Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-oxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50μmolL-1, four treatments with addition of 300μmolL-1 Zn or 250mgL-1 ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50μmolL-1, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1μmolL-1 Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) inshoots of barley plants exposed to 1 to 50μmolL-1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not ubjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300μmolL-1 Zn or 250μmgL-1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%-17.8% in shoots and 0.5%-19.7% in roots by adding 300μmolL-1 Zn, in 50mmolL-1 Cd stressed plants, and by 1.3%-7.4% in shoots of barley plants exposed to 1 to 50μmolL-1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300μmolL-1 Zn or 250μmolL-1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%-17.8% in shoots and 0.5%-19.7% in roots by adding 300μmolL-1 Zn, in 50μmolL-1 Cd stressed plants, and by 1.3%-7.4% in shoots and 2.6%-4.5% in roots by application of 250μmolL-1 ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.

A two-location experiment was carried out at five to six nitrogen levels to study the relationship etween chlorophyll-me-ter readings (SPAD values) and physiological or yield traits in short-season cotton. The results showed that there were highly significant (P<0.01) linear relationships between SPAD values and contents of both nitrogen and chlorophyll at each growth stage, and as well as with the daily increase in plant height during early flowering. The relationship between nitrogen concentration and SPAD was stronger when nitrogen was expressed on a leaf area (Na) rather than on a dry weight (Ndw) a dw basis. Significant curvilinear relationships were found between SPAD values at various stages and photosynthetic intensity, lint yield, and total boll number per hectare, respectively. Furthermore, the linear regressions between SPAD values and N. fertilizer levels were highly significant (P<0.01), and before the boll opening stage, the slopes of these regressions were similar (0.040-0.041) at the two locations. These data provided evidence that the chlorophyll meter could be used to determine sidedress N requirements of short-season cotton before boll opening stage. Critical SPAD levels for maximum lint yield were established as 32.4, 33.1, 35.0, 43.55, and 39.7 at early flowering, flowering peak, boll forming, the beginning of boll opening and boll opening stages, respectively. It was also established that 24.2-25.0kg hay1 increase in N application should be necessary for each unit decrease in SPAD value below the critical level.

A g reenhouse hyd roponic expe rimentwas conducedto studythe effects of cadmium (Cd; 0, 01, 10, 10 uMin nutrient solution) on yield and yield components as well as Cd concentration and accumulation in th ree cotton genopes (Simian 3, Zhongmian 16, Zhongmian 16-2). The results showed that Cd concent ration in diffe rent organs increased with increasing Cd levels in the nut rient solution in the ollowing order: root>petiole>xylem>f ruiting b ranch, leaf>phloem in vegetative organs and seed coat, seed nut>boll shell>fiber in reproductive organs There were significant genotypic differences in functional leaf and petiole Cd concent rations at 1 and 10μM Cd treatments, with the cultivar Simian 3 showing higher Cd concent rations and greater reductions in lint yield than the other two genotypes

Hydroponic experiment was carried out to study the effect of three Cd levels on glutathione (GSH), free amino acids (FAA), and ascorbic acid (ASA) concentration in the different tissues of 2 barley cultivars with di erent Cd tolerance. Cadmium concentration in both roots and shoots increased with external Cd level, while biomass and ASA concentration declined, and Wumaoliuling, a Cd-sensitive genotype was more affected than ZAU 3, a Cd-tolerant genotype. The effect of Cd on GSH concentration was dose- and time-dependent. In the 5d exposure, root GSH concentration increased in 0.5μM Cd treatment compared with control, but decreased significantly in 5μM Cd treatment, irrespective of genotypes. However, in the 10d exposure, GSH concentration in all plant tissues decreased with increasing Cd levels in the culture medium, and Wumaoliuling was much more affected than ZAU 3. Cadmium treatment greatly altered FAA concentration and composition in plants. The effect of Cd on glutathione (Glu) concentration in roots varied with genotypes. ZAU 3 showed a steady increase in root Glu concentration in both 0.5 and 5μM Cd treatments, while Wumaoliuling was decreased by 38.0% in 5μM Cd treatment, compared with the control. The results indicate that GSH and ASA are attributed to Cd tolerance in barley plants, and the relative less reduction in GSH concentration in ZAU 3 under Cd stress relative to the control may account for its higher Cd tolerance.