Question

write brief notes on nodal anatomy and its systematic value for plants

Answer 1

Nodal anatomy includes cutting sections of nodal and internodal regions of stem or branch of a plant and observe the origin and type of leaf gap and leaf trace.

Leaf trace - the vascular connection between leaf and branch or stem on which the leaf is attached is called the leaf trace.

Leaf gap- the gap formed above the joint of leaf trace and main vascular cylinder is called leaf gap or lacuna.

Unilacunar node- in this type nodes posses one leaf gap. Number of leaf traces per leaf gap may be one (Lantana camara) or two (Clerodendron spenden) or three (Withania somnifera) .

Bilacunar node- in this type nodes posses two leaf gaps.

Example- Phyla nodiflora

Nodes may be also trilacunar ( Azadirachta indica) and multilacunar (Coriandrum sativum).

Importance of nodal anatomy in plant systematics-

Nodal anatomy don't have prominent value in plant systematics. One can never identify any rank of a plant by only observing nodal anatomy. But it can be predicted if the plant is primitive or advance by observing xylem types and type of vascular cylinder, presence or absence of cambium, etc..