Directions: Study the following information carefully and answer the question given below.
Read the following passage carefully and answer the questions that follow:
Beneath the tranquil canopy of old-growth temperate and boreal forests lies a vast, subterranean biological network known colloquially among ecophysiologists as the "Wood Wide Web." This intricate web is formed by mycorrhizal fungal hyphaeโmicroscopic filamentous threads that establish intimate, mutually beneficial symbioses with tree root tips. Trees, utilizing their green crowns for photosynthesis, manufacture surplus energy-rich carbon compounds and transport up to thirty percent of their synthesized sugars down to the fungal mycelium. In return, the hyper-dense fungal network, possessing an absorptive surface area thousands of times greater than fine tree roots, mines the soil for otherwise inaccessible water, mineral phosphorus, and nitrogen to supply its host trees.
Beyond two-way nutritional reciprocity, breakthrough radiolabeling experiments demonstrate that mycorrhizal mycelia function as dynamic inter-tree conduits. Massive, deep-rooted "mother trees" allocate photosynthetic carbon and micronutrients to understory saplings languishing in deep shade, dramatically increasing sapling survivorship until canopy gaps open. Even more astonishingly, when a tree experiences an insect infestation or pathogen invasion, it synthesizes defensive volatile organic compounds and transmits chemical warning signals through the fungal network to neighboring conspecifics. Upon receiving these subterranean alarm pulses, adjacent trees preemptively activate defensive gene transcription, synthesizing distasteful tannins and protease inhibitors days before the actual pest arrives.
How do mature "mother trees" assist understory saplings in old-growth forests, according to experimental evidence?
๐ก Solution & Explanation:
Correct Answer: (A)
Core Concept: Reading Comprehension โ Factual Mechanism
Step-by-Step Solution:
1. Paragraph 2 explains: 'Massive, deep-rooted "mother trees" allocate photosynthetic carbon and micronutrients to understory saplings languishing in deep shade, dramatically increasing sapling survivorship until canopy gaps open.'
2. This matches Option (A) precisely.
3. Options B, C, and D are fabricated distractions unsupported by the passage.
Key Shortcut / Exam Tip: Inter-tree resource transfer occurs via the fungal network.