Structures for Reproduction and Behavior in Plants

Key Concepts

• Flowers
• Parts of flower
• Fruits
• Reproduction in plants
• Pollination and Fertilization
• Germination and life cycle of plants
• Other modes of reproduction
• Plants and their surroundings

Introduction: 

Plants have different parts like roots, stems, flowers, leaves, fruits, and seeds. These parts help them to survive and grow. 

These parts act like different components of a system that help the plant to perform various functions required for its growth, reproduction, behavior, and survival. We have studied the structures that help a plant grow and survive. In this session, we’ll learn about the structures that help a plant in reproduction and supports its behavior. 

Explanation: 

Most of the plants bear flowers. Flowers are the most beautiful and colorful part of a plant. They are the reproductive structures of a plant. They come in different shapes, sizes, and colors. 

Most of the time, flowers are brightly colored and fragrant; this helps attract insects and birds. The birds and insects help to transfer the pollen grains from one plant to another, which helps in reproduction. When the flowers mature, they develop into fruits and seeds in some plants. 

Parts of a flower: 

Fig. No.1: Parts of a flower 

Flowers come in various colors, shapes, and sizes, but most flowers share some common parts. Almost all flowers have four main parts, which are as follows: 

Petals: Petals are the outermost and most colorful part of a flower. Petals are colorful because their bright colors attract insects and birds for pollination. 

Sepals: Sepals are the green leaf-like structures present under petals and protect the flower buds from damage. 

Stamen: Stamen consists of the anther and filament, and produces pollen grains. This is often called the male part of the plant. 

Pistil: Pistil consists of the stigma, style, and ovary. It is often referred to as the female part of the plant. 

Fruits:  

In some plants, after maturation, the ovary develops into a fruit. Fruits are the fleshy substance that surrounds the seeds. It protects the seed. 

Fruits are also brightly colored so that animals get attracted to eat them. When animals eat these fruits, the seeds are dispersed through their feces. As a result, it helps in seed dispersal. 

Seeds: 

Seeds contain plant material that develops into a new plant. This plant material is called an embryo or seed leaf. Seeds are covered with a protective covering called the seed coat and have one or two cotyledons. Cotyledons serve as the food source for the baby plant till it can make its own food. 

Seeds have different shapes and sizes. A lot of plants produce seeds and store them in different structures. Fruits like peaches, oranges or apples store their seeds inside the fruit itself. Pea plants and beans have their seeds inside their pods. Corns have seeds on their cob; wheat has its seeds on the ear. Some flowers, like dandelions, have their seeds on the flower itself. Non-flowering plants like conifers have their seeds on the surface of their cones. 

Reproduction in plants: 

We know that all living things have the ability to reproduce. Reproduction is the process through which living things produce offspring. When they undergo reproduction, they make more of the same kind. For example, when maple trees produce seeds. The seeds can grow into new maple trees. 

Each seed carries information from the parent plants. The seed uses this information and food stored from the parent plant in the seed to grow into a new plant. The new plant will be like its parents. After seeds are produced, they may scatter away from the parent plant by various means. This gives the new plant more space to grow. 

Plants also reproduce by various means. In flowering plants, flowers are the structures used for reproduction. The pollen is considered as the male sex cells. The female part, i.e., the pistil, consists of the ovary, which produces female sex cells or eggs.  

Similarly, plants that do not bear flowers like conifers have male and female cones. The male cones carry the pollen, whereas the female cones consist of the egg or female sex cells. The male cones are smaller in size than the female cones.  

In order to reproduce, the male and the female sex cells should fuse together. 

Pollination: 

Pollination occurs when pollen grain is transferred from the male part of the flower/cone to the female part. Pollination can be carried out by several agents. A gust of wind can blow the pollen from anther of one flower to the pistil of another. Pollens are also transferred by water. Pollens are often transported by insects, birds, animals or other pollinators. Pollinators are the animals that transfer pollen from one flower to another.  

For instance, a bee sits on a flower to suck its nectar, pollen from the anther stick to its body. Now when the bee sits on another flower, the pollen falls from the bee’s body onto the stigma of that flower, and pollination takes place. 

Fertilization: 

Soon after pollination, fertilization takes place. When the pollen is transferred on the pistil, it grows a long tube for the pollen to reach the ovary. Fertilization occurs when the male sex cells merge with the female sex cells. It leads to the formation of a seed. 

Germination: 

We know that seeds come in different sizes and shapes but have the same parts. Every seed has an embryo that grows into a new plant and a food source that is protected by a seed coat. 

