How Does Light Affect Plant Growth?

Most of us take light for granted because it’s readily available and we only need it so that we can see clearly. Most plants, on the other hand, need light to make food!

Food, air, and shelter are the three basic human needs. For plants, these three needs are light, water, and air!

How does light affect plant growth?

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Photosynthesis is often taught poorly in today’s classrooms, while there used to be an entire unit devoted to it! We need plants more than they need us.

What is photosynthesis?

Photosynthesis is the ability of plants to make their own food. Plant growth is affected by light, and it will need to be available for photosynthesis to occur. Without light, plants can’t make food!

Chlorophyll is the green substance in plants! This green substance is responsible for absorbing light pigments, helping the plants carry out photosynthesis.

How Does Light Affect Plant Growth During Photosynthesis?

Now that we have reviewed photosynthesis, it’s time we understand the whole process along with light’s exact role!

Plants are autotrophs, meaning they are capable of making their own nutrients.

How do they go about it?

Plants absorb minerals and nutrients from the soil, taking in water through their roots and carbon dioxide through stomata to make food. Light is a plant’s main source of energy.

Most plants are grown in the open, utilizing the sun as their main source of energy. Recent technology has made growing bulbs possible, providing the exact light needed by plants for all growth stages!

Plants need water, carbon dioxide in the presence of chlorophyll, and sunlight to utilize oxygen molecules and glucose!

The glucose made is used by plants to enhance growth, whereas the oxygen molecules are released by the plants as a by-product. Trees and plants, in general, purify the air!

Plants take in the carbon dioxide we breathe out, releasing oxygen during photosynthesis. This only happens when plants are exposed to light. At night, plants take in oxygen and release carbon dioxide like us.

Light is Essential for Direct-Growth

Have you ever wondered why a plant’s stem grows straight upright? The few plants with stems that don’t grow upright are weak, known as parasitic plants depending on other plans for support.

What is the reason for this, or is it all just a coincidence?

Plants always grow towards the light if they can.

When exposed to light, the auxins hormone is produced, stimulating stems to grow towards the best available light source.

Plants derived from light will bend in almost any direction in search of a good source! Plants need light for growth, stems weakening otherwise.

A plant’s stem allows the passage of foods from the roots to the leaves. It houses an elaborate transport system not visible to the naked eye! Less food and water are able to be transported among a broken stem.

What happens when you don’t get enough food?

You’ll grow weak and thin. The same thing applies to plants! When the stem is weak and less food is transported to roots, the plant will weaken, affecting its growth. All this is due to lack of direct light!

Different plants store their food differently. Some store their food on leaves while others in the roots or stems. Light is always required for effective storage!

Sugarcane and cactus plants both store food in their stems.

Why do sunflowers face different directions at different times of day? They follow a pattern! As long as they are grown outdoors facing the sun, every sunflower faces the east in the morning and west in the evening.

Seasonal Effects

Some plants are naturally seasonal, relying on seasonal patterns to either flower, seed, or fertilize. Plants blossom during spring and summer in most countries with four seasons, when plants flower and bear fruit.

In other seasons with inadequate sunlight, most plants are dormant, and their sole purpose is to conserve energy. Some plants shed off their leaves and appear dry, only to rejuvenate back to life later in spring!

Are Artificial Lights as Effective as Sunlight?

More and more people are engaging in indoor farming where light is essential.

Technology has enabled us to create grow lights, in addition to natural light from the sun, that provide plants with the exact light they need for different stages of growth.

How effective is artificial light compared to sunlight?

You need an artificial grow light in a grow tent. There are thousands of brands to choose from, different grow lights offering different features.

When it comes to lighting for plant growth, the best type of bulbs are LEDs (Light Emitting Diodes).

Different Light Aspects that Affect Plant Growth


More intense light means more photosynthesis. This means more plant growth! In a grow tent, the light intensity can be adjusted by either reducing or increasing distance to plants.

Unfortunately, some grow lights emit heat harmful to the plants. The best brands offer an effective cooling system, ensuring little to no heat is emitted!


The longer plants are exposed to light, the higher the rate of growth. While you can’t manipulate sunlight duration, grow lights allow this and indoor gardening yields more returns!

Light Spectrum

Light is a form of energy that moves in electromagnetic waves. The full light spectrum includes 12 bands of different lights!

All these light wavelengths are essential for plant growth, but the red, blue, and violet spectrums are the most important.

Red Light Spectrum

Though this spectrum is the longest of all, it lacks energy. Red light supports flowering and blooming in plants! Inadequate red light slows a plant’s flowering.

Blue & Violet Light

While these are shorter light wavelengths, they are higher in energy. The blue spectrum light is essential in the vegetative phase of growth. Plants exposed to too little or no blue light will likely turn yellow.

Blue light helps in the formation of chlorophyll in the presence of magnesium.


Can grow light be as effective as sunlight? Yes!

Lighting is easy to control in a grow tent, while you can’t control the sun. Most grow lights are able to alternate lighting during vegetative phase and flowering.

Photo by Kajarima01