1. Organization of Tissue Systems
Anatomical study begins with identifying how cells are grouped into systems to perform physiological roles.
Major Tissue Systems
- Epidermal Tissue System: Includes epidermis, stomata, and epidermal outgrowths (trichomes). It provides protection and regulates gas exchange.
- Ground Tissue System: The "filler" tissue comprising parenchyma, collenchyma, and sclerenchyma. Includes the cortex, endodermis, pericycle, and pith.
- Vascular Tissue System: Consists of Xylem (water transport) and Phloem (food transport) arranged in vascular bundles.
2. Normal and Anomalous Secondary Growth
Secondary growth increases the girth (thickness) of the plant. While most dicots follow a standard pattern, some exhibit "anomalous" patterns due to unusual cambial activity.
Normal Secondary Growth
Involves the formation of a continuous vascular cambium ring that produces secondary xylem (wood) toward the inside and secondary phloem toward the outside.
Anomalous Secondary Growth (Practical Focus)
You are required to study specific examples through permanent slides or section cutting:
- Boerhaavia Stem: Shows anomalous primary structure (medullary bundles) and anomalous secondary growth where the cambium forms accessory rings.
- Mirabilis Stem: Characterized by the formation of successive rings of vascular bundles.
- Dracaena Stem: A rare example of secondary growth in a monocot, where a special cambium in the cortex produces oval-shaped vascular bundles.
3. Embryology: Ovule and Embryo Development
This section involves the microscopic study of the reproductive development within the flower.
Types of Ovules
- Orthotropous: Micropyle, chalaza, and funicle lie in a straight vertical line.
- Anatropous: The ovule is completely inverted (180°), bringing the micropyle close to the funicle (most common).
- Campylotropous: The ovule body is curved so that the micropyle and chalaza are not in a straight line.
Embryo Development
Study of the stages of Dicot Embryo development, typically in plants like Capsella:
- Proembryo stage.
- Globular stage.
- Heart-shaped stage.
- Mature embryo (with two cotyledons and a radicle).
4. Palynology: Pollen Morphology and Germination
Palynology is the study of pollen grains and spores.
Pollen Morphology
Pollen grains vary in size, shape, and surface architecture (exine patterns). Key features include:
- Apertures: Pores (porate) or furrows (colpate) through which the pollen tube emerges.
- Exine: The tough outer wall made of sporopollenin.
Pollen Germination (In Vitro)
The rate of pollen tube growth is studied by dusting fresh pollen into a drop of 10% sucrose solution on a cavity slide. Over time, the tube emerges and elongates, which can be measured under a microscope.
5. Exam Focus: Practical Tips & Viva Prep
Practical Tip: When doing section cutting for anatomy, always use a sharp blade and cut sections in water. Only the thinnest, most transparent sections should be selected for staining with Safranin (for lignified tissues like xylem) and Fast Green (for cellulose tissues like parenchyma).
Viva Questions
- Why is secondary growth anomalous in Dracaena? Because Dracaena is a monocot, and monocots typically lack cambium. Its secondary growth arises from a special meristematic zone in the ground tissue.
- What is the function of the tapetum? It is the innermost layer of the anther wall that provides nourishment to the developing pollen grains.
- What are medullary bundles? Vascular bundles found in the pith region (characteristic of Boerhaavia).
Common Pitfalls
- Over-staining: If the section is too dark, you cannot see the cell boundaries. Always wash away excess stain with water/alcohol.
- Air Bubbles: When mounting the slide with glycerin, lower the coverslip slowly with a needle to avoid trapping air.
Is there another unit available in the syllabus that you want notes for?
(Units for BOT: DSM-351 are now complete.)