Effect of watering regimen on chlorophyll fluorescence and growth of selected green roof plant taxa

Green roofs, or vegetative or living roofs, are an emerging technology in the United States. Because environmental conditions are often more extreme on rooftops, many xerophytic plants, especially Sedum, are ideal for extensive green roofs because they are physiologically and morphologically adapted to withstand drought. A greenhouse experiment was conducted to determine the effect of watering regimens on plant stress as measured by chlorophyll fluorescence (F-v/F-m), biomass accumulation, substrate moisture, and evapotransipiration on succulent plants of Sedum acre L., S. reflexum L., S. kamtschaticum ellacombianum Fisch., and non-Crassulacean acid metabolism (CAM) plants of Schizachyrium scoparium Nash and Coreopsis lanceolata L. Plants were grown at a substrate depth of 7.5 cm. Results indicate even after the 4-month period, Sedum spp. survived and maintained active photosynthetic metabolism to a greater extent than Schizachyrium and Coreopsis. Furthermore, when Sedum was watered after 28 days of drought, chlorophyll fluorescence (F-v/F-m) values recovered to values characteristic of the 2 days between watering (DBW) treatment. In contrast, the non-CAM plants required watering frequency every other day to survive and maintain active growth and development. Regardless of species, the greatest increase in total biomass accumulation and fastest growth occurred under the 2 DBW regimens.