Ls 1 - Sexual Reproduction in Flowering Plants

🌀 Before we deep dive, try revising these topics:-

  • Anatomy of a Flower

  • Morphology of a Flower

Reference Material

Revision Mindmap - Image.jpg

Sexual Reproduction in Flowering Plants - PPT

Sexual Reproduction in Flowering Plants - Yasmine Mam - PDF.pdf

BIOLOGY WORKSHEET 2 QP - Class 12 - Ls 1 - Yasmine mam.pdf

Class Test 1 - QP - Biology - Sugeeth Notes - 12 A - 29-03-2024.pdf

Hand-written

Ls 1 - Biology - Sugeeth Notes - 12 A - 27-03-2024.pdf

Biology - DBX Worksheet 1 - Sugeeth - 21-03-2024 - 12 A.pdf

What is a flower, anyway?

  • To the average person, flowers are of aesthetic, ornamental, social, religious and cultural value. They convey human emotions.

  • To a biologist, however, flowers are ::morphological and embryological marvels:: and the sites of sexual reproduction. ::📝 Frequently Asked Questions::

Pre-fertilisation: Structures and events

Before the actual flower is formed…

Hormonal and structural changes → Differentiation and further development of the floral primordium → Inflorescences (bear the floral buds and then the flowers) → The androecium and the gynoecium differentiate and develop.

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AI-generated imagery. Not accurate. Prompt: (Refer to the block in focus)

The Androecium

The androecium is a whorl of the flower, which is made up of Stamens. Now, stamens are the male reproductive units of the flowers. Each stamen is made up of two parts - the anther and the filament. The number and length of the stamens vary with each flower species.

📸 Perspective Corner

What does proximal refer to?

Proximal refers to the closer end of something. In this reference; we call the point where the filament attaches to the thalamus, 'proximal' because it is the part that is closer to the main parts of the plant, like the stem, etc.

Now, if something is called terminal, then it would refer to an "end" of the filament. The word "terminal" can differ with place of usage. Here, we will use the word "terminal" to refer to the further end of the filament.

  1. Filament

    The filament is a long and slender stalk that has a terminal structure called Anther attached to it. The proximal end of the filament is attached to the thalamus or the petal of the flower.

  2. Anther

    An anther is a bilobed structure (usually) that is terminally attached to the filament. This "bilobed" nature of the anther is usually visible in the transverse section of the anther. Each lobe had two theca, thus they are referred to as dithecous. A longitudinal groove runs lengthwise separating the theca.

Microsporangia

The structure of the anther, that we saw before, in effect, makes it a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe.

The microsporangia develop further and become pollen sacs. The pollen sacs run the entire length of the anther and are packed with pollen grains.

Questions for Practice

Define the following.

  1. Flower

  2. Sporogenous tissue

  3. Germ pore

  4. Autogamy

  5. Egg apparatus

  6. Synergid

  7. Filiform apparatus

  8. Geitonogamy

  9. Xenogamy

  10. Triple fusion

  11. Embryogeny

  12. Cotyledons

  13. Scutellum

  14. Dormancy

  15. Parthenocarpy

  16. Polyembryony

  17. Pre-fertilization events

  18. DOUBLE FERTILIZATION

  19. 7-celled and 8-nucleate structure

  20. WIND POLLINATION -

  21. INSECT POLLINATION -

  22. WATER POLLINATION

  23. Pre-fertilization events

  24. Coleorrhiza

  25. Coleoptile

  26. OUT-BREEDING DEVICES

  27. ARTIFICIAL HYBRIDIZATION

  28. AMPHIMIXIS

  29. APOMIXIS

  30. POLYEMBRYO

  31. ARRANGEMENT OF STEPS OF DEVELOPMENT OF EMBRYO

  32. HOMOLOGOUS STRUCTURE OF MONOCOT AND DICOT

Answer the following

  1. Mention one method by which pollen grains can be preserved.

  2. What is the Monosporic development of the embryo sac?

  3. Write the pollination pattern in the - Vallisnaria, Hydrilla, Zostera, and water lily.

  4. Why geitonogamy do is considered genetically autogamy?

  5. Explain the floral reward provided by the yucca plant. 38. How does self-incompatibility restrict autogamy?

  6. Give an account of the significance of double fertilization.

  7. Write the names of different layers of the anther. Mention the role of any one of these.

  8. If the ploidy on the egg is "n, what will be the ploidy of the endosperm of the same plant? Why endosperm is supposed to have nutritive tissue?

  9. What is the fate of floral parts after fertilisation?

  10. Differentiate between parthenocarpy and parthenogenesis. Give one example of each.

  11. Does apomixis require fertilization and pollination? Write any two ways by which apomictic seeds may be developed in angiosperms.

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