[Pollution Characteristics and Source Analysis of Heavy Metals in Farmland Soils in the Taige Canal Valley].

To determine the distribution characteristics of heavy metal pollution in farmland soils and related influencing factors in the Taige canal valley, and guarantee soil environmental quality and safety of agricultural products, 118 topsoil samples were collected from the Taige canal valley's farmland soils, and contents of chromium (Cr), mercury (Hg), arsenic (As), copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), and cadmium (Cd) were measured. A single factor index and comprehensive index were used to assess soil heavy metal contamination with the soil background value of the Taihu Lake basin as the evaluation standard. The multivariate statistical analysis and the geostatistical analysis were combined to identify and apportion the pollution sources of soil heavy metals. The results showed that:The average concentrations of Cr, Hg, As, Cu, Zn, Ni, Pb, and Cd in soils were 63.25, 0.25, 7.83, 35.24, 77.25, 31.48, 38.37, and 0.16 mg·kg-1, respectively, all of which except for Cr and As were higher than the local soil background values. The content of each heavy metal in most soil samples were lower than the risk screening values for soil contamination of agricultural land. The comprehensive index showed that the degree of pollution of soil heavy metals were at a slightly polluted level in 87.29%, moderately polluted level in 5.93%, and severely polluted level in 6.78% of the sampling. Hg, Cu, Zn, Pb, and Cd in the watershed soil were affected by agricultural activities and atmospheric deposition. Cr and Ni were affected by the parent material and industrial production activities. As was mainly derived from the parent material.

An evaluation of Frankliniella occidentalis (Thysanoptera: Thripidae) and Frankliniella intonsa (Thysanoptera: Thripidae) performance on different plant leaves based on life history characteristics.

To compare the performance of Frankliniella occidentalis (Pergande) and native Frankliniella intonsa (Trybom) on cucumber and tomato leaves in laboratory, life history characters were investigated, and life tables were constructed using the method of age-stage, two-sex table life. Compared with tomato leaf, there were shorter total preoviposition period (TPOP), higher fecundity, longer female longevity, and higher intrinsic rate of increase (r) of both F. occidentalis and F. intonsa on cucumber leaf. Meanwhile, on cucumber leaf, the shorter TPOP, higher fecundity, longer female longevity, and higher value of r were found on population of F. intonsa but on tomato leaf which were found on population of F. occidentalis. From above, cucumber leaf was the preference to population development of both F. occidentalis and F. intonsa compared with tomato leaf. Nevertheless, on cucumber leaf, population of F. intonsa would grow faster than that of F. occidentalis, which was the opposite on tomato leaf. As to the population development in fields, much more factors would be taken into account, such as pollen, insecticide resistance, and effects of natural enemies etc.

Feeding by whiteflies suppresses downstream jasmonic acid signaling by eliciting salicylic acid signaling.

Phloem-feeding whiteflies in the species complex Bemisia tabaci cause extensive crop damage worldwide. One of the reasons for their "success" is their ability to suppress the effectual jasmonic acid (JA) defenses of the host plant. However, little is understood about the mechanisms underlying whitefly suppression of JA-regulated defenses. Here, we showed that the expression of salicylic acid (SA)-responsive genes (EDS1 and PR1) in Arabidopsis thaliana was significantly enhanced during feeding by whitefly nymphs. Whereas upstream JA-responsive genes (LOX2 and OPR3) also were induced, the downstream JA-responsive gene (VSP1) was repressed, i.e., whiteflies only suppressed downstream JA signaling. Gene-expression analyses with various Arabidopsis mutants, including NahG, npr-1, ein2-1, and dde2-2, revealed that SA signaling plays a key role in the suppression of downstream JA defenses by whitefly feeding. Assays confirmed that SA activation enhanced whitefly performance by suppressing downstream JA defenses.