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 and water availability.
Researchers led by Prof. JIANG Yong from the Institute of Applied Ecology of the Chinese Academy of Sciences used a novel dual-labelling approach (15N and 32P) to quantify plant nitrogen and phosphorus re-allocation from roots to shoots during plant regrowth in a perennial grassland.
The researchers found that lower water availability decreased both nitrogen and phosphorus 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 nitrogen and phosphorus. This might be due to unchanged soil nitrogen availability and a greater diffusion barrier of soil available phosphorus. During the first two weeks of regrowth, nutrient re-allocation accounted for 48-97% of nitrogen and 58-79% of phosphorus acquired by shoots.
The study highlights the importance of root nutrient re-allocation to support shoot regrowth.
The study has been published online in Journal of Ecology and it was financially supported by the National Natural Science Foundation of China and the Youth Innovation Promotion Association of CAS.
Effects of nitrogen addition and high-frequency deficit irrigation on re-allocation of N and P from plant roots. (Image by WANG Ruzhen)
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