To study of transverse section of dicot (sunflower) stem.
Answers
Answer:
concept
The transverse section of the dicot root shows the following plan of arrangement of tissues from the periphery to the centre.
Rhizodermis or epiblema:
The outermost layer is made up of single layer of parenchymatous cells without intercellular spaces. Stomata and cuticle are absent.
Root hairs are always single celled.
2. Cortex:
Cortex consists of oval or rounded loosely arranged parenchymatous cells.
These cells may store food reserves.
3. Endodermis
It is made up of single layer of barrel shaped parenchymatous cells.
The radial and the inner tangential walls of endodermal cells are thickened with suberin. These thickenings are known as casparian strips.
But these casparian strips are absent in the endodermal cells which are located opposite to the protoxylem elements.
4. Stele: All the tissues present inside endodermis comprise the stele.
A. Pericycle
Pericycle is generally a single layer of parenchymatous cells found inner to the endodermis. Lateral roots originate from the pericycle.
B. Vascular system
Vascular tissues are in radial arrangement.
The tissue by which xylem and phloem are separated is called conjunctive tissue.
Xylem showes exarch and tetrarch condition .
Metaxylem vessels are generally polygonal in shape
5. Pith: Usually absent