【作者】 蔡冲；

【导师】 陈昆松；

【作者基本信息】 浙江大学 ， 果树学， 2006， 博士

【摘要】 论文以‘洛阳青’枇杷（Eriobotrya japonica Lindl.cv.Luoyangqing）果实为试材,研究采后枇杷果实组织成熟衰老木质化和冷害木质化的基本特征及其控制措施（LTC、1-MCP、ASA和乙烯）,深入探讨了采后枇杷果实品质变化的生物学特征与调控机制,为延长采后枇杷果实贮藏寿命提供依据。主要结果如下: 采后枇杷果实在20℃下成熟衰老过程中,EC增加,PPO活性增强和总酚含量下降,并伴随着组织酶促褐变发生,可溶性糖和有机酸含量减少;果实硬度持续增加,并与木质素积累呈显著正相关关系(r=0.95^**)。果实木质素合成相关酶中PAL活性在采后3d迅速增加,之后逐趋下降;采后8d中CAD、G-POD和S-POD活性均持续增加,与木质素积累均呈显著正相关关系,相关系数分别为r=0.97^**,r=0.98^**,r=0.99^**;果实组织中纤维素含量减少与木质素含量增加则呈显著负相关关系(r=-0.98^**)。研究认为采后‘洛阳青’枇杷果实组织木质化是成熟衰老的重要特征之一。 ‘洛阳青’枇杷果实0℃贮藏易发生冷害,其主要症状表现为组织木质化,果肉出汁率下降,O₂^.-积累,EC增加,果实组织褐变等,木质素生物合成相关酶PAL、CAD和POD等活性增加,木质素积累;冷害木质化及其相关变化在贮藏9d内尤为剧烈,经39-60d贮藏的果实转置20℃货架期,冷害症状更为明显。 适宜低温（5℃贮藏或5℃预贮6d,0℃贮藏的LTC贮藏方式）、5μl L^-1 1-MCP和1mmol L^-1 ASA等处理在推迟采后枇杷果实衰老进程或减轻冷害程度的同时,减缓了细胞木质化作用和果实硬度增加;相反,100μl L^-1乙烯处理则加速枇杷果实衰老进程或促进冷害的发生,增强细胞木质化作用,促使果实硬度增加。调控枇杷果实衰老或冷害进程等措施,均可有效调节木质化引致的果实硬度增加。 研究认为,‘洛阳青’枇杷果实采后衰老木质化与冷害木质化具有相似的生物学特征,其内在机制仍不清楚,需在现有研究基础上,进一步从组织学、发育生物学和分子生物学等层次深入探讨。更多还原

【Abstract】 Loquat (Eriobotrya japonica Lind1.) is non-climacteric fruit with short postharvest life. Biological characterization and regulations (such as LTC, 1-MCP, ASA and C2H4) of tissue lignification in relation to senescence and chilling injury was investigated in postharvest ’Luoyangqing’ fruit. The objectives of present study were to have a better understanding of the biological characteristics and regulation mechanism of quality changes in postharvest loquat fruit, to provide better strategies for longer storage of loquat fruit. Results were as followings:During postharvest storage at 20 °C, a series of physiological changes occurred in loquat fruit including the increase in EC, increase in PPO activity, decrease in total phenolic content, tissue browning, decrease in soluble sugars and organic acids. As the fruit senesced, fruit firmness increased steadily and showed a significant correlation with accumulation of lignin in the flesh (r=0.95**). Among the enzymes associated with lignin biosynthesis, phenylalanine ammonia lyase (PAL) activity increased rapidly during the first three days after harvest and then declined in the fruit flesh, while cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) activities showed a persistent rise over the whole 8 d. Accumulation of lignin in flesh tissue was also significantly correlated to the activities of CAD (r=0.97**), guaiacol-POD (G-POD) (r=0.98**) and syringaldazine-POD (S-POD) (r=0.99**). Cellulose content in flesh tissue decreased and showed a significant negative correlation with lignin content (r=-0.98**). Such results indicated that tissue lignification is a particular feature of ’Luoyangqing’ loquat senescence.During postharvest storage at 0℃, chilling injury occurred with symptoms of lignification, tissue browning, and a decrease in percentage juice, increase in superoxide free radical production, electric conductivity and lignification enzyme activities. Such chilling injury symptoms developed rapidly during the first 9 d cold storage at 0 ℃ and became more severe after fruit was moved to shelf life at 20 ℃.Where fruit ripening or chilling injury were retarded by either low temperature (storage at 5 °C or conditioned at 5 °C for 6 d before 0 °C storage) or 5 \il L"1 1-MCP or an application of 1 mmol L"1 aqueous ASA or enhanced by 100 ul L"1 ethylene treatment, fruit firmness and lignification were consistently retarded or enhanced accordingly.In a conclusion, similar biological characteristics of tissue lignification were found in relations to fruit senescence and chilling injury in ’Luoyangqing’ loquat fruit. Whether the same mechanism is responsible for the lignification under both situations remains unknown and a further study with the combination of histology, developmental biology and molecular biology will be carried out in our laboratory.更多还原