Effects of light environment on the induction of chlorophyll fluorescence in leaves: A comparative study of Tradescantia species of different ecotypes

In this work, using a PAM-fluorimetry technique, we have compared effects of plant adaptation to the light or dark conditions on the kinetics of chlorophyll a fluorescence yield in Tradecantia leaves of several species ( Tradescantia albiflora, Tradescantia fluminensis, Tradescantia navicularis, and Tradescantia sillamontana), which represent plants of different ecotypes. Two fluorescence parameters were used to assess photosynthetic performance in vivo: non-photochemical quenching (NPQ) of chlorophyll fluorescence ( q NPQ) determined by energy losses in the light-harvesting antenna of photosystem 2 (PS2), and PS2 operating efficiency ( Φ PSII). Comparative study of light-induced changes in q NPQ and Φ PSII has demonstrated that shade-tolerant Tradecantia species ( T. albiflora Kunth, T. fluminensis Vell.) reveal higher capacities for NPQ and demonstrate slower transitions between the ‘light-adapted’ and ‘dark-adapted’ states than succulent species T. navicularis and T. sillamontana, which are typical habitats of semi-deserts. We analyze the photosynthetic performance of Tradescantia species in the context of their adaptabilities to variable environment conditions. The ability of shade-tolerant plants to retain a relatively long-term (∼40–60 min) ‘memory’ for illumination history may be associated with the regulatory mechanisms that provide the flexibility of photosynthetic apparatus in response to fluctuations of light intensity.