Study On The Response Of 6 Species Of Green Roof Crassulaceae Plants To Drought Stress

Urban areas can benefit from green roofs as they help to reduce the negative impact of air pollution,counteract the urban heat island effect,and expand the urban green space.However,the current selection of roof greening plants is limited.To enhance the ecological benefits of green roofs,it is important to study the response of different plant species to drought stress and their drought resistance.This will enable the identification of more plant species that can be used for green roofs and improve the overall effectiveness of this approach.In this study,6 species of Crassulaceae(Kalanchoe blossfeldiana,Sedum lineare,Hylotelephium erythrostictum, Phedimus aizoon,Rhodiola rosea and Sedum sarmentosum)were selected and planted on the stainless-steel planting rack(60×60×20 cm)on the roof with a substrate thickness of 15 cm,perlite:vermiculite:peat soil=1:1:1.In this experiment,six groups of plants were watered every two days with 10L each time for a month before being subjected to drought treatment.The indexes of MDA,CAT,POD,SOD,Chl,RuBiSco,NADP-ME,PEPC,and other factors were determined on the 0,10,20,30,and 40d after drought treatment.The growth conditions were recorded through photography,and the changes in carbon content and specific leaf area were measured during normal growth time.Each treatment was repeated three times for biological accuracy.The results showed that:1.During the experiment,six species of Crassulaceae plants were grown on the roof and showed good growth within 0-20 days.By day 30,they had wilted to varying degrees but still maintained their basic ornamental and ecological value.However,after 40 days of drought treatment,all the plants lost their ornamental value.2.The plants were able to survive under the roof condition,with Sedum lineare and Phedimus aizoon showing the best performance throughout the growth period.In terms of subordinate function during drought stress(0-40d),the order was:Sedum lineare>Phedimus aizoon>Hylotelephium erythrostictum>Rhodiola rosea>Kalanchoe blossfeldiana>Sedum sarmentosum.These two species were able to grow normally in extensive roof greening, Kalanchoe blossfeldiana and Sedum sarmentosum have performed poorly in green roofs and require proper management,including frequent watering.It is suggested that they are not suitable for extensive green roofs.3.During drought stress,the content and activity of antioxidant enzymes in six Crassulaceae species changed on the 10th day and then increased,resulting in better growth compared to the 0th day.Therefore,a certain degree of drought stress is beneficial for the growth of these species.To balance the ornamental effect and ecological benefit of green roofs,it is recommended to irrigate within a frequency of 10-30 days.4.The study found that drought stress had a similar effect on the activity of RuBiSco, NADP,and PEPC enzymes in six Crassulaceae species.Additionally,the change trend of these three photosynthetic enzymes was consistent across all species.5.During drought stress of 0-40 days,the specific leaf area(SLA)of Kalanchoe blossfeldiana,Sedum lineare and Rhodiola rosea decreased.Rhodiola rosea showed the greatest decrease,by 76.42cm~2/g.On the other hand,the SLA of Hylotelephium erythrostictum,Phedimus aizoon and Sedum sarmentosum increased during this period.Among them,Hylotelephium erythrostictum exhibited the highest increase,by 43.53cm~2/g.6.During drought stress 40 days of growth,the carbon content of six species of Sedum lineare increased by 0.90 g/kg,while Sedum sarmentosum showed a decrease of 23.52g/kg.The order of carbon content change is:Sedum lineare>Kalanchoe blossfeldiana>Rhodiola rosea>Phedimus aizoon>Hylotelephium erythrostictum>Sedum sarmentosum.Roof greening is an essential method for enhancing the urban environment and increasing the potential for carbon sequestration.With the continuous progress of scientific research and the improvement of technical theories,along with the growing awareness of building energy conservation and environmental protection among residents,the benefits of green roofs have become more evident.Consequently,green roofs is expected to become a crucial aspect of urbanization in China.This study is aimed at promoting the development of green roofs and providing a foundation for the sustainable development of cities.