seed germination

How do plants procreate?

The procedure which enables plants to spawn offspring or new individuals genetically is known as reproduction. Reproduction in plants can be categorized into two distinct batches:

Reproduction through seeds

Reproduction by spores.

In this chapter, we are going to emphasize on plants ability to procreate through seeds and how these seeds can be nurtured into plants. 

Seed Formation

Alike humans, plants also reproduce through sperms and eggs. Pollens are released by male plants to impregnate the ovaries. These pollinated ovaries evolve into seeds and are disseminated in order to form new plants. During the development process of the impregnated ovaries, a surfeit of proteins as well as carbohydrates is accumulated within the seeds.

This act as a major source of food for the plants until it is able to develop its leaves. Then, the impregnated ovaries of the plants become mature enough to develop a hardened coat or an external cover of seeds. The coat shields the seeds from harsh climatic conditions and environmental circumstances. Seeds are dispersed to different places due to factors such as wind, water or other animals and thus new plants are created. 

Various Phases Involved In Seed Germination

The entire process of germination can be accomplished through the following five steps or stages: 

Absorption of Water: This is the initial step involved in the process of germination of seed is imbibition or “Absorption of Water”. In this stage, the seeds tend to swell due to the rehydration of cellular constituents. The bloating occurs with such great force that it instantly mutilates the “seed coats” and thus licenses the radical to ooze out in the form of primary roots. This absorption is feasible due to the rehydration of certain important elements such as anatomical and storage macromolecules, primarily the wall of the cells along with the proteins and repository polysaccharides.

Respiration: The absorption of water results in resumption of various metabolic activities within the “rehydrated-seed”. Originally, the respiration which is monitored in these plants is anaerobic owing to the energy which is delivered to them by glycolysis. But, as soon as this energy enters a living body, which is of the plants the respiration process transforms into an aerobic one. The seeds of underwater plants undergo the process of germination by utilizing a confined amount of dissolved oxygen from the water.

The terrestrial plant’s seed cannot germinate underwater because of their requirement of supplementary oxygen. These seeds extract oxygen from the air component present in the soil as almost all seeds are sown in loose soils in close proximity to the surface. Therefore, the seeds sown deeper into the soil face water-logging and do not succeed to germinate because of inadequate oxygen. 

Effect of Light on Germination of seeds: Light is a crucial element involved in the process of seed germination or gestation. The seeds that respond positively to light conductive to germination are termed as photo-blastic seeds. The three kinds of photo-blastic seeds are: Positive Photo-blastic seeds, Negative Photo-blastic seeds and lastly Non Photo-blastic seeds. The Positive Photo-blastic seeds can never germinate in absence of light. Negative Photo-blastic seeds cannot undergo germination if they are exposed to light. The seeds that are Non Photo-blastic can germinate under any condition or circumstances. The dependency of plants on light is regulated by the presence of a pigment in them known as “Phytochrome”.

Transition of Reserves through Seed Germination and Growth Regulation: Throughout the entire process of germination, the embryo cells maintain their metabolic activities and endure expansion and division. The preserved protein and starch require digestion, which is conducted through cellular conversion of energy. The plant hormones that induce dormancy suchlike Abscisic acid or ABA, play a crucial role in the prevention of germination. It is observed that concentration of ABA is directly proportional to the “onset of dormancy” of embryo during its phase of attaining maturity.

Evolution of the Embryo Axis into a Seedling: Following the segment of assimilation and translocation of food, the embryo cells present in the developing regions incline to being metabolically active. Eventually, the cells begin to evolve in terms of size by undergoing cell-divisions and appear as seedlings.

Key Factors Involved In Germination

 For the germination procedure to transpire, mentioned below are some essential conditions:

Adequate supply moisture or water: Germination cannot materialize until sufficient amount of water is provided. This is due to the property of seeds to absorb water during germination. Water tends to soften the “seed coat” to make it permeable and permit better exchange of gaseous content.

Favorable thermal conditions: Seeds have the capability to germinate within a wide range of temperature. Nevertheless, the seeds that are freshly harvested germinate only under a confined range of temperature.

Adequate supply of oxygen: Soil aeration is another significant condition required for germination of seeds. This is because; aerobic respiration is a key factor in germination through which the seeds acquire requisite energy for the development of embryo.

In Summary

Plants reproduce through seeds as well as spores.

The impregnated ovaries of the plants attain maturity to develop a hardened coat or an external cover of seeds.

The pollinated ovaries evolve to form seeds.

Germination occurs when the embryo ascends from dormant state and revels in active life

The various phases involved in seed germination are:

a.Absorption of water

b.Respiration

c.Effect of Light on Germination of Seeds

d.Transition of Reserves through Seed Germination and Growth Regulation

e.Evolution of the Embryo Axis into a Seedling

Key factors involved in germination are:

1.Adequate supply moisture or water

2.Favorable thermal conditions

3.Adequate supply of oxygen.