Survival without photosynthesis: physiological characterization of long-lived albino beech ( <i>Fagus sylvatica</i> )

Albinism is typically lethal in autotrophic plants due to the absence of photosynthetic pigments and functioning chloroplasts. Yet, rare exceptions occur where achlorophyllous individuals persist in natural ecosystems. We investigated the physiological, anatomical and isotopic characteristics of naturally occurring albino European beech (Fagus sylvatica L.) trees in the Moravian Karst, Czechia. One albino individual, estimated to be ~30 years old, represents an unprecedented case of long-term survival without photosynthesis in a woody angiosperm. Using a multi-parameter approach-including stable isotope analysis (δ13C, δ15N), pigment quantification, saccharide profiling, gas exchange, leaf anatomy, stomatal traits and microsatellite genotyping-we confirmed the absence of photosynthetic capability, explored potential mechanisms of carbon acquisition and assessed clonal affiliation of the albino to its neighbouring trees. An albino individual exhibited almost absent photosynthetic pigments and lacked differentiated thylakoids, and showed significantly reduced stomatal conductance and density. The CO2 release from albino leaves indicated predominant mitochondrial respiration even under the light conditions. Intriguingly, albino leaves accumulated higher concentrations of soluble sugars (notably glucose and fructose) and were enriched in δ13C, similar to mixotrophic orchids, suggesting heterotrophic carbon uptake. Microsatellite genotyping revealed that the albino individual is not genetically identical to any of the surrounding green trees, thus making root suckering unlikely. While partial mycoheterotrophy cannot be entirely excluded, the data strongly support a trophic strategy based on carbon translocation from an autotrophic donor through root connectivity. This study offers novel physiological insights into albino tree survival and illustrates the complexity of belowground integration in forest ecosystems.