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Growth of the halophyte Atriplex halimus on a green roof at the semi-arid Mediterranean region as affected by substrate type and irrigation regime

Tassoula, L., Papafotiou, M., Fouskaki, M.
Acta horticulturae 2017 no.1189 pp. 287-290
Atriplex halimus, Mediterranean climate, drought tolerance, grape pomace, green roofs, halophytes, irrigation scheduling, photosynthesis, plant height, root cuttings, second growth, soil, stomatal conductance, summer, Greece, Mediterranean region
Aiming to exploit native, drought tolerant plants for use on green roofs at the semi-arid Mediterranean region, the effect of substrate type and irrigation frequency on growth of the halophyte Atriplex halimus was investigated on an extensive green roof in Athens, Greece. Rooted cuttings were planted in December 2012 in experimental modules with a green roof infrastructure on a fully exposed second-floor flat roof and were kept in culture until September 2014. Two types of substrate, 10 cm deep, were used, one with soil, i.e. grape marc compost:perlite:soil:pumice (3:3:2:2, v/v) and a lighter one, without soil, i.e. grape marc compost:perlite:pumice (3:3:4, v/v). Two irrigation frequencies were applied during the two dry periods, i.e. every 5 days (normal) and 9 days (sparse) in summer 2013 and every 4 days (normal) and 7 days (sparse) in summer 2014, when substrate moisture was 17-20% and 5-9% for normal and sparse, respectively. At the first growth period (2013) plant height was promoted by normal irrigation, while the above ground fresh and dry weight in October 2013 was promoted both by normal irrigation and soil amended substrate. At the end of the second growth period (2014), dry weight of the above ground part of the plant was higher under normal irrigation, while plant height was not affected by any of the main factors. No evidence of damage to the plant photosynthetic apparatus was recorded in any of the treatments, while stomatal resistance (Rleaf) was increased in plants under sparse irrigation indicating water limitation. Plants grew well and looked similar in all treatments. Thus A. halimus is suitable for use on extensive green roofs in areas with semi-arid Mediterranean climate, with soilless (light weight) substrate and sparse irrigation.