Leaf growth and anatomy in the miohalophyte Puccinellia borreri in saline and non-saline environments.

The adaptive strategy of the halophyte Puccinellia borreri was evaluated by comparing some leaf growth parameters and leaf anatomy of plants naturally growing on salt mud flows in Northern Italy (Salse di Nirano), with those of plants experimentally transplanted in salt-free soil. Saline environment negatively affects leaf area and water content, whereas it positively influences leaf thickness, dry weight to fresh weight ratio and photosynthetic pigment contents. Leaf anatomy is consistently modified by the presence of conspicuous sclerenchyma and water storing cells and by reduced intracellular spaces. These xeromorphic characters indicate that this species in native habitat is affected by water stress more then by ion stress. The adaptive response leads to an apparent unflexible leaf model. This does not help to explain the tolerance of this species to frequent seasonal fluctuations in soil salinity, but does account for its low competitiveness with respect to other halo- tolerant species.