Premium
Effects of O 3 on alder photosynthesis and symbiosis with Frankia
Author(s) -
GREITNER CAROL S.,
WINNER WILLIAM E.
Publication year - 1989
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1989.tb02359.x
Subject(s) - frankia , symbiosis , photosynthesis , botany , biology , stomatal conductance , root nodule , bacteria , genetics
summaryAlnus serrulata (Aiton) Willdenow seedlings with and without root nodules formed by the nitrogen‐fixing actinomycete Frankia were exposed to clean filtered air or ozone (O 3 ) at 0.12 μl l −1 for 27 d (approximately 164 h total exposure). Gas exchange measurements on leaves and transmission electron micrographs of root nodule cells were made to detect any O 3 effects on the functioning of leaves and the root symbiont. Photosynthesis, stomatal conductance, and internal CO 2 , concentration were calculated for all plants in clean O 3 ‐free air more than three weeks after the fumigations began. Significant positive correlations between photosynthesis and conductance were found for leaves of control nodulated and unnodulated alders and O 3 ‐treated nodulated alders. There was a weak positive correlation between photosynthesis and conductance for unnodulated O 3 ‐treated seedlings measured in clean air. When O 3 ‐treated leaves were measured during fumigation with O 3 , no positive correlation between photosynthesis and conductance was found for either nodulated or unnodulated seedlings. Photosynthetic rates of leaves having the highest stomatal conductance values were decreased by O 3 for both nodulated and unnodulated plants. Transmission electron microscopy (TEM) revealed that after a 27 d exposure of shoots to O 3 , host root cells of nodules from O 3 ‐treated plants lacked organelles and showed extensive cytoplasmic breakdown. Hyphae and N 2 ‐fixing vesicles of Frankia appeared normal. The Frankia endophyte seems to be more resistant to O 3 than is the host root nodule cell. These results show that ambient levels of O 3 may reduce photosynthesis and bring about associated degradation in rhizosphere symbiosis.