| The azalea is one of the famous woody ornamental flowers in the world, belong to Ericaceae Rhododendron plants, which is a sort of beautiful plants with colorful flowers and strong ecological adaptability. China is extremely riched in wild Rhododendron resources, and its Hengduan Mountains region is the modern distribution center and multicenter of Rhododendron. However, it is difficult to carry out the revestigation work in this region which has vast territory and the geomorphology mainly with alpine and gorge. Plus years of deforestation, road construction, tourism development and other economic projects, at the same time, with the lack of effective protection or management, the resources in the area were damaged seriously. In this paper, it takes 4 years for the wild field investigation. Combined with the relevant researches, the athour studied the wild resources distribution particularly and analyzed the characteristics of their distribution and evolution. And then we screened 12 species, with low altitude acclimatization potential, to two altitude levels acclimatization experiment, in order to providing some reference for the conservation and landscape application of the Rhododendron plants.The main results were as follows:1. Investigated the distribution area of Rhododendron which were basically covered the whole generalized Hengduan Cordillera. And about 30 mainly locations were surveyed, totally have 5 Rhododendron subgenus,6 groups,35 subgroups,157 species (including varieties).2. West of Hengduan Mountains-at the southeast of Tibetarea and Himalayas-were highest center of vertical distribution and the narrow geographical distribution of transverse, with strong differentiation of groups in Rhododendron. In the middle of three parallel rivers area-at the western and northwest Yunnan-were the transition region of Southeast Tibet region and the West Sichuan area, riched of Rhododendron species. In the eastern edge of Qinghai Tibet Plateau in the west of Sichuan, there were more primitive taxa in Rhododendron relatively, represented by subsection fortunea, with the lowest vertical distribution center and widest transverse distribution, the area of the Rhododendron were mainly evoluted and developed to the southeast lower altitude region of China.3. Through the study of the geographical distribution pattern, it showed that Subgenus Hymenanthes were relatively the lower vertical distribution, and its evolution trend were suitable for the hot and humid environment in low altitude area. However, subgenus Rhododendron have the higher vertical distribution, while the evolution trend were adapted to cold, drought, windy environment of high altitude.4. From 157 species of Rhododendron, we choosed 12 species of Rhododendron using the comprehensive evaluation method, with a strong potential in low altitude acclimatization of R. fortunei, R. irroratum, R. delavayi, R. auriculatum, R. hunnewellianum, R. argyrophyllum, R.stamineum, R. decorum, R. hemsleyanum, R. discolor, R. liliiflorum, R. argyrophyllum subsp. omeiense, respectively.5. The research about low elevation domesticated of 12 Rhododendron species, showed that:at the altitude of 1750m domestication region, the total adapted rate was 79.17%, while unadapted rate was 2.92%, but in the 750m altitude the adapted rate was reduced to 60%, and the unadapted rate was up to 16.8%. However, the adaptability of R. irroratum, R. fortune and R. delavayi in 750 m altitude acclimatization was significantly higher than in the elevation 1750m domestication, and R. auriculatum and R. hunnewellianum also can be normally growth at altitude of 750m area. Wild seeds of these 5 species of Rhododendron have highly breeding seedling rate and abundant field resources, which had very high value and development prospects of exploitation and utilization. |
PDF Full Text Request