磷的有效性对菜豆生理生态特征的影响

研究了生长在３种不同磷水平下６种不同基因型菜豆的多项生理生态指标．结果表明：①Ｐ水平显著影响菜豆的光合、蒸腾、气孔导度、叶磷浓度、光能和水分利用率、磷利用率及生物量等；②在同一磷水平下，不同基因型菜豆的光合、气孔导度、光能和水分利用率显著不同；③在各基因型中。

Effects of rice straw on the cell viability, photosynthesis, and growth of Microcystis aeruginosa

Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore this mechanism, the growth, cell viability(esterase activity, membrane potential, and membrane integrity), photosynthesis, and cell size of M. aeruginosa were determined using fl ow cytometry and Phyto-PAM after exposure to rice straw extracts(RSE). The results show that doses from 2.0 to 10.0 g/L of RSE effi ciently inhibited the alga for 15 days, while the physiologic and morphologic responses of the cyanobacteria were time-dependent. RSE interfered with the cell membrane potential, cell size, and in vivo chlorophyll- a fl uorescence on the fi rst day. After 7 days of exposure, RSE was transported into the cytosol, which disrupted enzyme activity and photosynthesis. The cyanobacteria then started to repair its physiology(enzyme activity, photosynthesis) and remained viable, suggesting that rice straw act as an algistatic agent.

Mechanisms of Difference in Mn Efficiency Between Wheat and Oilseed Rape

By solution culture experiment, three wheat genotypes (Ttiticum aestivum L.) and two oilseed rape genotypes (Brassica napus L.) differing in Mn efficiency under Mn-deficient conditions were used to study mechanisms of the difference in Mn efficiency between wheat and oilseed rape. The results showed that there were significant differences in the abilities of MnIV reduction and acidification in root rhizosphere between the two species. Compared with wheat, oilseed rape had much higher reducing capacity and intensity of rhizosphere acidification under Mn-deficient conditions. Moreover, the higher ratio of functional leaves Mn/old leaves Mn in oilseed rape than in wheat was also an important factor for the different Mn efficiencies between the two species.

Optimization of medium and cultivation conditions for enhanced exopolysaccharide yield by marine Cyanothece sp. 113

Cyanothece sp. 113 is a unicellular, aerobic, diazotrophic and photosynthetic marine cyanobacterium. The optimal medium for exopolysaccharide yield by the strain was 70.0 g/L of NaCl, and 0.9 g/L of MgSO4 based on the modified F/2 medium for cultivation of marine algae. The optimal cultivation condition for exopolysaccharide yield by this cyanobacterial strain was 29℃, aeration, and continuous illumination at 86.0 μE/M^2/S. Under the optimal conditions, over 18.4 g/L of exopolysaccharide was produced within 12 days. This was so far the highest exopolysaccharide yield produced with strains of Cyanothece sp. obtained.

Dry-Matter Partitioning, Yield and Leaf Nutrient Contents of Tomato Plants as Influenced by Shading at Different Growth Stages

Pot-grown tomato plants (Lycopersicon esculentum Mill. cv. Maofen) was used to study the effects of three shading levels (0, 75% and 40%) for 8 days on dry matter partitioning, contents of nitrogen (N), phosphorus (P) and potassium (K) in leaves arid yield at three growth stages (early flowering (EF), peak flowering (PF) and later flowering (LF)). Shading reduced the dry weight of root and stem tissues at the EF and PF stages, but the 40% shading increased root dry weight and stem dry weight by 43.2% and 21.6%, respectively, at the LF stage. The influence of shading on the dry weight of leaves was very small at most growth stages. Shading had no effects on total leaf N, P and K contents at the EF and PF stages, showing that N, P and K absorption were regulated by the carbon assimilation at these two stages. The leaf N, P and K contents of 40% shaded plants at the LF stage were significantly increased. There were no obvious differences in leaf N and K contents between 75% and 40% shading treatments, but significant difference in leaf P contents was found between them at the LF stage. Shading significantly enhanced the fruit yield of 40% shaded tomato plants at the LF stage, but failed to affect the fruit yield of shaded plants at the EF stage. These showed that tomato could grow well and a better yield could be obtained if some moderate shading (i.e., 40% shading) was applied at the LF stage at summer midday.

