茎用莴苣肉质茎内绿色组织光合特性探析

Explore and Analysis on Photosynthetic Characteristics of Chlorenchyma Inside Succulent Stem of Asparagus Lettuce

为探讨茎用莴苣茎内深层绿色组织的光合潜力及可能的维持机制,为茎用莴苣产量和品质改良提供理论基础,用大田种植的茎用莴苣为材料,以叶片为参照,对比监测其上、中、下段茎内深层组织的叶绿素荧光特性以及叶绿素、水分和玉米素含量,并分析它们之间的关联。结果表明,茎用莴苣中、上段茎内绿色组织凌晨最大光化学效率Fv/Fm值在0.75以上,该水平与众多其他高等植物叶片相当,下段茎内组织Fv/Fm值则相对较低。从叶绿素荧光诱导动力学的结果看,上、中段组织光化学途径耗能占比较下段茎内组织大,下段茎内组织则以组成型能量耗散占比较大。此外,各茎段内组织的相对电子传递速率虽然显著弱于叶片,但和众多其他高等植物叶片相比,其绝对值并不低。叶片中以鲜质量为基础的叶绿素含量显著高于茎内组织,茎内组织又以中段茎含量最高。茎内组织比叶片含有更多的水分和玉米素,尤以中段茎最高。各段茎内组织叶绿素、水分和玉米素含量呈显著的正相关关系。据此认为,茎用莴苣茎内深层组织具有较强的光合潜力,茎内无光条件下高含量玉米素是促使茎内组织长期保持绿色状态的原因之一,而这些绿色组织内的叶绿素又可作为水分结合物,从而维持茎内高水分含量,直接影响茎用莴苣的产量和品质。

In order to explore and analyze the potential photosynthetic ability of deep green tissues inside stem of asparagus lettuce and possible maintain mechanism,so as to provide theoretical reference for improving the yield and quality of asparagus lettuce,this paper took field planted asparagus lettuce as material and leaves as reference,contrastively detected the chlorophyll fluorescence characteristics in the upper,middle and lower segments of deep tissue inside the stem,and chlorophyll,water and zeatin contents;and analyzed the relevance between them.The results showed that the values of maximum photochemical efficiency Fv/Fm in the middle and upper stem segments were above 0.75,amounting to the leaves of many other higher plants.While,the Fv/Fm value in the lower stem segment was relatively lower.Seeing from the results of chlorophyll fluorescence induction,the photochemical energy consumption of the upper and middle stem segments occupied bigger proportion than the lower segment.While,tissues in the lower segment took a larger proportion of constitutive energy dissipation.Besides,The relative electron transport rates in tissues of each asparagus lettuce stem were significantly weaker than that in leaves,but its absolute values were not low as compared with the leaves of many other higher plants.The content of chlorophyll based on fresh weight in leaves was significantly higher than that in stem tissues,of which that in the middle segment stem tissue was the highest.Stem tissues contained more water and zeatin content than the leaves.Especially,these contents in the middle segment tissues were the highest.The contents of chlorophyll,water and zeatin in each segment of stem tissues were positively correlated.Based on these data,we believed that the deep tissues of asparagus lettuce stem had stronger photosynthetic potential.The high content of zeatin could promote the tissues in stem keeping long-term green state under dark condition.At the same time,chlorophyll in these green tissues could be a matter maintaining high water contents in stem and directly influencing the yield and quality of asparagus lettuce.