Plant Hormones and Flowering Quiz

Study Notes

Cytokinins: Physiological Effects

Stimulate cell division and differentiation.
Promote growth of lateral buds and shoots.
Delay leaf senescence (aging).
Influence apical dominance by interacting with auxins.
Involved in chloroplast development and photosynthesis.

Red Light and Flowering in Short-Day Plants

Short-day plants flower when the night period exceeds a critical length.
Red light (R) is perceived by phytochrome, a photoreceptor.
Brief exposure to red light during the dark period converts Pr to Pfr.
Pfr inhibits flowering. A subsequent far-red (FR) pulse reverses this effect.
This interruption shifts the plant's perception of night length, preventing flowering.

Seed Germination Regulation

Light: Light signals (e.g., red light) can initiate germination in many species through phytochrome action.
ABA (Abscisic Acid): Acts as a germination inhibitor, maintaining seed dormancy. Its levels decline during germination.
Gibberellins: Stimulate germination by promoting enzyme production for breaking down stored food reserves. They counteract ABA's inhibitory effects.

Carbohydrate Classification

Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose).
Disaccharides: Two monosaccharides linked (e.g., sucrose, lactose, maltose).
Oligosaccharides: Short chains of 3-10 monosaccharides.
Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose, glycogen). Classification based on monomer type and linkage.

Amino Acid Classification (Flowchart Focus)

Flowchart would show branching based on the nature of the side chain (R group).
Branches would include categories such as: non-polar aliphatic, aromatic, polar uncharged, polar charged (acidic and basic). Specific amino acid examples should be given for each category (e.g., Glycine, Phenylalanine, Serine, Aspartic acid, Lysine).

Cyclization of Pentoses and Hexoses

In aqueous solution, pentoses (5-carbon sugars) and hexoses (6-carbon sugars) exist in equilibrium between open-chain and cyclic forms.
Cyclization involves the reaction of the carbonyl group (aldehyde or ketone) with a hydroxyl group within the same molecule, forming a hemiacetal or hemiketal ring.
Examples include the formation of the pyranose (six-membered ring) and furanose (five-membered ring) forms of glucose and fructose, respectively. The chair and boat conformations of the cyclic structures should be mentioned.

Enzyme Inhibition: Competitive vs. Non-Competitive

Competitive Inhibition: Inhibitor resembles substrate and competes for the enzyme's active site. Increased substrate concentration can overcome inhibition. Km increases, Vmax remains constant.
Non-Competitive Inhibition: Inhibitor binds to a site other than the active site, altering enzyme conformation. Substrate binding is unaffected, but enzyme activity is reduced. Km stays constant, Vmax decreases.

Vitamins as Coenzymes/CAM Pathway/Michaelis-Menten Constant (Short Notes)

Vitamins as Coenzymes: Many vitamins function as coenzymes, non-protein organic molecules that assist enzyme function. Examples: Vitamin B1 (thiamine) in pyruvate dehydrogenase, Vitamin B2 (riboflavin) in FAD, Vitamin B3 (niacin) in NAD.
CAM Pathway (Crassulacean Acid Metabolism): A photosynthetic adaptation in arid environments. CO2 uptake occurs at night, stored as malic acid. During the day, malic acid is decarboxylated to release CO2 for photosynthesis, minimizing water loss.
Michaelis-Menten Constant (Km): Represents the substrate concentration at which the reaction rate is half the maximum velocity (Vmax). It reflects the enzyme's affinity for the substrate; a lower Km indicates a higher affinity.

Description

Test your knowledge on the physiological effects of cytokinins, the role of red light in flowering for short-day plants, and the regulation of seed germination. This quiz covers key concepts and mechanisms in plant physiology, including the influence of hormones and light signals on plant growth and development.