Friday, 10 July 2020

Structure of Anther - CLASS 12 , Chapter 2, Lecture - 2

Sexual Reproduction in Flowering Plants
The Structure of Anther:

The male reproductive organ of a plant is the Androecium. Androecium is constitute of one or many stamens. The upper swallon part of stamen is called anther.  The development of anther takes place by more than one Archesporial cell , so it is Eusporangiate in origin.
                                                                                                    Anther is generally spherical and have following structures-    
1. Epidermis - Epidermis is the uppermost layer . It is single celled thick continuous layer . Epidermis is protective in nature . Epidermis is not Archesporial in origin .
2.Endothecium - Endothecium is present just below the epidermis. Endothecium is also single celled thick , continuous layer. The cells of Endothecium has deposition of alpha-cellulose in its inner wall and callose band in radial wall but the outer remain thin . Endothecium is Archesporial in origin. In some cells of endothecium the inner wall and radial wall deposition of alpha-cellulose and callose band is not present , this place is called stomium. At the point of stomium dehiscence takes place.
3. Middle layer - Middle layer is next to the Endothecium and 1 to 3 celled thick . Middle layer is Archesporial in origin . Middle layer have parenchymatous cells. Tapetum absorb nutrition from middle layer after which middle layer degenerates. so it shows ephemeral nature and degenerates in mature anther.
4. Tapetum - Tapetum is present next to the Middle layer . Tapetum is single celled and surrounds the pollen sac. Tapetum initially absorb nutients from the middle layer and convert it into special material depending upon the type of tapetum then after it pours it into the pollensac. Tapetum also secretes hormone and enzymes. The tapetum  layer is absent in mature anther. Tapetum layer is the nutritive layer.
5. Pollen sac - In a young or immature anther four pollen sacs are present. Pollen sacs are special chamber in which special cell called microspore mother cells are present. These cells meiotically divide to give rise microspores. Pollen sac is also called as microsporangia. 
 
Objective type questions ----- ( All these questions are asked in previous exams-)

1. Microsporophyll contains which among these -
a). Nucellus            b). Pollen grain
c). Pollen tube        d). All the above
2. Flowering in a biennial plant take place-
a). Many times       b). Ones
c). Twice                d). None
3. The nutritive layer is-
a). Exothecium      b). Endothecium
c). Tapetum            d).Sporogenous tissue
4. Archesporium gives rise to which structure in a flowering plant -
a). Wall and the tapetum
b). Only wall of the sporangium 
c).Only tapetum and sporogenous cells
d). Both wall and sporogenous cells
5. The function of tapetum is -
a). Support       b). Division
c). Nutrition     d). None
6. Meiotic cell division is present in-
a). Microspores  b). Megaspores
c). Tapetal cell    d). Spore mother cell
7. Which is correct for a anther wall
a). In between endothecium and middle layer tapetum is present
b). Just below the endothecium tapetum is present
c). Between endothecium and tapetum middle layer is present
d). Just below endothecium middle layer is present
8. Which layer secretes hormones and enzyes -
a). Epidermis       b). Tapetum
c). Endothecium   d). Middle layer
9. Which is not Archesporial in origin -
a). Endothecium   b). Middle layer
c).Tapetum           d). Epidermis
10. In which layer of the tapetum stomium is present -
a). Middle layer   b). Endothecium
c). Both                d). None

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