The yield of plants is reduced when they are exposed to stress at any point in their lifespan. Under stress circumstances, plants undergo various morphological, physiological, and biochemical alterations to adapt to diverse stress situations.
Plants produce a specialised hormone called stress hormone that helps them deal with stressful situations and recover from them more quickly. Abscisic acid (ABA) is a hormone that helps plants respond to and recover from a wide range of abiotic stressors, such as cold, heat, and drought.
In this piece, we will cover all there is to know about the stress hormone in plants, including Abscisic acid’s functions.
See also: Know about macronutrients in plants
What are stress hormones in plants?
Phytohormones or plant hormones are chemical compounds in plants, which help regulate several physiological processes. These chemicals are produced in small quantity. Plants are exposed to several types of stresses such as drought conditions, salinity, heat, cold temperatures, etc. The hormones have a crucial role to play during stress conditions as they help plant in adapting to adverse environmental conditions.
Phytohormones such as Jasmonates, Salicylates and ABA interact together and act in hormone signal transduction cascade, referred to as crosstalk, between hormones to form a defence network against environmental stresses.
What is abscisic acid?
Abscisic acid is the term given to the stress hormone in plants. It controls the process of abscission and dormancy, in addition to acting as an inhibitor of plant development. The ability of plants to handle stress is improved by the increased production of Abscisic acid that occurs when they are exposed to situations that are considered to be stressful.
Abscisic acid functions
Bud dormancy
Abscisic acid causes buds to enter a dormant state in preparation for the coming of winter.
Seed dormancy
Seeds can withstand drying out, and temperature swings better during their dormant period. Gibberellins are required for bud and seed germination because Abscisic acid prevents growth. Abscisic acid goes by the term dormant because of its role in causing plants to enter a dormant state.
Stoppage of cambium activity
As the onset of winter draws near, the production of Abscisic acid inhibits mitosis in the vasculature of the cambium.
Abscission
Abscisic acid encourages the falling off of fruits and flowers during the process of abscission.
Leaf senescence
A high concentration inhibits the production of RNA and protein in the leaves, which leads to their ageing.
Transpiration
Abscisic acid production speeds up during times of desiccation and other forms of stress. Stomata are prevented from closing as a result of the inhibitor, which in turn stops transpiration.
Resistance
Abscisic acid makes plants more resistant to the effects of various stressors, including low temperatures. As a result of this, it is also known as the stress hormone in plants.
Starch hydrolysis
During the germination process of wheat grains, the synthesis of gibberellin-mediated amylase is inhibited by Abscisic acid.
Flowering
Abscisic acid, when present in trace amounts, has been shown to stimulate flowering in some plants with short photoperiods, such as black currant and strawberry.
Parthenocarpy
It has been discovered that ABA may stimulate the growth of parthenocarpic structures.
Rooting
In rare instances, such as with Bean, Ivy, and Poinsettia, rooting of stem cuttings may be aided by using Abscisic acid.
Membrane potential
When ABA is present, the membrane of a cell takes on a more positive surface potential.
Controlled growth
This hormone is an opponent to gibberellins and neutralises the effects of many other growth-promoting hormones, hence regulating their activity. Regarding the formation and maturity of seeds, ABA plays a crucial role in regulating growth. It normally prevents duckweed and other species from growing, as well as preventing the germination of seeds.
Why is abscisic acid called a stress hormone?
Abscisic acid is referred to as the stress hormone as it is found to induce different responses in plants against stress conditions such as closure of the stomata during drought phase, seed dormancy and ensures germination of seed under ideal conditions.
Abscisic acid increases a plant’s tolerance to various stresses. It aids the seeds in withstanding desiccation, inducing dormancy in plants at the end of growing season and promoting the abscission of leaves, flowers, and fruits.
How do these stress hormones function during stress?
Abscisic acid (ABA) limits the plant growth in order to coordinate plant adaptation to stressful conditions such as salinity, cold, and heat, drought, etc.
Air temperatures above a certain level may result in excessive oxidative stress and membrane damage in the plant, which can collectively reduce photosynthetic and transpiration efficiencies.
Heat shock causes a rapid and transient increase in endogenous ABA levels in the plants. The hormone offers heat tolerance by raising the ROS levels to improve antioxidant capacity. Abscisic acid may also act as a thermo-priming hormone, which allows plants to respond more quickly and efficiently to heat stress.
The hormone helps enhance drought acclimation in plants and modulate levels of carbohydrates and energy status by accelerated transport and improved metabolism of sucrose to strengthen plant thermal tolerance.
What are some stress hormones in humans?
Hormones such as adrenaline and cortisol are released when we encounter stress. Adrenaline increases the heart rate, blood pressure and energy supplies. On the other hand, cortisol is the primary stress hormone, which causes an increase in sugars in the bloodstream, improves the brain’s use of glucose and availability of substances that repair tissues.
FAQs
Which hormone in plants regulates stress?
Abscisic acid is a stress hormone that increases plant tolerance to high temperatures. The phytohormone Abscisic acid (ABA) plays an important role in plant development by controlling how plants react to stress.
Numerous plant stress acclimation mechanisms rely heavily on the plant hormone ABA. Plants produce ABA in response to various water-related stressors, including drought, salinity, cold, and heat.
What effect does stress have on plant growth?
The slowing of plant development due to stress may be quantified in absolute or relative decreases in biomass accumulation or total biomass. One of the plants' quickest and most sensitive reactions to stress is the extension of their leaves, as shown in cereal plants in response to hyperosmotic stress.
From where does the stress hormone get released in plants?
ABA (Abscisic acid) gets synthesised in the chloroplast and thus produced in the leaves.
