Biology -Plants – Roots – Stems-Leaves -Important Points

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Plants -Parts and Structural Organization

The Root

The main functions of the root system are-

A- absorption of water and minerals from the soil

B- providing a proper anchorage to the plant parts

C- storing reserve food material and synthesis of plant growth regulators.

* The primary roots and its branches constitute the tap root system, as seen in the mustard plant.

* In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots.

*The root is covered at the apex by a thimble-like structure called the root cap. It protects the tender apex of the root as it makes its way through the soil.

* Hanging structures that support a banyan tree are called prop roots.

* Similarly, the stems of maize and sugarcane have supporting roots coming out of the lower nodes of the stem. These are called stilt roots.

The Stem

* The region of the stem where leaves are born are called nodes while internodes are the portions between two nodes.

* Underground stems of potato, ginger, turmeric, zaminkand, colocasia are modified to store food in them.

* Some stems perform the function of storage of food, support, protection and of vegetative propagation.

The Leaf

* A typical leaf consists of three main parts: leaf base, petiole and lamina.

* Leaves originate from shoot apical meristems. Leaf develops at the node and bears a bud in its axil. The axillary bud later develops into a branch.

*The lamina or the leaf blade is the green expanded part of the leaf with veins and veinlets.

Leaf Venation

* The arrangement of veins and the veinlets in the lamina of leaf is termed as venation.

* When the veinlets form a network, the venation is termed as reticulate. When the veins run parallel to each other within a lamina, the venation is termed as parallel.

* Leaves of dicotyledonous plants generally possess reticulate venation, while parallel venation is the characteristic of most monocotyledons.

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