Angiosperms characteristics in Hindi | Angiosperms | morphology of angiosperms

Salient characteristics of Angiosperms:
1.The angiosperms,number nearly 250,000 species and comprise lhe
'main vegetation oÎ the globe.
2. The plant which is a sporophyte is very large (at least the primitive
members are trees,while shrubs and herbs are considered to be derivative).
It is autotrophic (except in a few parasitic and saprophytic species) and is
differentiated into root,stem and Íeaves which are iraversed by vascular
strands. The xylem except for a very small number of species has vessels
besides other elements, while phloem consists of sieve tubes (with sieve
p'ates on transverse walls),companion cells and phloem parenchma.
Secondary growth is common due to the presence of active cambiu
3. They produce their reproductive structures in the form of flowers
which are simpiy the aggregation of stamens,(microsporopliyils) and: carpels
(megasporophylǐs), besides some nón-essential whorls of perianth.
4. The carpel(megasporophyll) is differentiated into stigma, style and
ovary;the latter enclosing the ovules which later develóp into seeds enclos-
ed in a fruit.
5.They are hetero sporous ; the asexual spores ie. the microspores
(pollen-grains) and megaspores (embryo sac-cells), produced in microspor-
angia(pollen-sacs) and megasporangia (nucellus) respectively.
6. The microspores (pollen-grains) leave the microsporangia and are
transported to thé stigma by the process of pollination which is effected by
wind, water and insects .etc.The megaspores, are, however,permarnently
retained in the,integumented megisporangia which remain attached to the
parent plant. till late after fertilization.
7. The gametophytes are very much reduced, lack chlprophyll, and are
nutritionally dependent upon the spprophyte. They never come in contact
with the soil. The male gametophyie is completely suppressed,represented
by the germinating microspore and pollen-tube, while the female game:ophyte
formed by the persistent megaspore, is. represented by 8-nucleated embryo
sac.
8.
The gametophytes do not bear any antheridia and archegonia,
9.
The sexual reproduction is oogamous.and consists in the fusion
a stationary cag and a nonmotile malc gamele which is carried to the
former by the polien-tube:Thus the angiosperms do not require water for
fertilization.
10. The fusion of the egg and one of the two male gametes results in the
formation of the oospore,While the second male gamete fuses with the two female gametes.
polar nuclei to form the endosperm nucleus. Thus there is double fertilization resulting in the formation of an embryo from the oospore and endosperm from the endosperm nucleus. The five extra nuclei in the embryo sac are thought to be vestiges of an archegonium and prollathus
11. The embryo is suspended at the end of a suspensor which pushes the former in the food-laden tissue of the endosperm and disappears in the mature seed.

12. Mature seed is endospermic or non-endospermic and contains either

one or two cotyledons. 13. Ovules and seeds are enclosed, being covered by the carpel (megaspo- rophyll). The carpel or groups of carpels at maturity constitute the fruit.

14. Alternation of generations is not well-prononunced. The dominant stage is sporophytic, represented by the independent plant, while the gametophytic stage is inconspicuous and very much reduced, being dependent in the main on the sporophyte due to the absence of chlorophyll
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Видео Angiosperms characteristics in Hindi | Angiosperms | morphology of angiosperms канала Chaudhary Munawar