Question

What is phytohormone

Answer 1

Plant hormones (also known as phytohormones) are chemicals that regulate plant growth. In the United Kingdom, these are termed 'plant growth substances'. Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations. Hormones regulate cellular processes in targeted cells locally and, moved to other locations, in other functional parts of the plant. Hormones also determine the formation of flowers, stems, leaves, the shedding of leaves, and the development and ripening of fruit. Plants, unlike animals, lack glands that produce and secrete hormones. Instead, each cell is capable of producing hormones. Plant hormones shape the plant, affecting seed growth, time of flowering, the sex of flowers, senescence of leaves, and fruits. They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity, and even plant death. Hormones are vital to plant growth, and, lacking them, plants would be mostly a mass of undifferentiated cells. So they are also known as growth factors or growth hormones. The term 'Phytohormone' was coined by Thimann in 1948[clarification needed]. Phytohormones are found not only in higher plants, but in algae too, showing similar functions,[1] and in microorganisms, like fungi and bacteria, but, in this case, they play no hormonal or other immediate physiological role in the producing organism and can, thus, be regarded as secondary metabolites.....hope u will like it...

Answer 2

Hi friend !

The plants do not have a nervous system and sense organs like ear ,nose ,mouth,etc like the animals , but they can still sense things.

The plants coordinate their behavior against environmental changes by using hormones.

The functions of control and coordination in plants is performed by certain chemical substances.These chemical substances are called plant hormones or phytohormones.

There are four major types of plant hormones [phytohormones] . which are involved in the control and coordination  in plants.These are :

1)Auxins

2)Gibberellins

3)Cutokinins

4)Abcisic acid

1)Auxins are the plant hormones which promote cell enlargement and cell differentiation. Auxins also promote fruit growth. Auxin hormone is responsible for phototropic and geotropic responses of plants.

2) Gibberellins are plant hormones which promote cell enlargement and cell differentiation in the presence of auxins. Gibberellins help in breaking the dormancy in seeds and buds. They  also promote fruit growth. Gibberellins stimulates elongation of shoots of various plants

3) Cytokinins are plant hormones which promote cell division in plants.They also help in breaking the dormancy in seeds and buds. The delay the ageing of leaves.Cytokinins promote opening of stomata .

4)Abscisic acid (ABA) is a  plant hormone which functions mainly as a growth inhibitor. Abscisic acid promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy]. It also promotes closing of stomata. Abscisic acid promotes falling of leaves.