Phosphorus reserves increase grass regrowth after defoliation.

Area of Science:

• Plant Physiology
• Nutrient Cycling
• Ecology

Background:

• Plants accumulate nutrients beyond growth requirements, termed luxury consumption, creating internal reserves.
• The role of these phosphorus (P) reserves in plant recovery after defoliation remains largely unexplored.
• Understanding P reserve dynamics is crucial for plant resilience in grazed ecosystems.

Purpose of the Study:

• To test if phosphorus (P) luxury consumption enhances plant tolerance to defoliation.
• To investigate the impact of P reserves on subsequent grass regrowth.
• To elucidate P remobilization strategies during regrowth.

Main Methods:

• Two experiments were conducted with four temperate grassland grass species.
• Experiment 1: Induced P luxury consumption through fertilization in *Sporobolus indicus*.
• Experiment 2: Assessed regrowth of *S. indicus* with contrasting P reserves on a P-deficient medium post-defoliation.

Main Results:

• *Sporobolus indicus* exhibited P luxury consumption under fertilization.
• Plants with higher P reserves showed significantly greater regrowth after defoliation.
• Regrowing tissues mobilized P from stubble, crown, and roots, indicating efficient P remobilization.

Conclusions:

• High phosphorus (P) reserves confer tolerance to defoliation in grasses.
• P luxury consumption supports compensatory growth under subsequent P deficiency.
• This study provides the first evidence linking P reserves to defoliation tolerance and improved regrowth.