In pollen grain who made the …

The tapetum is the innermost layer of the microsporangium. It provides nutrition to the developing pollen grains. It secretes enzymes, hormones and special proteins for the pollen grains to recognise compatibility. It also produces the exine layer of the pollen grains, which is composed of the sporopollenin. The tryphine that coats the pollen grains of Raphanus is tapetal synthesized and is composed of a fibro-granular and a lipidic component. The fibro-granular material is proteinaceous and is secreted by cisternae of the endoplasmic reticulum. The lipidic component is derived, mainly, from degraded elaioplasts. The fibro-granular material is applied to the pollen exine first, followed by the lipidic mass. The tryphine condenses during the final stages of pollen maturation and dries down to form a thick, highly viscous coating. The major part of the condensation appears to result from dehydration. The tryphine, extracted from the pollen by a centrifugal method and mounted in a membrane, appears to be capable of penetrating the outer layers of a stigma of the same species and, if the pollen from which it was derived is incompatible with respect to the stigma, the stimulation of the production of the callosic reaction body in a manner similar to an incompatible pollen tube. It is proposed that, in Raphanus, substances responsible for the initiation of at least two stages in the self-incompatibility system are held in the tryphine.