The regulation of root growth in response to phosphorus deficiency mediated by phytohormones in a Tibetan wild barley accession

Low phosphorus (LP) causes a dramatic change of root system architecture in plants, which is possibly mediated by signaling pathways of hormones. In order to understand the regulatory mechanisms of the root development under LP, we examined the potential role of phytohormones in response to LP using three barley genotypes, differing in LP tolerance, namely 2 Tibetan wild barley genotypes XZ99 (LP tolerant) and XZ100 (LP sensitive), and a cultivated barley ZD9 (LP moderately tolerant). The results showed that LP stress caused a number of changes in root development, with XZ99 having less primary root growth inhibition, more lateral root and root hair formation than the other two genotypes. Meanwhile, LP stress also resulted in the dramatic changes in plant hormone contents, with changed extent and pattern differing among the three genotypes. The relative expression of genes responsible for indole acetic acid (IAA) and ethylene synthesis in roots also showed a significant difference among genotypes in both control and LP conditions. It can be concluded that the root system of Tibetan wild barley XZ99 adapts to phosphorus deficiency by changing the signal transduction pathway mediated by auxin, ethylene and cytokinins. However, further studies are needed to elucidate the behaviors of the key genes involved in the hormone-related response.     

Application of sulfur fertilizer reduces cadmium accumulation and toxicity in tobacco seedlings (<Emphasis Type="Italic">Nicotiana tabacum</Emphasis>)

Greenhouse pot experiments were carried out to illuminate the mitigation effects of sulfur (S) on cadmium (Cd) uptake and toxicity in tobacco using two levels of exogenous sulfur of S1 and S2 containing 47 and 38% total S. Results showed that Cd1 and Cd2 treatments of 1 and 5 mg Cd kg^?1 soil increased leaf Cd concentration and accumulation but reduced plant height, net photosynthetic rate (Pn) and biomass, with a much severe response in Cd2 treatment. Application of S2 fertilizer alleviates Cd toxicity, markedly decreased Cd concentration and improved photosynthesis, compared with Cd1 and Cd2 alone treatment; but S1 only alleviated Cd toxicity when tobacco was subjected to Cd1 stress. Our results suggest that S2 fertilizer was more effective in reducing Cd accumulation and toxicity in Tobacco than S1, and highlights a promising approach of S fertilizer application to lower leaf Cd accumulation in order to ensure product safety of tobacco grown in Cd polluted soils.     

Differences in physiological and biochemical characteristics in response to single and combined drought and salinity stresses between wheat genotypes differing in salt tolerance

The combined drought and salinity stresses pose a serious challenge for crop production, but the physiological mechanisms behind the stresses responses in wheat remains poorly understood. Greenhouse pot experiment was performed to study differences in genotype response to the single and combined (D + S) stresses of drought (4% soil moisture, D) and salinity (100 mM NaCl, S) using two wheat genotypes: Jimai22 (salt tolerant) and Yangmai20 (salt‐sensitive). Results showed that salinity, drought and/or D + S severely reduces plant growth, biomass and net photosynthetic rate, with a greater effect observed in Yangmai20 than Jimai22. A notable improvement in water use efficiency (WUE) by 239, 77 and 103% under drought, salinity and D + S, respectively, was observed in Jimai22. Moreover, Jimai22 recorded higher root K⁺ concentration in drought and salinity stressed condition and shoot K⁺ under salinity alone than that of Yangmai20. Jimai22 showed lower increase in malondialdehyde (MDA) accumulation, but higher activities of superoxide dismutase (SOD, EC 1.15.1.1) and guaicol peroxidase (POD, EC 1.11.1.7), under single and combined stresses, and catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) under single stress. Our results suggest that high tolerance of Jimai22 in both drought and D + S stresses is closely associated with larger root length, higher Fv/Fm and less MDA contents and improved capacity of SOD and POD. Moreover, under drought Jimai22 tolerance is firmly related to higher root K⁺ concentration level and low level of Na⁺, high‐net photosynthetic rate and WUE as well as increased CAT and APX activities to scavenge reactive oxygen species.     

蚕蛹水解液的氨基酸分组分离法

采用７３２、７１７树脂对蚕蛹酸水解液进行分离。７３２树脂先将蚕蛹水解液粗略分成酸性、中性、碱性氨基酸,７１７树脂再将中性氨基酸分成甘氨酸－丙氨组酸和亮氨酸－异亮氨酸－缬氨酸组。其中亮、异亮、缬氨酸的含量达到７５．９％;同时还进行了脯氨酸的分离,经７１７树脂分离得到的脯氨酸的含量为５０．６％。     

Differences in Grain Ultrastructure,Phytochemical and Proteomic Profiles between the Two Contrasting Grain Cd-Accumulation Barley Genotypes

To reveal grain physio-chemical and proteomic differences between two barley genotypes, Zhenong8 and W6nk2 of high- and low- grain-Cd-accumulation, grain profiles of ultrastructure, amino acid and proteins were compared. Results showed that W6nk2 possesses significantly lower protein content, with hordein depicting the greatest genotypic difference, compared with Zhenong8, and lower amino acid contents with especially lower proportion of Glu, Tyr, Phe and Pro. Both scanning and transmission electron microscopy observation declared that the size of A-type starch molecule in W6nk2 was considerably larger than that of Zhenong8. Grains of Zhenong8 exhibited more protein-rich deposits around starch granules, with some A-type granules having surface pits. Seventeen proteins were identified in grains, using 2-DE coupled with mass spectrometry, with higher expression in Zhenong8 than that in W6nk2; including z-type serpin, serpin-Z7 and alpha-amylase/trypsin inhibitor CM, carbohydrate metabolism, protein synthesis and signal transduction related proteins. Twelve proteins were less expressed in Zhenong8 than that in W6nk2; including barley trypsin inhibitor chloroform/methanol-soluble protein (BTI-CMe2.1, BTI-CMe2.2), trypsin inhibitor, dehydroascorbate reductase (DHAR), pericentrin, dynein heavy chain and some antiviral related proteins. The data extend our understanding of mechanisms underlying Cd accumulation/tolerance and provides possible utilization of elite genetic resources in developing low-grain-Cd barley cultivars.