Examkin

Soru

Zorluk: ZorGrowth, Development, and Metamorphosis

A biological study recorded the growth parameters of germinating bean seeds (*Phaseolus vulgaris*) kept in total darkness over a ten-day period. Which statement correctly describes the trajectory of the seedling's dry mass and the underlying physiological process responsible for this outcome?

  1. Dry mass decreases because stored organic reserves in the cotyledons are catabolized during cellular respiration to supply metabolic energy.Cevap
  2. B
    Dry mass increases because water absorbed during imbibition directly synthesizes structural biomass within embryonic tissues.
  3. C
    Dry mass remains constant because dark reactions of photosynthesis utilize atmospheric carbon dioxide without requiring light energy.
  4. D
    Dry mass increases because inorganic mineral salts are continuously translocated upward through xylem vessels from the substrate.

Cevap

Dry mass decreases because stored organic reserves in the cotyledons are catabolized during cellular respiration to supply metabolic energy.
The correct answer highlights that dry mass measures organic content exclusive of water. When a germinating seedling is kept in total darkness, photosynthesis cannot take place to fix carbon. The embryo relies on stored nutrient reserves within the cotyledons, breaking them down via cellular respiration into carbon dioxide gas and water. The escape of carbon dioxide leads to a measurable net decrease in total dry mass.

Adım Adım Çözüm

1
Define dry mass versus wet (fresh) mass in biological growth measurement.
Dry mass represents the mass of organic matter remaining after all water is removed by drying at low heat.
Water content fluctuates with environmental hydration, making dry mass the standard for measuring true metabolic growth.
2
Analyze environmental constraints during germination in complete darkness.
In total darkness, the light-dependent reactions of photosynthesis cannot take place, preventing carbon fixation.
Without photosynthetic carbon fixation, no new organic molecules can be synthesized from atmospheric carbon dioxide.
3
Evaluate the metabolic source of energy for seedling development before light exposure.
The seedling oxidizes stored carbohydrates, lipids, and proteins in the cotyledons through cellular respiration to generate ATP, releasing carbon dioxide gas into the atmosphere.
The loss of carbon as released carbon dioxide causes a continuous net decline in total seedling dry mass until photosynthetic tissue becomes functional in light.

Anahtar Kavram

Dry Mass Measurement and Metabolic Cost during Seed Germination
Tahmini Süre:1m 50s
Bu soruyu puanla

Konular

Growth, Development, and Metamorphosis

Bu konudan daha fazla soru