The high red/far-red ratio supports the acclimation of fern Platycerium bifurcatum to high light.

ABSTRACT

BACKGROUND AND AIMS: High light causes disturbances in photosynthetic phosphorylation or damage to the photosystem II (PSII) structure or even assimilation tissues. The value of the red/ far-red ratio (R/FR) provides the plant with information on the environmental light conditions, regulating, among others, photosynthetic activity and pigment composition of the plant. The response of the photosynthetic apparatus of the sporotrophophylls and nest leaves of Platycerium bifurcatum, grown for 6 months at the low or high R/FR ratio, were studied. Later, the plants were transferred to high light (1,200 µmol quantum • m-2 • s-1). METHODS: Changes in PSII photochemical activity were determined based on non-destructive methods of chlorophyll a fluorescence kinetics analysis. The measurement of radiation reflectance from the leaves allowed to determine the content of selected pigments related to the photosynthesis process and to assess changes in the Photochemical Reflectance Index. The calculation of reflectance difference and sensitivity analysis was used to identify so-called "stress-sensitive wavelengths". RESULTS AND DISCUSSION: Plant growth at high R/FR ratio prepares photosynthetic apparatus of ferns to high light and enables more efficient conversion of absorbed photons. The increase in the amount of photoprotective compounds allows the protection against photoinhibition in the sporotrophophyll leaves that play key roles in plant nutrition and reproduction.