• Assertion (A) is True: Phloem companion cells supply ATP, chaperones, and informational macromolecules to enucleated sieve tube elements and specialize as transfer or intermediary cells for symplastic/apoplastic phloem loading.
• Reason (R) is True but Does NOT Explain (A): Sieve plates are modified end walls that connect sieve elements into continuous conduits; this structural detail does not account for the metabolic driving role of companion cells.
• Conclusion: Both (A) and (R) are true but (R) is NOT the correct explanation of (A).

Correct option: (2) Both (A) and (R) are true but (R) is NOT the correct explanation of (A).

• Statement (I) is True: According to the Münch pressure-flow hypothesis, translocation within an individual sieve tube element is strictly unidirectional, driven by hydrostatic pressure gradients that transport water and dissolved sugars at identical velocity.
• Statement (II) is True: Energy is consumed primarily during phloem loading at sources and unloading at sinks; translocation along the sieve tube pathway itself is largely a passive bulk flow process requiring minimal pathway energy in herbaceous stems.
• Conclusion: Both Statement (I) and Statement (II) are true.

Correct option: (1) Both Statement (I) and Statement (II) are true.

• Activated Diffusion Hypothesis: Proposed by T. G. Mason and E. Phillis (1936).
• Mechanism: Proposed that protoplasm within sieve tube elements accelerates solute movement through metabolic activation, increasing diffusion rates far beyond physical diffusion in water.

Correct option: (4) Mason and Phillis

• Protoplasmic Streaming Theory: Formulated by Hugo de Vries (1885).
• Concept: Hypothesized that active cyclosis (protoplasmic streaming) within the cytoplasm of sieve elements accelerates the distribution of solutes along the cell, with diffusion occurring across sieve plates.

Correct option: (1) De Vries