In order to explore the ecological reconstruction potential of mycorrhiza-inoculated mulberry plants in rocky desertification areas,simulated water stress environments were created by PEG 6000 at 0,10%,15%,20% and 25% mixed with the substrate.The mulberry saplings inoculated with Gigaspora rosea（F＋） were cultured for 5 months.Then the treated samplings（F＋） and the un-treated samplings（F-） of similar size were potted and subjected to simulated drought treatments.Eight days later,the structure features of the maturation region of the primary roots were examined microscopically in paraffin sections.The investigation showed that the maturation region of the primary root of Morus alba L.consisted of epidermis,cortex and vascular cylinder.Some root hairs grew from the epidermis.The inner-cortex rounded by the Casparian strip was distinct,with xylem and phloem spaced in-between.Under the condition of water stress of 0-10% PEG,the epidermis still existed in F-,and the cells in the cortex were normal.But the epidermis cells died and dropped,and the cells of the cortex were dehydrated and deformed when the PEG concentration was from 10 to 15%.In F＋,epidermis and root hair existed in the 0-20% of PEG.When the concentration of PEG was about 25%,most of the cortex cells were still morphologically normal.The structure of the primary phloem of the stele was affected by water stress in the last period,while the primary xylem was hardly affected by it.It was speculated that the improvement of drought tolerance of F＋ plants was attributed to the fact that inoculation of AM fungi could improve the resistance to water stress by the hyphal net which can absorb more water from the rhizosphere soil and deliver it to the cortex cells by intra-radical mycelium and,as a result,the water needed of plant growth was satisfied,the death or drop of the epidermis was postponed and the cortex cells survived longer.

In order to further explore the ecological reconstruction potential of mulberry(Morus L.) in adverse environment of the southwestern mountainous region,an investigation was conducted on the formation of mycorrhiza by arbuscular mycorrhizal(AM) fungi and root system of mulberry naturally growing at 170 ~175 m altitude of the Three Gorges Reservoir area.Moreover,AM fungi were used to inoculate potted mulberry saplings for evaluation of the effect of mycorrhiza to mulberry sampling growth.The results showed that about 82% of the mulberry root tips were colonized by arbuscular mycorrhizal fungi and developed into mycorrhiza in various degrees.There were hyphae,arbuscules,vesicules,spores and other structures in the mycorrhiza and accessory cells on external hyphae of the mycorrhiza.Mulberry saplings grown in both illuminated incubator and netted chamber were easily colonized by arbuscular mycorrhizal fungi.At 15 d after inoculation,there were hyphae adhered on the root and formed appressoria.The mycorrhizal colonization rate increased with time.The colonization rate of mulberry saplings in illuminated incubator was 40.56%±3.61% at 90 d after inoculation,and that in netted chamber were 46.82% ±4.10% and 50.72% ±5.32% at 70 d and 90 d after ino-culation,respectively.The inoculated mulberry saplings grew significantly better than the control on plant height,taproot length,root tip quantity per plant,total root tip length per plant,number of leaves per plant as well as the length,width and area of the third true leaf.The relative growth rates of root tip quantity per plant,total root tip length per plant and leaf area of the inoculated mulberry were over 100%,which remarkably enhanced the absorptive ability of root system and photosynthetic areas of the aerial part.These research results confirm that mulberry is a typical arbuscular mycorrhizal plant.Mycorrhiza is favorable to the growth of mulberry in extreme adverse environment,and inoculation with AM fungi could obviously promote mulberry vegetative growth.