Studies On Seed Germination Characteristics And Heat Resistance Of Several Wild Rhododendron L.

The Rhododendron has a broad application prospects,and it is a world-renowned garden flowers.Its seeds are small,resistant to storage and require high ecological environment.Introduction and domestication of Rhododendron is very difficult,and the seedling technology is not mature enough,so there is a single species of Rhododendron available in the construction of modern urban gardens in China.Therefore,the study on the germination characteristics of Rhododendron seeds and the heat tolerance of seedlings is of great significance to the screening and breeding of heat-resistant Rhododendron cultivars and the full utilization of rhododendron flower resources in China.This experiment mainly includes two parts:(1)In this study,Rhododendron discolor,Rhododendron oreodoxa,Rhododendron pingianum,Rhododendron ririei and Rhododendron pachytrichum were used as experimental materials to study the effects of different storage temperature,storage time,gibberellin concentration and culture temperature on the germination of 5 wild Rhododendron seeds.It was found that all the seeds of 5 species of Rhododendron had post ripening stage.The germination rate of Rhododendron discolor,Rhododendron pingianum and Rhododendron pachytrichum was higher after 6 months storage,and the seed vigor of Rhododendron oreodoxa and Rhododendron pachytrichum chinensis was higher than that of Rhododendron chinensis when stored for 3 months.In general,cryopreservation is better for keeping seeds alive.The germination rate of 5 kinds of Rhododendron seeds stored at 4 deg c and-20 deg c was higher than that of seeds stored at normal temperature.The germination rate of Rhododendron seeds could be improved by soaking gibberellin solution with a certain concentration.When the concentration of gibberellin is not suitable,the germination rate of Rhododendron seeds may be reduced.20 degrees Celsius is probably the best temperature for the seeds of Rhododendron discolor and Rhododendron pingianum.15 deg c is better for the cultivation of Rhododendron oreodoxa seeds and Rhododendron pachytrichum seeds.15 deg c and 2 deg c are suitable temperature for germination of Rhododendron pachytrichum.(2)With the seedlings of Rhododendron discolor,Rhododendron oreodoxa,Rhododendron pingianum and Rhododendron ririei as experimental materials,the effects of high temperature on the physiological characteristics of Rhododendron were studied.The results showed that the chlorophyll content was not necessarily related to the heat resistance of Rhododendron.The activity of SOD and CAT of Rhododendron rose first and then decreased with the increase of stress temperature.The POD activity of Rhododendron discolor and Rhododendron pingianum first decreased with the increase of temperature,and then increased.The POD activity of Rhododendron ririei increased with the increase of temperature while the POD activity of Rhododendron oreodoxa increased first and then decreased.The Rhododendron with higher heat resistance also showed greater changes in protective enzyme activity.Too high temperature will lead to the increase of membrane lipid peroxidation and malondialdehyde content,and it will also inhibit the activity of protective enzymes.In osmotic regulatory substances,both proline and soluble sugar reduce the harm caused by high temperature by accumulating their own content.But for different species of Rhododendron,the soluble sugar content has different changes.