What is Photosynthesis?

Photosynthesis is a chemical process in which plants use energy from sunlight to make their food, or glucose. During photosynthesis, carbon dioxide and water are combined to make glucose. The glucose is the plants food, and it is sent around the plant.

Xylem and Phloem

In plants, there are two main vessels: Xylem and Phloem. Xylem is a vessel that runs from the roots to the leaves of the plant. Phloem runs from the leaves to every other part of the plant. Xylem collects water from soil, and sends it up to the leaves. Once the process of photosynthesis is done, Phloem carries the glucose made to the rest of the plant.

Leaves

The leaves of the plant play a major role in photosynthesis. The leaves attract sunlight, and photosynthesis occurs in the leaves.

When light shines on the surface of the leaves, photosynthesis occurs inside. Water arrives from the soil, and carbon dioxide arrives from pores called stomata on the back of the leaf.

Parts of the Leaf

There are 7 parts of a leaf that play a role in photosynthesis.

Chloroplast: Chloroplast is a green structure that contains chlorophyll, which is used to absorb the energy from sunlight.

Palisade Cells: These are special column-shaped cells located under the upper surface. Most of the process of photosynthesis occurs here.

Vascular Bundle: This is where Xylem bring water and dissolved minerals to the leaf, and where Phloem takes away glucose to the rest of the plant.

Lower Epidermis: This is the underside of the leaf, where stomata are located.

Upper Epidermis: This is the layer of cells that forms the upper surface of the leaf. These cells have a waxy coating to reduce transpiration, which causes water to evaporate from the leaves.

Spongy Mesophyll: These are cells with large spaces in between where the gasses oxygen and carbon dioxide circulate.

Guard Cells: Stoma are made of two guard cells which move away from each other to open the pore when the sunshine, and move together to close it when it is dark.

Chlorophyll

Chlorophyll is a chemical pigment located in chloroplast that absorbs red and blue light from sunlight. It does not absorb green light, and it is reflected off. This is why leaves appear green to us.

The energy from the light absorbed by chlorophyll is used to power photosynthesis.

The Process of Photosynthesis

There are two phases of photosynthesis: light reaction and dark reaction

During light reaction, chlorophyll takes energy from red and blue pigments of sunlight. The energy is used to make ATP, which is an energy-carrying molecule. ATP is used to power dark reaction.

During dark reaction, an enzyme called rubisco combines water and carbon dioxide, and glucose is made.

The Waste Product

Oxygen is produced as a waste product of photosynthesis, and gets released into the air through the leaves.