Intraspecific variation in the use of water sources by the circum-Mediterranean conifer Pinus halepensis.

The relevance of interspecific variation in the use of plant water sources has been recognized in drought-prone environments. By contrast, the characterization of intraspecific differences in water uptake patterns remains elusive, although preferential access to particular soil layers may be an important adaptive response for species along aridity gradients. Stable water isotopes were analysed in soil and xylem samples of 56 populations of the drought-avoidant conifer Pinus halepensis grown in a common garden test.

Population divergence for heteroblasty in the Canary Island pine (Pinus canariensis, Pinaceae).

A heteroblastic (or vegetative phase) change is an abrupt manifestation in the general heteroblastic development during the ontogeny of plants. The Canary Island pine undergoes an especially marked and delayed heteroblastic change, including both the formation of secondary needles on dwarf shoots and the onset of preformed growth. To assess genetic and environmental effects on the heteroblastic change in this species, we followed plants from 19 populations at a dry site and a wetter site.