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The influence of CO 2 and O 3 , singly and in combination, on gas exchange, growth and nutrient status of radish ( Raphanus sativus L.)
Author(s) -
BARNES J. D.,
PFIRRMANN T.
Publication year - 1992
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.1469-8137.1992.tb02940.x
Subject(s) - raphanus , phytotron , carbon dioxide , shoot , hypocotyl , dry matter , horticulture , nutrient , chemistry , botany , zoology , biology , organic chemistry
SUMMARY Five days after emergence radish ( Raphanus sativus L. ev. Cherry Belle) plants were transferred to a phytotron at the GSF München, where they were exposed in four large controlled climate chambers to two atmospheric concentrations of CO 2 , (‘ambient’, daily means of ∼ 385 μmol −1 ; elevated, daily means of ∼ 765 μmol mol −1 ) and two O 3 regimes (‘non‐polluted’ air, 24 h mean of 20 nmol mol −1 ; polluted air, 24 h mean of 73 nmol mol −1 ). Leaf gas‐exchange measurements were made at intervals, and visible O 3 damage, effects on growth, dry matter partitioning and mineral composition were assessed at a final whole‐plant harvest after 27 d. In ‘non‐polluted air’ CO 2 enrichment resulted in a progressive stimulation in A sat , whilst there was a decline in g which decreased E (i.e. improved WUE i ). The extra carbon fixed in elevated CO 2 stimulated growth of the root (+ hypocotyl) by 43 %, but there was no significant effect on shoot growth or leaf area. Moreover, a decline in SLA and LAR in CO 2 ‐enriched plants suggested that less dry matter was invested in leaf area expansion. Tissue concentrations of N, S, P, Mg and Ca were lower (particularly in the root + hypocotyl) in elevated CO 2 , indicating that total uptake of these nutrients was not affected by CO 2 , and there was an increase in the C:N ratio in root (+ hypocotyl) tissue. In contrast, O 3 depressed A sat , (∼ 26%) and induced slight stomatal closure, with the result that WUE, declined. All plants exposed to ‘polluted’ air developed typical visible symptoms of O 3 injury, and effects on carbon assimilation were reflected in reduced growth, with shoot growth maintained at the expense of the root. In addition, O 3 increased the P and K concentration in shoot and root (+ hypocotyl) tissue, indicating enhanced uptake of these nutrients from the growth medium. However, there was no affect of O 3 on tissue concentrations of N, S, Mg and Ca. Interactions between the gases were complex, and often subtle. In general, elevated CO 2 counteracted (at least in part) the detrimental effects of phytotoxic concentrations of O 3 , whilst conversely, O 3 reduced the impact of elevated CO 2 . Moreover, there were indications that cumulative changes in source: sink relations in O 3 ‐exposed plants may limit plant response to CO 2 ‐enrichment to an even greater extent in the long‐term. The future ecological significance of interactions between CO 2 and O 3 are discussed.