An anther with malfunctioning tapetum often fails to provide viable male gametophytes. Give any one reason.

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Hint: The male gametophyte occurs within the male reproductive organ of the flower called stamens. The male gametes are termed pollen. The tapetum is a layer of specialized nutritive cells found within the anther which is the apical part of the stamen.

Complete answer: The male reproductive part of a flower is called stamen which consists of a stalk called filament and the apical part called the anther. The anther is a crescent-shaped structure that lies on the top of the filament and encloses the male gametophyte. The male gametophytes are formed in two processes called microsporogenesis and microgametogenesis. During microsporogenesis the mother cells which are diploid in nature undergo meiosis. This results in the formation of tetrads of haploid microspores that are released by enzymes secreted by tapetum. The tapetum is a layer of specialized cells that functions to provide nutrition to the growing microgametes. It is present within the walls of the anther. The released microspores from the tetrads enlarge and form a single large vacuole inside them. The nucleus of the microspore shifts toward the periphery of the cell wall. Then through asymmetric division, the microspore forms a small cell representing the male gamete and a large vegetative cell. All of these development stages are controlled and nourished by the tapetum. Thus, tapetum is necessary for the nutrition and development of pollen grains. Also, the tapetum serves as the source for precursor elements of pollen coat.
So, if the tapetum becomes malfunctions, the pollens will not be able to grow and develop properly. They will not get any nutrition and hence fail to form viable and functional gametes.

Note: The cells of the tapetum are usually larger having more than one nucleus. The cells of the tapetum divide by mitosis. The multinucleate cells of tapetum can provide nutrition to growing pollen as they have large nuclear constitutions. The tapetum also produces an enzyme called callase which is responsible for separating the tetrads formed during microsporogenesis.