A LOW RATIO OF RED/FAR-RED IN THE LIGHT SPECTRUM ACCELERATES SENESCENCE IN NEST LEAVES OF PLATYCERIUM BIFURCATUM

摘要

The fern Platycerium bifurcatum is a valuable component of the flora of tropical forests, where degradation oflocal ecosystems and changes in lighting conditions occur due to the increasing anthropogenic pressure. In ferns,phytochrome mechanism responsible for the response to changes in the value of R/FR differs from the mechanismobserved in spermatophytes. This study analyzed the course of ontogenesis of nest leaves in P. bifurcatum at twovalues of the R/FR ratio, corresponding to shadow conditions (low R/FR) and intense insolation (high R/FR). Thework used only non-destructive research analysis, such as measurements of reflectance of radiation from theleaves, their blue-green and red fluorescence, and the chlorophyll a fluorescence kinetics. This allowed tracing thedevelopment and aging processes in the same leaves. Nest leaves are characterized by short, intense growth andrapid senescence. The study identified four stages of development of the studied leaves related to morphologicaland anatomical structure and changing photochemical efficiency of PSII. Under the high R/FR ratio, the rate ofontogenesis of the leaf lamina was much slower than under the low R/FR value. As shown, the rapid aging of theleaves was correlated with faster decline of the chlorophyll content. It was shown that leaf senescence was accompaniedby accumulation of polyphenols, anthocyanins and carotenoids on the basis of reflectance and fluorescencemeasurements in the blue-green range.