Photosynthesis and photoinhibition in response to drought in a pubescent (var. minor) and a glabrous (var. palaui) variety of Digitalis minor

Ecophysiological differences on morphological and photosynthetic traits were studied in two varieties of a Mediterranean endemic species, Digitalis minor. These varieties are recognized according to its differences in pubescence: var. minor is pubescent while var. palaui is glabrous. Water status, leaf mass area, gas-exchange and chlorophyll fluorescence measurements were performed under two different water availability treatments: field capacity and 25% field capacity. The presence of leaf trichomes in var. minor is shown as an efficient mechanism in preserving photochemistry apparatus, when compared to the glabrous var. palaui. However, such differential pubescence did not imply a lower leaf water loss. Other intraspecific differences are found both in the photosynthetic behaviour and in leaf morphological traits between both varieties, especially higher photosynthetic and mesophyll conductance capacities for var. minor in respect to var. palaui. These results are discussed in terms of selection pressures and ecological success to link with actual and future scenarios derived from the climatic change. (c) 2006 Elsevier B.V. All rights reserved.