油葵根—茎过渡区子叶节区的研究

油葵根-茎过渡区发生位置较低.在下胚轴基部就已完成根-茎初生维管组织的转变过程.转变过程中初生木质部的原生与后生部分分离.分离后的原生木质部逐渐消失在基本组织中,不参与新维管组织的形成.初生韧皮部的分离不对称,4束中只有同侧两束分离.在下胚轴下部由根内间隔排列的四原型木质部和韧皮部转变形成6束外韧维管束.下胚轴中上部在6束外韧维管束之间发育形成8束新的外韧维管束.先后形成的两组维管组织在子叶节区发生分离形成内外两环.外环进入子叶,内环进入上胚轴.根据幼苗形态和解剖结构的变化特点,提出了油葵根-茎过渡区、子叶节区的具体区域界限,指出了油葵形成壮苗的形态解剖学依据.

A study on the root-stem transition region and cotyledon node in oil sunflower

The root-stem transition region of oil sunflower was found at a lower position and the transformation of primary vascular tissue from root to stem accomplished at the base of hypocotyledonary axis, In this transforming process, the separation of protoxylem and metaxylem of primary xylem occurred, After that, the protoxylem gradually disappeared in the parenchyma from its original place and did not become a part of the new vascular tissue, Asymmetrical separation was observed at the primary phloem, Of four bundles, two located at the same side were separated. Tetrarck xylem and phloem that were arranged alternatively in the root transformed into six collateral vascular bundles at the lower part of the hypocotyledonary axis. Then, eight new collateral vascular bundles were developed among six collateral vascular bundles at the middle-upper part of the hypocotyledonary axis. These two groups of vascular tissues further separated at the cotyledon node zone and formed an inner ring and an outer ring. The outer ring merged into the cotyledon and the inner ring entered the epicotyl. On the basis of the seedling morphology and anatomy characteristics, the researcher defined the specific region boundary for oil sunflower root-stem transformation region and cotyledon node zone and discovered the morphological and anatomical evidences for strong seedlings of oil sunflower.