Spermosphere models和盆栽试验结果表明，海岛棉（Gossypium barbadense L.）苗接种自生固氮菌（Azotobacter sp.）、巴西固氮螺菌NO40（Azospirillumbrasilense NO40）、多粘芽孢杆菌（Bacillus polymyxa CF）和根瘤菌（Rhizobium），和以自生固氮菌分别与其它3种供试菌种两者的混合菌，能增强棉花根际固氮酶活性和棉苗对氮的吸收，提高功能叶中氮、磷和叶绿素含量，从而有利于提高生物学产量，尤以自生固氮菌的促进效应最为显著。另一方面，混合菌处理较单一菌株处理，可以显著提高棉苗对氮的吸收，增加干物质积累提高皮棉产量，其中尤以固氮菌分别与根瘤菌或巴西固氮螺菌NO40的协同效应最显著。

A hydroponic experiment was carried out in a greenhouse to study genotypic differences in the effect of four Cd levels on lipid peroxidation and activities of antioxidant enzymes in barley plants during ontogenesis. A highly significant increase in malondialdehyde (MDA) content, and a stimulation of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were recorded in plants subjected to 1 and 5μM Cd. The effects increased with both Cd concentration in the medium and with time of exposure in 5μM Cd treatments. There was a highly significant difference in the alternation of all these parameters but CAT activity among the four genotypes. Wumaoliuling, which was relatively sensitive to Cd toxicity in terms of growth, biomass and chlorophyll content both in the previous and present studies, accumulated much more MDA when exposed to 5μM Cd than the three other relatively tolerant genotypes (Zhenong 1, ZAU 3 and Mimai 114). In contrast, the three tolerant genotypes maintained higher SOD and POD activities than Wumaoliuling over the whole duration of Cd exposure. The present investigation showed that Cdstress induced a concentration-and genotype-dependent oxidative stress response in barley leaves, characterized by an accumulation of MDA and the alternation pattern of antioxidative enzymes, mainly SOD and POD may be attributed to the genotypic difference in Cd tolerance.

Genotypic variation in kernel heavy metal concentrations was studied for barley cultivars grown in six locations of Zhejiang, China. These sites covered a wide range of soil and climate. The results showed that barley kernels produced at some sites contained heavy metals higher than MPC. Significant cultivar effects were identified, but these were less than the site effects. Although Genotype

A solution culture experiment was carried out in a greenhouse to study genotypic differences in the effect of cadmium (Cd) on biomass, root and shoot growth of barley during ontogenesis, by using four cultivars and four Cd levels. Barley (Hordeum vulgare L) plants exposed to 0.1μM Cd showed little difference (p>0.05), compared with control, in growth parameters and biomass accumulation during the first 30 days of Cd exposure, and a slight increase in the later days. Exposure to 1μM Cd induced a significant decrease and the deleterious effect became diminished with extended exposure of time, which may be attributed to an adaptation to Cd toxicity occurring during ontogenesis. Increasing Cd concentration in the medium to 5μM caused a sharp decline (p≤0.05) in all measurements and the deleterious effect of Cd became more obvious with extended exposure of time. There was a significant difference among 4 cultivars in the reduction of these parameters caused by Cd oxicity.Zhenong 1 and Wumaoliuling were the least and most affected, respectively. In addition, the difference among genotypes in their response to Cd toxicity basically remained consistent throughout the growth period.

A hydroponic experiment was carried out to study the genotypic di.erence in subcellular distribution and chemical form of Cd and Zn uptake and their interaction in four barley genotypes. Increased Cd level in the medium caused a signi.cant increase of Cd concentration in all fractions of oots/shoots, with most accumulation in FI (cell wall) and FIV (soluble). In root, the greatest amount of Cd was found in extraction solution of 2% HAC or 0.6M HCl, followed by 1M NaCl (20%), and lowest in xtraction of 80% ethanol or d-H2O. While in shoot, the highest value of Cd accumulation was recorded in the fractions extracted by 1 M NaCl and 2% HAC, followed by 0.6M HCl or d-H2O, and least in 80% ethanol extraction solution. There was a distinct di.erence among genotypes in Cd concentration in subcellular and chemical forms and it was found that the Cd-sensitive genotype Wumaoliuling, in comparison with the other three Cd-resistant genotypes, had higher Cd concentration in chloroplast-shoot/trophoplast-root (FII), membrane and organelle (FIII) and in inorganic and water-soluble Cd of roots, while lower in FI, FIV and pectates/protein integrated Cd. After 48h of Cd treatment, the plants were replaced into Cd-free nutrient solution and grown for 72h, a signi.cant decrease in Cd concentration of root FI was observed, with less Cd reduction in Wumaoliuling. In comparison with control (no Cd), addition of Cd signi.cantly increased Zn accumulation in chloroplast (FII), with least increase in Wumaoliuling. The Zn content in the other 3 fractions decreased signi.cantly with addition of Cd, especially in roots, while Wumaoliuling was the most severely a.ected genotype. Moreover, it could be suggested Zn supplement could signi.cantly reduce Cd concentration in root trophoplast and in shoot soluble fraction of Cd-treated plants. 2005 Published by Elsevier Ltd.