Q.1. In certain plants fertilisation is not obligatory for fruit production. Give Reasons.
A. 1.In certain plants fruits can be formed by parthenocarpy . Parthenocarpy is the natural or artificially induced production of fruit without fertilization of ovules, which makes the fruit seedless. eg. Banana. Parthenocarpy is also desirable in fruit crops that may be difficult to pollinate or fertilize, such as fig, tomato and summer squash.
Q. 2 What is apomixis?
A.2. Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development. eg. Asteraceae – asters, daisy, sunflower family and grasses.
Q.3. What is polyembryony?
A.3.. Polyembryony is a phenomenon where two or more embryos develop from a single fertilised egg.eg. Citrus- lemon, oranges
Q.4. Give some examples of plants showing Apomixis and Polyembryony.
A. 4. Apomixis – Asteraceae family – asters, daisy, sunflower family.
Polyembryony – Citrus- lemon, oranges
Q. 5 . NAME THE PARTS OF OVULE.
A.5.Ovule – The ovule is a small structure attached to the placenta by means of a stalk called funicle. The body of the ovule fuses with funicle in the region called hilum. Thus, hilum represents the junction between ovule and funicle. Each ovule has one or two protective envelopes called integuments. Integuments encircle the ovule except at the tip where a small opening called the micropyle is organised. Opposite the micropylar end, is the chalaza, representing the basal part of the ovule. Enclosed within the integuments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials. Located in the nucellus is the embryo sac or female gametophyte. An ovule generally has a single embryo sac formed from a megaspore through reduction division.
Q. 6. What is self incompatability?
A.6. Self incompatability is a genetic mechanism and prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
Q. 7. What is bagging and emasculation?
A.7.Removal of anthers from the flower bud of a bisexual flower before the anther dehisces using a pair of forceps is referred to as emasculation.
Emasculated flowers have to be covered with a bag of suitable size, generally made up of butter paper, to prevent contamination of its stigma with unwanted pollen. This process is called bagging.
Q.8. Distinguish between Syngamy and Tripple Fusion.
A.8.
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SYNGAMY |
TRIPPLE FUSION |
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Fusion of gametes in fertilisation. |
Fusion of sperm cells and two polar nuclei during double fertilisation in angiosperms. |
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Male gamete fuses with female gamete |
Male gamete fuses with central cell |
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Produces zygote and develops into embryo |
Produces endosperm cell and develops into endosperm |
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Result is diploid |
Result is triploid |
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Both male and female gametes are involved |
Only male gamete involved |
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Generative fertilisation. |
Vegetative fertilisation. |
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eg. animals and plants |
Only angiosperms |