The annular and spirally thickened conducting elements generally develop in the protoxylem when the root or stem is -
- Maturing
- Widening
- Elongating
- Differentiating
Answer
(3) Elongating
Solution
Protoxylem is formed first, while the root or stem is still growing in length.
Annular (ring-like) and spiral thickenings can be stretched without breaking,
these elements develop in the protoxylem when the organ is elongating; the later-formed metaxylem has reticulate and pitted thickenings.
Answer: (3)