Hormonal Transduction of Environmental Stresses

The evolutionary axiom "survival of the fittest" presumes universal stresses.Stress is the result of any constraining force or influence that limits normal growth and development.No earthly organism has ever lived its life cycle out without a stress burden.Stresses are erratic, unevenly cyclical, and ever-changing, so that avoidance of stresses for the production of today's crops may or may not be successful for the next month or the next year.Through aeons of time plants have developed under natural stress conditions.Adaptation allowed survival:Climate is the set of generalizations resulting from the assembling, analyzing, and summarizing of long-term weather records.The complex of environmental variables-temperature, radiation, precipitation, humidity, wind, and soil factors-to which a plant is exposed is the microclimate.All elements of the microclimate interact simultaneously and constantly on the plant during each stage of its growth and development and the plant environment must be described in terms of all influencing factors.While the plant reacts immediately to the current microclimatic environment, its genome is the result of adaptations to a much longer history of changing microclimates.Simple annual plants have evolved so that their growth and development coincide with a favorable microclimatic growth period that allows progression through the plant life cycle.The simplest case would be a plant in a continuously favorable microclimate for seed germination, development, growth, maturation, seed production, and seed dispersal.The cycle would continue as long as such a plant remained in the favorable microclimate.When the plant experienced less-than-optimum environmental conditions (stress) after relocation from the ideal microclimate, through seed or plantlet dispersal or through climatic changes, survival was low.After considerable time for adaptation, development of mutant plants that could survive in the less-than-optimal environment occurred.Adaptations, such as rosette formation and the requirement for a cold period between the rosette and seed formation phases enabled survival under adverse conditions.Biennials resulted.