Sporopollenin is an organic material that is present in the exine layer of the pollen grain. The exine layer is the outermost layer of the pollen grain, and it is composed of two layers: the outer layer called the ectexine, and the inner layer called the endexine. Sporopollenin is present in both layers of the exine.

Sporopollenin is a complex biopolymer that is highly resistant to degradation. It is composed of long-chain fatty acids and phenylpropanoids, which are linked together by ester and ether bonds. It is one of the most chemically inert organic materials found in nature.

The importance of sporopollenin in the exine layer of the pollen grain is that it provides mechanical strength and protection to the developing male gametophyte. It also protects the pollen grain from desiccation, UV radiation, and other environmental stresses.

In addition to its role in the exine layer of the pollen grain, sporopollenin is also present in the spore walls of some lower plants, such as ferns and mosses. In these plants, sporopollenin provides mechanical strength and protection to the spores.

In conclusion, sporopollenin is an organic material that is present in the exine layer of the pollen grain. It is an important component of the exine layer, providing mechanical strength and protection to the developing male gametophyte.

Sporopollenin is an organic material that is present in the exine of pollen grains.

Explanation:
• Pollen grains are the male gametophytes of flowering plants.
• They are produced in the anthers of flowers and are responsible for the transfer of male gametes to the female gametophyte (embryo sac).
• Each pollen grain is surrounded by a tough, protective layer called the pollen wall or sporoderm.
• The pollen wall is composed of two layers - the outer exine and the inner intine.
• The exine is the outermost layer of the pollen wall and is made up of a complex mixture of lipids, proteins, and carbohydrates.
• The exine is the layer that provides protection to the pollen grain against physical damage, desiccation, and microbial attack.
• Sporopollenin is a major component of the exine and is responsible for its toughness and resistance to degradation.
• Sporopollenin is one of the most chemically inert organic materials known and is highly resistant to heat, acids, and enzymes.
• The intine is the innermost layer of the pollen wall and is composed of cellulose and pectin.
• The intine is responsible for the growth and development of the pollen tube, which delivers the male gametes to the female gametophyte.

Therefore, it can be concluded that sporopollenin is an organic material that is present in the exine of pollen grains.