环状加厚：原生木质部导管和管胞的内层环状増厚。

Annular thickening rings of thickening laid down on the inner wall of protoxylem vessels and tracheids.

youdao

环状加厚：原生木质部导管和管胞的内层环状増厚。

Annular thickening rings of thickening laid down on the inner wall of protoxylem vessels and tracheids.

youdao