Question

Give an account of anatropus ovule. (4 mark)

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Answer 1

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Anatropous ovule is the most common type of ovules, which occurs in more than 80% of angiospermic families. The body of ovule is rotated by 180° and micropyle comes near to the funiculus. Chalaza and micropyle lie in the straight line but hilum is at 90° to micropyle.

Answer 2

Answer:

Anatropous ovule:

• this type is also called as inverted,because the micropyle end is facing towards downside.
• this type is present in most of the angiosperms consisting 87% of families

#ovule : is known as megasporangium,as it possess the female gamete.

☆Structures consisting anatropous ovule:-

• Integuments:

1. These are the outer protective layers consisting the nucellus.
2. after fertilization or maturity integuments get converted to testa and tegmen of seeds
3. most angiosperms ovule is bitegmic,consisting two integuments.

•Nucellus:

1. it is diploid tissue form most part of body of an ovule
2. cells of nucellus store starch thus provide nourishment to developing embryo.
3. Nucellus is completely consumed by some embryo or it persists. Those which have persistent nucellus are called perispermic seeds.,eg castor,coffee,black pepper etc

•Challaza:

1. it is also diploid tissue ,provide nourishment to developing embryo.
2. in some plants (oenothera,lilium) lignified cells are also present in chalaza form hypostase, which involves in conduction of water and minerals.
3. persistent challaza after growth called as challazospermic seeds , some embryo consume it completely during growth

•Micropyle:

1. it permits the entry of pollen tube during fertilization (porogamy)
2. it's remain unchanged, also occurs in seeds
3. Integuments are absent in the region of micropyle
4. some filiform apparatus present involves in attracting the pollen tube towards the micropyle

•Funicle:

1. its helpful in attachment of body of an ovule with placenta of carpel
2. it also contains vascular strand

•Embryo sac:

1. typical embryo sac is polygonum type,which is 7celled-8nucleated .
2. it originated from single funtional megaspore thus monosporic
3. its micropylar end having egg apparatus made up of two synergids and an egg cell.
4. while chalazal end having 3 antipodals.
5. in centre 2 polar nuclei forms a secondary nucleus.

hope it helps!