Effects of Waterlogging in Different Growth Stages on the Photosynthesis,Growth,Yield,and Protein Content of Three Wheat Cultivars in Jianghan Plain

To maintain high wheat grain yield in areas where frequent and periodic waterlogging occurs,the effects of waterlogging on the photosynthesis,growth,yield,and protein content of three wheat cultivars,namely Xiangmai55(X55),Jingmai102(J102),and Zhengmai9023(Z9023),in four different growth stages were investigated.Experiments were conducted in specially designed experimental tanks in the middle and lower reaches of the Yangtze River during the 2012-2013 and 2013-2014 wheat growing seasons in China.Results showed that X55 was the most susceptible to waterlogging,followed by J102 and Z9023.Chlorophyll content reduction and leaf senescence,which resulted in decreased green-to-total leaf number ratio,were induced to the greatest extents by waterlogging in booting and flowering stages,followed by milky stage.Meanwhile,chlorophyll content in flag leaf,plant height were significantly decreased by waterlogging in jointing stage but effectively recovered after waterlogging withdrawal,and recovery ability varied among the cultivars.Plant biomass and grain yield were most significantly decreased by waterlogging in booting and flowering stages,followed by milky and jointing stages.Grain protein content was also considerably affected by waterlogging depending on growth stage and cultivars.The decreased grain yield caused by waterlogging was mostly due to the sharp decline in 1 000-grain mass.Waterlogging led to reduced protein yield in all growth stages in three wheat cultivars.Above all,in this experiment,waterlogging decreased grain yield significantly,and waterlogging at booting stage and flowering stage was most serious.Comparing the three cultivars,X55 was most sensitive to waterlogging.

Photosynthetic and Growth Responses to Elevated [CO2] are Determined by Multiple Forest Ecosystem Conditions

The responses of photosynthesis and growth of forest trees to rising atmospheric carbon dioxide concentration [CO2] are modified by ecosystem conditions. With the exception of a few, the vast majority of empirical studies on the impact of future high CO2 levels on forest trees have focused on [CO2] alone or in combination with an environmental factor. This paper uses the case of CO2 × nutrient and CO2 × nutrient-related interactions to evaluate the relative value of single or multiple ecosystem factors in determining the responses of photosynthesis and growth to elevated [CO2]. A comprehensive literature search was conducted with Google Scholar. The findings show a consensus among studies that CO2 and nutrient availability have synergistic effects on photosynthesis and growth. However, combinations of nutrient availability with temperature or moisture modify the CO2 effect in ways different from nutrient availability alone. To increase the predictive power of empirical studies, it is recommended that conclusions on the responses of forest trees to elevated atmospheric [CO2] be based on interactions with multiple, rather than single, ecosystem conditions.

Response of Populus x canescens (Populus tremula x alba) to high concentration of NaCl stress

Populus x canescens was cultivated on solid substrate and treated by salt （150 mM NaCl）. The growth parameters including new leaf formation, height increment, diameter at the base increment, fresh and dry mass of leaf, stem, coarse root, and fine root were determined. The nutrient elements in leaves of samples under salt stress and the control, and the chlorophyll fluorescence of plants separated dark and light, initial fluorescence （Fo）, and maximum fluorescence （Fro） were measured. Results showed that 150 mM NaCI treatment resulted in growth reduction of Populus x canescens. Nutrient element contents in the foliage of plants under salt stress were different from that of control. The foliar N-concentrations of plants under salt stress were not affected. Contents of Na under salt stress were 120 times as much as that under control. However, contents of S, K, P, Ca, Mg, Fe, Mn under salt stress were less than that under control. Salt stress caused damage in the PSII reaction centers, i.e. photo-inhibition couldn＇t be repaired under dark situation. The yield of chlorophyll fluorescence showed that several parameters associated with PSII functions, e.g. Fv/Fo, Fv/Fm were not influenced at the first stage of salt stress treatment. However, after a period of time, PSII functions were significantly inhibited, which led to the decrease of carbon assimilation. These results suggest that salt stress （150 mM NaCl） did not affect photosynthetic chlorophyll fluorescence of Populus x canescens immediately. After four day of salt stress, PSII reaction centres were seriously damaged during photo-inhibition.

