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The Effect of Technetium‐99 and Environmental Conditions on Soybean Physiology
Author(s) -
Degenkolb Stephanie J.,
Neel James W.,
Papin Patrick J.
Publication year - 1994
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1994.00472425002300060020x
Subject(s) - photosynthesis , stomatal conductance , chemistry , adenosine triphosphate , chloroplast , metabolism , light intensity , botany , biophysics , biology , horticulture , biochemistry , gene , physics , optics
Technetium‐99 is considered a long‐term risk of nuclear energy because it has a long half‐life, mass 99 is produced at a high yield during nuclear fission, and Tc‐99 is taken up readily by aquatic and terrestrial organisms. Plants are an important intermediate of Tc‐99 food chain transfer to animals and humans. The present study investigated adenosine triphosphate (ATP), photosynthesis and structural responses of intact soybean seedlings [ Glycine max (L.) Merr. cv. Williams] to micromolar amounts of Tc‐99 under different ambient light levels. Adenosine triphosphate was measured directly in primary leaf extract after 6 d of exposure to Tc at varying concentrations (up to 5 µ M Tc‐99). The results indicated that under full light conditions (320 µmol photon m −2 s −1 ), soybean primary leaves contained nanomolar concentrations of ATP almost twice as high as for untreated plants. With a reduction of light intensity by 50%, primary leaf pertechnetate uptake and leaf ATP content were reduced regardless of Tc‐99 exposure levels. Gas exchange measurements with a Li‐Cor 6200 Portable Photosynthesis system indicated a significant decline of photosynthetic rate and a higher internal CO 2 accumulation under full light conditions, while stomatal conductance decreased as a function of Tc‐99 concentration. Several possible mechanisms of Tc interaction with chloroplast ultrastructure are proposed. A hypothesis related to the metabolic behavior of Tc in higher plants is presented.