M. Zunzunegui et al., Different phenotypic response of Halimium halimifolium in relation to groundwater availability, PLANT ECOL, 148(2), 2000, pp. 165-174
Halimium halimifolium (Cistaceae) is a shrub occurring on sandy substrates
in the Mediterranean region and is the principal element of the sandy veget
ation in Donana National Park (S.W. Spain). The annual cycles of leaf water
potential, stomatal resistance and shoot growth were studied in permanentl
y marked H. halimifolium plants. Three sites with different water availabil
ity at the stabilized sands of the Park - Monte Blanco (MB, top of the dune
s), Monte Negro (MN, depressions) and Monte Intermedio (MI, slopes of dune
ridges) - were chosen. The study was carried out during a period of extreme
drought. MN individuals showed the greatest growth, both in main shoot and
in ramets, less negative water potential values and lower stomatal resista
nce values than the other two areas, because individuals' roots could reach
the water table all year long. In winter there were no differences in pred
awn, midday and sunset water potential or in stomatal resistance values in
the three areas. In summer, MI individuals showed the most negative water p
otentials and the highest stomatal resistance, although they occupied an in
termediate position in the water table depth gradient. Under drought condit
ions MI individuals are the most affected, because they are acclimated to u
se ground water during the growth period, while MB individuals, that never
reach the water table, are acclimated to use found surface water and are, t
hus, better adapted to water scarcity.