Water droplets on a leaf

Water droplets on a leaf (Kyle Szegedi, Unsplash)

Needs of Plants

Let's Talk Science
Format
Readability
5.1
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Summary

Plants have specific needs - light, air, water, nutrients, and space - to survive and reproduce.

Almost all plants need these five things to survive: 

  • Light
  • Air
  • Water
  • Nutrients 
  • Space to grow
Most plants need light, water, air, nutrients and space to grow in order to survive
Most plants need light, water, air, nutrients and space to grow in order to survive (©2020 Let’s Talk Science).

Light

Plants usually get the light they need from the Sun. But they can also grow in artificial light. Plants use light energy to make a type of sugar called glucose. They use glucose as their energy source.

Plants make glucose in a part of their leaf cells called the chloroplast. Each chloroplast contains a green pigment called chlorophyll. It’s what allows the plant to absorb light energy. 

Plant cells with visible chloroplasts. The chloroplasts are the roundish, bright green ovals (Source Dr. phil.nat Thomas Geier, Fachgebiet Botanik der Forschungsanstalt Geisenheim
Plant cells with visible chloroplasts. The chloroplasts are the roundish, bright green ovals (Source: Dr. phil.nat Thomas Geier, Fachgebiet Botanik der Forschungsanstalt Geisenheim [CC BY-SA 3.0] via Wikimedia Commons).

If a plant doesn’t receive enough light, it will grow very slowly. But too much light can cause the plant and the soil it lives in to dry out. 

Different plants have different light requirements. Some need bright or direct light. Others can thrive in dimmer or indirect light.
 

Misconception Alert

Almost all plants need light to survive but there are a few special exceptions. Some parasitic plants like the corpse lily do not have chlorophyll and only get their energy by stealing it from other plants.

Air 

Air contains many gases. They include nitrogen, oxygen, carbon dioxide and water vapour. 

Graph showing the percentages of the different gases that make up air
Graph showing the percentages of the different gases that make up air (Source: Let’s Talk Science using an image by Life of Riley [CC BY-SA 3.0] via Wikimedia Commons).
Graph - Text Version

Air is made up of approximately 78 percent nitrogen, 21 percent oxygen,  one percent argon and 0.038 carbon dioxide. Air also has very small amounts of neon, helium, krypton, hydrogen and xenon.

Using energy from light, plants chemically combine carbon dioxide and water to create glucose and oxygen. This process is called photosynthesis
Plants also absorb oxygen gas from the air. Like animals, plants need oxygen to respire. Respiration is the process of breaking down molecules, like glucose, for energy.

Misconception Alert

Sometimes people think that plants use heat from the Sun for photosynthesis. Photosynthesis uses the Sun’s light energy, not its heat energy. Plants can photosynthesize in both warm and cold places. In fact, different plants have evolved to grow in different climates all around the world!

Water

Plants need water for photosynthesis. Absorbed by the roots, water travels through a plant’s stems to the chloroplasts in the leaves. Water also helps move nutrients from the soil into the plant. Too little water can cause a plant to wilt or droop. Too much water can cause a plant’s roots to rot.

The plant on the left (a) looks wilted, whereas the plant on the right (b) looks healthy
The plant on the left (A) looks wilted, whereas the plant on the right (B) looks healthy (Source: CNX OpenStax [CC BY 4.0] via Wikimedia Commons).

Misconception Alert

Plants can absorb small amounts of water through their leaves. But they get most of the water they need through their roots. 

Nutrients

Nutrients are substances that nourish a plant. In particular, plants need nitrogen, phosphorus and potassium. When dissolved in water, these nutrients get absorbed by a plant’s roots.  
If a plant can’t get the nutrients it needs from the soil, fertilizer can help. Fertilizer provides plants with essential nutrients and helps them grow faster.

Space to Grow 

All living things need space. A plant’s roots need space so that they can spread out and absorb water and nutrients. Its leaves need space so that they access light. When plants grow too close together, they have to compete for these resources.

 

These radish sprouts are very tall and thin because they are competing for resources
These radish sprouts are very tall and thin because they are competing for resources (Source: akiyoko via iStockphoto).

Without enough water, nutrients and light, plants can grow tall and thin or short and stunted. Overcrowded plants tend to be less healthy, which makes them more likely to suffer from disease. 

 

 

Learn More

What Does a Plant Need to Grow?

This article by BBC Bitesize, with videos and a quiz, explains why plants are important, and what they need to grow properly.

Photosynthesis for Kids

This article by Photosynthesis Education explores what's needed for photosynthesis, and what happens during the process.  

References

BBC Bitesize. (n.d.). What does a plant need to grow?

Fries-Gaither, J. (2009, March). Common misconceptions about plants. Beyond Penguins and Polar Bears.

Peterson, S. (n.d.). How the closeness of plants affect growth. SFGate.

Photosynthesis Education. (n.d.). Photosynthesis for kids.

Science Learning Hub. (2013, July 30). Fertiliser.

Soil Nutrient Management for Maui County. (n.d.). Essential nutrients. University of Hawai‘i.

Tilley, N. (2019, May 30). What makes plants grow: Plant growing needs. Gardening Know How.