Ar-Ar Dating of Baimazhai Nickel-Copper-（PGE） Sulphide Deposit and Its Significance, Southeast Yunnan Province, China

The Baimazhai Ni-Cu- （PGE） sulphide deposit in southeast Yunnan Province is hosted in mafic-ultramafic intrusions associated with the Permian Emeishan large igneous province. The deposit, one of several in the province, exhibits field and petrographic features suggestive of post-magmatic modification. The mafic-ultramafic intrusions that host the Baimazhai sulphide ores show near-pervasive to pervasive hydrothermal alteration, with the sulphides be- ing spatially associated with hydrothermal minerals such as biotite, amphibole and chlorite. This intimate association suggests that the sulphide ores were subjected to deformational and hydrothermal redistribution and textural changes resulting in disseminated and brecciated ores. Geochemically the Baimazhai sulphide ores are enriched in Cu, Pd and Au which, according to published studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar age data yielded plateau ages of about 160-170 Ma, which also supports the modification features of the sulfide ores.     

Chemical partitioning and remobilization of heavy metals from sewage sludge dumped in Dublin Bay

During the disposal of sewage sludge to the marine environment, chemical changes may alter the mobility of trace elements, thus affecting their potential toxicity and availability to marine organisms. Primary sludge from the Ringsend treatment plant in Dublin receives both domestic waste and trade wastes which contain heavy metals, and approx. 250,000 tons per annum is periodically dumped in Dublin Bay. The purpose of this study was to determine changes which may occur in the chemical partitioning of heavy metals in the sludge during disposal. Samples of sludge were collected from the treatment plant in July 1987. Sequential chemical extraction of heavy metals (Cu, Pb, Cd, Zn, Fe, Mn) was carried out in a nitrogen-filled glove box using 1 M ammonium acetate, 1 M sodium acetate, 0.1 M hydroxylamine HCl (pH 2), 0.2 M ammonium oxalate (pH 3), 30% hydrogen peroxide and concentrated HNO₃. Seawater-extractable metal was determined by mixing subsamples of sludge with filtered seawater from Dublin Bay for 2 h. Chemical partitioning of heavy metals among solid phases in the sludge residue was redetermined by sequential chemical extraction. Both sludge and dumpsite sediments were analysed for total heavy metal content and organic content. The sludge was found to be only slightly anaerobic with a water content of 88% and significant concentrations of some metals, notably copper and zinc. Most of the non-residual copper, lead and cadmium was found in the organic/sulphidic fraction of the sludge (hydrogen peroxide extract), while the dominant phase for zinc was the moderately reducible fraction (ammonium oxalate extract) and only iron and manganese had substantial proportions of metal in more labile phases. Agitation with seawater mobilized cadmium and manganese to a significant extent (56 and 43%, respectively) but negligible amounts of copper or lead (0 and 2%, respectively). However, significant changes in solid-phase partitioning of lead and zinc occurred resulting in mobilization from stronglybound to more labile fractions. No deleterious effects were found at the dumpsite but localized effects are possibly due to the increased mobility of zinc, lead and particularly cadmium.     

Linking Autophagy to Potential Agronomic Trait Improvement in Crops

Autophagy is an evolutionarily conserved catabolic process in eukaryotic cells, by which the superfluous or damaged cytoplasmic components can be delivered into vacuoles or lysosomes for degradation and recycling. Two decades of autophagy research in plants uncovers the important roles of autophagy during diverse biological processes, including development, metabolism, and various stress responses. Additionally, molecular machineries contributing to plant autophagy onset and regulation have also gradually come into people’s sights. With the advancement of our knowledge of autophagy from model plants, autophagy research has expanded to include crops in recent years, for a better understanding of autophagy engagement in crop biology and its potentials in improving agricultural performance. In this review, we summarize the current research progress of autophagy in crops and discuss the autophagy-related approaches for potential agronomic trait improvement in crop plants.     

Sink Strength Promoting Remobilization of Non-Structural Carbohydrates by Activating Sugar Signaling in Rice Stem during Grain Filling

The remobilization of non-structural carbohydrates (NSCs) in the stem is essential for rice grain filling so as to improve grain yield. We conducted a two-year field experiment to deeply investigate their relationship. Two large-panicle rice varieties with similar spikelet size, CJ03 and W1844, were used to conduct two treatments (removing-spikelet group and control group). Compared to CJ03, W1844 had higher 1000-grain weight, especially for the grain growth of inferior spikelets (IS) after removing the spikelet. These results were mainly ascribed to the stronger sink strength of W1844 than that of CJ03 contrasting in the same group. The remobilization efficiency of NSC in the stem decreased significantly after removing the spikelet for both CJ03 and W1844, and the level of sugar signaling in the T6P-SnRK1 pathway was also significantly changed. However, W1844 outperformed CJ03 in terms of the efficiency of carbon reserve remobilization under the same treatments. More precisely, there was a significant difference during the early grain-filling stage in terms of the conversion of sucrose and starch. Interestingly, the sugar signaling of the T6P and SnRK1 pathways also represented an obvious change. Hence, sugar signaling may be promoted by sink strength to remobilize the NSCs of the rice stem during grain filling to further advance crop yield.     

Diagenetic remobilization of manganese, iron, copper and lead in anoxic sediment of a freshwater pond

The diagenetic remobilization of manganese, iron, copper and lead in anoxic sediment of a freshwater pond, T Reservoir, Japan has been examined in an in situ submerged chamber system, through the interstitial water and sediment analyses. Manganese was released continuously from the sediment into the overlying water during the experiment, whereas iron was released from the sediment abruptly after the 2nd day of the experiment. The steep vertical concentration gradients of manganese and iron were observed in the interstitial water. The release of manganese and iron from the sediment is due to the dissolution of ferro-manganese oxides and hydroxides in the surface sediment under anoxic condition. In contrast to manganese and iron, copper and lead were not released from the sediment during the experiment, and their concentrations in the interstitial water were not significantly different from the values of the overlying water. The results show that the diagenetic remobilization of copper and lead in the sediment is negligibly small. It is likely that copper and lead are fixed into the sediment by some process other than the formation of sulfides.