Effect of Dark Septate Endophytic Fungus Gaeumannomyces cylindrosporus on Plant Growth, Photosynthesis and Pb Tolerance of Maize (Zea mays L.)

Dark septate endophytic （DSE） fungi are ubiquitous and cosmopolitan, and occur widely in association with plants in heavy metal stress environment. However, little is known about the effect of inoculation with DSE fungi on the host plant under heavy metal stress. In this study, Gaeumannomyces cylindrosporus, which was isolated from Pb-Zn mine railings in China and had been proven to have high Pb tolerance, was inoculated onto the roots of maize （Zea mays L.） seedlings to study the effect of DSE on plant growth, photosynthesis, and the translocation and accumulation of Pb in plant under stress of different Pb concentrations. The growth indicators （height, basal diameter, root length, and biomass） of maize were detected. Chlorophyll content, photosynthetic characteristics （net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration）, and chlorophyll fluorescence parameters in leaves of the inoculated and non-inoculated maize were also determined. Inoculation with G. cylindrosporus significantly increased height, basal diameter, root length, and biomass of maize seedlings under Pb stress. Colonization of G. cylindrosporus improved the efficiency of photosynthesis and altered the translocation and accumulation of Pb in the plants. Although inoculation with G. cylindrosporus increased Pb accumulation in host plants in comparison to non-inoculated plants, the translocation factor of Pb in plant body was significantly decreased. The results indicated that Pb was accumulated mainly in the root system of maize and the phytotoxicity of Pb to the aerial part of the plant was alleviated. The improvement of efficiency of photosynthesis and the decrease of translocation factor of Pb, caused by DSE fungal colonization, were efficient strategies to improve Pb tolerance of host plants.

Wheat Growth and Photosynthesis as Affected by Oxytetracycline as a Soil Contaminant

Extensive worldwide use of oxytetracycline （OTC）, a member of the tetracyclines, has resulted in its accumulation in soils, posing a potential risk to food production and safety. A pair of OTC-sensitive （Heyou 1） and OTC-tolerant （Yannong 21） wheat （Tritieum aestivum L.） cultivars was compared hydroponically at 0.01, 0.02, 0.04, and 0.08 mmol L-10TC in terms of wheat growth and photosynthesis. Biomass and shoot length decreased significantly with the addition of OTC, with the decreases in dry biomass and shoot length being 5.61%-13.75% and 3.33%-8.57% larger, respectively, for Heyou 1 than Yannong 21. Photosynthesis of Heyou 1 was suppressed by OTC as indicated by the significant decreases in photosynthetic rate （PN）, transpiration rate （TR）, and stomatal conductance （GS） and the significant increase in intercellular CO2 concentrations （CI）, at all OTC levels. Stomatal limitation （LS） and water use eftlciencies （WUE） of Heyou i also increased significantly, but not at 0.08 mmol L-10TC. However, photosynthesis of Yannong 21 was suppressed by OTC only at high OTC levels from 0.02 to 0.08 mmol L-1 as indicated by the decreases in PN, GS, TR, and LS; at 0.01 mmol L-10TC, PN, CI, GS, and TR significantly increased. It was noted that WUE of Yannong 21 was not affected by OTC addition. The results from this hydroponic test suggested that OTC had a potential risk to crop growth through inhibition of photosynthesis, requiring further confirmation with soil tests.