(a) Give four differences between root apex and shoot apex.
(b) Explain the development of the different types of endosperms in angiosperms.
a.
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Root apex
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Shoot apex
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1. Is sub -terminal in positions
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1. Occupies terminal position
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2. Is protected by a root cap
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2. Is protected by apical bud, young
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leaves & leaf primosdia
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3. It has no nodes and internodes
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3. It has nodes and internodes
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4. It does not bear any appendages.
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4. It bears lateral appendages
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b.
(b) There are three types of endosperms in angiosperms :
1. Nuclear endosperm:- It occurs in polypetalous dicotyledons. First few divisions of primary endosperm nucleus are not followed by cell wall formation, the nuclei thus produced remain free in cytoplasm of embryo sac.
2. Cellular endosperm - It occurs in gamopetalous dicotyledons. Wall formation commences with first division of primary endosperm nucleus. First wall is usually laid down transversely, but subsequent divisions are irregular.
3. Helobial endosperm - It occurs in members of order Helobiae. First division of nucleus is followed by formation of transverse wall which divides embryo sac into small chalazal and large micropylar chamber. Few divisions in chalazal chamber & it degenerates. Free nuclear division in micropylar chamber are followed by wall formation.
(c) (i) Capillary water is the large amount of water that is retained in the minute interstitial spaces in forms of thin films surrounding soil particles. It is the source of almost all the water that plant absorbs from soil.
(ii) Osmosis is the movement of water molecules from the region of low concentration to the region of high concentration through semi permeable membrane.
(iii) Aeroponics : A system where roots of plant are suspended into air and sprayed with oxygenated nutrient enriched water.
