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Class : XII, , BIO BOTANY, , I. TWO MARKS :, 1. Define Microsporogenesis., The stages involved in the formation of haploid microspores from diploid microspore mother cell through meiosis, is called Microsporogenesis., 2. Define Pollinium., In some plants, all the microspores in a microsporangium remain held together called pollinium. Example:, Calotropis, 3. List out the name of anther walls., a. Epidermis, b. Endothecium, c. Middle layers, d. Tapetum.., 4. What is Stomium, The cells along the junction of the two sporangia of an anther lobe lack these thickenings. This region is called, stomium., 5. What is Endothecium?, Endothecium: It is generally a single layer of radially elongated cells found below the epidermis. The inner tangential, wall develops bands of a cellulose The cells are hygroscopic., 6. Define Secretory tapetum., The tapetum retains the original position and cellular integrity and nourishes the developing microspores., II. THREE MARKS :, 7. Write the Functions of Tapetum:, • It supplies nutrition to the developing microspores., • It contributes sporopollenin through ubisch bodies thus plays an important role in pollen wall formation., • The pollenkitt material is contributed by tapetal cells and is later transferred to the pollen surface., • Exine proteins responsible for ‘rejection reaction’ of the stigma are present in the cavities of the exine. These, proteins are derived from tapetal cells., 8. Defferentiate between secretory tapetum and invasive tapetum:, Secretory tapetum, The tapetum retains the original position and cellular, integrity and nourishes the developing microspores, , Invasive tapetum:, Thecells loose their inner tangential and radial, walls and the protoplast of all tapetal cells, coalesces to form a periplasmodium

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9., , Writ e about pollenkit, Pollenkitt is contributed by the tapetum and coloured yellow or orange and is chiefly made of carotenoids or flavonoids., It is an oilylayer forming a thick viscous coating over pollen surface. It attracts insects and protects damage from UV, radiation., , III. FIVE MARKS :, 10., , 1x5=5, , Explain the Development of Male gametophyte:, The microspore is the first cell of the male gametophyte and is haploid. The development of male gametophyte, takes place while they are still in the microsporangium., The nucleus of the microspore divides mitotically to form a vegetative and a generative nucleus. A wall is laid, around the generative nucleus resulting in the formation of two unequal cells, a large irregular nucleus bearing, with abundant food reserve called vegetative cell and a small generative cell., Generally at this 2 celled stage, the pollens are liberated from the anther. In some plants the generative cell, gain undergoes a division to form two male gametes., The pollen is liberated at 2 celled stage. In 60% of the angiosperms pollen is liberated in 2 celled stage., Further, the growth of the male gametophyte occurs only if the pollen reaches the right stigma., The pollen on reaching the stigma absorbs moisture and swells., The intine grows as pollen tube through the germ pore. In case the pollen is liberated at 2 celled stage the, generative cell divides in the pollen into 2 male cells (sperms) after reaching the stigma or in the pollen, tube before reaching the embryo sac.