Understanding distribution and transport of carbon assimilates and photosynthesis contribution to grain yield in wheat spike is important in assessing the photosynthetic process under stress conditions. In this study, photosynthetic characteristics were evaluated in a pot experiment. Transport of spike photosynthates to grain was demonstrated using 14C isotope tracer technique. Yield and key enzyme activities of C3 and C4 pathways were examined after anthesis in wheat cultivars of different drought resistance. The ear net photosynthetic rate, chlorophyll content of the spike bracts (glume, lemma, and palea), and relative water content slightly decreased under water deficit in drought resistant variety Pubing 143 (Pub) during the grain filling stage, whereas all parameters decreased significantly in drought sensitive variety Zhengyin 1 (Zhe). Grain 14C-photosynthate distribution rate fell by 3.8% in Pub and increased by 3.9% in Zhe. After harvest, the water-use efficiency of Zhe dropped by 18.7% under water deficit. Rubisco activity in ear organs declined significantly under water deficit, whereas activity of C4 pathway enzymes was significantly enhanced, especially that of phosphoenolpyruvate carboxylase and NADP-malate dehydrogenase. Water deficit exerted lesser influence on spike photosynthesis in Pub. Ear organs exhibited delayed senescence. Accumulation of photosynthetic carbon assimilates in ear bracts occurred mainly during the early grain filling and photosynthates were transported in the middle of grain filling. C4 pathway enzymes seem to play an important function in ear photosynthesis. We speculate that the high enzyme activity of the C4 pathway and the increased capacity of photosynthetic carbon assimilate transport were the reasons for the drought tolerance characteristics of ears., S. Jia, J. Lv, S. Jiang, T. Liang, C. Liu, Z. Jing., and Obsahuje bibliografii
Clonal growth is of great importance for survival, growth, expansion, and resource utilization of some species. Knowing how clonal plants respond morphologically and physiologically to different light environments can be useful to explain their occurrence and abundance patterns under specific environmental conditions. Responses of clonal growth, leaf gas exchange, fluorescence emission, and photosynthetic pigment concentrations to different light environments (100, 60, 30, and 15%) were studied in Amomum villosum, grown in the traditional way for economic purpose in Xishuangbanna, southwest China. The results showed that A. villosum attained vigorous clonal growth under 30% and 60% light, with a higher plant height, number of ramets, stolon length, thicker stems and stolons. Shade-grown A. villosum possessed a larger leaf area than that of the sun-grown plants in order to capture more light. For A. villosum, the higher
light-saturated net photosynthetic rate, light-saturation point, larger fresh and dry biomass can explained the better clonal growth for A. villosum under 30% and 60% light. Amomum villosum attained the highest values of minimal chlorophyll fluorescence under 100% light and the lowest values of maximum photochemical efficiency of PSII under 15% light. Our findings indicated that the full irradiance was too strong and 15% light was too weak for A. villosum plants. It was also verified by higher concentrations of photosynthetic pigments in the shaded plants compared to those grown under full sun light. Our results suggested that A. villosum seemed to be adapted to moderate light environment (60-30%) which was indicated by vigorous clonal growth and higher photosynthesis. This information is very useful to select clonal species for rainforest or understory projects. The cultivation of A. villosum in rainforest should not be done under too strong (100%) or too weak light environment (less than 15%)., Y. H. Guo, C. Yuan, L. Tang, J. M. Peng, K. L. Zhang, G. Li, X. J. Ma., and Seznam literatury
a1_The carbon dioxide concentration in free air carbon dioxide enrichment (FACE) systems typically has rapid fluctuations. In our FACE system, power spectral analysis of CO2 concentration measured every second with an open path analyzer indicated peaks in variation with a period of about one minute. I used
open-top chambers to expose cotton and wheat plants to either a constant elevated CO2 concentration of 180 μmol mol-1 above that of outside ambient air, or to the same mean CO2 concentration, but with the CO2 enrichment cycling between about 30 and 330 μmol mol-1 above the concentration of outside ambient air, with a period of one minute. Three short-term replicate plantings of cotton were grown in Beltsville, Maryland with these CO2 concentration treatments imposed for 27-day periods over two summers, and one winter wheat crop was grown from sowing to maturity. In cotton, leaf gas-exchange measurements of the continuously elevated treatment and the fluctuating treatment indicated that the fluctuating CO2 concentration treatment consistently resulted in substantial down-regulation of net photosynthetic rate (PN) and stomatal conductance (gs). Total shoot biomass of the vegetative cotton plants in the fluctuating CO2 concentration treatment averaged 30% less than in the constantly elevated CO2 concentration treatment at 27 days after planting. In winter wheat, leaf gas-exchange measurements also indicated that down-regulation of PN and gs occurred in flag leaves in the fluctuating CO2 concentration treatment, but the effect was not as consistent in other leaves, nor as severe as found in cotton. However, wheat grain yields were 12% less in the fluctuating CO2 concentration treatment compared with the constant elevated CO2 concentration treatment., a2_Comparison with wheat yields in chambers without CO2 addition indicated a nonsignificant increase of 5% for the fluctuating elevated CO2 concentration treatment, and a significant increase of 19% for the constant elevated treatment. The results suggest that treatments with fluctuating elevated CO2 concentrations could underestimate plant growth at projected future atmospheric CO2 concentrations., J. A. Bunce., and Obsahuje bibliografii
