Roles of Arbuscular Mycorrhizas in Plant Nutrition and Growth: New Paradigms from Cellular to Ecosystem Scales

We have shown that the mycorrhizal pathway operates and arbuscular mycorrhizal -inducible P transporter genes are expressed in plants that respond positively to AM symbiosis and in those that do not

Sally E. Smith

2011

Scholarcy highlights

  • G and advanced microscopy, have provided new information that has overturned many aspects of these established models
  • Root systems of most land plants form arbuscular mycorrhizal symbioses in the field, and these contribute to nutrient uptake
  • Most early research on effects of AM colonization on plant P nutrition centered on plants grown in low-P soil with consistently large positive mycorrhizal growth response, and with higher total P than NM counterparts
  • Experiments with compartmented pots using 15NH4+ or 15NO3− supplied to extraradical mycelium consistently show higher 15N transfer to AM than to NM plants, transfer in soil from hyphal compartments to root hyphal compartment by mass flow and diffusion has never been completely eliminated
  • Plant growth responses to AM colonization are usually positive when soil phosphorus limits growth, some AM plants grow less than their nonmycorrhizal counterparts. Such growth depressions occur when colonization by AM fungi is high and when it is low and unlikely to result in high organic C use
  • This means that P delivery via direct pathway can be lower in AM than NM plants and that mycorrhizal pathway contribution cannot be determined from plant nutrient content
  • Studies of integration of plant and arbuscular mycorrhizal fungal nutrient uptake are beginning to provide alternative explanations

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