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Sexual Reproduction In Flowering Plants — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYSexual Reproduction In Flowering Plants4 Marks
Question
Write a short note on embryo development.###With a labeled diagram discuss stages in embryo development in a dicot.
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Answer

Embryo develops at the micropylar end of the embryo sac where the zygote is situated. Image
→ Most zygotes divide only after certain amount of endosperm is formed. This is an adaptation to provide assured nutrition to the developing embryo.
→ Though the seeds differ greatly, the early stages of embryo development (embryogeny) are similar in both monocotyledons and dicotyledons.
→ Figure depicts the stages of embryogeny in a dicotyledonous embryo. The zygote gives rise to the proembryo and subsequently to the globular, heart-shaped and mature embryo.
Dicotyledonous embryo:
→ A typical dicotyledonous embryo, consists of an embryonal axis and two cotyledons.
Image
(i) Epicotyl: The portion of embryonal axis above
the level of cotyledons is the Epicotyl, which terminates with the plumule or stem tip.
(ii) Hypocotyl: The cylindrical portion below the level of cotyledons is Hypocotyl that terminates at its lower end in the radicle or root tip. The root tip is covered with a root cap.
Monocotyledonous embryo :
→ Embryos of monocotyledons possess only one cotyledon.
Image
(i) Scutellum: In the grass family the cotyledon is called scutellum that is situated towards one side (lateral) of the embryonal axis.
(ii) Coleorrhiza: At its lower end, the embryonal axis has the radical and root cap enclosed in an undifferentiated sheath called Coleorrhiza.
(iii) Coleoptile: The portion of the embryonal axis above the level of attachment of scutellum is the epicotyl. Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure, the Coleoptile.

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A young couple married for 5 years is unable to bear a child in spite of not practicing any birth control method. Upon consultation, doctor advised them an assisted reproductive technology involving transfer of gametes into oviducts.
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  1. ZIFT
  2. JUI
  3. GIFT
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  1. What is the pre-requisite of this technique?
  1. Gamete formation should be normal.
  2. Fallopian tubes should be normal.
  3. Female should have thick endometrial lining.
  4. Male should be able to copulate the female.
  1. Assertion: GIFT is an in-vitro fertilisation technique.
Reason: In GIFT, gametes are fertilised outside the female body.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
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S. No
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A-Tapetum
B-Middle layer
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  3. 7
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