Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.

Seasonal and diurnal variations of atmospheric peroxyacetyl nitrate, peroxypropionyl nitrate, and carbon tetrachloride in Beijing

Atmospheric peroxyacetyl nitrate （PAN）, peroxypropionyl nitrate （PPN）, and carbon tetrachloride （CCl4） were measured from September 2010 to August 2011 in Beijing. PAN exhibited low values from mid-autumn to early spring （October to March） with monthly average concentrations ranging from 0.28 to 0.73 ppbV, and increased from early spring to summer （March to August）, ranging from 1.37-3.79 ppbV. The monthly variation of PPN was similar to PAN, with low values （below detection limit to 0.18 ppbV） from mid-autumn to early spring, and a monthly maximum in September （1.14 ppbV）. The monthly variation of CCl4 was tightly related to the variation of temperature, exhibiting a minimum in winter （69.3 pptV） and a maximum of 180.6 pptV in summer. Due to weak solar intensity and short duration, PAN and O3 showed no distinct diurnal patterns from morning to night during winter, whereas for other seasons, they both exhibited maximal values in the late afternoon （ca. 15：00 to 16：00 local time） and minimal values during early morning and midnight. Good linear correlations between PAN and PPN were found in autumn （R = 0.91）, spring （R = 0.94）, and summer （R = 0.81）, with slopes of 0.130, 0.222, and 0.133, respectively, suggesting that anthropogenic hydrocarbons dominated the photochemical formation of PANs in Beijing. Positive correlation between PAN and O3 in summer with the low slopes （AO3/APAN） ranging from 9.92 to 18.0 indicated serious air pollution in Beijing, and strong negative correlation in winter reflected strong O3 consumption by NO titration and less thermal decompositin of PAN.

Utilizing the γ-Irradiated Sodium Alginate as a Plant Growth Promoter for Enhancing the Growth,Physiological Activities,and Alkaloids Production in Catharanthus roseus L.

Sodium alginate is a polysaccharide that is largely obtained from the brown algae （Sargassum sp.）.It has been used as a wonderful growth promoting substance in its depolymerized form for various plants.The aim of this study was to find out the effects of various concentrations of γ-irradiated sodium alginate （ISA）,viz.,deionized water （control,T0）,20 （T1）,40 （T2）,60 （T3）,80 （T4）,and 100 ppm （T5） on the agricultural performance of Catharanthus roseus L.（Rosea） in terms of growth attributes,photosynthesis,physiological activities,and alkaloid production.The present work revealed that ISA applied as leaf-sprays at concentrations from 20 to 100 ppm might improve growth,photosynthesis,physiological activities,and alkaloid production in C.roseus L.significantly.Of the various ISA concentrations,80 ppm proved to be the best one compared to other concentrations applied.