Sunday, 12 July 2020

Microsporogenesis - Class 12 , Chapter 2 , lecture -4

Sexual Reproduction in Flowering plants

Microsporogenesis is the process of formation of microspores. Microsporogenesis takes place in pollen sac of Anther. Initially anther is a mass of homologous, undifferentiated, meristematic cells. Initially in the center of anther connective tissue forms the connective. Later on each each cell from the four corners of the anther, just below the epidermis becomes distinct from the rest of the cell and gets differentiated into the special cell known as Archesporial cell. Now the Archesporial cell divide mitotically to form two different type of cell i.e., Primary Parietal Cell and Primary Sporogenous Cell. The primary parietal cell divide mitotically to form the three layers of anther such as, Endothecium, Middle layer, Tapetum. Now the primary sporogenous cell divide mitotically to form sporogenous cell. Sporogenous cell again divide to form microspore mother cell (MMC/PMC). The microspore mother cell divide meiotically to form four haploid microspores. These four microspore reman intact, and covered by callose, this structure is called as tetrad. On maturity of microspore, the tapetal cell   release hormones and enzyme callase. Callase dissolve the callose and the pollen grain or microspore becomes free. 

Objective type Question-
1. Microsporophyll is called-
a). Androecium         b). Gynoecium
b). Filament               c). Ovary
2. Archesporial cells do not form-
a). Tapetum               b). Middle layer 
c). Endothecium        d). Epidermis
3). Microsporophyll contains which among these-
a). Ovule                    b). Pollen grain
c). Both                      d). None
4. Meiosis is observed in-
a). Primary parietal cell  b). Tapetal cell
c).Sporogenous cell        d). Microspore mother cell
5. The plant obtained from pollen grain culture is-
a). Haploid plant             b). Diploid plant
c). Heterosis                     d).Polyploid plant
6. Which is surrounded by  callose -
a). Middle layer 
b). Pollen grain 
c). Microspore mother cell
d). Egg
7. Pollen grain is formed by the meiotic cell division of-
a). Primary sporogenous cell
b). Primary parietal cell
c). Sporogenous cell
d). Microspore mother cell
8. Tetrad is a condition observed as-
a). Four microspore covered by callose
b). Four microspore free in pollensac
c). Microspore mother cell covered by callose
d). Four layers of the tapetum

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