Factors affecting Plant Growth: External Factors and Internal Factors

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Here we are going to discuss “Factors affecting Plant Growth: External Factors and Internal Factors“. Growth is affected by several factors which may be External or Internal. These factors ultimately affect the activity of Protoplasm of the cell. protoplasm affects the metabolism of the plant and if metabolism is disturbed, plant growth also gets affected.

We can categorise all these factors in two types, Environmental and Physiological factors. Physiological factors affect the absorption of water, minerals, photosynthesis, respiration processes on other hand environmental factors affects climatic and edaphic conditions. The effect of these factors is transmitted to one region to another region in the plant.

Factors affecting Plant Growth: External Factors

External factors are those factors which are affecting the plant externally or environmentally. These are some examples of external factors which affect plant growth.

1. Light

Light is a very important factor for plants. The intensity of light, quality of light, duration of light affects plant growth in many ways.

Factors affecting Plant Growth: External Factors and Internal Factors — External Factors of Plant Growth: Light

High light intensities induce dwarfism of the plant. due to this, plant which are situated on the hilltops are short in length whereas those plants which are situated in a valley are quite tall.
Weak light induces the photosynthesis and overall growth of the plant. Chlorophyll development in the plant also depends upon light. When light is not available, chlorophyll formation not takes place. In the absence of chlorophyll “Etioline” compounds are formed. “Etioline gives the yellow colour to the plant. This phenomenon is called etiolation. High intensity of light increases the rate of water loss or transpiration and reduces the rate of plant growth.
Different colours of light or wavelengths affect the growth of plants in many ways. Internodal growth is promoted by blue-violet colour whereas green colour light reduces the expansion of leaves.

2. Temperature

Factors affecting Plant Growth: External Factors — Plant Growth External Factors: Temperature

Red colour light promotes elongation. Ultraviolet rays are very important for the development of anthocyanin pigment. Size of the lamina of the leaf is increased by blue and violet colour.
Duration of light place a very important role in the growth of vegetative and reproductive structures of plants. Duration of light induces and suppress the flowering in the plants.
The temperature is different for different species. The minimum temperature for plant growth is 5 degrees celsius and optimum temperature for plant growth is 20-30 degree celsius in the Arctic zone whereas in tropical countries the optimum temperature for plant growth is 35-40 degree Celsius. The optimum temperature for a plant needed for the growth on the basis of the stage of the development. Every stage of development of the plant needs a specific temperature.

3. Water

Water is a universal solvent which is needed for various physiological processes. What direct affects the metabolism of plants. The plant cannot live without water.

The requirement of water is different for different types of plants. Those plants which are situated on the hills top needs a low amount of water whereas those plants which are situated in valley areas need more water.
Plants of hilly areas have an adaptation to save the water whereas plants of Valley areas don’t have adaptation to save water. Valley areas plants have broad leaves whereas hilly areas plants have any leaves.

4. Carbon dioxide (CO2)

plant growth factors: Carbon dioxide (CO2)

Carbon dioxide is very essential for the photosynthesis process. Photosynthesis is directly connected with the metabolism of the plant. Metabolism is directly connected with the growth of a plant. carbon dioxide concentration can increase or decrease the rate of photosynthesis. So that the CO2 affects the plant growth directly.

5. Oxygen

Where oxygen concentration is low and the concentration of carbon dioxide is high plants usually show stunted growth. Such condition is found in the soil which is poorly aerated. oxygen is very important for respiration.so that normal growth needs a sufficient amount of oxygen. Oxygen also plays a very important role during the G1 stage of cell division.

6. Mineral Salt

Plant growth gets abnormal when essential minerals are absent or in low quantity. The absence of Nitrogen prevents photosynthesis whereas the absence of iron prevents chlorophyll formation in the leaves of plants. Deficiency of chlorophyll leads to pale and sickly growth.

7. Pollutants

Pollutants affect plant growth in many ways. Automobile exhaust, peroxyacetyl nitrate PAN, pesticides have various kind of effects on plant growth. Fluoride is very dangerous for citrus and gladius plants. Where Ozone concentration is high the growth of tobacco plant is poor. Pine trees cannot survive under the high concentration of ozone gas. Cotton plants are very sensitive to ozone gas. So that we have to try to do not produce any kind of pollutant which are harmful to plants and animals.

Factors affecting Plant Growth: Internal Factors

1. Nutrition

Nutrition provides the raw material for the growth and development of plants. Nutrients are the source of energy for plants which is very important for differentiation after growth of the embryo. Carbohydrate/Nitrogen ratio determine the type of growth in plant development.

Carbohydrate/Nitrogen ratio stimulates wall thickening when they are in high concentration. Less protoplasm is formed in this situation. Thin soft wall produced when Carbohydrate/Nitrogen ratio is low. In this situation, more Protoplasm is formed.

2. Growth Regulators

Growth regulators are plant hormones which are responsible for the growth and development of the plant. Growth regulators are manufactured by living Protoplasm and essential for growth and development in each plant. Growth regulators include several phytohormones and some synthetic substances.

A. Auxins

Auxins promote the stem elongation in the plant during growth and development. Auxins promote the apical bud development and inhibit the growth of lateral Buds. The situation is called apical dominance. Example: Indole Acetic Acid (IA)

B. Gibberellins

Gibberellin is an endogenous plant growth regulator. Gibberellin is responsible for plant growth by promoting stem elongation. Because of this property of gibberellin acid is also known as”inhibitor of an inhibitor”.Gibberellins promote flowering in long-day plants, They are helpful in breaking seed dormancy, promote seed germination. Gibberellins are helpful in inducing parthenocarpy, helpful in overcoming genetic dwarfness of plants. Gibberellins are useful to increase sugar yield in sugarcane by promoting stem growth.

C. Cytokinins

Cytokinins can increase cell division by stimulating mitosis cell division. Cytokinins found naturally in plants but also have been synthesized by humans. By Increased mitosis, Cytokinins promotes plant growth. Cytokinins promote the formation of shoots and buds fruits and seeds.

D. Ethylenes

Ethylene is only a plant hormone which is found in gaseous form. It needed in very minute quantity. Ethylene stimulates or regulates the ripening of fruit in plants, Ethylene is also helpful for the opening of flowers.

E. Abscisic Acid (ABA)

Abscisic acid promotes abscission of plant leaves & fruits. In winter, Abscisic acid is produced in terminal buds to slows plant growth. it directs leaf primordia to develop scales. This procedure is to protect the dormant buds during the winter.

Here we have discussed “Factors affecting Plant Growth: External Factors and Internal Factors” we hope you like this article. if you have any query or suggestion, please leave a comment on the email. or contact us from contact us page.

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