Species-diversified plant cover enhances orchard ecosystem resistance to climatic stress and soil erosion in subtropical hillside

Naturally occurring plants in agroecosystem evidently play an important role in ecosystem stability. Field studies on the ecological effects of native plants conserved in orchard and their resistance to adverse climatic stress, and soil erosion were conducted from 1998 to 2001 in a newly developed Changshan-huyou (Citrus changshan-huyou Y.B. Chang) orchard. The experimental area covered 150 ha in typical red soil hilly region in southeastern China. The experimental design was a randomized complete block with six combinations of twelve plant species with four replications. All species used were native in the orchard. Plots were 15×8m^2 and separated by 2m buffer strips. Precipitation, soil erosion in rainstorm days and aboveground biomass of plant community when rainstorm days ended, soil temperature and moisture under various plant covers during seasonal megathermal drought period, antiscourability of soil with different root density under various simulated rainfalls were measured. Plant cover significantly decreased the daily highest and mean soil temperature and its daily variation in hot-drought season, but there was no significant difference of the alleviation among various plant covers. Plant covers significantly increased the soil moisture in seasonal megathermal drought period. Better moisture maintenance and soil erosion reduction was found when the plant species numbers in cover plant communities increased from one to eight. Higher root density in plant communities with higher species richness increased significantly the antiscourability of the soil. It was suggested that conserving plant communities with diversified native species could produce the best positive ecological effects on citrus orchard ecosystem stability.

Effect of Proline Pretreatment on Grapevine Shoot-Tip Response to a Droplet-Vitrification Protocol

Proline has been shown to accumulate in plants in response to biotic and abiotic stresses. Exogenous proline has thus been used for improving some plant cryopreservation protocols. Further enhancement of cryopreservation efficiency for in vitro grapevines could be expected if stresses linked to cryopreservation procedures could be reduced. We therefore studied the possible beneficial effect of proline in grapevine cryopreservation. Single-node explants from in vitro grown grapevine plantlets (Vitis vinifera L. cv Portan) were cultured on shooting media (half-strength MS + 1 μM BAP) containing no proline (control) or 50, 500, or 2000 μM filter-sterilized L-proline. Shoot tips excised from these microshoots were subjected to a PVS2-based droplet-vitrification procedure. Control and rewarmed explants were grown on a recovery medium containing 1 μM BAP. Shoot development on control medium and lower proline concentrations did not notably differ whereas the highest concentration of proline inhibited shoot development. Carry-over effects were observed since lower survival and regrowth were obtained both for non-frozen or LN-treated explants excised from micro-shoots obtained on the 2000 μM proline medium. No significant differences in survival and regrowth were observed for non-frozen explants subjected to pretreatment without LN exposure. A slightly enhancing effect (although non-significant) on post-cryopreservation survival was observed for explants derived from shoots developed on 50 or 500 μM proline, but no significant improvement of regrowth percentage was observed for these two conditions. Although a slight increase in survival could be observed, no significant beneficial effect of proline pretreatment on post-cryoconservation regrowth could be evidenced in our conditions. However, the 2-week period before explant excision could have allowed at least partial metabolism and catabolism of exogenous proline;the results observed could thus have been the consequence of complex interactions. Shorter proline treatments applied closer to the actual LN exposure step might produce different results and allow for clearer interpretation.

Coronatine Alleviates Water Deficiency Stress on Winter Wheat Seedlings

With the aim to determine whether coronatine （COR） alleviates drought stress on wheat, two winter wheat （Triticum aestivum L.） cultivars, ChangWu134 （drought-tolerant） and Shan253 （drought-sensitive） were studied under hydroponic conditions. Seedlings at the three-leaf stage were eultured in a Hoagland solution containing COR at 0.1 ~M for 24 h, and then exposed to 20% polyethylene glycol 6000 （PEG- 6000）. Under simulated drought （SD）, COR increased the dry weight of shoots and roots of the two cultivars significantly; the root/shoot ratio also increased by 30% for Shan253 and 40% for ChangWu134. Both cultivars treated with COR under SD （0.1COR-I-PEG） maintained significantly higher relative water content, photosynthesis, transpiration, intercellular concentration of CO2 and stomatal conductance in leaves than those not treated with PEG. Under drought, COR significantly decreased the relative conductivity and malondialdehyde production, and the loss of 1,1-diphenyl-2-picrylhydrazyl scavenging activity in leaves was significantly alleviated in COR-treated plants. The activity of peroxidase, catalase, glutathione reductase and ascorbate peroxidase were adversely affected by drought. Leaves of plants treated with COR under drought produced less abscisic acid （ABA） than those not treated. Thus, COR might alleviate drought effects on wheat by reducing active oxygen species production, activating antioxidant enzymes and changing the ABA level.

Alleviating Workplace Stress

The string of suicides at Foxconn has sparked concern about well-being and pressure on young factory workers At 6:20 a.m. May 25, 19-year-old LiHai climbed over the fence on the fifth floor of a dormitory

Ionome profiling and arsenic speciation provide evidence of arsenite detoxification in rice by phosphate and arsenite-oxidizing bacteria

Arsenite(As(III))as the most toxic and mobile form is the dominant arsenic(As)species in flooded paddy fields,resulting in higher accumulation of As in paddy rice than other terrestrial crops.Mitigation of As toxicity to rice plant is an important way to safeguard food production and safety.In the current study,As(III)-oxidizing bacteria Pseudomonas sp.strain SMS11 was inoculated with rice plants to accelerate conversion of As(III)into lower toxic arsenate(As(V)).Meanwhile,additional phosphate was supplemented to restrict As(V)uptake by the rice plants.Growth of rice plant was significantly inhibited under As(III)stress.The inhibition was alleviated by the introduction of additional P and SMS11.Arsenic speciation showed that additional P restricted As accumulation in the rice roots via competing common uptake pathways,while inoculation with SMS11 limited As translocation from root to shoot.Ionomic profiling revealed specific characteristics of the rice tissue samples from different treatment groups.Compared to the roots,ionomes of the rice shoots were more sensitive to environmental perturbations.Both extraneous P and As(III)-oxidizing bacteria SMS11 could alleviate As(III)stress to the rice plants through promoting growth and regulating ionome homeostasis.