Nitrogen (N) is an essential plant growth nutrient whose coordinated distribution from source to sink organs is crucial for seed development and overall crop yield. We compared high and low N use efficiency (NUE) Brassica napus (rapeseed) genotypes. Metabonomics and transcriptomics revealed that leaf senescence induced by N deficiency promoted amino acid allocation from older to younger leaves in the high-NUE genotype at the vegetative growth stage. Efficient source to sink remobilization of amino acids elevated the numbers of branches and pods per plant under a N-deficiency treatment during the reproductive stage. A ¹⁵N tracer experiment confirmed that more amino acids were partitioned into seeds from the silique wall during the pod stage in the high-NUE genotype, owing mainly to variation in genes involved in organic N transport and metabolism. We suggest that the greater amino acid source-to-sink allocation efficiency during various growth stages in the high-NUE genotype resulted in higher yield and NUE under N deficiency. These findings support the hypothesis that strong amino acid remobilization in rapeseed leads to high yield, NUE, and harvest index.

As a consequence of industrial development, soil Cd pollution leads to crop contamination by Cd, posing a threat to food safety and human health. Excessive accumulation of Cd in plants also inhibits their growth via oxidative stress damage to their photosynthetic systems. Through evolutionary selection, plants have developed a set of efficient strategies to respond to Cd in their environments. These include the accumulation and detoxification of heavy metals. Cd is absorbed by plant roots through the apoplastic and symplastic pathways and then translocated to plant shoots via xylem loading, long-distance transport, and phloem redistribution. Simultaneously, plants initiate a series of mechanisms to reduce Cd toxicity, including cell wall adsorption, cytoplasmic chelation, and vacuolar sequestration. This review summarizes current knowledge of Cd accumulation and detoxification in plants.