Shoot System- Definition, Characteristics & Functions

Shoot System: The world is home to a huge array of blooming plants. It might be herbs, bushes, or trees. They all exhibit structural commonalities, despite their differences in size, appearance, and environment. Without plants, life on Earth will come to an end. Plants provide nourishment to the majority of living species, either directly or indirectly. Plants provide oxygen to all living things. The blooming plant has two parts: one above ground (the shoot) and one below ground (the root). The stem, leaves, buds, and flowers make up the shoot. The vegetative portions are the base, stem, and leaves, whereas the reproductive parts are the flowers, fruits, and seeds. Continue reading to learn more about the shoot system and its purposes.

Shoot System: Major Systems in Plants

Basically, the plant body is divisible into two main systems, the underground root system and the aerial shoot system. The root system develops from the radicle and the shoot system from the plumule of the embryo.

Definition of Shoot System

A shoot system is the part of a plant found above the soil. It consists of the main stem, leaves, buds, branches, flowers, fruit and within the fruits, the seeds. The main axis of the shoot system is the stem.

Fig: Shoot System

Characteristics of Stem

1. It grows from the plumule.
2. It grows away from the soil and against gravity, which means it shows negative geotropism.
3. It grows towards sunlight. This shows positive phototropism.
4. The stem has nodes and internodes. The place on the stem where a leaf arises is called a node. The leafless portion of the stand between two successive nodes is called an internode.
5. The bud present at the tip of the stem is called the terminal bud or apical bud, which helps in the increase in length. Apical bud helps in lengthwise growth and increase the height of the plant. Buds present in the axil of the leaves (the axil of a leaf is the angle between the leaf petiole and the stem) called axillary buds, which give rise to new branches.
6. Buds that grow into new shoots are called vegetative buds, and those that grow into flowers are called floral buds.
7. The stem may be soft and green as in most herbs or hard and woody as in shrubs and trees.

Functions of Stem

1. Conduction of Water and food: The stem conducts water and dissolved minerals from the roots to the leaves. This also conducts food from leaves to other parts of the plant.
2. Support: The stem bears the branches, leaves, flowers and fruits and supports them.
3. Preparation of Food: When young, the green stem manufactures food by the process of photosynthesis.
4. Storage of Food: In some plants, the stem also stores food. This is seen in underground modified stems like potato, ginger, garlic, etc.

In some plants, stems are modified to perform certain special functions. They may be the secondary functions of the stem.
1. Food Storage: Underground stems store food and help in propagation. Rhizomes (as in ginger), tuber (as in potato), bulb (as in onion), corm (as in zaminkand, elephant’s foot) are examples of this type of modification.
2. Support: Tendrils, which are coiled lateral appendages, either bud or other stem parts, help in supporting plants. Passiflora, gourd are examples of this type of modification.
3. Protection: Thorns are the modified, hard, woody, axillary buds or terminal buds, which are used for protection. This is found in Bougainvillea, Duranta.
4. Photosynthesis: Young, green stem performs photosynthesis.
5. Phylloclades: They are xerophytic adaptations to check transpiration rate. This is found in cacti, like Opuntia.

Characteristics of Leaf

1. The leaf is a thin flattened, green structure.
2. It is borne on the node of the stem or branches and bears an axillary bud at its axil.
3. It is mostly green in colour due to the presence of the pigment chlorophyll.

Parts of a Typical Leaf

The typical parts of the leaf are Leaf-base, Petiole, Lamina, Midrib, Leaf-apex (or leaf-tip).

Fig: Parts of a Typical Leaf

Fig: Types of Leaves

1. Simple Leaf: A leaf having a single or undivided lamina is called a simple leaf. It is attached to a node and has an axillary bud in its axil. Examples: mango, shoe-flower, guava and money plant.
2. Compound Leaf: In a compound leaf, the lamina is divided into a number of smaller units called leaflets. These leaflets are borne on a common stalk called the rachis, which is attached to the node of the stem. There is a bud in the axil of a compound leaf, but there are no buds in the axils of leaflets. Rose, gram, tamarind and neem are a few examples of compound leaves.

Arrangement of Leaves

The arrangement of leaves on the stem is called phyllotaxy. Basically, three types of leaf arrangement are commonly found. They are called alternate, opposite, and whorled phyllotaxy.

Fig: Common Arrangements of Leaves on Stem

1. Alternate Arrangement: A single leaf arises at each node from side to side in an alternate fashion. Example: mango, sunflower, china-rose.

Fig: Alternate Arrangement

2. Opposite Arrangement: Two leaves arise at each node opposite to each other. Example: Guava, Jasmine.

Fig: Opposite Arrangement

3. Whorled Arrangement: More than two leaves arise at each node and are arranged in a circle/whorl. Example: Oleander, Asparagus.

Fig: Whorled Arrangement

Types of Venation in Leaf

Venation is the arrangement of veins in the lamina. It is of two types.
1. Reticulate Venation: The veins divide repeatedly and form a network in the lamina. Example: dicots like mango, peepal.
2. Parallel Venation: The veins run parallel to one another. Example: monocots like bananas, wheat, and palms.

