Chemical Control in Plants

Chemical Control in Plants

Definition

  • Plants use chemical signals such as plant hormones or phytohormones for growth, development and response to the environment.
  • Plant hormones including auxins, gibberellins, cytokinins, abscisic acid and ethylene play critical roles in this chemical communication system.

Auxins

  • Auxins are involved in cell elongation, apical dominance and phototropism.
  • They promote stem elongation by softening plant cell walls, allowing for water uptake and cell expansion.
  • Conversely, they inhibit the growth of lateral buds, resulting in a phenomenon termed apical dominance.
  • Auxins also steer plant growth towards light, a process known as phototropism.

Gibberellins

  • Gibberellins stimulate stem and internodal lengthening, as well as seed germination.
  • They function by breaking seed dormancy and stimulating the synthesis of digestive enzymes like amylase, which break down stored starch into glucose for the growing seedling.

Cytokinins

  • Cytokinins promote cell division and also influence cell differentiation.
  • They work in conjunction with auxins, supporting apical dominance by suppressing lateral bud growth and encouraging cell division in the main stem.

Abscisic Acid (ABA)

  • Abscisic acid (ABA) plays a role in closing stomata during drought, promoting dormancy in seeds and buds, and inhibiting shoot growth in contrast to gibberellins and cytokinins.
  • ABA accumulates in the tissues of dehydrated plants, leading to the closure of stomata by inducing turgor changes in the guard cells, thus minimising water loss.

Ethylene

  • Ethylene is a gaseous hormone that manages fruit ripening and various types of plant stress responses.
  • Climacteric fruits, like apples and bananas, are especially sensitive to ethylene, and their rapid ripening can be stimulated by this hormone.

Importance

  • Understanding chemical control in plants is crucial for agronomic practices, such as growth regulation, manipulation of crop yield and timing, and fighting against stress conditions.
  • It is also important for combating plant diseases and controlling invasive plant species.

Application in Agriculture and Horticulture

  • Given their pervasive influence on plant growth and development, plant hormones are widely used in agriculture and horticulture.
  • Manipulation of plant hormones allows for control over fruit ripening, flower induction, and growth regulation, among other things.