Anaerobic respiration / alcoholic fermentation in higher plant tissues (e.g., flooded roots):

• Under anoxic conditions, glycolysis generates pyruvate and NADH.
• Pyruvate is decarboxylated by pyruvate decarboxylase to acetaldehyde, releasing $\text{CO}_2$.
• Acetaldehyde is then reduced by alcohol dehydrogenase (ADH) into Ethanol, regenerating $\text{NAD}^+$ to sustain glycolytic ATP generation.

Physiological functions of phytohormones:

• Gibberellins break seed dormancy and induce hydrolytic enzymes (alpha-amylase) to trigger Seed Germination -> (IV).
• Indole-3-acetic acid (Auxin) stimulates Cell Elongation via the acid growth mechanism -> (III).
• 6-Benzylaminopurine (synthetic Cytokinin) functions as a Cell Division factor -> (II).
• Abscisic Acid maintains seed dormancy and prevents precocious germination, thereby mediating Inhibition of Vivipary -> (I).

Role of Plastocyanin in thylakoid electron transport:

• Plastocyanin is a water-soluble, peripheral copper-binding metalloprotein located in the thylakoid lumen.
• Its single catalytic copper ion alternates between $\text{Cu}^{2+}$ (oxidized, blue) and $\text{Cu}^+$ (reduced, colorless) as it shuttles electrons from the Cytochrome $b_6f$ complex to the reaction center of Photosystem I (P700).
• Cytochrome c oxidase is a mitochondrial enzyme, plastoquinone is a lipophilic quinone, and riboflavin is a vitamin cofactor.