Question

A T.S. of dicot stem is stained with iodine with proper procedure. Which of the following structures are expected to show blue colour?
A. Endodermis
B. Cortex
C. Pericycle
D. Phloem

Answer 1

Hint: The stem is the main stalk of the plant bearing branches, leaves, flowers and fruits.
The stem bears nodes and internodes.
The region on which the leaves are born is known as a node which may be axillary or terminal.
Stems perform various functions such as storage of food, support to plant, provide protection and help vegetative propagation.

Complete answer:
 Stem is the main stalk of the plant which bears leaves, flowers, leaves and fruits.
The stem bears nodes and internodes.
Stem is generally young green in colour but later becomes woody and dark brown.
A main function is spreading out branches bearing leaves, flowers and fruits.
Dicot stems have a well-defined epidermis along with the cuticle.
The internal structure of a dicot stem consists of
1. Epidermis
2. Hypodermis
3. Cortex endodermis
4. Pericycle
5. Vascular strand
6. Pith.
Examples of dicot stem are sunflower and cucurbita.
To test the presence of starch iodine is being used.
Blue color is due to the binding of starch with iodine.
The endodermis is the stem of dicot plants which is made up of parenchymatous cells and helps in storage of starch.
That’s why it is also called the starch sheath.
When stained with iodine, the endodermis will take up the blue colour due to the presence of starch.
Cortex consists of cortical cells which store carbohydrates.
Pericycle cells of vascular plants are used to provide support, structure, and protection to the plant.
Phloem tissue conducts a carbohydrate which is created in the leaves downward in plant stems.

So, the correct option is option A. Endodermis.

Note: In monocot stems, the vascular bundles are scattered throughout the ground tissue.
The rest of the stem is made up of ground tissue and vascular tissue.
The vascular tissue is arranged into bundles of xylem and phloem that are scattered throughout the ground tissue.