Answer: A defined nutrient solution containing all essential minerals in known concentrations, used to study mineral requirements and grow plants without soil.
- A A naturally occurring soil extract that researchers collect, filter, and dilute before applying it to hydroponic growing systems
- B A defined nutrient solution containing all essential minerals in known concentrations, used to study mineral requirements and grow plants without soil
- C A pesticide and fungicide blend regularly applied to hydroponically grown plants to protect their developing root systems from insect pests and fungal infection
- D A hormone-supplemented growth medium developed mainly for propagating plant tissue cultures under sterile laboratory conditions
Correct answer: B. A defined nutrient solution containing all essential minerals in known concentrations, used to study mineral requirements and grow plants without soil
Explanation: Hoagland solution (developed by D.R. Hoagland) is a precisely defined aqueous solution containing all essential mineral nutrients. It is the standard medium for hydroponic experiments studying mineral nutrition, deficiency symptoms, and uptake mechanisms in plant physiology research.
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.