Mycology

• Ultracentrifugation in Plant Virus Purification:
• Statement (I) is true: Differential high-speed sedimentation (typically $80,000-120,000\times g$ in a preparative ultracentrifuge) pellets dense virions, significantly improving virus recovery and yield from crude clarification extracts.
• Statement (II) is true: High-speed pelleting allows viral nucleocapsids to sediment to the tube bottom while low-molecular-weight host contaminants, soluble proteins, ribulose bisphosphate carboxylase (RuBisCO), and polyphenols remain in the supernatant, achieving simultaneous purification and concentrated pellet recovery.
• Conclusion: Both Statement (I) and Statement (II) are true (Option 1).

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

• Cephalic Setae in Tylenchida:
• Sensory Setae: Cephalic setae are elongated, hair-like sensory projections on the head (cephalic region). While common in marine and free-living aquatic nematodes (Enoplida), they are extremely rare among the plant-parasitic order Tylenchida.
• Subfamily Atylenchinae: The unique tylenchid genera Atylenchus and Eutylenchus (subfamily Atylenchinae / family Tylenchidae) possess distinct cephalic setae on their lip region.
• Other Genera: Typical tylenchids like Tylenchus and Malenchus lack cephalic setae.
• Conclusion: Genera (A) and (C) only possess cephalic setae (Option 1).

Correct option: (1) (A), and (C) only,

• Hydrostatic Skeleton and Turgor in Nematodes:
• Body Turgor Mechanics: Nematodes maintain a high internal hydrostatic pressure ($7.5-15\text{ kPa}$, up to $45\text{ kPa}$) in the pseudocoelomic fluid, which acts against the rigid, non-elastic multi-layered collagenous cuticle to maintain cylindrical body shape and power sinusoidal locomotion.
• Evaluation of Statements:
• Statement (I) is incorrect because hypodermal cells secrete cuticle and store glycogen/lipids, but do not directly generate internal body turgescence.
• Statement (II) is evaluated: while pseudocoelomic hydrostatic pressure provides the physical turgor, in examination keys both statements were judged incorrect regarding the cellular origin of turgor (Option 2).

Correct option: (2) Both Statement (I) and Statement (Il) are incorrect