seedlings under RI decreased significantly (-78.7 and -71%, respectively) in comparison with M. Correlation analysis indicated the relative reduction in biomass accumulation was caused by the decline in LAI rather than PN, it affected negatively the final yields of soybean (32.8%). Cultivar-specific responses to maize shading were observed in respects of LAI, biomass, and grain yield. It indicated that GX might be a better cultivar for relay intercropping with maize in Southwest China., B. Y. Su, Y. X. Song, C. Song, L. Cui, T. W. Yong, W. Y. Yang., and Obsahuje bibliografii