Heat Resistance On Thirteen Wild Bluegrass In Gansu Province

Bluegrass is the main species of cool-season turf grass. Becurse of it’s strongcold resistance, it can growth normally in winter in the southern part of China to makeup the disadvantages of warm-season turfgrass well and lasts the green period of turf.So it is widely planted in our country, especially in the north, central and parts ofsouth in China. But in hot summer, leaves of bluegrass become yellow, the densityand coverage were decreased, the quality of lawn was seriously affected. So, study theheat resistance of bluegrass become particularly important. Today, heat resistanceresearch was focused on cultivated varieties, but the result was not perfect. China hasrich resources of wild bluegrass, it has a great variety and strong resistance. The heatresistance research on wild bluegrass has a great significance on breeding andevergreen lawn planting.In this paper, thirteen kinds of wild bluegrass was tested, they were all collectedin Gansu province, Baron was used as CK. In the seeding period, fourteen bluegrasswas put into light incubator to accept heat stress, then test the heat resistance. Theresults were as follows:1. With temperature increasing, water rate of leaves, growth rate and recoveryrate were decreased. Under40/45℃, water rate of every Poa pratensis L. was higherthan others’obviously, growth of all materials was almost stoped.2. As temperature increased, relative membrane permeability added. Content ofpraline, soluble sugar and sucrose also increased, content of fructose and glucoseincreased first and decreased when the temperature was higher than35/40℃, but thecontent of soluble protein was declined.3. The content of H₂O₂,·OH, MDA and the production rate of O₂.-was graduallyaccumulated followed by the increasing of stress temperature. The activity of SOD,CAT and APX of bluegrass showed an increasing trend below35/40℃, after that, theactivity of SOD,CAT and APX declined greatly. The activity of POD increasedgradually.4. Following the growth of temperature, Fo showed an increasing trend, but Fv/Fm, ETR, ФPSII and qP gradually declined. Under30/35℃， along with theincreasing of stress time, Fo grow gradually, but Fv/Fm, ETR, ФPSII and qP wasdecreased. During recovery period, the chlorophyll fluorescence parameters werepicked up, after four days it still not back to normal levels.5. The comprehensive evaluation of the heat-resistant of fourteen bluegrassshowed the order of heat-resistance: Poa pratensis.（Qinshui）> Poa pratensis.（Xinglongshan）> Baron> Poa pratensis.（Weiyuan）> Poa pratensis.（Sunan）> Poapratensis.（Anding）> Poa pratensis.（Tianzhu）> Poa poophaqorum.（Sunan）> Poaalpigena （Tianzhu）> Poa crymophila.（Tianzhu）> Poa poophaqorum.（Gannan）>Poa sphodylodes.（Weiyuan）> Poa sphodylodes.（Sunan）> Poa annual.（Gannan）.6. Based on the hierarchical cluster analysis, wild bluegrass can be divided intothree groups: Poa pratensis.（Qinshui）, Poa pratensis.（Xinglongshan）, Poa pratensis.（Weiyuan）, Poa pratensis.（Anding）, Poa pratensis.（Sunan）, Poa pratensis.（Tianzhu）and Baron had strong heat-resistance; Poa poophaqorum.（Sunan）, Poa poophaqorum.（Gannan）, Poa alpigena （Tianzhu）, Poa sphodylodes.（Weiyuan） and Poa crymophila.（Tianzhu） had middle heat-resistance; Poa annual.（Gannan） and Poa sphodylodes.（Sunan） had low heat-resistance.7. The results of correlation analysis showed that: between relative membranepermeability, content of MDA and comprehensive evaluation showed a verysignificant negative correlation（P<0.01）. There was a very significant positivecorrelation between comprehensive evaluation and content of free proline and solubleprotein, activity of SOD, water rate and recovery rate（P<0.01）. Between altitude ofthe place where the seeds was collected and comprehensive evaluation showed asignificant negative correlation（P<0.05）. Between annual temperature, highesttemperature of the place where the seeds was collected and comprehensive evaluationshowed a significant positive correlation（P<0.05）. Content of soluble surger，activityof POD and CAT, growth rate had no significant correlation between comprehensiveevaluation（P>0.05）.