BIO BOTANY [2 Mark Questions]

Adventitious roots are those arising from plant parts other than radicle. Fibrous roots are seen in monocots. In monocots, the primary root arising from radicle is short – lived & soon replaced by the lateral roots arising in bunches from the base of stem. Thus fibrous roots are adventitious in origin.

Though potato tuber is found underground, it is a stem since it possess axillary buds & scale leaves.

Two morphological characters to differentiate monocots from dicots:

1. Monocots have fibrous roots and dicots have tap root system.
2. Monocot leaves show parallel venation, whereas dicot leaves show reticulate venation.

Musa is a monocarpic perennial because it grows for several years but produces flowers and fruits once in its life time.

The apical part of the leaf is modified into pitcher and the leaf tip is modified into lid of pitcher.

Pneumatopores are the special above-ground roots growing above the surface of water seen in plants growing in water logged soils. These pneumatopores has small pores that facilitate the intake of oxygen by roots.

Epiphytic plants like Vanda develop special type of roots containing sponge – like tissue called velamen. These spongy tissue helps in absorbing the atmospheric moisture and utilize it for their photosynthetic activity.

Rhizome of ginger is a underground stem not a root because, it possess nodes, internodes, scale leaves & buds, which are the characteristics of stem.

Two examples for angiospermic plants producing adventitious roots:

1. Buttress root of Bombax.
2. Prop (Pillar) root of Ficus benghalensis.

Plant:

1. Carrot
2. Colocasia
3. Aloe

Modified part for food storage:

1. Root
2. Stem
3. Leaves

The edible part of onion is stem covered by fleshy leaves (bulb). The edible part of ginger is underground stem (rhizome).

Yes, roots of certain epiphytic & climbing plants develop chlorophyll and turn green to perform the function of photosynthesis. Such a root is called photosynthetic root or assimilatory root. E.g., Tinospora.

Corm:

1. Stem is succulent underground
2. Presence of erect growing tips.

Rhizome:

1. Stem is horizontal underground
2. Presence of lateral growing tips.

Sometimes, small stipule like outgrowths are found at the base of leaflets of a compound leaf. They are called stipels.

Arecaceae, Musaceae, Zingiberaceae and Poaceae.

Functions:

1. Storage
2. Protection
3. Support
4. Reproduction

Examples:

1. Aloe
2. Opuntia
3. Nepenthes
4. Bryophyllum

Branching pattern is determined by the relative activity of apical meristem.

Pseudobulb is a short erect aerial storage or propagating stem of certain epiphytic and terrestrial sympodial orchids, e.g. Bulbophyllum.

There are three main parts in a typical leaf:

1. Leaf base (Hypopodium)
2. Petiole (Mesopodium) and
3. Lamina (Epipodium).

Musa is a monocarpic perennial, since it produces flowers and fruits only once and die after a vegetative growth of several years.

Based on habit plants are classified into herbs, shrubs, climbers (vines) and trees.

Rolling or folding of individual leaves is called as ptyxis.

When the leaf is directed vertically upwards, as in many monocotyledons, it is said to be ‘ isobilateral leaf. Example: Grass.

When the leaf is more or less cylindrical and directed upwards or downwards, as in pine and onion, etc., the leaf is said to be centric.

Occurence of two different kinds of leaves in the same plants is called heterophylly. Heterophylly is an adaptation of aquatic plants.

Mango leaf is a simple leaf. A simple leaf is the one, where the petiole bears a single lamina.

Phyllotaxy is to avoid over crowding of leaves and expose the leaves maximum to the sunlight for photosynthesis.

The mode of arrangement of leaves on the stem is known as phyllotaxy.  There are 4 types of phyllotaxy:

1. Alternate
2. Opposite
3. Temate and
4. Whorled.

Stipulate & Exstipulate Leaves:

1. Leaves with stipules are called stipulate leaves.
2. Leaves without stipules are called exstipulate or estipulate leaves.

In some grasses (Monocots) an additional out growth is present between leaf base and lamina. It is called ligule.

The arrangement of veins and veinlets on the leaf blade or lamina is called venation. Venation is classified into two types:

1. Reticulate venation and
2. Parallel venation.

Stipules are the two lateral appendages develop at the leaf base of dicot plants. Stipules protects the leaf in bud condition.

A leaf with petiole is said to be petiolate. e.g. Hibiscus. Leaves that do not possess petiole is said to be sessile, e.g. Calotropis.

Petiole is the bridge between leaf and stem. Petiole or leaf stalk is a cylindrical or subcylindrical or flattened structure of a leaf which joins the lamina with the stem.

In legumes leaf base become broad, thick and swollen which is known as pulvinus. e.g., Clitoria.

The part of the leaf attached to the node of the stem is called leaf base. It protects growing buds at its axil.

Photosynthesis, transpiration, gaseous exchange and protection of buds.

All the leaves of a plant together are referred as phyllome.

The mode of arrangement of branches on a stem is known as branching. There are two main types of branching:

1. Lateral branching and
2. Dichotomous branching.

Bulb is a condensed, conical or convex stem surrounded by fleshy scale leaves. There are two types:

1. Tunicated (coated) bulb and
2. Scaly bulb.

Perennial and some biennial herbs have underground stems, which are generally known as root stocks. Root stock functions as a storage and protective organ.

Between dextrose & sinistrose climbers:

1. Dextrose: Clockwise coiling climbers are called dextrose, e.g. Dioscorea alata.
2. Sinistrose: Anti – clockwise coiling climbers are called sinistrose. e.g. Dioscorea bulbifera.

Creepers are plants growing horizontally closer to the ground and produces roots at each node. e.g., Oxalis.

Climbing helps to display the leaves towards sunlight and to position the flower for effective pollination.

Majority of angiosperm possess upright, vertically growing erect stem. They are:

1. Excurrent
2. Decurrent
3. Caudex and
4. Culm.

Buds arising at any part other than stem are known as adventitious bud. e.g., Begonia.

Buds based on their origin & functio:

1. Based on origin, buds are classified into (a) Terminal or Apical bud and (b) Lateral or Axillary or Axil bud.
2. Based on function, buds are classified into (a) Vegetative bud and (b) Floral or Reproductive bud.

Stem is positively phototropic & negatively geotropic.

Node & Internode:

• Node: The point from which the leaf arises is called node.
• Internode: The region between two adjacent nodes is called intemode.

Radicle gives rise to root. Plumule gives rise to shoot.