The effect of salinity and CO₂ enrichment on the growth and anatomy of the second trifoliate leaf of <i>Phaseolus vulgaris</i>

Abstract

The effect of CO 2 and NaCl on the second trifoliate leaf of Phaseolus vulgaris L. was studied. Salt reduced leaf area and volume. Volume density of the palisade mesophyll was increased and that of the intercellular spaces and abaxial epidermis was reduced. Salt increased the numbers of epidermal and palisade cells per unit area and the stomatal density of the abaxial epidermis but reduced the numbers of cells per leaf. Salt reduced stomatal indices of both epidermal surfaces, cell volumes, relative leaf expansion rate, leaf plastochron index, leaf fresh and dry weights, and specific leaf area. Elevated CO 2 increased leaf area and volume, reduced the density of epidermal and palisade cells and increased fresh and dry weights. Cell areas and volumes of epidermal and palisade cells, but not stomates, were increased. Elevated CO 2 partially overcame some salinity effects such as leaf area, volume, specific leaf area, and relative leaf expansion rate. Leaf fresh and dry weights, leaf volume, palisade and spongy mesophyll tissue volume, and the numbers of palisade and epidermal cells per leaf equalled controls. Under high CO 2 , epidermal and intercellular space volume, cell areas, stomatal index, and the volume density of intercellular spaces and abaxial epidermis were reduced, and the volume density of the palisade mesophyll increased. Leaf thickness, palisade cell length and volume, volume density of spongy mesophyll, and succulence were greater than controls in salt and high-CO 2 leaves. High CO 2 had more effect on salt-stressed than unstressed plants in leaf weight, thickness, and cell volume.Key words: CO 2 enrichment, leaf growth, leaf anatomy, Phaseolus vulgaris, salinity.