Impact of K deficiency on leaves and siliques photosynthesis via metabolomics in Brassica napus

Abstract

Potassium (K) deficiency is known for its impact on photosynthesis via the synthetic constraints of CO2 diffusion and assimilation. However, insights in the different responses of net photosynthetic rate (A) to K depletion inside primary metabolites, produced specifically by each organ, remain to be elucidated. Leaves and siliques of Brassica napus were investigated to clarify the responses of A, the CO2 conductance and that of main metabolism pathways under K deficiency. Leaves were far more sensitive to K deficiency, displaying simultaneous decreases in A and CO2 diffusion reflected in a broader range of metabolites. To compensate the carbon starvation under K deficiency, leaf metabolic profile was adaptively regulated thorough downregulation of the carbon flux into carbohydrates and organic acids and upregulation of nitrogen-rich amino acids. Significant relationships between leaf A and sugars, organic acids and amino acids were observed. In comparison with leaves, the carbon shortage observed in siliques was negligible or even absent, with no obvious change in carbon flux through the glycolysis and tricarboxylic acid cycle pathways. Proline represented the only metabolite that correlated positively with silique A. These results provide new insights into differences in photosynthetic responses to K deficiency between leaf and non-leaf organs based on the potential metabolic processes involved.