Priming effects of phytometabolites and hormones on rooting characteristics in tall fescue exposed to water stress

Abstract

Extensive rooting is a key factor regulating plant growth. The objectives of this study were (a) to determine how priming of plants with phytometabolites and hormones, including trehalose (Tre), glycine betaine (GB), spermidine (Spd), brassinolide (BR), and strigolactone (SL), affect rooting characteristics in tall fescue (Festuca arundinacea Schreb.) exposed to water stress, and (b) to identify the effective concentration for each compound affecting root elongation and lateral root proliferation. Roots of seedlings were incubated for 12 h in solutions containing four concentrations of each compound (Tre, GB, Spd, BR, or GR24 [a synthetic analog of SL]) and grown in nutrient solution containing polyethylene glycol 8000 (PEG) solution to induce water stress (−0.5 MPa osmotic potential). Priming of plants with all compounds stimulated root growth under PEG‐induced water stress, and the effects were dose dependent. Glycine betaine at 10 mM and GR24 at 1 μM mainly enhanced main root elongation. Spermidine at 0.1 mM was promotive to main root formation and elongation. Trehalose at 0.3 mM increased main root length, lateral root length and number. Brassinolide at 0.1 nM was effective in stimulating elongation and formation of both main roots and lateral roots. Trehalose, GB, Spd, BR, and SL promoted root growth, but differentially regulated lateral root proliferation or main root elongation in tall fescue exposed to water stress. Future research may investigate whether these compounds may synergistically or coordinately regulate root growth and underlying mechanisms for the differential regulation of main roots and lateral branching by each compound individually or interactively.