Study On Summer Dormancy Of Three Cool-season Turfgrass In Subtropical Area

Three widely applied cool-season turf grasses-Festuca arundinacea Schreb.,Poa pretensis L.and Agrostis stolonifera L.from home and abroad were studied in this experiment,whose natural summer dormant characters were studied from appearances,growth,Physiological and Biochemical responses under sub-tropic climate.The main results as following:1.4 Agrostis stolonifera L.lawns GA2,GAck,GA5 and GA4 entered dormancy at the first ten-days of August,the middle ten-days of August and the last ten-days of August respectively after the high temperature(include the average air temperature and the soil(5-10cm) temperature) above 30℃lasting 38d,38d,48d and 58d.When the high temperature descend to about 28℃, they released dormancy at the first ten-days of September,the middle ten-days of September and the last ten-days of September respectively after their dormancy lasting 41d,31d,31d and 21d. Poa pretensis L.lawns(P07 and Pck) entered dormancy at the last ten-days of July and the first ten-days of August respectively when the high temperature above 30℃lasted 27d and 38d.P07,Pck released dormancy at the middle ten-days of October and the first ten-days of September respectively after dormancy lasting 20d and 82d,when the temperature fell to 28.4℃and 24.5℃respectively.Another 2 Poa pretensis L.lawns(P03,P06) and 4 Festuca arundinacea Schreb. lawns(98-1,98-2,98-5 and Fck) didn't enter dormancy.2.The growth rate of 4 Agrostis stolonifera L.lawns was about 4.59mm/d before dormancy, and descended to about 0.24mm/d in dormancy period,and ascended to about 1.67mm/d after releasing dormancy.The growth rate of dormant Poa pretensis L.lawns(P07,Pck) was about 3.56mm/d before dormancy,and descended to about 0.31mm/d in dormancy,and ascended to 2.12mm/d after dormancy.The ANOVA analysis indicated that there were a significant difference among the growth rate before dormancy,in dormancy and after dormancy(P＜0.05).In over-summer period,the growth rate of non-dormant lawns P03 and P06 was about 2.6mm/d,and the 4 Festuca arundinacea Schreb.lawns' was between 5.00mm/d to 7.52mm/d.3.The average aboveground biomass of 4 Agrostis stolonifera L.lawns descended quickly in dormancy,only about 36.1%of those before dormancy,ascended to 46.8%than those after dormancy.Root biomass showed stabilization before dormancy,in dormancy and after dormancy, which was about 19.9g/m²;The aboveground biomass,Root biomass and rhizome biomass of dormant Poa pretensis L.lawns(P07,Pck) descended in dormancy,and were 54.4%,50.8%, 50.6%,71.8%,68.9%and 86.5%respectively,and continued to descend after dormancy;The aboveground biomass,root biomass and rhizome biomass of non-dormant Poa pretensis L.lawns(P03,P06) descended in over-summer period,but showed stabilization relatively;The aboveground biomass and root biomass of Festuca arundinacea Schreb.lawns(98-1,98-2,98-5 and Fck) kept invariableness and ascended a little,and descended with different extent after summer.4.The average scores of turf quality of Agrostis stolonifera L.lawns was about 6.1 before dormancy,and descended to about 2.4 in dormancy,and ascended to 3.7 respectively after dormancy;The average scores of dormant Poa pratensis L.lawns(P07 and Pck) was about 5.3 before dormancy,and descended to 3.8,4.6 respectively in dormancy,and Pck's ascended to 4.8 after dormancy.Both of non-dormant Poa pratensis L.lawns(P03 and P06) 'score was 5.0 in over-summer period,and P03's descended to 4.2 and P06's ascended to 5.3 after summer;turf quality of the 4 Festuca arundinacea Schreb.lawns had high scores in over-summer period,which the average score was 5.73.5.There was a high significant difference for the water content of dormant lawns among before dormancy,in dormancy and after dormancy(P＜0.01),the water content of leaf of the dormant lawns was the lowest in dormancy period,which was between 60.41%to 64.70%.The chlorophyll content of 4 Agrostis stolonifera L.lawns descended in August,the chlorophyll content of 4 Poa pratensis L.lawns descended form July to September,but the chlorophyll content of 4 Festuca arundinacea Schreb.lawns showed stability,which were between 1.26mg/g to 1.31mg/g.The carbohydrate content of dormant lawns descended obviously when they entered dormancy,but the non-dormant lawns' ascended in July and August when the dormant be in dormancy instead.Soluble Protein content of the materials descended in summer,but the content ranged in a little scope which was 0.1-0.15mg/g,and ascended gradually after summer.The praline content of all materials ascended in July and August when the temperature was the highest in summer,and descended after summer.6.From the middle ten-days of July to the middle ten-days of August when the air average temperature was 31.2℃,there was a high significant difference in net photosynthetic rate of different materials(F=5.887,P＜0.01).The net photosynthetic rate of 4 Festuca arundinacea Schreb.lawns was the lowest at the middle ten-days of August which was between 4.85μmol·m^-2·s^-1 to 7.65μmol·m^-2·s^-1;The net photosynthetic rate of Poa pratensis L.lawns(P03 and Pck) was the highest at the middle ten-days of August,which was 15.23μmol·m^-2.s^-1 and 18.27μmol·m^-2.s^-1 respectively,P06's showed stability which was about 10.99μmol·m^-2·s^-1,P07's descended from 16.07μmol·m^-2·s^-1 at the middle ten-days of July to 9.66μmol·m^-2·s^-1 at the middle ten-days of September;the net photosynthetic rate of Agrostis stolonifera L.lawns(GA2,GA4 and GA5) was the lowest at the middle ten-days of August which were 13.12μmol·m^-2·s^-1,10.27μmol·m^-2·s^-1 and 11.88μmol·m^-2·s^-1,GAck's was the highest at the middle ten-days of August which was 16.09μmol·m^-2·s^-1.7.From the middle ten-days of July to the middle ten-days of August,there was a high significant difference in transpiration rate of different materials(F=10.815,P＜0.01).The transpiration rate of 4 Festuca arundinacea Schreb.lawns was the lowest at the middle ten-days of August which was between 1.69mmolH₂O·m^-2·s^-1 to 3.45mmolH₂O·m^-2·s^-1;The transpiration rate of 4 Poa pratensis L.lawns was the highest at the middle ten-days of July,which was between 5.83mmolH₂O·m^-2·s^-1 to 9.90mmolH₂O·m^-2·s^-1;The transpiration rate of Agrostis stolonifera L. lawns(GA2,GA4 and GA5) was the lowest at the middle ten-days of August which was between 8.27mmolH₂O·m^-2·s^-1 to 13.09mmolH₂O·m^-2·s^-1,GAck's was the highest at the middle of August, which was 8.21mmolH₂O·m^-2·s^-1.