【作者】 孙会军；

【导师】 王倩；

【作者基本信息】 中国农业大学 ， 蔬菜学， 2003， 硕士

【摘要】 自毒作用是导致西瓜连作障碍的重要因素之一，本试验主要研究了西瓜自毒物质—苯甲酸、肉桂酸对西瓜根尖超微结构和根细胞保护酶的影响。结果如下： 苯甲酸、肉桂酸处理能显著抑制西瓜胚根生长。随着苯甲酸、肉桂酸处理浓度的增加，胚根生长速度下降，胚根短，侧根增多，根尖组织褐变。对胚根显微结构及超微结构的观察发现：苯甲酸、肉桂酸处理可导致根尖细胞细胞核变形，核仁异常，细胞质稀疏，液泡增多、变大。 苯甲酸、肉桂酸处理可影响西瓜根细胞保护酶活性，但其作用方式、作用强度随处理浓度及酶的种类而异。苯甲酸、肉桂酸处理可抑制过氧化物酶(POD)活性，随着处理浓度增加，酶活性逐渐下降；对超氧化物歧化酶(SOD)活性的影响，苯甲酸、肉桂酸表现出促进和抑制双重作用，即低浓度苯甲酸、肉桂酸处理可提高酶活性，而高浓度处理则导致酶活性下降；对于硝酸还原酶(NR)，只有肉桂酸表现出促进和抑制双重作用，即低浓度肉桂酸处理可提高NR的活性，高浓度处理则降低NR活性，苯甲酸处理对硝酸还原酶活性则只表现出抑制作用；苯甲酸、肉桂酸对根细胞质膜H~+-ATPase活性的影响比较复杂，在低浓度下(＜0.250mmol／L)先下降，而后有上升趋势(0.250～0.500mmol／L)，既而随处理浓度(＞0.500mmol／L)的增加又下降。对于POD、SOD、NR酶活性的影响，苯甲酸的作用强度大于肉桂酸，而对根细胞质膜H~+-ATPase活性的影响，则是肉桂酸大于苯甲酸。 苯甲酸、肉桂酸处理可增加根细胞膜透性。随着苯甲酸、肉桂酸处理浓度的提高，西瓜幼苗根系的相对电导率不断提高，且苯甲酸的作用大于肉桂酸。更多还原

【Abstract】 Autotoxicity is one of the important factors that result to monoculture. Benzole acid and cinnamic acid are two main autotoxins. This research work concerns on the effect of benzole acid and cinnamic acid on watermelon radicle ultrastructure and seeding root cell protective enzymes. The results are as follows:Benzoic acid and cinnamic acid significantly inhibited watermelon radicles elongation, and with the increasing of benzoic acid and cinnamic acid concentration, the growth speed decreased. The radicles were short, more side root, and root tip tissue became brownish. Through the observation to the radicle’s ultrastructure it was found that benzoic acid and cinnamic acid can result to root tip nuclei irregular, nucleolus abnormal, and cytoplasm sparse. Vacuoles became more and bigger.Benzoic acid and cinnamic acid significantly influenced cell protective enzymes of watermelon seeding root, and the effects are distinct to different enzymes and concentrations. Benzoic acid and cinnamic acid reduced peroxidase (POD) activity, and with the treated concentration increasing, peroxidase (POD) activity continuously reduced. Effects on superoxide dismutase (SOD) activity expressed double functions of promotion and control: Superoxide dismutase (SOD) activity increased at low phenolic acids concentration, but decreased when the concentration was higher. To nitrate reductase (NR) activity, only cinnamic acid expressed double functions of promotion and control. NR activity could be increased at low cinnamic acid, but be decreased under higher concentration. Benzoic acid couldn’t promote NR activity even under low concentration. Effects of benzoic acid and cinnamic acid on plasma membrane H+-ATPase activity was complicate: reduced at first under low concentration (<0.250mmol/L) and then increased (0.250~-0.500mmol/L), but decreased another once when concentration was more higher (>0.500mmol/L). Effects on POD, SOD, NR activity, benzoic acid treated was more significant than cinnamic acid treated, but to plasma membrane H+-ATPase activity, the effects of cinnamic acid treated was more significant than benzoic acid treated.Benzoic acid and cinnamic acid increased membrane permeability of watermelon seeding root. With the concentration increasing, the relative conductance rate continuously be raised, and the increasing degree of benzoic acid treated was more than cinnamic acid treated.更多还原