Protective enzyme activity and physiological properties of four mulberry varieties affected by drought stress in the Panxi Region of Sichuan Province, China

In order to identify the effects of drought stress on protective enzyme activity and physiological properties, four mulberry varieties, i.e.,＇Nanye- 1＇, ＇Yunsang- 1＇, ＇Xinyizhilai＇ and ＇Husang-32＇ in the Panxi Region of Sichuan Province, China, were selected. The activity of superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT） in four mulberry varieties was determined. Soluble protein, soluble sugar, proline, net photosynthetic rate and transpiration rate of mulberry leaves were analyzed. The results show that during the early stages of drought stress, protective enzyme activities in four mulberry varieties continually increased. However, prolonged and intensified drought stress decreased their activities. After re-watering, they gradually returned to normal levels. Under drought stress and after re-watering, ＇Nanye-l＇ and ＇Yunsang-l＇ clearly showed smaller changes in soluble protein content than the ＇Xinyizhilai＇ and ＇Husang-32＇ varieties, whereas changes in their soluble sugar content were clearly greater than these last two varieties. When water deficit was protracted and intensified, ＇Nanye-1＇ and ＇Yunsang-1＇ still showed higher net photosynthetic, transpiration rates and water-use efficiency than ＇Xinyizhilai＇ and ＇Husang-32＇.

Growth responses of gypsy moth larvae to elevated CO2： the influence of methods of insect rearing

The effects of elevated CO2 on foliar chemistry of two tree species （Populus pseudo-simonii Kitag. and Betula platyphylla） and on growth of gypsy moth （Lymantria dispar L.） larvae were examined. Furthermore, we focused on the comparison of results on the growth responses of larvae obtained from two methods of insect rearing, the nochoice feeding trial performed in the laboratory or in situ in open-top chambers. On the whole, both primary and secondary metabolites in the leaves of the two tree species were significantly affected by main effects of time （sampling date）, CO2 and species. Elevated CO2 significantly increased the C： N ratio and concentrations of the soluble sugar, starch, total nonstructural carbohydrates, total phenolics and condensed tannins, but significantly decreased the concentration of nitrogen. Higher contents of total phenolics and condensed tannins were detected in the frass of larvae reared in elevated CO2 treatments. Overall, the growth of gypsy moth larvae were significantly inhibited by elevated CO2 and CO2- induced changes in leaf quality. Our study did not indicate the two methods of insect rearing could influence the direction of effects of elevated CO2 on the growth of individual insects; however, the magnitude of negative effects of elevated CO2 on larval growth did differ between the two insect rearing methods, and it seems that the response magnitude was also mediated by larval age and host plant species.

Broussonetia papyrifera controls nutrient return to soil to facilitate its invasion in a tropical forest of Ghana

Aims Non-native invasive plants can alter soil chemistry through litter production and decomposition to facilitate their invasion.However,the important roles of these underlying processes in plant invasion remain poorly understood,particularly in tropical forest ecosys-tems.Here,we compared litter production,quality and decompos-ition of two invasive species(Broussonetia papyrifera and Cedrela odorata)and two co-occurring native species(Celtis mildbraedii and Funtumia elastica),and soil properties under them to elucidate their roles in the invasion of a tropical forest in Ghana.Methods Leaf litter production rates were determined using 36 mesh traps installed in the study area,while litter quality and soil physico-chemical properties were determined using standard protocols.A 6-month decomposition experiment using the litterbag technique was conducted to compare the decomposition rates of the species.Important Findings Litter production varied among the species and over time,with B.papyrifera producing 0.35-4.27 tons ha−1 y−1 from October to January;the other species produced 0.03^(-1).74 tons ha−1 y−1 over the same period.In the litterbag experiment,B.papyrifera recorded the lowest mass remaining(11-36%),followed by C.odorata(17-51%),F.elastica(31-55%)and C.mildbraedii(48-62%)in that order.Broussonetia papyrifera had the highest nitrogen(3.91%)and phosphorus(0.24%)but lowest lignin(12.20%)concentrations and the lowest C:N(10.87)ratio,indicating higher litter quality com-pared to the other species.Soil under B.paprifera was richest in phosphorus and nitrogen compared to the other species.Overall,our results indicate that the production of more nutrient-rich and rapidly decomposing leaf litter by B.papyrifera may constitute an important positive feedback mechanism driving its invasion and impacts in this tropical forest.