Effect of Senescence Phenotypes and Nitrate Availability on Wheat Leaf Metabolome during Grain Filling

Abstract

The capacity for optimising grain yield depends largely on the timing of senescence and the processes underlying efficient remobilisation and cycling of nutrients from source tissues to the developing grain. This study describes how metabolism is adjusted during senescence in response to varying nitrogen application rates after anthesis. A comprehensive metabolite analysis was performed in field-grown Avalon/Cadenza using segregating doubled haploid wheat genotypes having contrasting traits relating to timing of the onset of senescence. Correlative matrices of metabolites and yield parameters determined the metabolic networks that underlie these phenotypes, and were helpful for identifying unique metabolites that are indicative of timing of senescence. They also revealed robust correlations between steady increases in hexose levels, a late senescence phenotype and high straw yield associated with low N fertiliser levels. Tryptophan, cis-aconitate, phosphate and 1-kestose demonstrated strong perturbations in response to nitrogen availability and progression towards developmental senescence. A comprehensive metabolic map of wheat leaf primary metabolites yielded a cumulative readout of processes that occur during developmental ripening and contribute to grain filling in plants with differential senescence timing.

Metabolic Responses to Contrasting Levels of N Fertilization during Ear Leaf Transition from Assimilation to Remobilization at Grain Filling in Maize

“…Altogether, such response represents an additional common node between N-sufficient and N-deficient plants' physiology during leaf transition from assimilation to remobilization. N-deficient plants also had reduced level of leaf serine which is a marker for induced photorespiration and senescence (Tercé-Laforgue et al, 2004: Diaz et al, 2005 as has been reported in sunflower (Agüera et al, 2010) and wheat (Heyneke et al, 2019).…”

Understanding the Relationships between Free Asparagine in Grain and Other Traits to Breed Low-Asparagine Wheat

“…These varieties show delayed senescence, leading to a prolonged green phenotype, and generally have higher yields and better stress tolerance, although this leads to a trade-off with protein and micronutrient content due to the yield dilution effect [ 52 ]. Heyneke et al [ 53 ] undertook an experiment comparing the leaf metabolome of early and late senescing wheat lines and found that asparagine content in the leaf decreased as senescence progressed, but not significantly. The ratio of asparagine to aspartic acid (as well as the ratio of glutamine to glutamic acid) did increase significantly, though, in both early and late senescing lines, as senescence progressed.…”