Ramie (Boehmeria nivea L.) is an important crop that serves as fine fiber material, high protein feedstuff, and valuable herbal medicine in China. However, increasing salinity in soil limits the productivity. We investigated in a greenhouse experiment responses to salinity in two ramie cultivars, Chuanzhu-12 (salt-tolerant cultivar, ST) and Xiangzhu-2 (salt-sensitive cultivar, SS), to elucidate the salt tolerance mechanism of this species. Salinity stress substantially reduced both chlorophyll and carotenoid contents. In addition, net photosynthesis, transpiration rate, stomatal conductance, intercellular CO2 concentration, and the ratio of intercellular CO2 to ambient CO2 were affected, less in ST. Nevertheless, salinity stress markedly improved water use efficiency and intrinsic water use efficiency in both species. Moreover, relative water contents, soluble proteins, and catalase activity were substantially impaired, while proline accumulation and superoxide dismutase activity were enhanced substantially, more in ST. Furthermore, noteworthy increase in peroxidase activity and decrease in malondialdehyde content was recorded in ST, whereas, in SS, these attributes changed conversely. Overall, the cultivar ST exhibited salt tolerance due to its higher photosynthetic capacity, chlorophyll content, antioxidative enzyme activity, and nonenzymatic antioxidants, as well as reduced lipid peroxidation and maintenance of the tissue water content. This revealed the salt tolerance mechanism of ramie plants for adaptation to salt affected soil., C.-J. Huang, G. Wei, Y.-C. Jie , J.-J. Xu, S.-Y. Zhao, L.-C. Wang, S. A. Anjum., and Obsahuje seznam literatury
In order to test the effects of irrigation depth on winter wheat photosynthesis, four treatments were applied in a field experiment using PVC growth tubes (identical amounts of water were applied on the land surface, and at 60, 75, and 90% of the depth for the winter wheat root distribution, denoted as D0, D60, D75, and D90, respectively). Compared to the surface irrigation treatment D0, the leaf area index, chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration increased with irrigation depths. The values of these indicators obtained by the underground irrigation treatment D75 were higher than those of D60 and D90, and thus D75 was found to be the optimum irrigation depth. Furthermore, a positive but not significant correlation (r = 0.62) between carbon isotope discrimination (Δ13C) and grain yield was found. This study improves our understanding of the mechanism of underground water distribution control with depth, and the efficiency of
water-saving irrigation for winter wheat., L. J. Zheng, J. J. Ma, X. H. Sun, X. H. Guo, J. Jiang, R. Ren, X. L. Zhang., and Obsahuje bibliografii
In a field experiment, two winter wheat (Triticum aestivum L.) cultivars, Tainong 18 (a large-spike cultivar) and Jinan 17 (a multiple-spike cultivar), were treated with 78% (S1), 50% (S2), and 10% (S3) of full sunshine (S0, control) from anthesis to maturity to determine the responses of photosynthetic characteristics and antioxidative enzyme activities in a flag leaf. Compared with S0 treatment, the chlorophyll (Chl) content and maximal efficiency of photosystem II (PSII) photochemistry (Fv/Fm) of flag leaves were enhanced in treatments S1 and S2. From 0 to 7 d post flowering, the Chl content and Fv/Fm in S3 were also higher than those in S0, but significantly lower than those in controls, respectively. With the increase of shading intensity, the effective quantum yield of PSII (ΦPSII) was promoted; whereas, the ratio of Chl a/b declined. Compared with S0, treatments S2 and S3 significantly suppressed the activities of superoxide dismutase (SOD) and peroxidase (POD), net photosynthetic rate (PN), and contents of total soluble sugar, nevertheless, S1 treatment showed positive effects on the above parameters. Under the same shading condition, Jinan 17 had larger Chl content and higher activities of PSII and antioxidative enzymes, but lower malondialdehyde (MDA) content than Tainong 18. The results indicated that multiple-spike cultivar was more advantageous for the Huang-Huai-Hai Plain, where shading problem occurs later during the growth period, than the large-spike cultivar, because of the lesser damage in a flag leaf and better photosynthetic function of the former one. Wheat plants under S1 shading condition had relatively high activities of antioxidative enzymes and a low degree of membrane lipid peroxidation, which was in favor of stress resistance, maintaining high PN duration, and accumulation of photosynthates in wheat plants., C. Xu ... [et al.]., and Obsahuje bibliografii
