Finally, All living organisms have a characteristic that they can produce their own kind. The production of the offspring from the parents is called reproduction. Plants are living beings. They must reproduce to spread and transmit their genes to future generations. Plants can create sapling through either sexual or asexual reproduction.
Plants have two distinct multicellular stages in their life cycles. This phenomenon is called the alternation of generations. These two distinct multicellular stages are the haploid gametophyte and the diploid sporophyte. This is drastically different from most types of animal reproduction, where there is only one multicellular stage: a diploid organism that produces single-celled haploid gametes.
Reproduction in Plants – Alternation of Generations
Alternation of generations is typical in plants, algae, and fungi. Plants alternate between the haploid gametophyte and diploid sporophyte and and asexual and sexual reproduction. Consequently, the plant life cycle is the alternation of generations. The ability of the plants to reproduce asexually and sexually helps them to adapt in different environments.
The alternation of generations is dependent upon the nature of the plant. The dominant generation is haploid in Bryophytes , and the gametophyte contains the main plant. The diploid is the dominant generation in tracheophytes, and the sporophyte consists of the main plant.
The plant’s life cycle in one of the two generations is dominant over the other. The plants in the dominant generation live longer and grow larger. The plants in the non-dominant age are small and is hardly visible.
The dominant generation in vascular plants is the sporophyte, while in non-vascular plants is the gametophyte.
The alternation of generations comprises of the following stages:
- The diploid sporophyte has a structure called sporangium.
- The sporangium undergoes meiosis and forms haploid spores.
- The spore develops into a haploid gametophyte.
- The gametophyte has the reproductive organs which undergo mitosis to form haploid gametes.
- The gametes fertilize to form a haploid zygote which matures into a mature sporophyte. This cycle keeps repeating.
Reproduction in Plants – Stages of Alternation of Generations
A diploid zygote is formed by the fusion of two haploid gametes. This results in a sporophyte. The sporophyte develops reproductive organs known as sporangia when it reaches maturity. This is one of the key point in the phenomena of alternation of generations.
Reproduction in Plants – Sexual Reproduction
Sexual reproduction requires genetic material (DNA) from two parents. The parent plants have female and male sex cells, called gametes. The genetic material from the female and male gametes combine to produce offspring. This process is called fertilization. In this process, the flowers of the plants participate in reproduction.
Plant seeds produced through fertilization contain genetic material from both parents. Consequently, the offspring are not genetically identical to either of the parent plants. This genetic diversity can help them survive if there are changes in environment.
Flowering plants (unlike non flowering plants) reproduce sexually through a process called pollination. The flowers contain male sex organs called stamens and female sex organs called pistils. The anther is the part of the stamen that contains pollen. This pollen must be moved to a part of the pistil called the stigma.
Reproduction in Plants-Pollination
Plants can either self-pollinate or cross-pollinate. Self-pollination happens when a plant’s pollen fertilizes its ovules. Cross pollination occurs when the animals or wind move pollen from one plant to fertilize the ovules on a different plant.
The advantage of cross-pollination is that it promotes genetic diversity. Some of the plants have features that prevent self-pollination. One such feature is that pollen and ovules that develop at different times.
Pollinators are animals that carry pollen between plants. Many pollinators are insects, like bees, moths, butterflies, and beetles. Some birds, including hummingbirds, also play a role.
Likewise, certain mammals, like bats and rodents, move pollen between plants. The smell and colors of flowers often attract pollinators. Pollen will stick to a pollinator’s body as it feeds on the flower’s nectar.
Reproduction in Plants- Fertilization
Fertilization is the next step after pollination. Once it reaches the pistil, the pollen must fertilize an egg inside the stigma. This egg is called an ovule. Fertilization process creates fruits that contain seeds. Some fruits are fleshy, like oranges and watermelons.
Others are dry, like acorns or walnuts. These fruits are a portion of attractive food for various animals. After digesting fruit, animals expel waste that contains seeds. This way, seeds can take root and grow in places far from the plants that produced them.
