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Response of Soybean to Low Concentrations of Ozone: I. Reductions in Leaf and Whole Plant Net Photosynthesis and Leaf Chlorophyll Content
Author(s) -
Reich P. B.,
Schoettle A. W.,
Raba R. M.,
Amundson R. G.
Publication year - 1986
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/jeq1986.00472425001500010008x
Subject(s) - photosynthesis , cuvette , ozone , chlorophyll , chemistry , horticulture , respiration , chlorophyll a , botany , zoology , agronomy , biology , physics , organic chemistry , quantum mechanics
Since most commercially grown soybean plants in the USA are subjected to low or moderate levels of ambient O 3 pollution it is important to understand whether exposure to O 3 influences CO 2 exchange in this species. Therefore, for 8 weeks soybean ( Glycine max cv. Hodgson) plants were exposed to O 3 for 6.8 h daily in controlled environment chambers. Four treatments were used: 0.01, 0.05, 0.09, and 0.13 µ L L −1 O 3 in filtered air. Net photosynthesis (P n ), dark respiration, and chlorophyll content were measured in all treatments for both individual leaves of various ages and for whole plants. Measurements of CO 2 exchange were made nondestructively with an infrared gas analysis system using either plexiglass cuvettes (leaves) or continuously stirred tank reactors (plants). The P n of whole plants was reduced by 10, 11, and 22% in the 0.05, 0.09, and 0.13 µ L L −1 treatments, respectively, compared with the 0.01 µ L L −1 treatment. Among individual leaves of similar ages, exposure to O 3 also resulted in declines in P n and this occurred at all leaf ages. There was a significant linear relationship between P n and O 3 concentration for both individual leaves and for whole plants. Chlorophyll contents of whole plants and individual leaves were also reduced by O 3 exposure. Chlorophyll content and P n were correlated with each other for both individual leaves and whole plants. Changes with leaf age were typical for P n and for chlorophyll content. There was no apparent effect of O 3 treatment on dark respiration. The observed reduction in P n at low levels of O 3 (coupled with reports of O 3 ‐induced reduction in growth and yield) suggests that ambient O 3 pollution in the USA is currently causing decreased P n in field‐grown soybean which can lead to a significant loss in yield.