小麦种子根的发育解剖

小麦胚胎发育过程中通常形成5条幼根(少数可形成6条),这些根统称为种子根,中间最先发生的为初生根.初生根的原基在胚胎发育的早期就在胚轴的一侧发生,原基细胞由不规则到规则排列。侧生种子根的原基在胚胎发育后期才出现,通常成对发生,并且是由胚轴上的节(盾片节和胚芽鞘节)维管束外方的细胞形成。侧生种子根的发育明显较初生根的快,分化能力也较强,后生木质部导管母细胞出现早,数目较多.因此,小麦胚胎发育过程中从胚轴上形成的这些侧生的种子根,形态上,仍应看作是一些不定根,其结构特征与后来形成须根系的不定根的比较近似。

THE DEVELOPMENTAL ANATOMY OF THE SEMINAL ROOT OF WHEAT

Wheat embryo usually gives rise to five seminal roots in matured earyopsis,although,the sixth root might develop in some cases.The first one is known as the primary root.Primary root emerged early,and its primodium was distinctly originated from the proembryo and could be gradually identified as three layers of initials.Lateral seminal roots emerged later from the embryonic axis in pairs,and originated from the surrouding cells of the procambium.Dif- ferentiation of lateral roots was much more vigorous than that of the first seminal root(pri- mary root),and,its mother cells of metaxylem vessel appeared soon,Lateral seminal roots usually had more metaxylem vessels.In short,only the first root is the primary root,the lateral seminal roots are adventitious in nature,since their structures are similar to those of other adventitious roots.