High-Dosage Gamma Irradiation Alters Lotus (Nelumbo nucifera Gaertn.) Seedling Structure: A Morphological and Anatomical Perspective

The lotus (Nelumbo nucifera Gaertn.) is an ornamental aquatic plant, highly valued in Asian cultures for its religious symbolism, culinary uses, and medicinal properties. However, the lotus exhibits low genetic diversity in nature, which limits the genetic resources available for breeding programs. Gamma irradiation is an effective method for inducing genetic variation in lotus breeding. The present study examines the gamma sensitivity of lotus seedlings, along with the morphological and anatomical changes induced by various gamma dosages. The results showed that high-dose gamma irradiation (≥100 Gy) significantly inhibited seedling growth and altered most anatomical parameters, each exhibiting distinct dose–response patterns except for midrib diameter. The 100 Gy treatment resulted in the maximum stem diameter, while root diameter peaked at 500 Gy, and the highest dose (600 Gy) produced the largest petioles. Gamma irradiation also triggered tannin accumulation and reduced aerenchyma formation in the leaves. The obtained results demonstrate organ-specific responses to gamma irradiation in the lotus, with leaves being the most sensitive, while petioles, stems, and roots exhibited more variable dose-dependent effects.