放牧强度对宁夏盐池荒漠草地土壤与植被恢复的影响

以宁夏盐池县荒漠草原为研究对象,设置3个放牧强度:围栏封育(NG,no grazing)、中度放牧(MG,moderate grazing)、重度放牧(HG,heavy grazing),运用主成分分析与路径分析对草地质量进行综合评价,比较不同放牧条件下草地植被和土壤理化性质的差异,以期为退化草地生态系统恢复与重建提供理论指导。结果表明:NG处理下草地植被生物量较MG和HG处理分别提高10.78%和74.85%,植被高度与盖度显著提高31.21%~131.27%和26.03%~93.29%。NG处理的土壤机械稳性团聚体以粒径>0.25 mm的大团聚体为主,HG处理以<0.25 mm的微团聚体为主,不同放牧处理的土壤水稳性团聚体粒径>0.25 mm的大团聚体占比、表层土壤水稳性团聚体的平均质量直径和几何平均直径大小依次为:NG>MG>HG;NG处理下的土壤供肥潜力、土壤供肥强度和土壤综合质量显著高于HG。综上所述,围栏封育下的草场植被、土壤结构和肥力恢复效果更好,对土壤的综合质量有明显的改善作用,是适合的草地生态恢复措施。

Phytoremediation capacity of the hyperaccumulator Solanum nigrum L.and Solanum lycopersicum L.cultivars at the flowering stage in cadmium-polluted soil

Dear Editor,Remediation of cadmium(Cd)-contaminated soil is a popular topic in global environmental science.Phytoremediation using hyperaccumulators or certain plants to accumulate and remove Cd from polluted soils is a promising approach.Wei et al.(2005)first described Solanum nigrum L.as a Cd hyperaccumulator.Subsequently,various aspects of S.nigrum,including the protective effects on proline,physiological and biochemical responses,earthworms,arbuscular mycorrhizal fungi,and fertilizers and the intercropping with Solanum photeinocarpum,have been extensively studied(Xu et al.,2009;Khan et al.,2014;Wang et al.,2015;Tang et al.,2017;Yang et al.,2019).

Population genomic analysis reveals domestication of cultivated rye from weedy rye

Rye(Secale cereale)is an important crop with multiple uses and a valuable genetic resource for wheat breeding.However,due to its complex genome and outcrossing nature,the origin of cultivated rye remains elusive.The geneticist N.I.Vavilov proposed that cultivated rye had been domesticated from weedy rye,rather than directly from wild species like other crops.Unraveling the domestication history of rye will extend our understanding of crop evolution and upend our inherent understanding of agricultural weeds.To this end,in this study we generated the 8.5 Tb of whole-genome resequencing data from 116 worldwide accessions of wild,weedy,and cultivated rye,and demonstrated that cultivated rye was domesticated directly from weedy relatives with a similar but enhanced genomic selection by humans.We found that a repertoire of genes that experienced artificial selection is associated with important agronomic traits,including shattering,grain yield,and disease resistance.Furthermore,we identified a composite introgression in cultivated rye from the wild perennial Secale strictum and detected a 2-Mb introgressed fragment containing a candidate ammonium transporter gene with potential effect on the grain yield and plant growth of rye.Taken together,our findings unravel the domestication history of cultivated rye,suggest that interspecific introgression serves as one of the likely causes of obscure species taxonomy of the genus Secale,and provide an important resource for future rye and wheat breeding.

The effects of different electrode materials on seed germination of Solanum nigrum L.and its Cd accumulation in soil

The effects of different electrode on Solanum nigrum L.seed germination were determined.The result showed that germination percentage(GP)of seeds in treatment T2(titanium elec-trode)was 26.6%higher than in control(CK,without electric field).High potassium and calcium concentrations were beneficial for seed enzymatic activity in treatment T2,which could partly explain the increase in GP.Cd accumulation(μg/pot)in S.nigrum treated with any electric field was significantly higher(p<0.05)than in CK without electric field.Specif-ically,Cd accumulation under the treatment T3(stainless steel electrode)was the highest both in roots and shoots;this accumulation in shoots and roots were 74.7%and 67.4%higher for stainless steel than in CK.This increase must have been associated with a higher Cd concentration in plants and did not exert a significant effect on the biomass.In par-ticular,Cd concentrations in roots and shoots under stainless steel treatment were both significantly higher than in CK(p<0.05),which had to be related to the higher available Cd concentration in the soil in the middle region.Furthermore,it could be attributed to al-tered soil pH and other soil properties.Moreover,none of the biomasses were significantly affected(p<0.05)by different electrode materials compared to CK.