Hormone and phenol levels during germination and osmopriming of tomato seeds, and associated variations in protein patterns and anatomical seed features

Abstract

Seeds of tomato (Lycopersicon esculentum Mill., variety Castle rock) were osmoprimed in polyethylene glycol 6000 (PEG; 20%) or K2HPO4 (200 mM) solution for 8 hours, 3 days or 7 days, while another group of seeds were left in water for the same periods. The GA3/ABA ratio was the most important hormone factor, which promoted germination in seeds soaked in H2O and led to improved germination performance. This ratio showed slight variations between hydroprimed and osmoprimed seeds after 8 hours, but afterwards, from 3 to 7 days, it was gradually increased in the osmoprimed seeds and was substantially elevated in seeds germinating in H2O. Changes in the concentrations of phenolic compounds suggested their possible role in germination silencing in the osmoprimed seeds, but at relatively low concentrations. Protein patterns showed no marked variations in hydroprimed and osmoprimed seeds after 8 hours, but different types were observed, particularly after 7 days. A comparison of the protein banding patterns of seeds after 1 day and 7 days in the osmoconditioning solutions (PEG or K2HPO4), H2O, GA3 or ABA showed certain treatment-specific protein bands, particularly in PEG and ABA solutions. Longitudinal sections of seeds (after 3 days) showed lysis of the micropylar endosperm and radicle protrusion in H2O or GA3, whereas in PEG or K2HPO4 solution the radicle expanded inside the seed and the micropylar endosperm was completely intact. In ABA solution, the whole endosperm was compact and the seed became extensively desiccated.