Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
Answers
"The expansion in girth of stems of woody angiosperms is called secondary development. The tissues associated with auxiliary or secondary development are the two parallel meristems namely vascular cambium and cork cambium.
The step and its significance are as follows:
(I) Vascular cambium is a vascular layer present among xylem and phloem (vascular tissues). It is in charge of the cutting off vascular tissues, later it frames a total ring.
(ii) The cambial ring winds up dynamic and starts to cut off new cells, both towards the inwards and the external sides.
(iii) The cells cut off towards substance, develop into auxiliary xylem and the cell cut off towards outskirts, develop into optional phloem.
(iv) The cambium is commonly more dynamic on the internal side than the external. Thus, the measure of optional xylem created is more than the auxiliary phloem and before long structures a smaller mass.
(v) The essential and optional phloem get continuously pounded because of the proceeded with arrangement and gathering of auxiliary xylem.
(vi) The essential xylem is that as it may, stays pretty much flawless, in or around the inside.
(vii) At a few places, the cambium frames a thin band of parenchyma, which goes through the optional xylem and the auxiliary phloem in the spiral headings. These are the optional medullary beams.
(viii) The stem keeps on expanding in bigness because of the movement of vascular cambium. "