Why root have exarch while stem has endarch vascular bundles?
Answers
The cells of vascular bundles develop from the procambial cells.
In endarch condition, the protoxylem develops from the innermost procambial cells and progresses outwards. Hence metaxylem appear towards outside and protoxylem appears towards innerside.
Whereas in exarch condition, the protoxylem develops from the outermost procambial cells and progresses inwards. Due to this the metaxylem appear towards innerside and protoxylem towards outside.
Out of the two conditions, endarch is considered advanced whereas exarch condition is considered primitive.
During root-stem transition, the arrangements of xylem and phloem changes which leads to the endarch condition in stem which was initially exarch in root.
Out of the two conditions, endarch is considered advanced whereas exarch condition is considered primitive. During root-stem transition, the arrangements of xylem and phloem changes which leads to the endarch condition in stem which was initially exarch in root.