Patterns of seed dormancy and germination as related to plant phylogeny and ecological and geographical conditions of their habitats

Patterns of seed dormancy and germination were screened across over three thousand plant species as related to plant phylogenetic positions. The patterns of seed dormancy differed in large taxa (as classified by Takhtajan) and evolved in parallel in the various classes and even divisions. Thus, in more primitive taxa, e.g., dicotyledonous angiosperms (subclasses Magnoliidae and Ranunculidae), several subclasses of monocotyledonous plants, and also in the primitive gymnosperm families, under developed embryo is the most frequent cause of dormancy (morphological and morphophysiological types). In evolutionarily advanced taxa (the families in the subclass Asteridae, the family Poaceae, and such gymnosperm families as the Pinaceae, the Taxodiaceae, etc.), the embryo is usually well developed, and dormancy is of a physiological nature, usually non-deep, or totally absent. In addition, seed properties depend on the taxonomic position of the particular species within a genus. Thus, evolution molds the physiological patterns of seed dormancy, which manifest themselves in large taxa and indicate their ancient origin. Species-specific variations in the patterns of seed dormancy and germination within a genus infer that these patterns continue to evolve under the influence of the current ecological and geographical conditions of plant habitats.