Source-sink metabolic relationships shape ß-aminobutyric acid-induced response on flax growth (Linum usitatissimum)

Pontarin N1,2, Tchoumtchoua J1, Gredelj M1, Quero A1, Molinie R1, Mathiron D3, Van Bohemen AI1, Fontaine JX1, Sarazin V2 and Mesnard F1

  1. Biologie des Plantes & Innovation (BIOPI), UPJV, Amiens, France.
  2. Laboulet Semences, Airaines, France.
  3. PFA, Amiens, France.

At every moment of their lives, plants are constituted of organs at different stages of development. Therefore, plant response to any environmental stimuli could be considered the sum of different interrelated responses, each typical to the various physiological stages coexisting in the same plant. For leaves, the stage of development is generally assigned on the basis of their photosynthetic and metabolic independence, so we can distinguish three populations of leaves: source, transition and sink leaves. β-aminobutyric acid (BABA) is a non-protein amino acid synthesised by plants in a hormone-like response to stress. When exogenously applied, BABA is a powerful priming agent of plant natural defences, active against 80 different pathogens and pests, and a variety of abiotic stresses. Though, at the treatment doses, BABA engenders a growth delay. Within this context, this study aims to characterise BABA-induced response on flax growth in a spatio-temporal fashion. Firstly, flax source, transition and sink leaves were differentiated based on their relative growth rate and their metabolic composition via multivariate analysis. Secondarily, BABA-induced response on the growth of those leaf populations was evaluated during a time frame of ten days. The contribution of expansive and structural growth to the overall leaf growth was assessed by measuring fresh mass, dry mass, leaf surface, water content and transpiration. For further understanding, metabolic changes were investigated by metabolic profiling through GC-MS and LC-MS, and osmotic potential was measured. We observed that BABA-induced response was characterised by an early expansive growth retardation, followed by the recovery of a new homeostatic state, characterised by a lower deposition of biomass. The metabolic reorganisation played a central role in growth regulation, revealing how the various phases of the response were driven by the leaf populations, in different but coordinated fashions.