Reproduction in plants

 Reproduction in Plants

Reproduction in plant

To most of us flowers are the integral part of many ceremonies of our life. Flowers add depth and interest to landscapes.

Is that all flowers signify to us?
Flowers not only look pretty but are also important in making seeds. Have you ever wondered, what role the seed play? How do most plants reproduce ?
Reproduction is the process by which living being give rise to its own kind. It is one of the most important characteristics of all living being it multiplies the number of individual of a population and ensure the continuity of life.

Flowers

What is the Plant reproduction?

 Plant reproduction is the production of new offspring in plants which can be accomplished by sexual or Asexual Reproduction. Sexual reproduction produce offspring by the fusion of gametes resulting in offspring genetically different from the parent or parents

 Modes of reproduction

Plants exhibit two modes of reproduction, namely 
Asexual and Sexual. In addition some plants multiply by vegetative propagation

Asexual Reproduction:  It involves simple division of the plant body into two or more plants or the formation of spores under unfavourable conditions, i.e., Harsh environmental condition which are not suitable for plant to survive.

Vegetative Propagation: It is also a type of asexual reproduction in which a cell, tissue or a part of plant body develop into a new organism.

Sexual Reproduction: It takes place by the formation of seeds. These developed from the zygote formed by the fusion of male and female gametes. In this case, two (male and  female) parents are needed to give rise to new individual.

Read it also:-  Importance of Plants 

Asexual Reproduction

In Asexual reproduction, a single parent is able to reproduce on its own. Gametes are not formd and so there is no union of gametes. Common forms of a sexual reproduction are budding, fission, fragmentation and spore formation.

Budding

Microscopic organisms such as yeast reproduce asexually by budding. In this process a small bulb like projection comes out from the parent cell. It is called Bud.  The bud gradually grows and get separated from the parent cell and form and yeast cell. The new yeast grows, matures and produce more yeast cells. If this process continues for sometime, a large number of yeast cells are produced in a short time.

Fission

Infusion, and individual divides into (binary fission) or more  (multiple fission)new individual. It is a common bacteria.

Fragmentation

Fragmentation is commonly found in green algae. In Algae the filament just breaks into two or more fragments by the force of wave, wind or rain. Each of these fragments grows upto for a new filament. This process is seen in Spirogyra (pond scum), growing in stagnant water. Fragmentation is also seen in liverworts and mosses.

Spore formation

Spore are tiny spherical asexual reproductive bodies. These have a thick wall to withstand extreme condition of environment. The spores develop in a structure called sporangium. Mature spores keep floating in the air. Since they are tiny and very light, they are flown long distances. They can remain in the air for a long time.

Vegetative Propagation

 Root, stem and leaves are called vegetative parts of a plant. In vegetative propagation, new plants are produced from Roots and stems and leaves. All the plants produced by vegetative propagation from one plant are exact copies (clones) of the parent plant and has same genes. Potato, sweet potato, Delhi, banana, garlic, mint, grapes and roses are grown by vegetative propagation.There are a number of natural as well as artificial or man-made methods of vegetative propagation.

Natural methods of vegetative propagation

Natural methods of vegetative propagation are possible by different parts of plant as follows:

By roots

Roots of Dahlia, sweet potato and Asparagus become swollen due to the food stored in them.  these are called root tuber When left in the soil, new plant are produced from these Roots.

By stems

The underground and subaerial stem are specially modified for vegetative propagation.
 Underground stems these are of the following types:

Stem tuber of potato

• Tuber: potato is an underground stem tuber that is swollen due to food stored in it. It has buds in the depression called the eyes.These buds give rise to new plants. The stored food is used by the new plants to grow.(Each eye of potato represent a node of the stem from which a leaf arises). (Budspresent in the eye of potato tuber presents an axillary bud.It develops into the aerial part of the plant).
• Rhizome: It is an underground stem that bears buds.These buds grow to give rise to new plants. Rhizome is found in ginger and turmeric.

• 

  Rhizome of ginger 

•  Bulb: It is a very short underground stem surrounded by fleshy scale leaves. The scale leaves store food. Bulb is found in onion. In the spring stem shoots up from the centre of the scale leaves to form a new plant.

  

  Bulb of onions 

• Subaerial stems: In grasses, mint,Oxalis,Chrysanthemum and strawberry,vegetative propagation of occurs by subaerial stem.In them, root and aerial branches arising from nodes forming the new plant.

By Adventitious Buds on Leaves

Leaf with buds and plantlets on the margin 

The fleshy leaves of Bryophyllum bear  adventitious buds in the notches present along the margin. When Such a leaf falls on the soil,each buds grow into an independent plant.

 Plants with fleshy stem such as cacti,it produce new plants when their parts get detected from the main plant body. Each detected part can grow into a new plant.

