Photosynthetic Adaptation of Solanum dulcamara L. to Sun and Shade Environments: II. Physiological Characterization of Phenotypic Response to Environment.

Photosynthetic and growth properties of Solanum dulcamara L. were studied under controlled environments. The 200 experimentally tested plants were clonal replicates of five field-collected individuals, three from fully exposed habitats and two from deeply shaded habitats. After 4 weeks of growth in one of eight environmental treatments, each plant was measured for leaf adaxial and abaxial conductance to water vapor, specific leaf weight, chlorophyll per square decimeter of leaf, photosynthetic unit size, light-saturated photosynthetic rate, total leaf area, and total leaf, stem, and root dry weights. Changes in light level influenced photosynthesis and growth of each plant more than changes in water availability or temperature. It is strongly suggested that the primary adaptive response of the tested individuals to changes in levels of light involves the regulation of leaf thickness.