modification of angiosperms

What are Angiosperms?

Angiosperms are seed-bearing plants where seeds are enclosed in an ovary within the fruit, and sporophylls are organized into flowers. They are classified into monocots and dicots.

Identify the primary tropisms of a plant root.

Roots are positively geotropic (grow toward gravity), positively hydrophobic (grow toward water), and negatively phototropic (grow away from light).

List the four main regions of a root.

1. Root cap: The tip of the root for protection.
2. Meristematic zone: Region of active mitosis (apical meristem).
3. Elongation zone: Where new cells enlarge.
4. Maturation zone: Where cells specialize (e.g., xylem, phloem, and root hairs for absorption).

Define Taproots versus Adventitious roots.

• Taproots: Grow vertically downward from the radicle; typical of dicots.
• Adventitious roots: Grow from any part of the plant other than the base of the stem or the radicle (e.g., banyan tree).

Describe the types of Taproot modifications for food storage.

• Conical: Wider at the top, tapering to the bottom (e.g., carrots).
• Fusiform: Tapered at both ends, wider in the middle (e.g., radishes).
• Napiform: Very large at the top, tapering sharply like a tail (e.g., turnips).
• Tuberous: Swollen and fleshy with an irregular shape.

How do roots assist in nitrogen fixation?

Legumes have nodular roots (root nodules) containing bacteria that transform atmospheric nitrogen into nitrates. They contain hemoglobin-like proteins to reduce oxygen concentration, aiding the process.

What are Pneumatophores?

Pneumatophores are respiratory roots that grow upwards in waterlogged areas. they contain lenticels on their surface to facilitate gas exchange (O{2} and CO{2}).

Differentiate between Prop roots and Stilt roots.

• Prop/Pillar roots: Grow from branches to the ground to support the main axis (e.g., banyan tree).
• Stilt/Brace roots: Grow obliquely downward from the side of the stem, common in monocots like maize (Zea mays).

Define Nodes, Internodes, and Buds.

• Nodes: Parts of the stem where leaves arise.
• Internodes: The space between two successive nodes.
• Buds: Undeveloped shoots or stems from which new leaves and flowers arise.

What are the common forms of Erect Stems?

• Clums: Solid nodes and hollow internodes (jointed appearance).
• Caudex: Unbranched stem with a crown of leaves at the top.
• Excurrent: Tapering from base to apex with acropetal branching.
• Decurrent: Main stem branches out significantly after initial growth.

Name the three categories of Stem Modifications.

1. Underground: For food storage (e.g., rhizome, tuber, bulb, corm).
2. Sub-aerial: For vegetative reproduction (e.g., runners, offsets, stolons, suckers).
3. Aerial: For various functions (e.g., tendrils, thorns, phylloclades, cladodes, bulbils).

What is the difference between Phylloclade and Cladode?

• Phylloclade: A flattened stem with many distinguishable nodes and internodes, often with spines (e.g., Opuntia).
• Cladode: A phylloclade consisting of only 1 or 2 internodes.

Differentiate between Petiolate and Apetiolate leaves.

• Petiolate: Leaves that arise from a stalk called a petiole.
• Apetiolate: Leaves that lack a petiole (also known as sessile leaves).