Key Techniques In The Domestication And Cultivation Of Rosa Praelucens Byhouwer In Kunming

Rosa praelucens Byhouwer is endemic to China and is the only one decaploid Rosa species everreported up to data. With its tree-like shape, large and vividly colorful flowers, it is also a veryimportant alpine ornamental plant and germplasm resources for rose breeding which can be greatlyexploited and utilized. However, because of the very low seed germination rate, R. praelucens is oftenpropagated by root sprouting in natural conditions, which makes it susceptible to extinction due toglobal climate change and habitat fragmentation. In this study, the natural distribution andmorphological traits of R. praelucens were investigated for several years. Graft techniques and rootcutting techniques were developed, and the growth of the achieved plantlets was surveyed. Also, thegrowth, morphological traits and photosynthetic characters of R. praelucens under different growingconditions in Kunming and original habitat in Shangrila were compared in order to probe the possibilityof introducing it to and domesticating it in Kunming and to find out the possible key factors. The resultswere the following:1)R. praelucens distributed naturally at the Xiaozhongdian Meadow and Reshuitang Meadow inShangrila county of Northwestern Yunnan, with a longitude of99°43′24″⁹9°52′02″, latitude of27°29′28″²7°41′17″and altitude of3210³282m.3surviving populations were found in LianheVillage, Naisi Village and Heping Village, respectively. The morphological traits among populationswere significantly different and the individuals were rich in morphological diversity. Buds began tosprout at the middle of April and stopped growing at the beginning of November, with a whole growingphase of182-193days and dormant phase of183-184days in Shangrila.2)Survival rate of bud graft and stem graft of R. praelucens was75.78⁹9.56%in different seasonand the plantlets could grow vigorously. The survival rate of stem graft in February was highest. Thesurvival rate and rate of growing into plantlets of bud graft in August and February were also high. Thesurvival rate of root cutting in February was60⁶9.330%, but that of root cutting in summer was only3.92¹5.680%. The plantlets from root cutting grew slowly and weakly.3)Leaves of R. praelucens plants outside in Kunming began to fall at the end of December. Thedormant phase was42⁶5days and the growing phase was as long as300-323days. The shoots grewfast in summer. Because of the long growing phase and long photosynthesis time, plants couldaccumulate more biomass and keep a more vigorous growth, which might be the reason why the newshoots of plants in Kunming were longer and stronger than those in Shangrila. In Kunming, outsideplants flowered and fruited earlier than those in greenhouse. The new shoots of plants in greenhousestarted to grow earlier but could not flower and fruit normally because of summer dormancy caused byhigh temperature in greenhouse.4)R. praelucens plants propagated by graft would begin to flower after3-4years, but the leaves,flowers and hips were all smaller than those in Shangrila. In Kunming, the plants flowered2monthsearlier than those in Shangrila, but the florescence was almost the same long as that in Shangrila and themain ornamental traits kept unchanged. Outside plants introduced to Kunming could survive the wintercoldness and summer hotness without any additional protection and could grow well, flowering andfruiting normally. Also, only common diseases and pests which could be prevent and controlled easily were found to infect and injure the plants. So, R. praelucens were acclimated in natural environment ofKunming and could be introduced to Kunming successfully.5)Compared with plants in Shangrila, Light compensation point （LCP） and CO₂compensationpoint （CCP） of R. praelucens plants in Kunming increased, and light saturation point （LSP） and CO₂saturation point （CSP） slightly decreased, but the changes were slightly. Light-saturated photosyntheticrate (P_max) and maximum carboxylation rate (V_cmax) of the plants in Kunming declined to79.87%and87.51%that of plants in Shangrila, respectively. The stomatal conductance （G_s） declined to43.60%inorder to decreas transpiration rate （Tr） to adapt to low relative humidity in Kunming. Lower content ofchlorophyll a and b in the leaves of plants in Kunming could reduce the absorption of excess lightenergy in Kunming. Furthermore, Photosynthetic nitrogen use efficiency of plants in Kunmingincreased by increasing the partitioning coefficient in Rubisco （P_R）, electron transfer （P_B） andlight-harvest components （PL）. The above results suggested that R. praelucens could be introduced toKunming, but some agricultural measures were necessary to create a better growing environment.6)R. praelucens plants grew well when fertilized with7.5g CO（NH₂）₂、4.541g KH₂PO₃、1.062gK2SO4, per plant month, the N:P:K ratio of which was about7:4:1. Lower N content could not satisfythe growth and too much N could restrain the growth. Lack of N and unsuitable N:P:K ratio both wouldhave very bad effect on the growth of new shoots.The above results showed that R. praelucens plantlets propagated by graft had better resistance andadaptability. Physilogical regulation of its leaves could decrease the negative effect of excess light andhigh temperature on R. praelucens plants in Kunming. It was realizable to introduce it to and cultivate itin Kunming for Ex Situ conservation and domestication if suitable cultivation measures were carriedout.