Review: Why do some plants have leaves with red or purple undersides?

From green to red: Urban heat stress drives leaf color evolution

“…The stress-induced accumulation of anthocyanins is a common plastic response throughout the plant kingdom, and constitutive red leaves—those that accumulate pigment even in the absence of stress—are known in many other cultivated and wild species ( 40 , 42 , 54 ). However, the evolutionary dynamics of the red leaf phenotype are not well understood ( 40 , 42 , 54 ).…”

“…The stress-induced accumulation of anthocyanins is a common plastic response throughout the plant kingdom, and constitutive red leaves—those that accumulate pigment even in the absence of stress—are known in many other cultivated and wild species ( 40 , 42 , 54 ). However, the evolutionary dynamics of the red leaf phenotype are not well understood ( 40 , 42 , 54 ). The natural variation of leaf color in O. corniculata can serve as a model system for studying leaf color evolution, as the species is small in size, is distributed worldwide, and has a rapid life cycle, which allows for experimentation in both laboratory and field conditions.…”

“…1A). Several studies on inducible leaf reddening (e.g., winter leaves) suggest that such a color change has an adaptive role in light attenuation and antioxidant protection during environmental stresses (38)(39)(40)(41)(42)(43). Receiving bright light under environmental stress, such as cold, heat, and dry conditions, can result in excess energy capture relative to photosynthetic ability.…”

“…The excess sunlight energy causes photoinhibition of photosynthesis, formation of reactive oxygen species (ROS), and greater photooxidative damage (44). Red pigments in leaves (e.g., anthocyanin) are thought to alleviate these stress conditions by two different physiological mechanisms: intercepting light (light attenuation) and/or neutralizing ROS directly via antioxidants (38)(39)(40)(41)(42)(43). Urban ground surfaces, which are mostly characterized by being impermeable, are subject to higher temperatures than green surfaces (fig.…”

Exposure to Light of the Abaxial versus Adaxial Side of Detached Kalanchoë blossfeldiana Leaves Affects Anthocyanin Content and Composition Differently

“…Environmental stress caused by inverting the leaves so that their abaxial surfaces are exposed to strong light causes them to redden as a result of anthocyanin accumulation [ 57 ]. The photoprotection hypothesis is currently the best-supported explanation for abaxial reddening to suppress excess light falling on the surface of inverted leaves or passing through adaxial cell layers [ 58 ].…”