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.