Genotypic variation in UV-B absorbing compounds of hazelnut pollen grains

Abstract

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.

Keywords

• UV-B radiation
• pollen grain
• ultraviolet-absorbing compounds
• sporopollenin

Fındık polen tanelerinde UV-B absorplayıcı bileşiklerin genotipik varyasyonu

Abstract

Polen taneleri oldukça hassas üreme yapılarıdır ve UV-B radyasyonu da dahil olmak üzere çevresel streslere karşı dayanım için yapısal ve biyokimyasal mekanizmaları kullanırlar. Bu çalışmada, dört farklı Corylus avellana genotipine (Sarı, Palaz, Kara, Yomra) ait polen tanelerinin sitoplazmik, hücre duvarına bağlı ve sporopolleninle ilişkili fraksiyonlardan izole edilen UV-B absorplayıcı bileşiklerin UV-B absorbsiyon kapasitesi değerlendirilmiştir. Çalışmada, spektral analizler, sitoplazmik ve duvar bağlı fraksiyonlarda 280–315 nm arasında genel bir azalma, sporopollenin fraksiyonunda ise artış eğilimi göstererek fraksiyonlara özgü farklı absorbans paternlerini ortaya koymuştur. Tüm genotipler içerisinde en yüksek UV-B absorbsiyonunun sitoplazmik fraksiyonda gerçekleştiği, bunu sırasıyla sporopollenin ve duvar bağlı fraksiyonların izlediği belirlenmiştir. Genotipe özgü örüntüler belirgin olup, Palaz genotipi sitoplazmik absorbsiyonda en yüksek değeri gösterirken, Sarı genotipi sporopolleninle ilişkili absorbsiyonda öne çıkmış, Kara ise tüm fraksiyonlarda en düşük değerlere sahip olmuştur. Temel bileşenler ve ısı haritası kümeleme dahil çok değişkenli analizler, genotipler ve UV-B absorplayıcı bileşik fraksiyonları arasında belirgin ayrışmaları doğrulamıştır. Bu bulgular, UV-B absorplayıcı bileşiklerin dağılımındaki kalıtsal farklılıkların genotipler arası fotokoruyucu potansiyel farklılıklarına katkıda bulunduğunu göstermektedir. UV-B’ye karşı doğal savunma kapasitesi yüksek olan fındık genotiplerinin belirlenmesi, artan UV-B maruziyeti altında üreme dayanıklılığını artırmaya yönelik ıslah stratejilerine yol gösterebilir.

Keywords

• UV-B radyasyonu
• polen tanesi
• ultraviyole absorplayıcı bileşikler
• sporopollenin

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