Evaluation of water stress tolerance of some species suitable for extensive green roofs

Green roof technology is influenced by temperate northern European experiences, especially when it comes to plant selection. The Mediterranean climate is quite particular and the use of native plants on green roofs could prove more appropriate. Trials with Cerastium biebersteinii and Potentilla neumanniana were carried out to test their performance. Plants have been potted in a substrate of pumice, volcanic lapilli and peat and maintained through three irrigation regimes, one unrestricted and two very restricted in water supply, in order to evaluate their tolerance to water stress. Growth parameters, content of carotenoids, chlorophyll and proline were determined. Both species showed growth and physiological parameters consistent with survival even at the worst irrigation level.