Root, Stem, Leaf

Introduction

Vegetative parts like root, stem and leaves along with other parts like flowers and their tiny buds are vital parts of plants, although these structures are very varied, tailored to different plant species’ demands and environments. These organs are equally crucial to the plants as much as plants are necessary for the survival of human beings.  

 Let us learn the functions and features of each plant organ separately.

The functions and characteristics of various vegetative plant parts are:

1)  Roots- Plant roots are organs that provide anchoring for the plant and take in water and nutrients into the plant body, allowing plants to grow taller and faster. Roots are usually found below the soil’s surface, but they can also be aerial or aerating, meaning they grow up above the ground. 

Types of Roots

• Taproot- The taproot of a plant is a thick root that grows directly downward under the earth and is usually grown into a vegetable plant. The taproot produces other tiny roots, making it the plant’s primary and dominant root. Taproots include radish, carrots,beetroot,etc.
• Fibrous roots- These types of roots grow close to the ground and are long roots grown together in large numbers. They are all of one equal size. They usually grow horizontally in various directions. Examples of the fibrous root system can be grass, rosemary,coconut tree,etc
•  Adventitious roots-Adventitious roots originate from an organ other than the root—usually a stem, but occasionally a leaf. They’re especially abundant on underground stems like rhizomes, corms, and tubers, making it possible to replicate many plants vegetatively from stem or leaf cuttings—for example, sugarcane, banyan tree, etc.

Functions of Roots 

• Assist in firmly anchoring the plant in the soil
• Helps in water and nutrient absorption from the soil
• Some roots serve as nutrient storage organs

• Some roots have been genetically engineered to perform vegetative reproduction 
• to avoid soil erosion by holding soil particles together

2)  Stems- A vascular plant’s stem has two primary structural axes.It is generally a cylindrical organ but it may vary in shape in different plants.It bears nodes and internodes. It also provides attachment area for leaves, branches, flowers and fruits. It transports nutrients to all aerial parts of the plant. Branches are usually bear nodes that may form leaves, buds or thinner branches and the internodes separate the nodes from one another. 

Structure of the Stem

Dermal tissue, ground tissue and vascular tissue are the three main tissues that make up the internal structure of the stem as well as are present in other parts of the plant also. 

1. Dermal tissue covers the stem’s exterior surface and serves to waterproof, protect, and regulate gas exchange.
2. The ground tissue, which fills in around the vascular tissue, is mostly of parenchyma cells. It plays a role in photosynthesis on occasion if chloroplasts are found inside their cytoplasm.
3. Vascular tissue helps in long-distance transport of water, minerals and food and also provides structural support. Examples are xylem and phloem.

Functions of Stems

• Support for leaves, flowers, and fruits
• The stems maintain the leaves in the sun while also providing a home for the plant’s blooms and fruits
• The xylem and phloem transport nutrients between roots and the shoots 
•  Nutritional storage
• Cells found in the stem produce new live tissue every year

Types of Stem

Aerial stems- These are a type of stem that grows in the air and is phototropic. These stems can be found above ground and serve a variety of purposes.

Aerials come in a variety of shapes and sizes when modified:

• Thorns- These plant-protecting stem changes show as hard, woody, and pointy outgrowths. Roses, for example.
• Tendril stems- are slender, twining strands that allow a plant to climb on  other surfaces while seeking support
• Subaerial stems- These run parallel to the ground and produce roots at intervals called nodes. These are weak so cannot stand erect thus creep on ground. Few type of subaerial stems are given below-
• Runner – It has a creeping stem with long internodes and grows parallel to the ground. The nodes on the lower surface produce adventitious roots at regular intervals. A runner emerges from the axils of the aerial stem’s lower leaves e.g. doob grass
• Offset- It is shorter and thicker than runners and are frequently found in water plants e.g. water hyacinth
• Underground stems- These stems stay close to the ground and develop aerial shoots that ascend above them. Their roots are visible on the surface. Food storage and perennation are the functions of these stems. These stems can also be propagated vegetatively. They are of different types:

3)  Leaf- A leaf is a flattened green protrusion from a vascular plant’s stem defined in botany. Leaves create food for plants that nourish and support all terrestrial creatures, as they are the principal sites of photosynthesis. Leaves are an essential aspect of the shoot system .

Structure of a Leaf

Each leaf consists of epidermis, mesophyll, and vascular tissues.

• Epidermis- It is the outermost layer of leaves. Generally it is one cell in thickness and is present on the upper as well as lower surface of the leaf. It has an additional layer called cuticle which is composed of a waxy substance termed as cutin secreted by the epidermal layer. The cuticle helps in water retention within the leaf cells

Stomata are found on the leaf epidermis either only on upper epidermis or lower epidermis or on both the layers. The guard cells surround the stomata, which govern water flow in vapour state from the epidermis.

•  Mesophyll- The leaf’s middle layer is made up of parenchymatous cells called mesophyll cells. Depending on the type of cells discovered, it is divided into palisade and spongy mesophyll layers. The chloroplasts are found in this stratum
•  Vascular tissues- They include the xylem and phloem, which perform the transportation of food and other nutrients.This tissue is present inside the veins and veinlets of the leaf

Types of leaves:

There is a large variety of leaves present in the world.The categorisation  of leaves is based on their shape, size, and presence or absence of petiole. Depending on shape of  leaf lamina these are of following types-

• Linear leaves
• Oblong leaves
•  Acicular leaves 
• Reniform leaves 
• Ovate  leaves  

Depending on the presence or absence of petiole leaves are of two types-

• Petiolate leaves
• Sessile leaves

Functions of Leaves

• Photosynthesis-Photosynthesis converts carbon dioxide, moisture or water into sugar, which is the leaf’s fundamental purpose. For photosynthesis the indispensable materials besides water and carbon dioxide are sunlight and chlorophyll.Photosynthesis produces simple sugars, which are then converted into different macromolecules needed to create the plant body and other components
• Transpiration- When the plant absorbs more water than its requirement, it is expelled through tiny pores called stomata present on leaf surfaces. Therefore, transpiration helps in removing water by evaporation

Conclusion

The plant body is composed of certain structures, undoubtedly the essential organs of plants which are termed as vegetative organs . Without them, plants have  no way to grow to their full potential. Each of these parts has its distinguishing feature and characteristics. Plants are very crucial for the existence of human beings. Therefore, we need to save plants and let them grow in their natural habitat, as they are beneficial to us. The intake of carbon dioxide leads to release of oxygen when plants do photosynthesis. Oxygen is the most important chemical element for the survival of all life forms.