Effects Of Different Levels Of Root Rot Pathogenic Fungi Infection On Angelica Sinensis Root Anatomical Structures And Physiological Indices

Angelica sinensis is the perennial herb with very high medicinal value,belong toumbrelliferae, is one of the precious traditional Chinese medicinal materials.In recentyears, with the demand for Angelica sinensis increasing, planting area being expandedconstantly, rotation period shortened,cropping and alternate cropping area have beenincreasing,resulting in Angelica sinensis root rot became more and more serious yearby year. Angelica sinensis root rot is a soil-borne diseases mainly caused by Fusarium.Currently, the research on Angelica sinensis root rot is rarely and focused on theseparation and identification of pathogens,antimicrobial substance screening,etc.While morphological features of the infected root, the mechanisms of pathogenicand the changes in the body’s defense enzymes activity after infection have not beenreported.In this study, health and susceptible Angelica sinensis plants were collected fromWeiyuan in Dingxi, Gansu Province. First,the roots of Angelica sinensis were studiedthrough freehand slicing,paraffin sections and ultrathin sectioning technique,observedunder an optical microscope and electron microscope,in ordering to clear theanatomical structure and the way of pathogen invasion. Second,three pathogenic fungiisolated from infected Angelica sinensis were tiebacked with different inoculumconcentration, the activity of PAL and PPO in leaves were measured every five days afterinoculation. From the experimental results we can obtain the following conclusions:Angelica sinensis has a typical dicotyledonous plants root structure,the secondarystructure of Angelica sinensis composed of two parts,periderm and cylinders,peridermconsists of three parts, from outside to inside were cork, cork cambium andphelloderm.The secondary phloem consisted of sieve cells, phloem parenehymas, phloemfibers and secretory canal, which occupied more than60％of the diameter of root andthe parenchymas cells are abundant in starch grain and other inclusions,thedistribution of starch granules along the phloem rays radiating.The secondary xylemconsisted of three parts,vessels, xylary radials and parenchyma cells,which hadseveral ridges of pmtoxylem, xylary radial and the phloem ray were conspicuous. Fungal invasion of cells in two forms, mycelium and spores, they infected thephloem parenchymas through cork, cork cambium, and arld phelIoderm, and thenformed pelotons, and expand their area of infestation. They even invaded the xylemand destroyed vessels. Further study also found that starch grains is the main place forfungal colonization, pathogenic fungi penetrated or wrapped around them, utilizingnutrients to live and breed.In healthy root starch grains distribution widely, in largequantities and gathered into a group, while in infected root,in small number and smalldistribution range,the more serious the disease, the less starch grains.The result show that after single inoculation and complex inoculation Angelicasinensis root rot pathogenic fungi,the activity of PPO and PAL has been improved,inaddition to individual low concentrations similar to the control. The two enzymeshave shown a decreasing trend after the first rise, infection-inducing activity ofpathogenic bacteria have shown a time course, and began to lag phase, activityincreased slowly, followed rose rapidly, reaching a peak of activity,finally sharpdecline.The trends are not entirely consistent of different strains treatment.Mixedinoculation activity peaked later than the time of occurrence of some singlevaccination.The result also showed that there was correlations between the inoculumconcentration and the PAL activity regardless of the Third strains. For PPO, whethersingle inoculation or complex inoculation, between activity and concentration had nosignificant correlation.