Study On Stress Resistance Of Two Species Of Machilus Nees

Machilus pomifera and Machilus cicatricosa are all Lauraceae evergreen trees,born in low-altitude mountain broad-leaved forests,endemic to Hainan.It is not only an excellent garden tree species,but also has potential value in forestry production and life production.However,in Guangdong area,these two species are not widely promoted and applied.And the growth indexes,physiological and biochemical indexes of Machilus pomifera and Machilus cicatricosa under different stress conditions were studied.The final purpose is that find the best suitable habitat for the growth of these two plants,which could provide reference for garden application and tree species selection.The main experiment results are as follows:(1)The study of the physiological and biochemical indexes of the two species of Machilus in shading stress were shown that the leaf weight of the leaves was decreasing with the light gradually reduced,and Machilus pomifera seedling height growth,stem growth and biomass were the highest under 70% light treatment,Machilus cicatricosa seedling height growth,stem growth and biomass were the highest under 100% light treatment.Chlorophyll a,chlorophyll b and total chlorophyll content of Machilus pomifera showed up-down-up trend,and chlorophyll content of Machilus cicatricosa were increasing with the decreasing of light intensity.The experiment results were analyzed by variance analysis and principal component analysis,results showed that the seedling height growth rate and biomass of these two kinds of Machilus were the main stress performance indicators test.Machilus pomifera in 70% light grows the optimal time section,and Machilus cicatricosa are more suitable for growing in full sunlight environment.(2)The study of the physiological and biochemical indexes of the two species of Machilusin drought stress were showed that with the increase of days RWC decreased gradually,the chlorophyll a,chlorophyll b and total chlorophyll content and SO D activity of the two plants were increasing after the mild drought,the content of proline was increasing;The content of MDA in Machiluspomifera increased after the mild drought.The content of MDA in Machilus cicatricosa increased with drought days showed a steady growth trend,and the increase was smaller.The test results by comprehensive analysis of variance analysis and principal co mponents showed that Machiluspomifera could still keep a high metabolism under mild drought stress,and when Machilus cicatricosaunder severe drought stress also can improve the chlorophyll content to maintain photosynthesis.(3)The study of the physiological and biochemical indexes of the two species of Machilusin low temperature showed that: With the decreasing temperature and prolonging the time of stress,the RWC of Machiluspomifera and Machilus cicatricosawere decreasing slowly,and the SOD activity firstly increased and then decreased,the content of MDA increased;The content of soluble protein and proline with Machiluspomiferat were increasing firstly and then decreasing.The content of soluble protein and the proline with Machilus cicatricosawere generally increasing slowly as the temperature decreases.Based on the analysis of variance and principal component analysis results revealed that the two species of Machilus had a good cold tolerance,when Machiluspomiferaand Machilus cicatricosawere treated at 0? for 24 h and 72 h,still can improve osmoregulation adjustment substances to resist the damage caused by the low temperature.