The use of experimental model for investigating response of plants structures and anatomy to radiation

Ionizing radiation as environmental factor, causes adaptive processes that affect plant and anatomical changes caused by the accumulation of radioactive substances. This study aimed to investigate the effect of radiation on the structure and anatomy of Phaseolus vulgaris L. leaves in three generations under conditions of a model experiment involving root uptake of Sr-90. Plants were grown in soil samples with high levels of specific activity of Sr-90 (5x108 Bq/kg), selected from the former Semipalatinsk testing site. The adaxial and abaxial epidermal layers and mesophyll thickness were used as the main structural and anatomic parameters. Leaf samples were taken after full formation and preserved in a Copenhagen mixture before irradiation. The dose rates from internal and external radiation for Phaseolus vulgaris L. were determined. Due to Sr-90 being 9.5x10-1 Gy, this indicates the manifestation of adaptive responses, rather than the effect of hormetic response. The distribution of Sr-90 among the organs of Phaseolus vulgaris L. is represented by a series decreasing from “leaves>stems>fruits”. Significant changes in the thickness of adaxial and abaxial epidermal layers, as well as mesophyll thickness in the leaf lamina (p<0.05), were observed in 3 successive generations. Maximum values of structural and anatomical indicators were noted in leaves of the first generation, with lower values typical for second and third generations, and minimum values for the control group. The thickness of mesophyll in experimental groups of 1st, 2nd, and 3rd generations is on average 38%, 36%, and 21% higher than in the control group; thickness of adaxial epidermis 23%, 17%, and 9%; thickness of abaxial epidermis 20% and 8%. The results of the study characterize one of the mechanisms of plant adaptation at the organ-tissue level to ionizing radiation and confirm the special role of leaves as an organ where 90Sr accumulates and is fixed.