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Photosynthetic and anatomical responses of Eucalyptus grandis leaves to potassium and sodium supply in a field experiment

Battie Laclau P., Laclau J.P., Beri C., Mietton L., Almeida Muniz M.R., Cersózimo Arenque B., De Cassia Piccolo M., Jordan-Meille L., Bouillet J.P., Nouvellon Y.. 2014. Plant, Cell and Environment, 37 (1) : p. 70-81.

DOI: 10.1111/pce.12131

Although vast areas in tropical regions have weathered soils with low potassium (K) levels, little is known about the effects of K supply on the photosynthetic physiology of trees. This study assessed the effects of K and sodium (Na) supply on the diffusional and biochemical limitations to photosynthesis in Eucalyptus grandis leaves. A field experiment comparing treatments receiving K (+K) or Na (+Na) with a control treatment (C) was set up in a K-deficient soil. The net CO2 assimilation rates were twice as high in +K and 1.6 times higher in +Na than in the C as a result of lower stomatal and mesophyll resistance to CO2 diffusion and higher photosynthetic capacity. The starch content was higher and soluble sugar was lower in +K than in C and +Na, suggesting that K starvation disturbed carbon storage and transport. The specific leaf area, leaf thickness, parenchyma thickness, stomatal size and intercellular air spaces increased in +K and +Na compared to C. Nitrogen and chlorophyll concentrations were also higher in +K and +Na than in C. These results suggest a strong relationship between the K and Na supply to E.?grandis trees and the functional and structural limitations to CO2 assimilation rates.

Mots-clés : eucalyptus grandis; plantation forestière; photosynthèse; fertilisation; potassium; sodium; analyse de tissu foliaire; feuille; morphologie végétale; séquestration du carbone; brésil; indice foliaire; parcelle expérimentale

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