Natural priming of Wigandia urens seeds during burial:: effects on germination, growth and protein expression

To determine whether seeds of the weedy shrub Wigandia urens, from the Valley of Mexico, undergo natural priming when buried in soil, comparative experiments were performed with seeds: (1) harvested directly from the plants; (2) buried in three natural habitat conditions; and (3) laboratory primed with polyethylene glycol. Seeds were sown in a growth chamber and in a shade house. final germination percentages, emergence, germination and emergence rates, survival and initial growth were determined. Burial and priming enhanced the germination and emergence parameters evaluated in the laboratory and in the shade house. Effects of treatments on survival were not significantly different. Nevertheless, burial improved emergence and mean survival, and induced differences in specific leaf area of seedlings that could have ecological significance. Heat-stable proteins were extracted and electrophoresed. Proteins formed in W. urens seeds during burial had molecular weights (14-21 kDa) similar to those reported for late embryogenesis abundant (LEA) proteins induced by priming in other species. Nevertheless. the presence and abundance of proteins expressed (14-23, 36 and more than 45 kDa) differed among control, primed and buried seeds. During soil burial, molecular and physiological responses were induced that were similar to the effects of priming.