Responses Of Three Species Of Ornamental Grass Seedlings To Drought Stress Physiology And Morphology

Peuuisetum alopecuroides,Festuca glauca ’Freddy’,Stipa tenuissima&’Pony Tails’ all have the characteristics of high ornamental value,strong reproductive ability,wide adaptability,strong stress resistance,simple maintenance and management,and are widely used in landscaping.However,there are few reports on the drought resistance of the three countries at home and abroad.In this study,we used P.alopecuroides,F.glauca ’Freddy’,and S.tenuissima ’Pony Tails’ as research materials.They were subjected to natural soil water loss stress test.The effects of natural drought stress on the growth and morphology of the aerial parts and underground parts of plants,and their effects on physiological characteristics were studied.In order to determine the drought tolerance of three ornamental grasses,to explore their response mechanisms to the physiological and morphological characteristics of drought stress,to provide guidance for the water management of the three ornamental grasses during planting,and also to provide a theoretical basis for their application in gardening.The results of the study are as follows:1.Under drought stress,the leaf length and plant height of the three ornamental grasses showed an upward trend.With the extension of the stress time,the leaf length and plant height increased slowly and always lower than the control group.2.Under drought stress,the relative growth rates of the three ornamental grasses showed a downward trend.With the prolongation of stress time,the relative growth rate of P.alopecuroides sharply decreased from 71.05%to 17.91%,and that of F.glauca ’Freddy,andS.tenuissima ’Pony Tails’ gradually decreased from 69.39%and 83.11%to 31.94%and 37.38%,respectively.As far as the relative growth rate is concerned,F.glauca ’Freddy’ has a stronger ability to fight drought,followed by S.tenuissima ’Tony Tails’ and P.alopecuroides.3.Under drought stress,the total biomass of the three ornamental grasses showed an upward trend.With the prolonged drought treatment time,the plant biomass increased.Stress 24-30d comlpared stress 18-24d,the biomass of P.alopecuroides decreased by 0.423 1g,and that of F.glauca ’Freddy’ decreased by 0.0157g,while that of S.tenuissima ’Pony Tails’ was reduced by 0.0278g.The biomass of stems and leaves of P.alopecuroides and S.tenuissima’Pony Tails’ was significantly affected by drought stress than their root biomass.The biomass of F.glauca ’Freddy’ root was significantly affected by drought stress compared with stem and leaf.The biomass of each organ of P.alopecuroides had the largest decline compared with CK,followed by F.glauca ’Freddy’ and S.tenuissima ’Pony Tails’.4.Under drought stress,the total length of roots,root surface area,root projection area,total root volume,and root average diameter of all three ornamental grasses showed a trend of rising first and then decreasing.Stress 0-12d contributes to the growth of plant roots.After 12 days of stress,the plant roots began to respond to drought stress.Stress 18-30d,the inhibition of plant root growth was enhanced by drought stress,and the inhibition of P.alopecuroides root system was stronger than that of F.glauca ’Freddy’ and S.tenuissima ’Pony Tails’.The root average diameter of P.alopecuroides and F.glauca ’Freddy5 began to decrease after 18 days of stress.And that of S.tenissima ’Pony Tails’began to decreased after 12 days of stress.Stress 18-30d,the root average diameter of P.alopecuroides decreased by 0.1409mm,that of F.glauca ’Freddy’ decreased by 0.0649mm and that of S.tenuissima ’Pony Tails’ decreased by 0.0376mm.The results showed that-this stress period had the greatest inhibitory effect on the root average diameter of P.alopecuroides,followed by F.glauca ’Freddy’,and S.tenuissima’Pony Tails’.5.Under drought stress,the chlorophyll content of the three ornamental grasses showed a downward trend.Under the same treatment,the chlorophyll content of P.alopecuroides had the largest decrease compared with that of CK,and the chlorophyll content of S.tenuissima ’Pony Tails’ was the smallest.With regard to the decrease in chlorophyll content,the drought-resistance of the three ornamental grasses was:S.tenuissima ’Pony Tails’>F.glauca ’Freddy’>P.alopecuroides.6.Under drought stress,the SOD,POD and CAT activities of the three ornamental grasses all increased first and then decreased.At the 18th day of stress,the activities of SOD and CAT of the three species of ornamental grasses reached the maximum,and the activities of POD of the three species of ornamental grasses reached the maximum at the 24th day of stress.Among them,the activities of SOD and POD were dominated by S.tenuissima ’Pony Tails’,followed by F.glauca ’Freddy’,and P.alopecuroides were the least.In CAT activity,F.glauca’Freddy’>P.alopecuroides>S.tenuissima ’Pony Tails’.7.Under drought stress,the soluble protein content of P.alopecuroides rose first and then decreased.F.glauca ’Freddy’ and S.tenuissima ’Pony Tails’ showed a trend of decreasing first and then increasing.S.tenuissima ’Pony Tails’ accumulated most abundant the soluble protein content during the stress period,followed by F.glauca ’Freddy’ and P.alopecuroides.8.Under drought stress,the proline content and MDA content of the three ornamental grasses showed an upward trend.The accumulation of proline content from high to low was in order of F.glauca ’Freddy’,S.tenuissima ’Pony Tails’,P.alopecuroides.The accumulation of MDA content in order from high to low is P.alopecuroides,F.glauca ’Freddy’,and S.tenuissima ’Pony Tails’.