Plant ion deficiency: causes and symptoms
Infection and response • Plant disease (biology only)
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Mineral ions and their roles
Mineral ions describe dissolved charged atoms or molecules that plants absorb from soil. Key examples include nitrate (NO3−) and magnesium (Mg2+). Nitrate supplies nitrogen for amino acids and proteins; magnesium forms the central atom in chlorophyll molecules, enabling light capture for photosynthesis . Absorption of mineral ions occurs mainly at root hair cells by active transport when soil concentrations are low. Active transport moves ions against a concentration gradient using metabolic energy, preventing loss of nutrients from the plant into the soil .
Nitrate deficiency - cause and effect
Cause: Low nitrate availability in the soil or impaired uptake by roots reduces nitrogen supply for protein and nucleic acid synthesis. Active transport cannot compensate if available nitrate is too scarce or roots are damaged . Effect: Reduced protein synthesis limits cell division and enlargement, producing stunted growth and smaller, pale plants with reduced biomass and yield. Stunted growth reflects slowed overall development rather than a single damaged organ .
Magnesium deficiency - cause and effect
Cause: Insufficient magnesium in the soil reduces the plant’s ability to synthesise chlorophyll because magnesium occupies the central position in the chlorophyll molecule. Poor magnesium uptake often follows low soil concentration or root uptake issues . Effect: Decreased chlorophyll levels cause chlorosis, a yellowing of leaves that begins in older leaves and spreads. Loss of chlorophyll reduces photosynthetic rate, lowers glucose production and weakens growth; severe chlorosis reduces plant vigour and yield .
Identification and limiting factors
Identification relies on visible symptoms and knowledge of their causes: stunted growth suggests nitrate shortage; interveinal yellowing or overall yellow leaves suggests magnesium shortage. Other signs such as spots, malformed leaves or pest presence indicate different problems and require separate diagnosis . Limiting factors include soil mineral concentration, root health, and environmental conditions (water, pH, temperature). Active transport requires energy from respiration, so low temperature or poor root condition limits ion uptake and can worsen deficiency symptoms .
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