Irrigation of 'Green walls' is necessary to avoid drought stress of grass vegetation (Phleum pratense L.)

In summer 2017, many weeks with humid weather conditions, but also a pronounced heat period were registered. During this period, considerable physiological responses were observed and respective recovery after subsequent days of heavy precipitation. Phleum pratense showed reductions in stomatal conductance (−148.6 ± 118.8 mmolm−2 s−1), relative water content (−9.3 ± 10.1%) and midday leaf water potential (−0.3 ± 0.5 MPa) on the test plot during heat days. Upon precipitation, differences in water relations between plots ceased within few days. Results indicate that integrated irrigation systems are a necessary component of living wall systems.