The widespread Mediterranean Pinus pinea showed exceptionally low genetic diversity and low differentiation between traits in the adult phase. We explored the adaptation potential of seedlings from four main Iberian provenances during their regeneration phase. We assessed the variability of shoot growth, allometry, physiological traits, and phenotypic plasticity to the interactive effect of light and water environments during 8-month moderate water-stress cycle and after one-week heat wave. The effect of shade and drought was mainly orthogonal whatever the provenance. The inland La Mancha provenance showed higher shoot growth and biomass compared to the southern coastal Depresión-del-Guadalquivir provenance. Following the heat wave, La Mancha presented higher net photosynthetic rates, a lower decrease in maximal quantum efficiency of PSII, and a higher accumulated relative height growth, thus, showing an adaptive advantage. The observed differences corroborated the ecological grouping of the provenances along latitudinal and inland-coastal gradients. We confirmed the high adaptive plasticity of Pinus pinea to the unpredictable Mediterranean environment., M. Pardos, R. Calama., and Obsahuje bibliografii
The responses of photosynthesis and growth to increasing CO2 concentration ([CO2]) were investigated in Hippophae gyantsensis and H. rhamnoides subsp. yunnanensis, which are endemic at the Qinghai-Tibet Plateau and phylogenetically related, but distributed parapatrically in divergent regions. Seedlings of the two species were grown at ambient [AC; 360 μmol(CO2) mol-1] and elevated [EC; 720 μmol(CO2) mol-1] [CO2] in growth chambers. The responses to EC were significantly different between the two species. EC induced an increase in photosynthesis, stomatal conductance, intrinsic water-use efficiency, apparent quantum efficiency, total dry mass, and a decrease in photorespiration rate, maximum carboxylation rate of Rubisco, and maximum electron transport rate in H. gyantsensis compared to those in H. rhamnoides subsp. yunnanensis. Moreover, a significant increase in leaf nitrogen content and a decrease in root/shoot ratio was also observed in H. gyantsensis. H. gyantsensis showed a significantly higher specific leaf area than that of H. rhamnoides through treatments. Relative to H. rhamnoides subsp. yunnanensis, H. gyantsensis showed a greater potential to increase photosynthesis and growth to cope with the increasing [CO2] and it might expand its distribution range in the future., F. Ma, T. T. Xu, M. F. Ji, C. M. Zhao., and Obsahuje seznam literatury
We studied photosynthetic capacity, growth, sap flow, and water-use efficiency in young trees of ‘Pink Lady’ apple (Malus domestica) that were exposed to 60 d of moisture stress. Three irrigation schemes were tested in the greenhouse: well-watered control; drought; or alternate deficit irrigation (ADI). Compared with the drought-stressed plants, those treated via ADI showed better height growth, larger scion diameters, and greater total leaf area, as well as significantly increased gains in dry biomass and rootstock diameters. However, their performance was still significantly lower than that demonstrated by continuously well-watered plants. Sap flow was greater under ADI than under drought, but less than under control conditions. The average rate of net photosynthesis, total amount of irrigation water applied, and dry biomass gain had highly significant and positive linear correlations with long-term water-use efficiency (WUEL). The same was true between average stomatal conductance and WUEL. By contrast, instantaneous water-use efficiency (WUEI) was very significantly and negatively correlated with WUEL. In addition, values for WUEL were much higher from well-watered plants when compared with either drought-stressed trees or those treated per ADI. Therefore, our results indicate that, although ‘Pink Lady’ apple normally has high WUE, it still consumes a large amount of water. Therefore, the practice of ADI following a period of long-term drought could be used to improve growth and WUEL by this cultivar., X. P. Sun ... [et al.]., and Obsahuje bibliografii
The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populus maximowiczii Henry X P. × berolinensis Dippel - Oxford clone) in an open top chamber experiment carried out at the Curno facilities (Northern Italy). Chlorophyll (Chl) a fluorescence parameters (from both modulated and direct fluorescence) were assessed at different hours of the day (predawn, morning, midday, afternoon, and evening), from June to August 2008. This paper compares the results from predawn (PD, before sunrise) and afternoon (AN, in full sunlight) measurements, in order to evaluate the role of high sunlight as a factor influencing responses to ozone stress. Sunlight affected the maximum quantum yield of primary photochemistry (decrease of Fv/Fm) thus indicating photoinhibition. The effective quantum yield (ΦPSII) and the photochemical quenching (qP) were enhanced in the afternoon with respect to the predawn, whereas the nonphotochemical quenching (NPQ) was reduced. The effect of ozone was detected with fluorescence on well watered plants in the first week of July, before the onset of visible symptoms. As far as Fv/Fm are concerned, the differences between ozone-treated and control plants were statistically significant in the predawn, but not in the afternoon. Ozone exerted only minor effects on drought exposed plants because of the reduced stomatal ozone uptake, but effects on the IP phase of the fluorescence transient were observed also in drought-stressed plants., R. Desotgiu ... [et al.]., and Obsahuje bibliografii