L’adaptation au milieu chez les plantes vasculaires


P Collin

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L'Année Biologique


In response to extreme conditions, plants exhibit a variety of adaptations that are important in the maintenance of plant community. Adaptation may be defined as heritable modifications in physiological or developmental attributes that improve the fitness of an organism under conditions of its environment. Adaptations are selected by three types of constraint: climatic, edaphic and biotic. Water act as a key element in the plant distribution and many morphophysiological traits are conditioned by water, directly or indirectly. Plant have developed a wide variety of mechanisms for surviving in habitats exposed to episodic or prolonged periods of frost. The extreme altitude and latitude reached by plants are revealing of the capacity of some plants to resist to cold. The photosynthetic apparatus of plants is capable of optimally efficient absorption and utilization of visible radiation because light availability vary considerably in intensity, duration, and space. Nutrient-poor environments or toxic soils have a well adapted plant community like carnivorous plants in peat swamp land and halophytes in salted soils. In habitats exposed to stress, the interplay of numerous stressors restricts the area on which a particular plant species can survive. Morphological and biochemical traits as been selected to withstand constraints under given conditions and thus plants possess various adaptations. Global changes in the atmospheric composition and climate are able to affect vegetation dynamics and could induce changes in plant distribution. Adaptation will therefore be a key element in the survival of the plant community.