烤烟品种云烟85烟叶的成熟度 Ⅱ.成熟度与保护酶活性及膜脂过氧化作用的关系

Studies on leaf maturity of Yunyan 85, a variety of flue-cured tobacco Ⅱ. Relationship between maturity and endogenous protective enzyme activities, cell membrane-lipid peroxidation

对烤烟品种云烟85下二棚、腰叶、上二棚不同成熟度的鲜叶超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性、细胞膜相对透性(RP)及丙二醛(MDA)含量进行测定,并进行烘烤验证和化学成分分析.结果表明:最适采收期烟株下二棚叶和腰叶特征为叶片呈淡黄或黄多绿少,主脉全白发亮,1/2至2/3支脉变白,茸毛脱落较多,叶尖叶缘稍枯;上二棚叶特征为叶片全黄,主脉全白发亮,2/3以上支脉变白,茸毛大部分脱落,叶尖叶缘呈枯尖枯边.若各部位烟叶按该标准采收,叶片中与活性氧代谢有关的SOD、POD及CAT酶活性下降较快,活性氧积累,膜脂过氧化作用加剧,MDA含量增加,RP增大,导致膜结构损伤和破坏,细胞结构的变化有利于烟叶调制和提高品质,烘烤后的烟叶等级高,特别是上等烟和上中等烟比例高,烟叶化学成分较协调.

Fresh leaves of different maturities from lower, middle and upper parts of the stalks of Yunyan 85, a variety of fluecured tobacco were determined superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities, relative permeability of cell membrane (RP) and malonaldehyde (MDA) content. Then, those leaves were subjected to fluecuring trial and chemical composition analysis. The optimal appearance of lower and middle leaves for priming was greenish or light yellow in color, with the main veins completely white, 1/2 to 2/3 lateral veins turning white, a lot of tomenta falling off, and the rims and tips of leaves beginning to wither. Meanwhile, the optimal appearance of upper leaves for priming was yellow in color, with the main veins completely white, 2/3 to all of the lateral veins turning white, most of tomenta falling off, and the rims and tips of leaves having withered. when the leaves at different parts of the stalks were primed according to the normal appearance of maturity mentioned above, their SOD, POD and CAT activities decreased rapidly. This resulted in the accumulation of the active oxygen, which in turn increased the lipid peroxidation of the plasma membrane and promoted the accumulation of MDA, and caused the increase of the RP of the plasma membrane. Which was favorable for leaves curing and quality improvement, such as the increasing of superior leaves and proper ratios of chemical compositions.