In themelon, the Vat (monogenic, dominant) resistance gene governs both an antixenotic reaction to the melon aphid Aphis gossypii Glover (Homoptera, Aphididae) and a resistance to non-persistent virus transmission, restricted to this vector species. We investigated the behavioural features and tissue localisation of the antixenosis resistance by the electrical penetration graph technique (EPG, DC system).We also compared the chemical composition in amino compounds and proteins of the phloem sap collected from two isogenic lines of melon (Cucumis melo L.), carrying the Vat gene or not. All behavioural and chemical data indicated that this resistance is onstitutive. EPG analysis clearly showed that access to phloem, although delayed by alterations in pathway activities, was not impaired in terms of frequency of access or initiation of feeding. The most striking feature was, however, a very reduced duration of ingestion from phloem of resistant plants, making this compartment one of the tissues where the effects of the Vat gene are unambiguously expressed. This was confirmed by clear differential activity of phloem extracts in artificial no-choice bioassays. Chemical analyses have shown that phloem saps from the two isogenic lines were extremely similar in profiles of ninhydrin positive compounds, and contained a low total amount of free amino acids (less than 10mM). Out of more than 40 distinguishable peaks in the chromatograms (protein and non-protein amino acids, as well as small peptides), only five differentiated the two genotypes. Two of them were increased in the resistant genotype: glutamic acid and a major unknown peak, probably a non-protein amino acid (different from pyrazolyl-alanine, a Cucumis-specific amino acid). The three others were depressed in resistant plants, and included the sulphur amino acid cystine and a peptide peak partly composed of the cysteine-ontaining peptide glutathione (reduced form). Sap collection also showed that phloem exudation rates, as well as total protein and glutathione levels, were depressed in phloem sap from resistant plants. Such data are all indicative of a modified phloem-sealing physiology, linked to sulfhydryl oxidation processes, in plants carrying the Vat gene. The originality of the mechanism of Vat resistance to aphids is discussed.

通过生活在甜瓜和棉花上的棉蚜Aphis gossypii Glover的行为，研究棉蚜的寄主专化型及其形成的行为机理。生物学观察显示：两类棉蚜在寄主植物相互交换以后，定居数显著减少，棉花蚜型棉蚜的繁殖系数及若虫存活率显著下降，说明棉蚜存在甜瓜蚜型和棉花蚜型两种寄主专化型。通过刺探电位技术研究棉蚜的取食行为，以探索其寄主专化型形成的行为机理。结果表明：甜瓜蚜型棉蚜在棉花上的取食行为容易被中断，但其口针定位韧皮部的能力并没有显著削弱；而棉花蚜型棉蚜在甜瓜上的取食行为受到更大的影响，口针无法顺利定位至韧皮部，并在2h内根本无法在筛管内取食。生物学观察和EPG取食行为分析都显示：与甜瓜蚜型棉蚜相比，棉花蚜型棉蚜对寄主的要求更严格——寄主专化程度更高，对寄主的利用率更高。

为在分子水平上快速精确地研究生物的进化关系，提出了分子进化研究中的几个常用统计量及其计算方法。根据这些统计量探测正选择作用，并确定特定基因的进化速度或年龄。这些统计量包括核苷酸同义替换数d （Ka）、Ka/Ka、DNA多态性和遗传距离等。通过植物抗性基因的一个实例揭示了这些统计量在阐明进化机制过程中的重要性。

采用棉蚜Aphis gossypii－甜瓜Cumumis melo－黄瓜花叶病毒（cucumber mosaic virus, CMV）体系，研究棉蚜获毒后在空气中禁食对其保持并传播CMV的影响。结果表明：获毒后的禁食时间与棉蚜传毒效率呈负相关。运用EPG（Electrical penetration graph）及其即时显示、即时中断技术研究分析棉蚜禁食后的早期传毒行为细节，结果显示：禁食处理没有显著影响pd（potential drop，电势落差）数目和1stpd（穿刺过程中出现的第一个pd波形）前穿刺时间这两个重要指标，但禁食处理能引起pd波的两个亚波形pdII-1和pdII-2持续时间的显著减短。进一步分析未禁食棉蚜传毒作用与pd亚波形的关系，显示传毒可能与pdII-2的持续时间相关（p＝0.06）。因此pdII-2的持续时间可能是与棉蚜传毒相关的一个行为指标。本研究还建立了新的高效而稳定的获毒方法——5pd获毒法，与传统的5分钟获毒法相比，获毒效率显著提高。

以小麦（Triticum aestivum）、青菜（Bassica chinensis）和萝卜（Raphanus sativs）3种作物为受体，对薄荷（Menthahaplocalyx）化感物质的作用进行了研究。结果表明：薄荷根分泌物显著促进小麦幼苗和幼根的生长，显著抑制青菜幼苗和幼根生长，显著促进萝卜幼苗而抑制其幼根生长。薄荷地上部分水浸液显著抑制青菜、萝卜的种子萌发和幼苗、幼根的生长；萝卜比青菜更敏感、幼根比幼苗更敏感；随着化感物质浓度的降低，抑制作用逐渐减弱、消失，甚至转变为促进作用。水浸液经氯仿、石油醚萃取后，剩余水相浓度变小、水势升高，但其抑制作用反而更加强烈。这说明，这种极其强烈的抑制作用不是低水势而是化感物质造成的；而且，剩余水相的抑制作用被同样具有抑制作用的石油醚相和氯仿相组分所削弱，即化感组分之间存在拮抗作用。剩余水相经大孔树脂进一步分离得到的3个组分都极显著地促进青菜幼苗的生长。这表明，水相强烈的抑制作用是由起极显著促进作用的3个组分的混合物产生的，且排除了水势降低的影响。但组分2显著抑制青菜、萝卜种子的萌发和幼根的生长。