Phenotypic plasticity

Iris Sammarco

Summary

Plants are continuously exposed to fluctuating environmental conditions. As sessile organisms, they have a restricted capacity to select the features of their environment; hence, it is crucial for them to respond to environmental changes successfully. A way how plants can cope with environmental changes is phenotypic plasticity (i.e. the ability of one genotype to produce more phenotypes when exposed to different environments). Despite the importance of phenotypic plasticity in plant adaptation to environmental changes, the molecular mechanisms underlying phenotypic variation remain still largely obscure.

Phenotypic plasticity seems to be regulated by epigenetic modifications (i.e. histone modifications, DNA methylation and RNA molecules), which affect phenotypes by regulating gene activity. Interestingly, epigenetic modifications are partly heritable across mitotic and (to some extent) meiotic cell divisions, suggesting that they may mediate phenotypic responses even across clonal or sexual generations (i.e. transgenerational plasticity). In particular, epigenetic modifications seem to be better maintained across clonal than sexual generations. Thus, transgenerational plasticity may be more relevant for clonal species, as it may allow them to bypass their potentially low-standing genetic diversity. However, if and when plastic responses are inherited across generations is further complicated by several factors, such as the predictability of the offspring environment and specific plant characteristics (e.g. sex, genotype and species). Furthermore, plastic responses can also occur independently of epigenetic modifications when they are mediated, for example, by physiological and developmental events or maternal seed provisioning. Thus, the combined effects of all these variables make the study and understanding of phenotypic plasticity difficult.

This chapter aims to overview the variables affecting phenotypic plasticity and the potential role of phenotypic plasticity in rapid plant adaptation to environmental changes.