Nitrogen and sulfur uptake and remobilisation in canola genotypes with varied N- and S-use efficiency differ at vegetative and maturity stages

Abstract

Eight canola genotypes chosen from a preliminary screening study with either high or low nitrogen (N) and/or sulfur (S) efficiency indices were tested for consistency in S and/or N efficiency between vegetative stage and maturity. Soil labelling was used to assess 15N/N or 34S/S uptake, and a leaf feeding–labelling technique was used to study transport and remobilisation of N and S. Plants were grown under glasshouse conditions using deficient or adequate N and/or S supply. Nitrogen and S uptake in plants was assessed using the following criteria: growth, N and/or S concentration, and 15N and/or 34S atom excess in above-ground plant parts. Transport and remobilisation of N and S were assessed via the same assessment criteria in plants at 2 days (1st harvest) and 6 days (2nd harvest) after commencement of leaf-labelling. Genotype Wesway was more efficient than Westar in taking up N during the vegetative stage as well as in remobilising N from leaves, stems, and siliques to seeds at maturity. Genotype Surpass 402 CL appeared to be more efficient than Karoo in taking up S during the vegetative stage and particularly during the maturity stage, but was less efficient than Karoo in remobilising S from leaves and stems to siliques and seeds at maturity. Soil and leaf labelling techniques using 15N and 34S appeared to be useful tools for studying uptake, transport, and remobilisation of N and S during the vegetative and maturity stages in canola genotypes differing in N- or S-use efficiency.