TN Board Biology: Angiospermic Ovule & Pollen Grain Structure (Notes & Diagrams)
Welcome to our comprehensive Concept Guide and Chapter Notes for TN Board Biology. In this post, we cover crucial exam topics from Plant and Animal Reproduction, including the detailed structure of a pollen grain (மகரந்தத்தூள்) and a step-by-step breakdown of a typical angiospermic ovule. Whether you are preparing for your Class 10 or Class 12 board exams, mastering these diagrams and key botanical terms is essential for maximizing your scores.
Important Biological Diagrams & Study Resources
படம் 17.8 மகரந்தத்தாள் மற்றும் மகரந்தத்தூளின் அமைப்பு (Structure of Stamen and Pollen Grain)
Below are the key Tamil terms and their corresponding biological parts for the structure of a stamen and pollen grain. Ensure you memorize these labels for your diagram questions:
- மகரந்தத்தாள் (Stamen - Male reproductive part)
- மகரந்தப்பை (Anther - Pollen-bearing part)
- மகரந்தக் கம்பி (Filament - Stalk of the stamen)
- உடல் உட்கரு (Vegetative nucleus / Tube nucleus)
- உற்பத்தி உட்கரு (Generative nucleus)
- எக்ஸைன் (Exine - Thick, protective outer layer of pollen)
- இன்டைன் (Intine - Thin inner layer of pollen)
- வளர்துளை (Germ pore - Opening in the exine)
- உற்பத்தி செல் (Generative cell)
Board Exam Important Question: Angiospermic Ovule
Question: With a neat labelled diagram, describe the parts of a typical angiospermic ovule.
Exam Tip: For 5-mark questions, always draw a neat, proportional diagram. Place all your labels neatly on the right side of the drawing using straight lines. Accompany the drawing with point-wise explanations of each part.
Structure of a Typical Angiospermic Ovule
An angiospermic ovule (also known as a megasporangium) contains the female reproductive cells. The main parts are:
- Funiculus: The basal stalk that attaches the ovule to the placenta of the ovary.
- Hilum: The junction point where the body of the ovule attaches to the funiculus.
- Integuments: The protective outer cell layers surrounding the ovule. Most angiosperms have two layers (outer and inner integuments).
- Micropyle: A narrow pore or opening at the tip of the ovule where the integuments are absent. It allows the pollen tube to enter during fertilization.
- Chalaza: The basal expanded portion of the ovule situated exactly opposite to the micropylar end.
- Nucellus: The central mass of parenchymatous tissue enclosed by the integuments. It provides vital nourishment to the developing embryo sac.
- Embryo Sac (Female Gametophyte): Located deep within the nucellus, this sac contains the crucial cells for reproduction: the egg apparatus (one egg cell and two synergids) near the micropyle, the central cell with secondary nuclei, and three antipodal cells near the chalaza.
Additional Reference Diagrams for Revision
Below is a collection of essential slides and diagrams covering chapters in your syllabus. Make sure you practice these routinely before the board exams.
