Characteristics of Photosynthetic Fluorescence of Dominant Submerged Plants in Nanjishan Wetland of Poyang Lake in Winter

Based on the investigation of the species and frequency of submerged plants in Nanjishan Wetland of Poyang Lake in the winter of 2013,chlorophyll contents and photosynthetic fluorescence characteristics of the dominant submerged plants were studied using chlorophyll fluorescence imaging method. The results indicate that the major submerged plants of Nanjishan Wetland in Poyang Lake in winter included Hydrilla verticillata,Vallisneria natans,Najas minor,Potamogeton pectinatus,Nymphoides peltatum,Myriophyllum verticillatum and so on,and the dominant species were mainly H. verticillata and V. natans in different submerged plant communities. The chlorophyll content of H. verticillata is higher than that of V.natans,and the photosynthesis intensity of H. verticillata is stronger than that of V. natans. The value of Ca / Cb of H. verticillata is not large,which shows that the light-harvesting capacity of H. verticillata＇s chlorophyll is considerable in different sampling sites. The highest value of QY-max of V.natans is up to 0. 732,while the lowest value is only 0. 465; the highest value of QY-max of H. verticillata is 0. 677,while the lowest value is 0. 556.All values of QY-max of the submerged plants were lower than 0. 8,which shows that the submerged plants in Nanjishan Wetland of Poyang Lake may be subjected to certain external stress,which indicates that the external stress might cause some damage for the PSII reaction centers.

Resilience of oilseed rape plants to drought stress after exogenous application of AM1,an ABA-mimicking ligand

AM1(ABA-mimicking ligand)is a newly identified signaling molecule for plants during drought tolerance.To investigate the potential role of AM1 in response of rapeseed to drought stress,we conducted experiments by growing rapeseed plants under different levels of drought stress with or without applying AM1 or ABA in a rain shelter.The results indicated that drought significantly inhibited rapeseed growth by damaging the photosyn-thesis system,increasing active oxygen accumulation,destroying the oxidative system,and worsening membrane lipid peroxidation.Exogenously applied AM1 and ABA both relieved the damage to rapeseed that was induced by drought stress.Compared with the drought-treated rapeseed,the AM1 treatment significantly improved plant height,number of greelp leaves,root collar thickness,leaf area,dry matter weight,and root cap ratios of rapeseed.In addition,Pn,Gs,Ci,Tr were significantly increased by the AM1 treatment.The AM1 treatment also alleviated the drought induced reductions in Fv/Fm,ΦPSII,qN and ETR;induced an increase in NPQ;and resulted in decreased active oxygen accumulation and membrane lipid peroxidation.Although the ABA treatment relieved photosynthetic fluorescence and antioxidation system parameters to some extent,the effect was inferior to AM1 treatment.Yield under AM1 treatment was higher than that under ABA treatment but was still far lower than that of normal water supply control.In summary,AM1 is functionally similar to ABA in terms of drought relief and regulation,moreover has a better effect.

Effects of nitrogen and salt on growth and physiological characteristics of processing tomato under drip irrigation

Xinjiang of China is one of the three largest planting bases of processing tomato in the world,but soil salinization has restricted the production of tomato processing.In order to study the effects of soil nitrogen,salt and their interaction on growth and physiological characteristics of processing tomato under drip irrigation,different amount of nitrogen fertilizer were added to reconcile different salt stress to explore the response mechanisms of growth and yield of processing tomato to soil nitrogen and salt contents with a two-year experiments.The results showed that the effects of soil salinity on the growth and physiological characteristics of processing tomato were significantly greater than that of input of nitrogen fertilizers.The higher soil salt content(≥5.0 g/kg)significantly inhibited the growth of processing tomato.The increase in addition of nitrogen fertilizer could alleviate the salt inhibition and promote the growth of processed tomato with the increase of soil salt content,and the maximum nitrogen application rate was 300 kg/hm2.The linear plus platform was selected to determine the nitrogen effect models of non-saline-alkali soil and weak saline-alkali soil,but the square root nitrogen effect model of moderate saline-alkali soil was selected to accurately predict the yield of processing tomato.It was suggested that the processing tomatoes should be planted in moderate saline-alkali soil to achieve higher yields due to lower input of nitrogen fertilizer,potentially reducing fertilizer costs and maximizing profits from high processing tomato yields.The results have a strong guiding significance for planting of processing tomato on saline-alkali land and appropriate fertilization to increase the yield of processing tomato.