sexual reproduction in flowering plants Flashcards
What is flower ?
reproductive unit meant for sexual reproduction
Prefertilisation events that occur in flowering plants give what change to plant and why ?
Hormonal, structural changes occur lead to differentiation & development
of floral primordium, inflorescence are formed bearing floral buds.
What is stamen ? What are its part in a body ?
Stamen is male reproductive part in a flowering plant , and it consist of two part in its body :- 1) a long slender and stalk structure called filament . 2) the terminal generally bilobed structure called the anther .
—————– end of filament is attached to the thalamus or petal of flower .
Proximal end
( Distal end of filament is attached to the bilobed anther ) .
What can you describe about anther ?
Anther is a part of stamen , a typical angiosperm anther is bilobed , and each lobe have two theca ,so all over 1 anther is tetrathecous. ( one lobe in dithecous ). And this theca is divided by a groove which goes longitudinally to seperate them .
The bilobed nature of an anther is very distinct in ——————- section of the anther .
transverse
The anther is ——————- structure , consisting of four ——————— loacted at the corners , two in each lobe .
1) tertragonal
2) microsporangia
Pollen sacs are developed from ——————.
microspornagia
What are the name of the microsporangium walls , and how many of them are present around one microsporangium?
1) Epidermis
2) Endothecium
3) middle layer ( short lived :-ephemeral)
4) Tapetum
first 1,2,3 perform protection and help in dehiscence of anther but 4 one provide nourishment to the anther .
Why only tapetum give nourishment to pollen grains ?
Tapetum in only wall with nourishing material and it have dense cytoplasm and generally have more than one nucleus .
What are other work of tapetum beside giving nourishment to pollen grains ?
1) secrete pollen kit
2)help in entomophily
3)secrete sporopollenin :— ubisch bodies :—enter microsporangia :—- form exine .
4)tapetum :– 1) polyploidy 2)polyteny
What is epidermis thickening called ?
exothecium ( outer coat of the anther )
What is the importance of endothecium in an anther ?
Endothecium is a fibrous band / thickening made up of alpha cellulose present only on tangential wall, points where thickening is absent known as stomium { forms line of dehiscence }
What is a sporogenous tissue ?
When the anther is young , a group of compactly arranged homogenous cell called the sporogenous tissue occupies the centre of each microsporangium.
Which is innermost layer of an anther ?
tapetum
What is a Microsporogenesis ?
The process of formation of microspore from pollen mother cell through meoisis is called microsporogenesis.
How microspore tetrads are form ?
As the anther develops , the cell of sporogenous tissue undergo meiotic division to form microspore tetrads .
What is the process of making pollen grains from sporogenous tissue ?
In each microsporangia of anther there are sporogenous tissue (2n) present which turn into pollen mother cell as it gets nourished . Then this PMC (2n) perform meiotic division to make 4 microspore (n) , callase enzyme to digest callose and make 4 microspore cell free . then these microspore goes through mitotic division to develop pollen grains . A pollen grain have 1generative cell(gc) and 1 vegetative cell (vc), which is covered by exine and intine . To remember pollen grain is not a male gametophyte . Now this pollen grain will go through maturation and its generative cell will go through a mitotic division and make 2 male gametophyte .
study of pollen grains
palynology
What things are consist in angiosperm male gametophyte ?
2 male gametes and one vegetative cell
What is the structure of pollen grains ?
Pollen grains are generally spherical measuring about 25-50 micrometers in diameter. It has prominent two layered wall.
What are the two layers of pollen grains that help them to survive for a long time period ?
The hard outer layer called the Exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures
