[Review on the effects of heavy metal pollution on herbivorous insects]. / é‡é‡‘å±žæ±¡æŸ“å½±å“æ¤é£Ÿæ€§æ˜†è™«çš„ç ”ç©¶è¿›å±•.

Heavy metal pollution is one of the thorniest issues in the world, which is a serious threat to ecosystems and food security. As an important link of food chain and food web in the ecosystem, herbivorous insects play important role in the transfer and accumulation of heavy metals. Consequently, more and more attentions have been paid on the potential effects of heavy metal pollution on herbivorous insects. Here, we reviewed the effects of heavy metal pollution on herbivorous insects with literature publshied during 2007 to 2018. Herbivorous insects were exposed to heavy metals pollution via four ways, including insect diets or food added with inorganic heavy metals, field exposure with heavy metals, "soil/substrate-plants-herbivorous insect" food chain and in vitro injection. Excessive accumulation of heavy metals in insect body results in decreased survival rate, reproductive capacity and population growth, the retarded growth and development. Physiological and biochemical toxicity of heavy metal pollution to herbivorous insects included cell ultra-structure destruction and DNA damage, decreased amount of energy materials, and changes in enzymes acti-vity and gene expression levels. However, herbivorous insects can resist heavy metal stress by producing metallothionein and enhancing activity of detoxification enzymes etc., which probably results in their adaptive evolution to heavy metal stress at low intensity or long-term and even improve their tolerance to other stresses (e.g., pesticides).

[Effect of Bt rice straw returning in soil on the growth and reproduction of Eisenia fetida.] / Bt水稻秸秆还田对赤子爱胜蚓生长发育和生殖的影响.

Bacillus thuringiensis (Bt) protein can enter the soil through Bt crops straw returning to field, which may affect the growth and reproduction of soil animals, such as earthworms. Here, Bt rice (b2B138) and conventional rice (Anfeng A) straw were returned in soil to evaluate the impact of Bt rice on Eisenia fetida. Two varieties of rice straw were added into soil to breed E. fetida at the rates of 2.5%, 5%, 7.5% and 10%. The survival rate, relative growth rate, reproduction of earthworm, the Cry1Ab content in soil-straw mixture and earthworm were detected after 7, 15, 30, 45, 60, 75, 90 d. The results showed that Bt rice straw returning at higher concentrations (7.5% and 10%) inhibited the survival rate of E. fetida. Bt rice straw returning had no adverse effect on relative growth rate (RGR) of E. fetida. Bt rice straw treatment improved the reproduction of earthworms under 5%, 7.5% and 10% straw returning in soil. Enzyme-linked immunosorbent assay (ELISA) results indicated that immunoreactive Cry1Ab was detectable in soil-straw mixture and E. fetida from Bt rice treatments, and a strong decline was observed in soil-straw mixture with the increase of treated time. Therefore, Cry1Ab released from Bt rice straw returning at 2.5% and 5% concentration had no adverse effects on the growth and reproduction of E. fetida.

[Effects of lead stress on the growth and reproduction of Spodoptera litura fabricius (Lepidoptera:Noctuidae)].

Standard artificial diet was added with different concentration lead (Pb) to feed herbivorous insect Spodoptera litura larvae to study their growth and reproduction under the effects of Pb stress. With the increasing concentration Pb in the diet, the survival rate and body mass of the larvae at their different development stages (larvae, pupae, and adults) decreased. The minimum concentration of Pb which caused the significant decrease of the survival rate was 100 mg x kg(-1), and that caused a remarkable decrease of body mass was 50 mg x kg(-1). After fed with the diet containing 25-200 mg x kg(-1) of Pb, the duration of laying eggs was significantly shortened. With increasing concentration Pb in the diet, the oviposition rate and fecundity of female adults decreased significantly, the average mass of one thousand eggs was significantly less than that of the control, and the hatching rate of the eggs laid by adults was also decreased significantly. All the results suggested that Pb stress had significant inhibition effects on the growth and reproduction of S. litura.

[Effects of Bt corn straw insecticidal proteins on enzyme activities of Eisenia fetida].

Bacillus thuringiensis (Bt) proteins released from Bt corn can enter soil ecosystem via returning straw into field, root exudation, and pollen fluttering-down. In this study, the straws of Bt corn and its near-isogenic non-Bt line were added into soil with an application rate of 5% and 7.5% to breed Eisenia fetida, and the total protein content and the activities of acetylcholine esterase (AchE), glutathione peroxidase (GSH-PX), catalase (CAT), and superoxide dismutase (SOD) in E. fetida were determined after 7 and 14 days. Under the same application rate of the straws, the total protein content and GSH-PX activity of E. fetida decreased while the AchE, CAT, and SOD activities increased on the 14th day, compared with those on the 7th day. The Bt corn straw increased the SOD activity and decreased the AchE and GSH-PX activities, but had less effects on the total protein content and CAT activity, compared with non-Bt corn straw. All the results suggested that Bt corn straw had no inhibitory effect on E. fetida total protein but could inhibit the AchE and GSH-PX activities, and could not induce CAT activity but induce SOD activity within a short time.

[Effects of reduced nitrogen application on the yield, quality, and economic benefit of sugarcane intercropped with soybean].

A two-factor field experiment of randomized block design was conducted in Guangzhou to investigate the effects of reduced nitrogen application on the yield, quality, and total biomass dynamic of sugarcane as well as the economic benefit of the sugarcane population under different sugarcane/soybean intercropping patterns. Neither N application nor intercropping pattern had significant effects on the yield and quality of sugarcane, and no significant differences were observed in the yield and quality of sugarcane among all treatments. The land equivalent ratio (LER) of sugarcane/soybean intercropping at different N application levels was from 1.36 to 2.12, suggesting that sugarcane/soybean intercropping had higher LER than monoculture sugarcane. The total dry matter (except root) of sugarcane in all treatments increased with plant growth, and the growth pattern fitted sigmoid function. At lower nitrogen application level, the eigenvalues of the dynamic dry matter accumulation model were more coordinative, compared with those at higher nitrogen application level, which meant that in the later case, sugarcane had an advanced peak growth time and shortened fast-growth duration, and thereby, its yield decreased. Therefore, it was possible to reasonably adjust nitrogen application level to improve the eigenvalues of the sugarcane dynamic dry matter accumulation model, and accordingly, to achieve high yield. The population economic benefit under sugarcane/soybean intercropping was 3.2%-26.3% higher at lower than at higher nitrogen application level, suggesting the increase of the economic benefit of sugarcane population under reduced nitrogen application. Among the treatments, 1:2 sugarcane/soybean intercropping had the best economic benefit.