Coordination in plants

​Coordination in plants

• It is the mechanism through which plants adapt themselves in response to changes in the environment.

• Different parts of the plants are working together in this mechanism so that plants can function well.
  
  

Coordination

• Plants secrete various hormones in response to changes in the environment and to coordinate their growth and development.

• These hormones are the chemical compounds released by the plant cells when stimulated by the environment.
  
  

Coordination

Plant hormones

• Plant hormones, also known as phytohormones, are natural chemical compounds that help in the regulation of different kinds of physiological processes in plants.

• These hormones are secreted in particular plant tissues and taken to target sites, where they generate specific responses. They play significant role in coordinating growth and development of the plants as well as provide response to both internal and external signals.

Plant hormones

• There are two kinds of plant hormones.

• Growth promoters, such as auxins, cytokinins, and gibberellins, help in the growth of the plants.

• Growth inhibitors such as abscisic acid and ethylene inhibit the growth of plants.

Auxins

• Auxins are the hormones that play a crucial role in cell elongation, apical dominance, and the formation of roots and fruits.

• They also influence the growth of plants in response to light and gravity, also known as phototropism and geotropism, respectively.

Cytokinins

• Cytokinins are the hormones required for cell division and cell differentiation in the plants.

• They promote the growth of lateral buds, delay senescence, and stimulate the secretion of proteins and nucleic acids.

• Cytokinins are also responsible for regulating apical dominance.

Gibberellins

• Gibberellins help with stem elongation, seed germination, and flowering in plants.

• They are responsible for internode elongation.
  
  
  

Abscisic Acid(ABA)

• ABA plays an important role in plants in response to environmental stresses, such as drought and high salinity. Hence, it is also known as the stress hormone.

• It inhibits the plant growth by promoting seed dormancy and controlling stomatal movement during water stress.
  

Ethylene

• Ethylene promotes fruit ripening, leaf abscission, and senescence. It is responsible for the root growth and development.

• Ethylene is unique among plant hormones, as it is a gaseous compound.

Growth movements

• There are two kinds of growth movements in plants.

• They are directional movement and non-directional movement.

• Both of these movements rely on environmental stimuli like gravity, light, touch, chemicals, etc.

Growth movements

• Directional movements are also known as trophic movements, as they occur in the direction of the stimulus. These movements are essential for the growth of the plants.

• Nondirectional movements are known as nastic movements, as only the parts of plant movements are involved in response to the stimulus. These movements do not provide growth to the plants.

Directional movement-phototropism

• It is the movement of plants in response to light.

• If the movement of plants is towards light, it is known as positive phototropism; for example, stems grow in the direction of light.

• If the movement of plants is away from light, it is known as negative phototropism; for example, roots grow away from light.

Directional movement-geotropism

• It is the movement of plants in response to gravity.

• If the movement of plants is towards gravity, it is known as positive geotropism; for example, roots grow towards gravity.

• If the movement of plants is away from gravity, it is known as negative geotropism; for example, stems grow away from gravity.

Directional movement-hydrotropism

• It is the movement of plants in response to water or moisture.

• If the movement of plants is towards water, it is known as positive hydrotropism; for example, roots grow towards water.

• If the movement of plants is away from water, it is known as negative hydrotropism; for example, shoots of the plants grow away from water.

Directional movement-chemotropism

• It is the movement of plants in response to chemicals such as harmful acids, salts, etc.

• If the movement of plants is towards chemicals, it is known as positive chemotropism; for example, a pollen tube growing towards an ovule.

• If the movement of plants is away from chemicals, it is known as negative chemotropism; for example, roots grow away from chemicals such as harmful acids.

Nondirectional movement-thigmotropism

• It is the movement of plants in response to touch.

• If the movement of plants is towards touch, it is known as positive thigmotropism; for example, tendrils growing around support.

• If the movement of plants is away from touch, it is known as negative thigmotropism; for example, roots growing away from rocks.