Question

Biologically most resistant plant material is
A. Sporopollenin
B. Lignin
C. Suberin
D. Cutin

Answer 1

Hint:- One of the biological products that is most resistant is one that is very durable and conserved in soils and sediments. These are both from inorganic and organic compounds prone to chemical degradation. It is the most inert biological substance and is found in the plant spores and pollen grains of the stronger outer wall.

Complete answer:
Sporopollenin is a strongly cross-linked, incredibly stable carbon, hydrogen, and oxygen polymer found chemically intact in sedimentary rocks around 500 million years old. It makes up the outer layer (exine) of plant spores and pollen and is in the shape of a hollow exine or microcapsule when it is collected. Exines resemble, in scale and morphology, the spores and pollen from which they are derived.
Lignin is a class of complex organic polymers which, in the support tissues of vascular plants and some algae, form key structural materials. In the forming of cell walls, especially in wood and bark, lignins are particularly important because they lend rigidity and do not easily rot.
Suberin, cutin and lignins are complex, higher cell-wall macromolecules of the plant epidermis and periderm, creating a defensive shield. The lipophilic structure of Suberin, a complex polyester biopolymer, is composed of long-chain fatty acids called suberin and glycerol.
Cutin, which covers all aerial surfaces of plants, is one of two waxy polymers that are the primary components of the plant cuticle. Cutan, which is much more easily retained in the fossil record, is the other significant cuticle polymer.
From these discussions we can conclude that Sporopollenin is the biologically most resistant plant material. Therefore the correct answer is option (A).

Note:- There are phenolic, alkane, alkene, ketone, lactone, and carboxylic acid classes on the surface of sporopollenin exine. It can also be derivatized in a variety of ways that have given rise to applications in fields such as peptide synthesis-supported solids, catalysis and ion-exchange chromatography. It also endows antioxidant function with the presence of the phenolic groups on sporopollenin.