Metabolic acclimation of source and sink tissues to salinity stress in bermudagrass (Cynodon dactylon).

Salinity is one of the major environmental factors affecting plant growth and survival by modifying source and sink relationships at physiological and metabolic levels. Individual metabolite levels and/or ratios in sink and source tissues may reflect the complex interplay of metabolic activities in sink and source tissues at the whole-plant level. We used a non-targeted gas chromatography-mass spectrometry (GC-MS) approach to study sink and source tissue-specific metabolite levels and ratios from bermudagrass under salinity stress. Shoot growth rate decreased while root growth rate increased which lead to an increased root/shoot growth rate ratio under salt stress. A clear shift in soluble sugars (sucrose, glucose and fructose) and metabolites linked to nitrogen metabolism (glutamate, aspartate and asparagine) in favor of sink roots was observed, when compared with sink and source leaves. The higher shifts in soluble sugars and metabolites linked to nitrogen metabolism in favor of sink roots may contribute to the root sink strength maintenance that facilitated the recovery of the functional equilibrium between shoot and root, allowing the roots to increase competitive ability for below-ground resource capture. This trait could be considered in breeding programs for increasing salt tolerance, which would help maintain root functioning (i.e. water and nutrient absorption, Na+ exclusion) and adaptation to stress.