Artificial methods of Vegetative Propagation:

Vegetative propagation is a simple, fast and less expensive method of plant propagation. It is, therefore, commonly used in Horticulture and Agriculture. The techniques used are stem cutting, layering, grafting and tissue culture.

 Stem cutting:-   In this method, cutting of healthy young branch of a plant having leave buds is planted in the moist soil. Cutting develops roots and grows into a new plant. This method is used to propagate plants like detected, Bougainvillea  Chameli rose and sugarcane.

Vegetative propagation in rose by stem cutting 

Layering :- In layering, a young branch is bent towards the ground and covered with moist soil forming a layer. After sometimes root develops from the covered part.The branch is then cut off from the parent plant and allowed to grow into a new plant. This method is commonly used by Gardeners to develop plants like Jasmine,Vines and Bougainvillea.

Layering in jasmine

Grafting :-  Grafting is common method used in horticulture to develop new varieties of ornamental plants and fruit trees. In this method a bud or cutting with buds of one plant called scion is kept over the cut stem of a rooted plant call the stock. The scion and the stock are then firmly tied together.

Tissue culture (micropropagation):-
 In tissue culture method, a small piece of tissue called explant is cut off from the growing tip of the plant. The cells of the tissues are separated and kept in a nutrient medium. The cells of the tissue divide regularly and form and organise the cell mass called callus.
The callus is transferred into another nutrient medium containing plant hormones. The cells of callus in this nutrient medium divide and differentiate into root and shoot and form.

Plantlets :- Plantlets so formed are grown in pots filled with soil.Asparagus,Chrysanthemum, Orchid and many other plants are now grown by this method .

Sexual  Reproduction:-

 Sexual reproduction occurs as a result of fusion of male and female gametes. Gametes are produced in separate male and female reproductive organs of flower, which may be present in the same plant or in separate male and female plants. The male gametes in plants are called Pollen Grain and female gametes called the Ova.

Parts of flower

Flower:-The reproductive part of a plant Usually a flower contains both male and female parts such flowers are called bisexual flowers. The flowers which contain either stamen or pistil are called unisexual flowers.
 Both male and female unisexual flowers may be present in the same plant or in different plants. Mustard, Rose Petunia etc. have bisexual flowers. Maize,papaya cucumber etc. produce unisexual flowers.

Stamen- The male reproductive part of a flower.
Each stamen is formed of swollen apical part, the anther and long Slender stock called the filament full stop inside the anther pollen grains are formed.

Pistil- The female reproductive part of a flower 
Pistil consists of stigma,style and ovary. The ovary contains one or more ovules. The female gametes or the egg is formed in the Ovules. The ovule develop into seeds after fertilization. In sexual reproduction male and female gemets fuse to form a zygote.

Mechanism(Process) of Sexual Reproduction 

Sexual reproduction in plants involve the following steps:-

• Pollination
• Fertilization
• Formation of seed 
• Formation of fruit
• Germination of seed

Pollination:- The transfer of pollen grains from the anthers to the stigma of pistil is known as pollination. 

Pollination in plant

This is the first step in the process of seed formation. Pollination takes place with the help of some external agent such as wind, water, insects, Birds or animals.These external agents are called agent of pollination.

Pollination is of two types self 

pollination and cross pollination

•  Self Pollination: In this process, pollen lands on the stigma of the same flower or different flower of the same plant. 
• Cross pollination in this process for land on the stigma of a flower borne on a different plants of the same kind.

 Fertilization

 On reaching the stigma, pollen grains grows out into a thin Pollen tube. It extends through the style, reaches the ovary and enter the ovule. The Pollen tube contains two male gametes one of which fuses with the female gamete egg nucleus and form a zygote .The process of fusion of male and female gamete is called fertilization.

Fruit and Seed Formation 

After fertilization, following changes occur in the flower:

•  The fertilised egg grows(zygote) into the embryo.Embryo has two parts, namely the shoot forming part called plumule and root forming part called radicle.
• The ovary grows into a fruit and other parts of the flower fall of.
•  The ovules develop into seeds.

 A seed is a mature ovule that contains the embryo and the stored food. It is enclosed by a seed coat formed of two covering.
A fruit is the seed bearing structure of flowering plant. Actually it is the ripened ovules of the fruit. 
Fruits maybe fleshy and juicy  or dry and hard . Mango,apple and orange are fleshy and juicy fruits where is almond and walnut dry and hard fruits.

Germination of Seed

Germination in plants

 After the dispersal, on reaching the moist soil, the seed swells up by observing water. A seed contains a baby plant or embryo.The embryo start growing under favourable condition. 
First of all the radicle start growing and pushes down in the soil and form the root. Then,the plumule start growing up in the air and form the shoot and develop leaves. The leaves begins to prepare food by the process of photosynthesis.