Question

What is Dicotyledonae?

Answer 1

Hint: Plants like oaks, roses, mustards, cacti, sunflowers etc come under dicot plants. These plants have characteristics like having two cotyledons, having netlike leaf veins, usually in four or five petals and have a ring- like vascular system.

Complete step by step answer:
Dicots one of the two classes of angiosperms. Dicots are flowering plants which are characteristic to have two embryonic or seed leaves.

Dicot stem:
- Epidermis- This is the outermost layer composed of parenchymatous cells which is usually a single layer of cells. These are closely packed cells, with no intercellular spaces. The outer tangential wall is thick and deposited with a fatty substance that is cutin which presents as a separate layer called the cuticle.
- Cortex: This is an inner tissue to the epidermis. In some dicot plants, the cortex is simple and undifferentiated. In the majority of dicot plants, this is composed of four zones that are hypodermis, outer cortex, inner cortex, endodermis.
- Stele: This is the central vascular cylinder which is composed of four components that are pericycle, vascular bundle, medullary rays and pith.
The pericycle is located inner to endodermis which may be completely parenchymatous, completely sclerenchymatous forms bundle cap or a mixture of parenchymatous or sclerenchymatous alternating bands.
Vascular bundle located inner to pericycle which is developed from procambium and is arranged as a broken ring. It is composed of xylem and phloem where xylem is placed inner to cambium and phloem is placed outer to the cambium. Dicot vascular bundles are conjoined that is the presence of xylem and phloem together where xylem is endarch that is protoxylem towards the interior, open with cambium and collateral or biocollerteal.

Dicot root:
Dicot roots have main features as follows:
- Epidermis: This is the outermost layer covered with cuticles which also has trichomes and few stomata present on the stem.
- Vascular bundles in dicot plants have ring arrangement, conjoint and open vascular bundles. The protoxylem is an endarch and sclerenchymatous bundle cap present above the phloem.
- Pith in dicot plants is large in size.
- Cortex: This is further divided into three subzones
- Hypodermis which is present below the epidermis and collenchymatous cells.
- The cortical layer which is below hypodermis, thin- walled parenchyma cells with intercellular space.
- Endodermis which is the innermost layer of cortex, rich starch grains so it is referred to as a starch sheath.


Dicot leaf:
- The leaves of the plants have veins that form a branched type pattern, unlike monocots, in which they run parallel.
- The veins are actually netted or webbed present on the whole surface of the leaf.

Dicot seed:
- There are two cotyledons in the seeds of these plants that actually emerge from the soil when the seed germinates.
- They then turn green and form the first two leaves for the new plant.

Dicot flower:
- The flower parts are usually present in fours or fives. In many plants, they are found in multiples of either number.
- These dicot flower parts include petals, sepals and pistils, or the reproductive parts of the plant.

Note:
- In monocots, the vascular bundles in the stem's present as cross- section are usually scattered or more complex of an arrangement as compared to dicots.
- Bicollateral is a medium patch of xylem laying in- between two phloem patches which is a characteristic of Cucurbitaceae.