Seeds need the appropriate amount of water, air, the right amount of temperature to grow or germinate. Under appropriate conditions, the seeds will sprout. 

First, the seed coat opens up, and a root pushes through the crack. Next, a small stem starts growing upwards. One or two leaves appear on this stem forming the seedling. All seeds grow this way, and this process is known as germination.  

A seedling is a young plant that grows from a seed. It needs the right amount of water, light and nutrients in order to grow. As the seedling grows, it comes out of the soil. Leaves start to grow from the stem and use sunlight to make food. The plant uses the food to grow into an adult plant with flowers. The flowers are then pollinated again, and new seeds are formed. If the new seeds germinate, they can develop into new plants. Then the cycle continues. 

Life cycle of plants: 

Some plants mature within days, while some take years to mature. However long it takes, all seeds go through the same phases. The life cycle of a plant comprises the stages of germination, maturity, reproduction, and death. Some plants grow, reproduce and die in a single season, for example, seasonal crops, while others can live for years, for example, giant trees. Death marks the end of a plant’s life. When a plant dies, its life ends, but its life cycle does not. Since plants produce new seeds their life cycle continues. 

Reproduction by other modes: 

Not all plants have reproductive organs like flowers, cones or spores. Such plants use different parts in order to reproduce, which includes: 

Runners: Runners are a part of a stem that grows along the ground and can make form plants. Example: Strawberries 

Cuttings: A part of a plant that has been clipped and can produce a new plant. Most of the time, a cutting is a leaf or a stem. A whole new plant can grow from the cutting.  

 

Bulbs:  A bulb is a stem that grows underground. Tulips and onions grow from bulbs. 

Tubers: A tuber is a storage part of a plant. Potatoes are examples of tubers. If we plant a potato by itself, more potatoes will grow. 

Plants and their surroundings: 

Plants cannot move, but they can respond to changes in their environment. A stimulus is something that causes a living thing to react. Plants respond to a stimulus by changing its direction or pattern of growth. A stimulus can be anything like light, water or gravity. 

Plants respond to light by growing in the direction of the source of light. They respond to water by growing their roots toward the water’s source. The roots of most plants grow downward—towards the gravitational pull, whereas the stems of most plants grow upward, away from gravity. 

These responses of plants to light, water, and gravity are called tropisms. A tropism is the reaction of a plant to something in its environment. Plants also show tropisms to chemicals and heat.  

Adaptations in plant: 

The sunflower moves its head and follows the sun as it changes its direction. Thorns are a modification of leaves. They are developed to deter away herbivores. Cactus has a waxy coating on their leaves and stem to prevent water loss. The stem is thick, green and filled with water. Leaves are reduced to spines to keep herbivores away. In conifers, the plant is tall and cone-shaped so that snow can fall off easily.  

Summary:

• Flowers are reproductive parts of the plants. They are brightly colored and fragrant to attract birds and insects for pollination.
• Flowers have four main parts- the petals, sepals, stamen and pistil. Petals are brightly
• colored and attract insects; sepals are green in color and protect the flower bud.
• Stamen consists of anther and filament and is also known as the male part of the plant.
• Pistil consists of stigma, style and ovary and is also known as the female part. In some plants, the ovary develops into fruits on maturation. Fruits are fleshy substances that surround the seeds.
• • Seeds contain the embryo, which then develops into a new plant. Different plants store
• seeds in different structures. • Plants reproduce by combining the male and the female sex cells, which are present on
• the flower or on the cone. Pollination refers to the transfer of fallen from the anther to stigma and is carried out by wind, water or pollinators.
• Pollinators are animals like insects, birds or herbivores that transfer pollen from one flower to another.
• Fertilization takes place after the pollen is transferred to the pistil. The pistil grows a long tube to transfer the pollen to the ovary, where fertilization takes place.
• A seed consists of the embryo, food source and seed coat. When conditions are right, the seed germinates
• Germination is the process where the embryo breaks the seed coat and develops roots
• and small stem.
• The germinated seed develops into a seedling, which in turn grows into an adult plant with flowers. The flowers again produce seeds which in turn develops into a new plant This is the life cycle of plants.
• Some plants reproduce by other modes like runners, cuttings, tubers and bull Plants respond to changes in their surroundings and exhibit tropism. Plant show tons
• towards water, light gravity and even chemicals and heat Plants also have adaptations like thorns, spines, etc.