Establishment ofdroughttolerantvegetationisessentialfor
the sustainabilityofextensivegreenroofswhenirrigationisnot
installed. Thisstudyexploredtheimpactsofwateringregimes
on droughttolerancepotentialofgreenroofplantsbyexamin-
ing morphologicalandphysiologicaldataofroots.Itwasfound
that deficitwateringattheearlyplantingstagetendedtoinduce
thinner rootsizeandhigherroot:shootratiosin S. lineare. These
changes inroottraitswerelikelytopositivelyaffectrootactivity
and droughttoleranceofplantsunderdroughtstressinexten-
sive greenroofsystems.Althoughfrequentwateringtendedto
produce biggerplantbiomassandfrondentvegetation,itmight
also leadtobiggerrootsizeandlowerroot:shootratios,which
appeared toresultinlowerrootactivity,higherrootmortality
and poorerdroughttoleranceperformanceunderseveredrought
stress onarooftop.Anappropriatedeficitwateringregimeatthe
early plantingstagemaycontributetobetterdroughttolerance
of greenroofvegetation.Fromapracticalviewpoint,whatone
is reallydoingisacclimatingplantstodroughtconditions,but
the irrigationfrequencyshouldbecurtailedslowlyandnotallat
once.