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Effects of elevated CO 2 and/or O 3 on growth, development and physiology of wheat ( Triticum aestivum L.)
Author(s) -
BARNES JEREMY D.,
OLLERENSHAW JOHN H.,
WHITFIELD CLARE P.
Publication year - 1995
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.1995.tb00013.x
Subject(s) - cultivar , phytotron , photosynthesis , stomatal conductance , anthesis , shoot , transpiration , dry matter , horticulture , chemistry , agronomy , zoology , botany , biology
Two cultivars of spring wheat ( Triticum aestivum L. cvs. Alexandria and Hanno) and three cultivars of winter wheat (cvs. Riband, Mercia and Haven) were grown at two concentrations of CO 2 [ambient (355 pmol mol −1 ) and elevated (708 μmol mol −1 )] under two O 3 regimes [clean air (< 5 nmol mol −1 O 3 ) and polluted air (15 nmol mol −1 O 3 at night rising to a midday maximum of 75 nmol mol −1 )] in a phytotron at the University of Newcastle‐upon‐Tyne. Between the two‐leaf stage and anthesis, measurements of leaf gas‐exchange, non‐structural carbohydrate content, visible O 3 damage, growth, dry matter partitioning, yield components and root development were made in order to examine responses to elevated CO 2 and/or O 3 . Growth at elevated CO 2 resulted in a sustained increase in the rate of CO 2 assimilation, but after roughly 6 weeks' exposure there was evidence of a slight decline in the photosynthetic rate (c.‐15%) measured under growth conditions which was most pronounced in the winter cultivars. Enhanced rates of CO 2 assimilation were accompanied by a decrease in stomatal conductance which improved the instantaneous water use efficiency of individual leaves. CO 2 enrichment stimulated shoot and root growth to an equivalent extent, and increased tillering and yield components, however, non‐structural carbohydrates still accumulated in source leaves. In contrast, long‐term exposure to O 3 resulted in a decreased CO 2 assimilation rate (c. ‐13%), partial stomatal closure, and the accumulation of fructan and starch in leaves in the light. These effects were manifested in decreased rates of shoot and root growth, with root growth more severely affected than shoot growth. In the combined treatment growth of O 3 ‐treated plants was enhanced by elevated CO 2 , but there was little evidence that CO 2 enrichment afforded additional protection against O 3 damage. The reduction in growth induced by O 3 at elevated CO 2 was similar to that induced by O 3 at ambient CO 2 despite additive effects of the individual gases on stomatal conductance that would be expected to reduce the O 3 flux by 20%, and also CO 2 ‐induced increases in the provision of substrates for detoxification and repair processes. These observations suggest that CO 2 enrichment may render plants more susceptible to O 3 damage at the cellular level. Possible mechanisms are discussed.