Re-allocation of nitrogen (N) and phosphorus (P) from roots is an important nutrient-use strategy for plant growth when nutrient availability to plants is low or when aboveground parts are removed or damaged (e.g., by grazing and fire). However, quantifying root nutrient re-allocation is quite challenging, and it remained elusive for how root nutrient re-allocation responding to changes in nitrogen (N) and water availability. 

Recently, Prof. JIANG Yong’s Lab from the Institute of Applied Ecology of Chinese Academy of Sciences, used a novel dual-labelling approach (¹⁵N and ³²P) to quantify plant N and P re-allocation from roots to shoots during plant regrowth in a perennial grassland.  

They found that lower water availability decreased both N and P re-allocation in N-rich conditions. This might be derived from the exhaustion of nutrient reserves in roots.  

In N-poor conditions, however, lower water availability showed no impact on both uptake and re-allocation of N and P. This might be due to unchanged soil N availability and a greater diffusion barrier of soil available P. During the first two weeks of regrowth, nutrient re-allocation accounted for 48-97% of N and 58-79% of P acquired by shoots.  

The study highlights the importance of root nutrient re-allocation to support shoot regrowth. 

The study entitled “Re-allocation of nitrogen and phosphorus from roots drives regrowth of grasses and sedges after defoliation under deficit irrigation and nitrogen enrichment” has been published online in Journal of Ecology. 

This study was financially supported by National Natural Science Foundation of China and Youth Innovation Promotion Association CAS. 

 

Fig 1. A diagram showing the effects of nitrogen addition and high-frequency deficit irrigation (HFDI) on re-allocation of N and P from plant roots (Image by WANG Ruzhen)