XVI International Botanical Congess

Mangroves in many disparate families share traits enabling them to persist in coastal wetland habitats, and thus constitute an excellent model system in which to study physiology in an evolutionary context. Recent comparative studies reveal that consistent evolutionary shifts in hormonal physiology may underlie some of these apparent adaptations. For example, a convergent reduction in production of ABA (a versatile phytohormone controlling both seed dormancy and whole-plant responses to osmotic stress) occurs in viviparous embryos of four families of mangroves, upland relatives exhibit no such reduction. This loss" of ABA in mangroves and other tropical species is frequently associated with both evolutionary colonization of wetland habitats and loss of seed dormancy, and may result from selective trade offs between regulation of flood tolerance by the maternal plant and exposure of the embryo to environmental stress.