新耕作制度下河北省冬小麦病虫草害发生状况的研究

为明确新耕作制度下河北省冬小麦病虫草害发生状况。通过对河北省山前平原、黑龙港和冀东平原32个点进行监测及农户问卷普查,分析了冬小麦主要病虫草害种类、发生特点和变化原因。结果表明：新耕作制度下,河北省麦田主要病虫草害分别高达15、20、21种,其中白粉病、纹枯病、赤霉病、蚜虫、麦蜘蛛和吸浆虫等为主要病虫,杂草以播娘蒿为主。麦田病虫草害发生特点为部分次要病虫害上升为主要病虫害、杂草种类变化复杂、部分病虫危害呈北移东扩趋势和小麦玉米连带受害现象突出等。综合分析其原因为新耕作制度的实行保护了病虫草害的栖息地,提高了有害生物的危害基数,加速了病虫草害在不同地区、地块的传播等。另外,气候变暖和抗病品种缺乏也是影响小麦病虫草害发生的重要因素。     

Comparison of the responses to NaCl stress of two pea cultivars using split-root system

Two pea (Pisum sativum L.) cultivars were compared: cv Lincoln and cv Douce de Provence. Seedlings grown for 14 d on standard medium were challenged for 21 d with salt using a split-root system. This protocol allowed salt-treated plants to absorb nutrients through a part of their root system maintained in control medium (C), the other part of the root system being placed in medium added with 75 mM NaCl (S). Full salt treatment (S/S) resulted in severe but non-lethal growth inhibition, high concentration of Na⁺ and Cl⁻ in leaves, and decrease in leaf K⁺ and chlorophyll contents. The two latter effects were more pronounced in Lincoln than in D. Provence. Growth inhibition was partially (Lincoln) or totally (D. Provence) alleviated in S/C configuration, and K⁺ content was less diminished than in full salt treatment. S/C treatment mitigated Na⁺ and Cl⁻ accumulation in Lincoln, but not in D. Provence. Thus, in the latter cultivar, growth inhibition by salt in S/S condition likely did not result from excessive Na⁺ and Cl⁻ accumulation in leaves. Increased electrolyte leakage from leaf tissues evidenced damages to leaf cell plasma membrane of both cultivars in S/S condition. However, damages to chloroplasts, as inferred from chlorophyll loss, were much pronounced in Lincoln than in D. Provence. Antioxidant enzymic activities in leaves were measured as proxies for oxidative stress. Catalase activity was stimulated by S/S treatment in both cultivars, but superoxide dismutase (Fe and Cu/Zn isoforms) and gaiacol peroxidase activities were augmented only in Lincoln. The absence of superoxide dismutase activity stimulation by salt in D. Provence could signify either that constitutive activity was sufficient to ensure protection against oxidative stress, or that intrinsic salt tolerance of this cultivar mitigated cellular oxidative stress. Thus, intraspecific variability for salt response exists between pea cultivars presenting similar growth sensitivity to salt.