PLANT REPRODUCTION

 

In biology, reproduction is an important event in every species for perpetuation.

The process of reproduction in plants has been studied by most physiologists, molecular biologists and plant geneticists.

Considerable quantum of information on plant reproduction is available in scientific literature.

It is interesting to look into that information for our understanding of plants and their life-cycle.

Although we see every day thousands of plant species around us, in our gardens, in others’ gardens, on the roadside, on the wasteland, in parks and forests, we fail to think about their life-cycle.

One of the hobbies to develop and become a full-fledged botanist is to look around and try to understand those plants which grow around us.

I used to think of them very often, whenever I get some time to relax.

Plants are really helping human beings by offering food, materials for shelter and medicine to cure diseases.

Such useful plants which grow around us and some we grow in gardens or pots or rooftops depending on the space available are really the useful companions of us.

Ornamental plants really beautify our houses.

Only a few people get interested in plants, although many more do not hate them.

Plant reproduction has been studied at the physiological, biochemical, genetic and molecular levels.

It has been shown that several different kinds of molecules can control the transition to flowering. the roadside, on the wasteland, in parks and forests, we fail to think about their life-cycle.

When it occurs and why this happens are some of the preliminary questions anyone can pose.

Flowers are the organs of reproduction in plants.

We see some plants flower only in summer or in winter and some others flower throughout the year irrespective of seasons.

The initiation of reproduction generally requires the perception and response to the appropriate environmental factors like different wavelengths and duration of light and temperature.

These factors play an important role to change the metabolism of plants and cause the initiation of reproductive apices suppressing the vegetative structure.

It has been shown that a number of different kinds of molecules can control the transition to flowering.

They include carbohydrates, plant hormones (auxins, gibberellins, cytokinins) and calcium.

The mechanism of action of these metabolites is being worked out for understanding the physiology of reproduction with a certain degree of precision.  

The flower primordial thus produced start growing into a bud containing the male and female structures called the stamens and carpels.

The stamens consist of a filament topped by a complex anther structure within which we find pollen grains (microspores).

The carpels develop into the female organs – the pistil with stigma (the receptor of the pollen), style and ovary (the basal part where the ovules are present).

When both stamens and carpels are present in the same flower, it is called ‘perfect.’

The male and female flowers may be on a single plant (monoecy) or on separate plants (dioecious) like in palmyra.

Flowers are colourful with brightly coloured petals often play an indirect role in reproduction, attracting pollinating agents like birds and insects.

The colour of the petal is produced by the presence of pigments like anthocyanins.

In-plant reproduction, pollination is the primary process that starts by the transfer of pollen grains to the pistil type called stigma.

The pollens deposited on the stigma start growing by producing a tube called pollen tube which grows through the pistil and reaches the embryo sac.

The sperm cell from the pollen tube meets the egg cells and fertilization takes place.

Although many pollen tubes grow to reach the egg cells, only one can fertilize one egg cell; the rests of them die without getting a chance.

The fusion of the male sperm cell with the egg cell ultimately results in successful fertilization.

The net result is the birth of an embryo and its development is coordinated not only with that of the endosperm but also with that of the fruit which is formed by the ovary.

Plant reproduction from the transformation of vegetative to reproductive apex to the formation of fruits is an interplay of hormones and many metabolites with the involvement of various genes which trigger the whole process.

The plants perpetuate through reproduction by producing a huge quantity of seeds.

A portion of which is consumed by humans as food for their survival.

Thus Nature has produced plants for human survival through their reproduction. - NARA