(Image credit: Aneduard)

Have you ever wondered why plants need sunlight? Sunlight is one of the ingredients needed by a plant to feed it. Plants are referred to as autotrophs because they use energy garnered from the sun to make their own food. This process is called photosynthesis

Why Do Plants Need Sunlight? 

Planting a plant in soil and then watering it is not enough for the plant to grow. The plant, like you or me, needs food. Incredibly, plants have the ability to feed themselves. Sunlight is one of the most important building blocks to creating the food the plant needs. 

Plants can’t use the light energy they absorb to make food. Instead, the light energy is converted to chemical energy. This isn’t the end of the process however.

Process of Photosynthesis

Plants harness the energy from the sun and, via a chemical reaction, convert it to chemical energy. This chemical energy is then combined with water and carbon dioxide in the air to make glucose, a type of sugar that nourishes the plant. This process is called photosynthesis. All plants, algae and some microorganisms perform photosynthesis. 

Carbon dioxide enters the plant through tiny pores in its leaves, flowers, branches, stems and roots. The plant also generally uptakes water through its root system

The absorbed energy from the sun causes a chemical reaction that breaks down the carbon dioxide molecules and re-appropriates them as glucose and oxygen gas. The oxygen is released from the tiny pores in the plant's features which animals then use to breath. The glucose is broken down by mitochondria into energy used for growth. 

Are There Any Plants That Don’t Need Sun?

Plants are very good at adapting to their environment. In some areas of the world however, sun is lacking and the plant isn’t able to photosynthesize. There are then two methods by which a plant can survive without sunlight. 

The first are parasitic plants -- those that have evolved to absorb nutrients and water from other plants without photosynthesizing themselves. Basically parasitic plants are using another plant's energy to survive. 

The second type of plant that can survive without photosynthesis is called saprophytic. Saprophytic plants like coral root orchids feed and utilize energy from decomposing organic material found in the soil. The organic matter is usually fungi. 

Other than these two types, plants cannot survive without the sun for any length of time. There are of course low light plants but even they need some sun exposure or artificial light throughout the day. 

Amy Grant

Amy Grant has been gardening for 30 years and writing for 15. A professional chef and caterer, Amy's area of expertise is culinary gardening.