Analysis of processes associated with sugars loading in the phloem and participating in the acclimation to salt stress in Arabidopsis thaliana
Résumé
Salt stress can disrupt plant growth and productivity. Glycophyte plants can set up a tolerance to salt stress by adjusting their metabolism and the activity of their vascular tissues, processes that can usually benefit from a progressive acclimation. The aim of this work is to study in Arabidopsis thaliana the adaptive processes associated to the carbohydrate metabolism and allocation between source and sink organs in plants submitted to salt stress with or without acclimation. Physiological and metabolic modifications under acclimation were investigated through the analysis of plant growth, and of accumulation of sugars and proline in the leaves and floral stem. The anatomical modifications taking place in the stem and in the vascular tissues were studied through measuring the diameter of the stem, the area of the vascular tissues in the transverse sections and the number of irregular vessels in the xylem poles. Fourier Transform Infrared Spectroscopy (FTIR) was used for analysing the composition of the secondary cell walls of the xylem in flower stem sections. The results indicated that an acclimation to salt stress had no beneficial effects on the tolerance to high NaCl concentrations, similar plant growth reductions occuring with or without acclimation. Nevertheless, in the floral stem of plants submitted to salt stress, fewer collapsed vessels were observed in the xylem after acclimation. No significant effect was observed on the area of vascular tissues in contrast to plants without acclimation. The analysis of FTIR’s spectra showed for stressed plants a significant modification in the content of lignin. Significant variations in polysaccharides and pectins were also observed. In the leaves and in the floral stem plants submitted to salt stress with or without acclimation, we also observed differences in the accumulation of sugars and proline. These results will be discussed regarding the effects of salt stress of carbon allocation.