Reproduction is the process by which living organisms produce their young ones. Plants reproduce either sexually or asexually.
Sexual mode of reproduction
This type of reproduction involves two organisms of opposite sex, the male and the female. Reproductive organs in plants produce gametes – ovules (eggs) and pollen grains.
1.Egg is the female gamete produced by ovary.
2.Pollen grains are male gametes produced by stamens.
3.A zygote is the future individual formed by the fusion of an egg and a pollen grain. Zygote develops into a seed.
4.Seeds enclose embryo, the future individual until favourable conditions prevail for the development of embryo into a plantling.
Reproductive structures of a plant
Flowers are the reproductive structures which help the plant to undergo the process of sexual reproduction. These are the most attractive parts of the plant. A flower may have a stalk-like structure called the pedicel which helps in its attachment to the plant.
Structure of a flower
A complete flower is made up of four whorls on it. These are sepals, petals, stamens and the pistil. These four whorls are attached to flattened tip of the flower called as receptacle.
a) Sepals and petals are termed to be accessory whorls or vegetative whorls as they do not take part in the formation of zygote.
b) Stamens and pistil are termed to be reproductive whorls as they play vital role in the formation of zygote.
Formation of fruit
Ovary grows in size due to formation of seeds. This well-grown fertilised ovary becomes the fruit. A fruit can have any number of seeds in it. Fruits can be fleshy or dry in nature.
Seeds require sufficient amount of sunlight and water to germinate. Seeds falling under the parent plant compete for these factors. Hence, seeds get scattered for proper germination and growth. Seed dispersal is a method of scattering seeds by different agents like water, animals, birds, wind or insects to long distances.
Agents for seed dispersal
Nature appoints different agents for the dispersal of seeds. In some plants, fruits along with seeds are dispersed to long distances. But in many plants only the seeds get dispersed to long distances. Different agents of dispersal include wind, water, birds and animals.
Wind: Seeds which are light and have hairy structures are blown away by wind to long distances. e.g. Calotropis.
Water: Coconut seeds become light as they ripen and dry. As they fall into water, they float on the water surface. They are carried to long distances by flowing water. The pond water is adapted for seed dispersal through water.
Birds: Birds like parakeets feed on fruits along with seeds. As they fly to different places, seeds come out along with their droppings. e.g. Guava
Animals: Animals like monkeys feed on fruits. They throw the seeds at different places. This helps in seed scattering. Some seeds have hook like structures with which they cling on to animals moving to different places. e.g. Xanthium
Bursting: It is also a method of seed dispersal. Fruits in the form of pods burst open exposing the seeds to environment. The force with which they burst also scatters the seeds to long distances. e.g. Balsam. Drumstick seeds are also dispersed by the explosion of fruits.