Functions of Leaf

1. Photosynthesis: Leaves absorb carbon dioxide from the air, water from the soil, and with the help of chlorophyll, in the presence of sunlight produce sugar. This process is called photosynthesis. The leaf is often called ‘the food factory’ of the plant.
2. Transpiration: A plant absorbs large quantities of water from the soil but utilizes only a very small part of it. The excess water is given out by the plant through the stomata on the leaves, in the form of water vapours. This process is known as transpiration.
3. Storage: Few leaves are modified and help in storage of food. Example: Cabbage, Spinach, etc.

Modification of Leaf

1. Support-leaf Tendrils: In some plants, leaves are modified into long, slender, coiled structures called tendrils.
2. Protection-leaf Spines: Spines protect the plant from grazing animals. They also prevent loss of water by transpiration, and help the cactus to conserve water.
3. Storage of Food-scale Leaves: In some plants, the scale leaves are modified to store food. They become thick and fleshy. Example: onion.
4. Vegetative Propagation: In some plants, leaves develop epiphyllous buds along the leaf margin. These buds give out fibrous roots and grow into new plants. Example: Bryophyllum.
5. Insect-catching Leaves: In some plants, the leaves are modified to trap insects. These plants are called Insectivorous or carnivorous plants. Example: pitcher plant, venus-fly trap, bladderwort.

The Flower

They are highly compressed, and modified shoots typically meant for sexual reproduction. They are often brightly coloured and with aroma.

Parts of Typical Flower

A typical flower has four main parts, namely calyx, corolla, androecium and gynoecium. The flower is borne on a stalk called a pedicel. The tip of the pedicel is somewhat swollen. This swollen part of the pedicel is called the thalamus. Thalamus bears all the four whorls of a flower.

1. Calyx: It is the outermost whorl of a flower, made up of sepals. They protect the flower in the bud stage.
2. Corolla: It is the second whorl of a flower, made up of petals. These are usually brightly coloured and often scented.
3. Androecium: One of the two essential whorls of the flower, composed of stamens, which are the male parts of a flower. Each stamen consists of filament and anther. The anther contains the pollen grains in four pollen sacs. The pollen grains contain the male reproductive cells or gametes.
4. Gynoecium: This is the innermost whorl of the flower, composed of one or more female reproductive units called carpels. There are three parts, stigma, style and basal ovary inside which the ovules are present.

Functions of a Flower

1. Flowers help in sexual reproduction. They produce male and female gametes.
2. They attract pollinators by their bright colour or nectar or aroma, which helps in the transfer of pollen grains and eventually fertilization.

The Fruit

Fruit is a fertilized and ripened ovary. A fruit generally consists of two parts, namely the fruit wall or pericarp and the seeds. If the fruit wall, which develops from the ovary wall, is dry and thin, it is called a dry fruit. Example: pea, gram.

Functions of Fruit

1. Fruit protects the seeds from injury, animals and other unfavourable climatic conditions.
2. It also helps in the dispersal of seeds.

The Seed

1. A seed is a mature and fertilized ovule. A seed consists of an embryo and one or two cotyledons, and a seed coat.
2. The embryo has the radicle and the plumule, which develops into root and shoot systems, respectively.
3. The cotyledons generally store reserve food material for the growing embryo. Example: bean, pea, gram, groundnut.
4. In some seeds, the cotyledons are thin and do not store food. The food is stored in a tissue called the endosperm. Example: rice, wheat, maize, castor.

Types of Seed

Based on the number of cotyledons, seeds are further classified into two types, and they are:
1. Monocotyledonous: The embryo consists of an embryo axis and has only one cotyledon.
2. Dicotyledonous: The embryo consists of an embryo axis and has two cotyledons.

Summary

The plant’s shoot system is an extension that grows above the earth from the plumule of the seed embryo. Because the stem is the most important portion of the shoot system, the terms shoot and stem are often used interchangeably.

The shoot system’s morphology and physiology are more complicated than the plant’s root system. The major stem is the vertical axis, which is divided into two parts: nodes and internodes.

Internodes are the segments in the centre of two nodes, whereas nodes are the segments where the leaves are fixed. A shoot is a highly branching and complicated plant structure that holds leaves, buds, flowers, and fruits in place.

Frequently Asked Questions (FAQs) on Shoot System

Q.1. What is the function of the Shoot System?
Ans: Shoot system is called the production unit of the plant. The shoot system consists of stem, leaves, flower, fruit and seed. Shoot System is responsible for Photosynthesis and Reproduction.

Q.2. What is the root system and shoot system?
Ans: Root System: The part of the plant which grows below the soil due to gravity is called the root system.
Shoot System: The part of the plant which grows above the soil is called the shoot system.

Q.3. What are the three types of arrangements of leaves?
Ans: Alternate, Opposite, and Whorled are the three types of leaves based on the arrangement.

Q.4. What is the Shoot of the tree?
Ans: A shoot is a part of a plant that grows above the ground portion of a tree directly bearing leaves, as contrasted with roots and branches.

Q.5. Which three parts make up a plant’s shoot system?
Ans: The shoot system consists of stems, leaves, and the reproductive parts of the plant (flowers). The shoot system generally grows above ground, where it absorbs the light needed for photosynthesis.

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