Dynamics of cold acclimation and complex phytohormone responses in Triticum monococcum lines G3116 and DV92 differing in vernalization and frost tolerance level

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Cold stress response was compared in the crowns, leaves, and roots of Triticum monococcum DV92 spring line and G3116 winter line. The cold exposure was associated with a rapid increase of water saturation deficit, which resulted in a strong up-regulation of abscisic acid. Simultaneously, other stress hormones: salicylic acid, aminocyclopropane carboxylic acid (precursor of ethylene), and jasmonic acid decreased. The stress application resulted in a decrease of hormones associated with stimulation of cell growth and division (gibberellins, cytokinins, and auxin). During the acclimation phase of the stress response, the plants increased their frost tolerance and started the accumulation of dehydrins. Active gibberellin, cytokinins, and auxin were elevated; more rapidly in the spring line. Abscisic acid decrease was accompanied by a gradual increase of the other stress hormones. Simultaneously, the up-regulation of phenolic acids was observed, including ferulic and sinapic acids, which may be involved in the stabilization of auxin levels as well as antioxidative functions. After 21 days, the spring line DV92 exhibited its maximum of active cytokinins, which indicates the onset of the early stage of reproductive development. The winter line fulfilled its vernalization requirement after 42 days, as indicated by a decrease of frost tolerance and dehydrin levels, accompanied by similar growth hormone changes as in DV92. The similarities and differences between einkorn and common wheat in a long-term cold response are discussed.