🌱 Environmental Factors Affecting Plant Growth: A NEET & CBSE Guide

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Introduction

Plant growth is a highly sensitive and dynamic process that depends on both internal hormones and external environmental factors. Environmental conditions act as triggers, enhancers, or inhibitors of various stages of growth and development. For students preparing for NEET, Class 11 and 12 CBSE, understanding these factors is essential both for conceptual clarity and application in exams.

In this blog, we’ll explore the main environmental factors that influence plant growth, backed by NCERT guidelines, real-life examples, and important facts. Let’s dive in!


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🌞 1. Light

Light plays a vital role in the process of photosynthesis and photomorphogenesis.

Key Roles:

Photosynthesis: Light is the ultimate energy source.

Photoperiodism: The duration of light determines flowering in plants (short-day, long-day, and day-neutral plants).

Phototropism: Plants bend toward the light source due to auxin distribution.


NEET Point:

Plants detect light through phytochrome and cryptochrome pigments.

CBSE Tip:

Always remember that light intensity, quality (wavelength), and duration all affect plant behavior.


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🌡️ 2. Temperature

Temperature influences enzyme activity, membrane fluidity, and rate of biochemical reactions.

Optimal Temperature Ranges:

Cool Season Crops: Wheat, peas (15–25°C)

Warm Season Crops: Rice, maize (25–35°C)


High Temperature Effects:

Inhibits enzyme activity

Denatures proteins

Causes wilting due to transpiration


Low Temperature Effects:

Freezing injury

Reduced metabolic rate

Dormancy in seeds



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💧 3. Water

Water is essential for:

Photosynthesis

Turgor pressure

Transport of nutrients and hormones

Cell division and enlargement


Important Note:

Water stress or drought can:

Reduce plant height

Delay flowering

Cause stomatal closure (affecting CO₂ intake)


MCQ Hint:

The first visible effect of water deficiency is reduced cell enlargement.


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🌬️ 4. Air and Carbon Dioxide

Carbon dioxide is required in photosynthesis and stomatal regulation.

CO₂ and Photosynthesis:

Elevated CO₂ levels can increase plant yield

But if levels become too high, it may cause stomatal closure


Wind:

Affects transpiration rate

Can mechanically damage plants (lodging in cereals)

Affects pollination in anemophilous plants (wind-pollinated)



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🧪 5. Nutrients and Soil

Plants need 17 essential nutrients, divided into:

Macronutrients: N, P, K, Ca, Mg, S

Micronutrients: Fe, Mn, Cu, Zn, B, Mo, Cl, Ni


Soil pH:

Influences nutrient availability

Most plants grow best in pH 6-7.5


Deficiency Symptoms:

Yellowing of leaves (Chlorosis) — Lack of nitrogen or magnesium

Stunted growth — Lack of phosphorus

Leaf curl — Lack of potassium



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🧊 6. Gravity

Gravitropism (or geotropism) is the plant's growth response to gravity.

Roots: Positive gravitropism (grow downward)

Shoots: Negative gravitropism (grow upward)


This is regulated by the distribution of auxins in response to gravity.


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🌬️ 7. Atmospheric Humidity

Humidity affects:

Transpiration rate

Stomatal movement

Water absorption


Low humidity increases transpiration and may lead to wilting.


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🌪️ 8. Biotic Factors

Pathogens (bacteria, fungi) and pests (insects, mites) affect growth.

Symbiotic relationships (e.g., Rhizobium in legumes) promote growth.


Competitive Factors:

Weeds compete for light, water, and nutrients, reducing crop yield.


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📌 Summary Table for Quick Revision

Factor Effect on Plant Growth Example

Light Affects photosynthesis and flowering Sunflower turns towards light
Temperature Alters enzyme activity and growth rate Tomato fails to set fruit in cold
Water Essential for turgidity, transport, and photosynthesis Wilting in dry soil
CO₂/Air Required for photosynthesis Elevated CO₂ increases yield
Soil/Nutrients Provide essential elements Nitrogen-deficient leaves turn yellow
Gravity Directs root and shoot orientation Roots grow downwards
Humidity Affects transpiration Wilting in dry air
Biotic Pests/pathogens can damage plants Aphids feeding on leaves



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📚 Conclusion

Understanding environmental factors that influence plant growth is crucial for NEET aspirants and CBSE Biology students. Each of these factors plays a unique and interconnected role in the development, reproduction, and productivity of plants.

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