Exogenous Nitric Oxide Involved in Subcellular Distribution and Chemical Forms of Cu^(2+) Under Copper Stress in Tomato Seedlings

Nitric oxide（NO）,a bioactive signaling molecule,serves as an antioxidant and anti-stress agent under abiotic stress.A hydroponics experiment was conducted to investigate the effects of sodium nitroprusside（SNP）,a NO donor,on tomato seedlings exposed to 50 μmol L-1CuCl 2.The results show that copper is primarily stored in the soluble cell sap fraction in the roots,especially after treatment with Cu＋SNP treatment,which accounted for 66.2% of the total copper content.The copper concentration gradually decreased from the roots to the leaves.In the leaves,exogenous NO induces the storage of excess copper in the cell walls.Copper stress decreases the proportion of copper integrated with pectates and proteins,but exogenous NO remarkably reverses this trend.The alleviating effect of NO is blocked by hemoglobin.Thus,exogenous NO is likely involved in the regulation of the subcellular copper concentrations and its chemical forms under copper stress.Although exogenous NO inhibited the absorption and transport of excess copper to some extent,the copper accumulation in tomato seedlings significantly increased under copper stress.The use of exogenous NO to enhance copper tolerance in some plants is a promising method for copper remediation.

High rodent abundance increases seed removal but decreases scatter-hoarding and seedling recruitment along an elevational gradient

The distributions of small rodents in mountainous environments across different elevations can provide important information regarding the effects of climate change on the dispersal of plant species.However,few studies of oak forest ecosystems have compared the elevational patterns of sympatric rodent diversity,seed dispersal,seed bank,and seedling abundance.Thus,we tested the differences in the seed disperser composition and abundance,seed dispersal,seed bank abundance,and seedling recruitment for Quercus wutaishanica along 10 elevation levels in the Taihang Mountains,China.Our results provide strong evidence that complex asymmetric seed dispersal and seedling regeneration exist along an elevational gradient.The abundance of rodents had a significant negative correlation with the elevation and the seed removal rates peaked and then declined with increasing elevation.The seed removal rates were higher at middle and lower elevations than higher elevations but acorns were predated by 5 species of seed predators at middle and lower elevations,and thus,there was a lower likelihood of recruitment compared with those dropped beneath mother oaks at higher elevations.More importantly,the number of individual seeds in the seed bank and seedlings increased with the elevation,although dispersal services were reduced at sites lacking rodents.As conditional mutualists,the rodents could possibly act as antagonistic seed predators rather than mutualistic seed dispersers at low and middle elevations,thereby resulting in the asymmetric pattern of rodent and seedling abundance with increasing elevation to affect the community assembly and ecosystem functions on a large spatial scale.