Kelp is a large edible perennial algae. The sporophyte is large, brown, flat and banded. It is divided into leaf blade, stalk and fixator, and the fixator is pseudorhizoid. The leaves are composed of epidermis, cortex and pith. There are sporangia in the lower part of the leaves. It has mucus cavity and can secrete slippery substance. The tree branch of the fixator is used to attach the seabed rocks and grow in the sea with low water temperature. Kelp is an important marine resource with low cost and rich nutrition.
Kelp belongs to the sub frigid zone algae, which is an endemic species in the North Pacific. There are also some kelp distribution in the Atlantic Ocean. Most of the kelp is distributed in the northern hemisphere, while a small amount is also distributed in the southern hemisphere, generally growing on the bottom rocks of the subtidal zone. The growth of kelp is mainly affected by temperature, light, nutrients and plant hormones.