Plants' responses to novel environmental pressures

Plants have been exposed to multiple environmental stressors on long-term (seasonal) and short-term (daily) basis since their appearance on land. During the last decades, however, plants have been frequently exposed to sudden changes in their environment (imposed by global change) which indeed involves the acclimation/adaptation syndrome of living organisms. The frequency of these unpredictable \u2018stress\u2019 events is expected to increase further in the near future. Such severe, even transient alterations in environmental stimuli (variables) represent new challenges to plants, which do not possess the \u2018flight\u2019 strategy usually displayed by other organisms. Plants have developed, however, a multiplicity of highly integrated adjustments, involving morpho-anatomical, physiological and biochemical traits, to cope with challenges imposed by novel, harsher environments: these constitute the \u2018flight strategy of sessile organisms\u2019. Interestingly, several habitats threatened by the novel stresses are biodiversity hotspots. For example, Mediterranean basin, in which high light growing plants face heat waves coupled with the scarcity of rainfall of increasing frequency and severity, represents just 2% of the earth\u2019s land area, but account for 16% of the world\u2019s plant species. This implies that plants have been and are capable to display a wide range of acclimation/adaptation strategies to cope with most unfavorable environments. Nonetheless, the unpreceded rate at which climate changes may exceed the capacity of plants to acclimate and adapt successfully to the novel environmental pressures, further exacerbated by an increase in anthropogenic pressure. Understanding the mechanisms through which plants respond to new challenges posed by the concurrent effect of different stress agents is crucial, as obvious, to develop strategies of biodiversity conservation and ecosystem functionality. This is exactly the focus of this Research Topic. Review, Opinion as well as Original Research articles are welcome covering basic and applied research on plant functioning under adverse environmental conditions. The frequency of extreme stress events, mostly due to the concurrent effects of different stressors, is increasing particularly in the arid and semi-arid regions, which represent indeed among the most fragile ecosystems worldwide. Papers dealing with the effects of multiple stress agents on plant functioning are, therefore, particularly welcome. We are, however, also interested to receive contributions dissecting response mechanisms (from molecular to organism and whole-plant levels) of plants to a wide range of individual stressors, with a view to a rapidly changing climate, covering plant responses from other regions of the world. These include, but are not limited to drought and heat stress, excess light stress (including UV radiation), cold, ozone and rising CO2 concentration, and their combinations. Theories that predict the plant behavior, acclimation and plant plasticity are also inside the scope of this topi