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
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
Photosynthetic parameters, growth, and pigment contents were determined during expansion of the fourth leaf of in vitro photoautotrophically cultured Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400-700 nm): low, LI 60 µmol m-2 s-1; middle, MI 180 µmol m-2 s-1; and high, HI 270 µmol m-2 s-1]. During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants. Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (FV/FM) and actual (ΦPS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching. Nevertheless, net photosynthetic oxygen evolution rate (PN) did not decrease consistently with decrease in Chl content, but exhibited a typical ontogenetic course with gradual increase. PN reached its maximum before full leaf expansion and then tended to decline. Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves and changed their typical ontogenetic course. and B. Radochová, I. Tichá.
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
The cold stress effect on early vigour and photosynthesis efficiency was evaluated for five industrial chicory varieties with contrasting early vigour. The relationships between the growth and physiological parameters were assessed. The varieties were examined at three growth temperatures: 16 (reference), 8 (intermediate) and 4 °C (stress). The effect was measured using physiological processes (growth, photosynthesis, chlorophyll a fluorescence), and pigment content. The analysis of the measured growth parameters (dry leaf and root mass, and leaf area) indicated that temperature had a significant effect on the varieties, but the overall reaction of the varieties was similar with lowering temperatures. The photosynthesis and chlorophyll a fluorescence measurements revealed significant changes for the photosynthesis (maximum net photosynthesis, quantum efficiency, light compensation point and dark respiration) and chlorophyll a fluorescence parameters (photochemical and non-photochemical quenching) with lowering temperatures for Hera and Eva, two extremes in youth growth. No significant differences could be found between the extremes for the different temperatures. The pigment content analysis revealed significant differences at 4 °C in contrast to 16 and 8 °C, especially for the xanthophyll/carotenoid pool, suggesting a protective role. Subsequently, the relationship between the physiological processes was evaluated using principal component analysis. At 4 °C, 2 principal components were detected with high discriminating power for the varieties and similar classification of the varieties as determined in the growth analysis. This provides a preview on the possible relationships between photosynthesis and growth for industrial chicory at low temperatures. and S. Devacht ... [et al.].
Natural and commercial Salix clones differ in their ecophysiological response to Zn stress This study was carried out to determine the effect of different zinc concentrations on the ecophysiological response of Salix clones: four commercial clones (“1962”, “1968”, “Drago”, and “Levante”) selected for short rotation coppice, and one natural clone, “Sacco”, obtained from a contaminated area. Gas exchanges, chlorophyll a fluorescence (JIP-test), relative chlorophyll content, and biometric parameters were measured in plants grown for fifteen days in soil containing Zn concentrations of 0, 300, 750, and 1,500 mg(ZnCl2) kg-1. Ecophysiological response to metal stress differed in dependence on the Zn concentration and clone. At the low Zn concentration (300 mg kg-1), the absence of any significant reductions in parameters investigated indicated an efficient plant homeostasis to maintain the metal content within phytotoxic limits. Stomatal limitation, observed at 750 and 1,500 mg kg-1, which was found in all clones after three days of the treatment, might be caused by indirect effects of metal on guard cells. Among commercial clones, “Drago” was more sensitive to Zn stress, showing inhibition of growth, while “1962” clone showed a downregulation of PSII photochemistry following the slowdown in the Calvin-Benson cycle. On the contrary, the natural Salix clone (“Sacco”) performed better compared to the other clones due to activation of a photosynthetic compensatory mechanism., A. Bernardini, E. Salvatori, S. Di Re, L. Fusaro, G. Nervo, F. Manes., and Obsahuje seznam literatury