Assessment of the UV-B absorbing compounds' absorbance levels in pollen grains of hazelnut genotypes

Pollen grains, as highly sensitive reproductive units, rely on structural and biochemical mechanisms to withstand environmental stressors, particularly UV-B radiation. This study evaluated the UV-B absorbance capacity of UV-B absorbing compounds extracted from cytoplasmic, wall-bound, and sporopollenin-associated fractions of pollen grains from four Corylus avellana genotypes (Sarı, Palaz, Kara, Yomra). Spectral analyses revealed distinct fraction-specific absorbance patterns, showing a general decrease between 280–315 nm in the cytoplasmic and wall-bound fractions, whereas the sporopollenin fraction exhibited an increasing trend. Spectrophotometric analyses revealed that the cytoplasmic fraction exhibited the highest UV-B absorbance across all genotypes, followed by the sporopollenin and wall-bound fractions. Genotype-specific patterns were evident, with Palaz showing the highest cytoplasmic absorbance and Sarı displaying superior sporopollenin-associated absorbance, while Kara consistently recorded the lowest across all fractions. Multivariate analyses, including principal component analysis and heatmap clustering, confirmed distinct groupings among genotypes and UV-B absorbing compounds fractions. These findings suggest that inherent variability in UV-B absorbing compounds distribution contributes to differential photoprotection potential among genotypes. Identifying hazelnut genotypes with stronger inherent UV-B defense capacity may inform breeding strategies aimed at improving reproductive resilience under increasing UV-B exposure.