Physiological Responses Of Rhododendron Annae Mycorrhizal Seedlings Under Drought Stress

The azaleas class mycorrhizal(Ericoid mycorrhizas,ERM), indicate that several root systems of the Ericaceae branch form a special commensal which lives internally.Although China has the most spreadability of Ericaceae, we don’t have enough study report on it, on contraries, other countries have more and profoundly. The Rhododendron annae is an indeciduous and alpine Ericaceae which is mainly distributed in Guizhou and Yunan province of China, and which has a high level ornamental value. As limited by the heredity, it is less anti-arid, even if it is the initial factor to astrict of migration for cultivating. This article will present the experiment of inoculating the Rhododendron anna and the ERM and of cultivating the roots of Rhododendron anna by a simulation test which means to place them in a drought-nature-like circumstance, to get the goal that how the inoculated roots respond to the drought in order to provide the theoretical aid to the migration cultivating, and to increase their survival rate. This article get through diverse standard of moisture and the recover capacity after persistent dryness. In this research,contain the water content, Biomass, root shoot ratio, Osmotic adjustment,tmalonaldehyde, Antioxidant system and the photosynithesis of leaves.Research results are as follow:1.Selected by former researcher who has screened out four bacterial strains(TY02, TY21, TY29, TY35) which are benefit to the Rhododendron anna root to inoculate with the ERM, after 120 days cultivation with normal water, press-stained it with acid fuchsine,there is a obvious difference:(p>0.05),TY35(57.6%)>TY29(51.5%)> TY02(44.6%) > TY21(36.8%)>CK(0), between the infected rate of different inoculated ERM and the appetency of different bacterial strains, it shows that a dependency of host with different bacterial strains.2.Exercised by comparing inoculated ERM( TY02, TY21, TY29 and TY35) with CK, then cultivated them in the greenhouse by potting them under the soil which isdivided by four sorts of water level: normal(80%-90%), light(65%-75%),medium(50%-60%) and few(35%-45%), then detected their shapes and physical indexes. And results shows:(1) Under the drought, the height, diameter, physical measures, growth of mycorrhizal seedlings and above and under of roots of Rhododendron anna are all evidently increased by inoculated roots ERM, especially under the water level of light with inoculated TY35.(2) Under the drought, mycorrhizal seedlings of Rhododendron ann are so able to strengthen their drought resisting ability by increasing the osmosis substances(such as dissoluble sugar, dissoluble albumen and dissociative proline) and water content of leaves, to strengthen the activity of protective enzyme(that is SOD,POD, CAT), to decrease the MDA that to protect the botany form drought. While with few water level, the MDA content is highly increased, and active oxygen is over produced which beyond the elimination ability of cell membrane, thereby induces abundant accumulation of active oxygen lead to grave degradation of photosynthetic pigments and lipid peroxidation, nevertheless the MDA is still less than CK.Morphologically, with the increasement of dryness, certain of leaves will be frizzy or even sere, especially for CK seedling. Inoculated ERM are capable to remit the drought, particularly when TY29 and TY35 are under water level of light and medium.3.Exercised by comparing the 4 inoculated ERM(TY02, TY21, TY29 and TY35)and CK which were cultivated in the greenhouse by potting under naturally drought condition, to detect the shape of different ERM under drought and after water recover and related physical indexes. And the results are:(1)Under the persistent drought, the height, diameter, physical measures of mycorrhizal seedlings are higher than CK in the same period. As ERM can increase the water content in leaves and decrease the wane of water saturation, so they can increase the ability of water content, then lighten the harm form drought and in the same time mycorrhizal seedlings can adjust osmosis substances to adapt to drought by increasing dissoluble sugar and dissoluble albumen and decreasing the MDA. Thus, after 15 days water recover, the physical measure and osmosis substances of mycorrhizal seedlings recover better than CK,but different inoculated mycorrhizal seedlings has different level of resilience.(2)Under drought, with the increasement of dryness, the balance of free radicals composition and reaction of protective enzyme will be broken, lipid peroxidation will be worse, however the mycorrhizal seedlings MDA content will be still less than CK, but the antioxidant enzyme activity is always higher, so it can reduce the harm from drought. Then after water recover, the quantity of number of mycorrhizal seedlings MDA will be reduced, but the activity of SOD, POD, CAT, NR will be increased, conclusion that to inoculate ERM can not only improve the enzyme to enhance drought resisting ability of Rhododendron anna, but also can strengthen its recover ability after suffering drought for a long time.