Studies on Pongamia pinnata （L.） Pierre leaves： understanding the mechanism（s） of action in infectious diarrhea

While data are available on the effect of medicinal plants on intestinal motility and their antibacterial action, there is a paucity of information on their mode of action on various aspects of diarrheal pathogenicity, namely colonization to intestinal epithelial cells and production/action of enterotoxins. Crude decoction of dried leaves of Pongamia pinnata was evaluated for its antimicrobial （antibacterial, antigiardial and antirotaviral） effect; and its effect on production and action of enterotoxins （cholera toxin, CT; Escherichia coli labile toxin, LT; and E. coli stable toxin, ST）; and adherence of enteropathogenic E. coli and invasion of enteroinvasive E. coli and Shigellaflexneri to epithelial cells. The decoction had no antibacterial, antigiardial and antirotaviral activity, but reduced production of CT and bacterial invasion to epithelial cells. The observed results indicated that the crude decoction ofP. pinnata has selective antidiarrheal action with efficacy against cholera and enteroinvasive bacterial strains causing bloody diarrheal episodes.     

Isolation and physiological characteristics of a premature senescence mutant in rice （Oryza sativa L.）

A rice pse(t) (premature senescence, tentatively) mutant line, was isolated from 4500 independent T-DNA inserted transgenic lines. The symptoms of premature senescence appeared more severely than those of the control plants (Zhonghua 11,japonica) at the last development stage. To characterize the mutant and provide basic information on the candidate genes by mapping to a physical region of 220-kb, experiments were carried out in two phytotrons under controlled temperature of 24 ℃ and28 ℃, respectively. The content of chlorophyll, soluble protein and MDA (malondialdehyde), net photosynthesis, the antioxidant enzyme activities of SOD (superoxide dismuase) (EC 1.15.1.1) and POD (peroxidase) (EC 1.11.1.7) and the peptidase activities of leaves were measured from top to bottom according to the leaf positions at the flowering stage. Compared with the control plant,the mutant showed the following characteristics: (1) Higher net photosynthesis rate (Pn) appeared in the 1 st and 2nd leaves, contents of chlorophyll and soluble protein were also higher in the 1 st leaf; (2) The activities of SOD, POD and peptidase were higher according to the leaf position from top to bottom; (3) The symptom of premature senescence was accelerated in the mutant at 28℃treatment. The MDA content and the SOD and POD activities between the 24 ℃ and 28 ℃ treatment mutants were not significantly different. Content of chlorophyll and soluble protein of leaves mutant decreased rapidly at 28 ℃ treatment. The results show that pse(t) is sensitive to high temperature. The probable function of PSE(T) is discussed.     

Effects of zinc on cadmium uptake by spring wheat （Triticum aestivum, L.）： long-time hydroponic study and short-time ^109Cd tracing study

To investigate effects of Zn on Cd uptake by spring wheat (Triticum aestivum, L.) in solution culture, long-time hydroponic experiment (1 month) (Experiment 1) and short-time Cd isotope (109Cd) tracing experiment (24 h) (Experiment 2) were conducted. In Experiment 1, spring wheat (cv. Brookton) was grown in nutrient solution at uniform cadmium concentration of 20μ mol/L and 10 zinc concentrations (0, 1, 5, 10, 20, 100, 200, 500, 1000, 2000 μ mol/L). In Experiment 2, spring wheat seedlings,pre-cultivated in complete nutrient solution, were treated with 109Cd of uniform activity and the same series of Zn concentrations as those in Experiment 1 for 24 h. Cd concentrations in shoots and roots in Experiment 1 increased marginally but not consistently with Zn increasing at Zn rates of 1～200 μmol/L, and then decreased significantly at high rates (＞200 μ mol/L). In Experiment 2, the response of 109Cd activities in shoots and roots to increasing Zn was greatly similar to the response of Cd concentrations to Zn increasing in Experiment 1. The results of the two experiments indicated that the short-time and long-time exposure of spring wheat to Zn had similar effects on Cd accumulation.     

Identification of quantitative trait loci and epistasis for root characteristics and root exudations in maize （Zea mays L.） under deficient phosphorus

The phosphorus uptake （PU） in above-ground parts of plant, root characteristics and root exudations as well as the quantitative trait loci （QTLs） associated with these characteristics were determined for a F2：3 population derived from the cross of two contrasting maize （Zea mays L.） genotypes, 082 and Yel07. A total of 241 F2：3 families were evaluated in replicated trials under deficient phosphorus conditions in 2007 at two sites （Kaixian County and Southwest University, Chongqing, P. R. China）. The results show pleiotropy and close linkage among QTLs. Four common regions in different environments were in bnlg100- bnlg1268b （bins 1.02） for QTL of H＋, bnlg1268a-umc1290a （bins 1.09） for QTL of AP （acid phospbatase activity）, dupssrl5- P 1MT/a （bins 6.06） for QTLs of PU （phosphorus uptake） and RW （root weight）, and P IM3/d-P1M3/g （bins9.04） for QTLs of PU and AP. These QTLs are non-environment or minor QTLs x environment. By epistatic analysis, three main QTLs and eighteen QTLs x QTLs interactions were detected for the seven measured characteristics. These QTLs may affect trait expression by epistatic interaction with the other loci, and make a substantial contribution to phosphorus utilization efficiency, which should be considered when breeding maize varieties with high P efficiency. Two regions were detected in dupssrl 5- P1MT/a （bins 6.06） for QTL of RW and P1M3/d- P 1M3/g （bins 9.04） for QTL of PU and AP. They were detected in two different environments and by two methods of QTL analysis, which were useful for marker-assisted selection.     

Field demonstration of reduction of lead availability in soil and cabbage （Brassica Chinensis L.） contaminated by mining tailings using phosphorus fertilizers

A field demonstration of reduction of lead availability in a soil and cabbage （Brassica Chinensis L.） contaminated by mining tailings, located in Shaoxing, China was carried out to evaluate the effects of applications of phosphorus fertilizers on Pb fractionation and Pb phytoavailability in the soil. It was found that the addition of all three P fertilizers including single super phosphate （SSP）, phosphate rock （PR）, and calcium magnesium phosphate （CMP） significantly decreased the percentage of water-soluble and exchangeable （WE） soil Pb and then reduced the uptake of Pb, Cd, and Zn by the cabbage compared to the control （CK）. The results showed that the level of 300 g P/mE soil was the most cost-effective application rate of P fertilizers for reducing Pb availability at the first stage of remediation, and that at this P level, the effect of WE fraction of Pb in the soil decreased by three phosphorus fertilizers followed the order： CMP （79%）〉SSP （41%）〉PR （23%）; Effectiveness on the reduction of Pb uptake by cabbage was in the order： CMP （53%）〉SSP （41%）〉PR （30%）. Therefore our field trial demonstrated that it was effective and feasible to reduce Pb availability in soil and cabbage contaminated by mining tailings using P fertilizers in China and PR would be a most cost-effective amendment.