Chlorophyll variation mutants are important materials for studying chlorophyll metabolism, photosynthesis, chloroplast biogenesis and related physiological processes. In this study, a chlorophyll-deficient soybean mutant (cd1) was isolated by screening M 2 progenies of cultivar ÔNannong 86-4Õ treated with 0.4% ethyl methanesulfonate. cd1 displayed yellow-green leaves from seedling stage V1 to fully flowering stage R2, abnormal chloroplasts, lower total chlorophyll content (30-66% reduction), lower plant height and lower seed yield compared to its wild-type control. Genetic analysis demonstrated that the visible yellow-green trait was controlled by a single recessive nuclear gene. Subsequently, the cd1-mutant gene was mapped at a 6.9-cM interval on chromosome 10, flanked by two simple sequence repeat markers Satt633 and Sat_291. These results provide us with the opportunity to study a novel gene regulating chlorophyll synthesis.

Wolbachia influence the fitness of their invertebrate hosts. They have effects on reproductive incompatibility and egg production. Although the former are well characterized, the mechanistic basis of the latter is unclear. Here, we investigate whether apoptosis, which has been implicated in fecundity in model insects, influences the interaction between fecundity and Wolbachia in the planthopper Laodelphax striatellus. Wolbachia-infected females produced about 30% more eggs than uninfected females. We used the terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labeling staining to visualize apoptosis. Microscopic observations indicated that the Wolbachia strain wStri increased the number of ovarioles that contained apoptotic nurse cells in both young and aged adult females. The frequency of apoptosis was much higher in the infected females. The increased fecundity appeared to be a result of apoptosis of nurse cells, which provide nutrients to the growing oocytes. In addition, cell apoptosis inhibition by caspase messenger RNA interference in Wolbachia-infected L. striatellus markedly decreased egg numbers. Together, these data suggest that wStri might enhance fecundity by increasing the number of apoptotic cells in the ovaries in a caspase-dependent manner. Our findings establish a link between Wolbachia-induced apoptosis and egg production effects mediated by Wolbachia, although the way in which the endosymbiont influences caspase levels remains to be determined.

Salinity and waterlogging are worldwide environmental constraints to crop production. In this study, plants of winter wheat were grown in pots in the semi‐field with transparent waterproof top and subjected to salt (ST), waterlogging (WL) and their combination (SW) stresses since 7 days after anthesis (DAA). The effects of ST, WL and SW on the contents of sugars, free amino acid (FAA), starch, protein, Na+ and K+ in flag leaves, stems and grains were investigated during grain filling stage. ST and SW significantly reduced total soluble sugars (TSS) and sucrose contents in both vegetative organs and grains, and fructan content in stems. ST and SW also reduced FAA contents in stems and grains, whereas they increased FAA content in flag leaves. This resulted in a significant decrease in the ratio of TSS to FAA under ST and SW stresses in flag leaves. Moreover, ST and SW increased Na+ content, whereas they reduced K+ content, which resulted in a reduction in K+/Na+ ratio, especially during the late filling stage. In addition, ST and SW caused a reduction in starch and protein accumulations in grains. Finally, the temporal (time‐course) and spatial (different organs) responses of sugars, FAA, Na+ and K+ to ST, SW and WL and their relationships to grain starch and protein formation were further investigated.

Summary Organic carbon (OC) and nitrogen (N) storage in soil plays an important role in global climate change and in maintaining food security. Pollution of soil with heavy metals has occurred in many parts of the world, but their effects on soil OC and N have not been well addressed. Relevant data were extracted from peer‐reviewed journal papers and analysed by a meta‐analysis to determine how long‐term heavy metal pollution affected soil OC and N status. Plant biomass decreased significantly because heavy metals in soil decreased soil OC and N concentrations by 5.0 and 17.9%, respectively, but increased the C/N ratio by 5.1%. The largest reductions in soil OC and N concentrations were in soil more strongly polluted by metals. The changes in soil OC and N with metal pollution varied with climatic conditions. More substantial decreases in OC and N concentrations were likely to occur in polluted soil with large background contents of OC and low pH. Overall, heavy metals were linked to greater reductions in soil OC and N concentrations in natural ecosystems than in agro‐ecosystems. These results provided a quantitative evaluation of the effects of heavy metal pollution on the decrease in soil C and N concentrations and, therefore, on global climate change. Further consideration should be given to changes in the cycling of C and N in soil polluted with metals in natural and agro‐ecosystems.

SUMMARYAn inventory of topsoil soil organic carbon (SOC) content in household farms was performed in a village from a red earth region in Jiangxi Province, China in 2003. In this region, the farmland managed by each household is fragmented, consisting of several plots of land that are not necessarily adjacent to each other. A statistical analysis of SOC variation with land use and household management type, and with crop management practices was conducted. Plot size ranged from 0·007 to 0·630 ha with a mean of 0·1 ha, and SOC content ranged from 1·72 to 25·2 g/kg, varying widely with a variety of land management and agricultural practices, arising from individual household behaviours. The mean SOC content in plot size <0·1 ha was 20% lower than in plot size ⩾0·1 ha. SOC of dry crop plots was 70% lower than that in rice paddies, and SOC of plots contracted from the village was almost double that of plots leased from other householders. Moreover, a 30% increase in SOC was observed with green manure cultivation, and a 55% increase under triple cropping. The difference in SOC levels between the least and most favourable cases of household land management and agricultural practice was up to 150%. The results suggest that policies targeted at crop management alone may not deliver the expected SOC benefits if household land management is also not improved.