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Dose-dependent effects of gamma radiation on lettuce (Lactuca sativa var. capitata) seedlings

Abstract Purpose: The objectives of this study were to determine the effects of gamma radiation on lettuce growth and development, as well as on the content of photosynthetic pigments in 28 days lettuce leaf. Materials and methods: Lettuce dry seeds were exposed to a 60Co [Cobalt-60] gamma source at doses ranging from 2–70 Gray (Gy). The photosynthetic pigment content was determined spectrophotometrically. Results: Our results showed that an irradiation dose between of 2–30 Gy enhanced the growth parameters (final germination percentage, germination index, root and hypocotyl length) as compared to untreated plants. Seed germination test revealed that 30 Gy irradiation dose induced the highest increase of growth parameters, while at 70 Gy a significant decrease of plant vegetative growth was recorded. The results indicated that exposing the seeds at doses ranging from 2–30 Gy enhanced the photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids) content, while at higher doses (70 Gy)) the decrease of the assimilatory pigments was noticed. Conclusion: The present results suggested that seed treatment with gamma radiations (0–30 Gy) was effective in stimulating plant growth and development, as well as the content of assimilatory pigments. At a higher dose of 70 Gy, there was a drastic reduction in the length of shoots and roots and also in the total chlorophyll content. These observations confirm that ionizing radiation stimulates physiological parameters up to certain low doses, and then it inhibits these parameters at higher doses.