give detailed structure of exine of pollen
Answers
In general, most pollen walls are composed of two major distinct layers: the exine, accumulated primarily by sporopollenin, and the intine, mainly composed of pectin and cellulose. ...Exine has a key role in the initialpollen–stigma adhesion in dry-stigma plants.
Most pollen grains consist of three distinct parts. The central cytoplasmic part is the source of nuclei responsible for fertilization. The other parts constituting the wall of the grain are an inner layer, the intine, and an outer layer, the exine. The intine consists, at least in part, of cellulose or hemicellulose. The outer and most durable layer, the exine, is very resistant to disintegration; treatment with intense heat, strong acids, or strong bases has little effect upon it. The constituents of the exine have been termed sporopollenins. The internal parts of the pollen grain are easily broken down, whereas the exine layer, and thus the general form of the pollen grain, is easily preserved in various kinds of sediments; the quality of preservation may vary with different environments.
In general, most pollen walls are composed of two major distinct layers: the exine, accumulated primarily by sporopollenin, and the intine, mainly composed of pectin and cellulose. ... Exine has a key role in the initial pollen–stigma adhesion in dry-stigma plants