Reproduction in Plants- Asexual Reproduction
Asexual reproduction only requires DNA from one parent. It creates offspring that are genetically identical to the parent. Genetically similar offspring are called clones. Clones lack genetic diversity. It also makes them less adaptable to changes in the environment. This makes them more susceptible to disease. In this process, generally, the leaves, stems and roots participate in reproduction.
The new plants are produced with the help of the seeds of a plant. In this process, the flowers of the plants participate in reproduction.
There are different methods of asexual reproduction. They include vegetative propagation and fragmentation.
Vegetative propagation does not require seeds or spores. Instead, offspring grows from a part of the parent plant. In different plants, vegetative propagation happens in different ways. Here are a few examples.
- Garlic, onions, and tulip plants all reproduce using genuine bulbs. These short underground stems are also called scaly bulbs. These leaves form a papery covering called a tunic. New bulbs grow off of the parent bulb’s basal plate.
- Crocuses reproduce using corms, which are similar to genuine bulbs. However, a corm doesn’t have as many layers.
- Potato plants reproduce using tubers. These underground growths produce new plants from stems or growing points called eyes.
- Ginger plants reproduce using rhizomes. These stems grow sideways along the soil or just below the surface. They branch apart to produce new points of growth.
- Strawberry plants reproduce using stolon. They look like branches growing along the ground. Stolon anchor themselves to the ground and develop roots. And these roots grow into new plants.
Reproduction in Plants- Fragmentation
Fragmentation is another form of asexual reproduction. Fragmentation involves new plants growing from small parts of the parent plant that fall to the ground. For example, animals or the wind can break stems or leaves off plants. This is one of the ways that plants like liverworts and mosses reproduce.
Horticulturists often use asexual reproduction through fragmentation to grow new plants. They do this by cutting a leaf off a plant and placing it in water or soil. This process is often called propagating from cuttings.
Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma. The goal of every living organism, including plants, is to create offspring for the next generation. One of the ways that plants can produce offspring is by making seeds. Seeds contain the genetic information to create a new plant.
Flowers produced by plants use to make their seeds.
Seeds will be produced only when pollen is transferred between flowers of the same species. A species has defined as a population of individuals capable of interbreeding freely with one another. However, due to geographic, reproductive, or other barriers, they do not interbreed with members of different species.
Plant Reproduction – Pollination Process
The flowers has to rely on vectors to move pollen. These vectors can include water, birds, wind, butterflies, bats, insects, and other animals that visit flowers. These animals or insects which transfer pollen from plant to plant are referred to as pollinators.
Pollination is the result of an animal’s activity on a flower. The pollinator is either eating or collecting pollen for its protein and other nutrients. Additionally, it may be sipping nectar from the flower when pollen grains attach themselves to the animal’s body.
As the animal visits another flower for the same reason, pollen can fall off onto the stigma and may result in the successful reproduction of the flower. Once on the stigma, pollen may germinate. This means that a “pollen tube” forms on the sticky surface of the stigma and grows into the plant’s ovule.
This growth can result in either of the following scenario:
- Successful fertilization of the flower and the development of seeds and fruit; or,
- Partially fertilized plant, in which the fruit and seeds do not develop fully develop; or,
- The plant completely fails to get pollinated and may not reproduce at all.
The plants can be either:
- Self-pollinating which effectively means the plant can fertilize itself; or,
- Cross-pollinating in which the plant needs a vector (a pollinator or the wind) to transmit the pollen to another flower belonging to the same species.
Plants have two kinds of parts:
- Vegetative Parts – These are the parts of the plant that plays a major role in the life cycle of a plant such as preparation of food, transmission of food, water and nutrients. For Example, roots, stems and leaves.
- Reproductive Parts – These are the parts of a plant that play a major role in the reproduction process in plants, For Example, flowers, fruits
- Shoot – A young plant is often termed as a shoot. Generally, a shoot is that part of the plant which has stems, leaves and flowers.
- Node – It is a part of the stem or branch of a plant from where the leaf arises.
- Vegetative Buds – Sometimes buds are present in the leaves that are capable of developing into shoots. These are called Vegetative Buds.
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