Fact sheet 7: Plasticity and adaptation

Iris Sammarco

Plants are continuously exposed to fluctuating environmental conditions. Since they are sessile organisms, they have a restricted capacity to select the features of their environment; hence, it is crucial for them to successfully respond to environmental changes. Phenotypic plasticity is considered one of the major means by which plants can cope with environmental factor variability. Phenotypic plasticity is the ability of one genotype to produce more than one phenotype when exposed to different environments [1]. It includes all types of environmentally induced changes, such as behavioral, physiological, morphological and life-historical traits, and can be expressed either within the lifespan of a single individual, i.e. intragenerational plasticity [2] or across generations, i.e. intergenerational plasticity [3].

Different types of plasticity can be found in nature, such as continuous or discrete, reversible or irreversible, and adaptive or non-adaptive. Plasticity is discrete if it results in alternative phenotypes referred to as polyphenisms, whereas it is continuous when it is genetically controlled, known as genetic polymorphism. It is reversible if it occurs within a single generation, whereas it is transgenerational when the conditions experienced in one generation interact with conditions experienced by subsequent generations [4]. Plasticity can be adaptive when it provides a fitness benefit, non-adaptive if it is an inevitable response to a physical process or resource limitations [5, 6].

The mechanisms underlying phenotypic plasticity are still poorly understood. At the most fundamental level, all plastic responses originate at the level of individual cells, which receive and process signals from their environment. Alterations in gene expression in response to environmental changes produce the broad variations in physiology, morphology, behavior, etc., thus regulating phenotypic plasticity. Recent studies suggest that phenotypic plasticity can be mediated through epigenetic mechanisms [7, 8, 9, 10, 11, 12], which can be also involved in transgenerational inheritance [13, 14, 15, 16, 17, 18, 19]. The most studied epigenetic mechanism is DNA methylation which has been shown to alternatively increase variation in response to stressful conditions [13, 20] and has known effects on ecologically important phenotypes [21, 8, 11, 22]. Epigenetic effects could provide a rapid source of phenotypic variation without any change in genetic variation [23, 24], thus representing a potential mechanism for rapid adaptive responses to heterogeneous conditions.

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