Study On Allelopathy In Continuous Cropping Obstacle Of Panax Ginseng

Ginseng continuous cropping obstacle problem has become an important factor which restricts industrialization of ginseng.Many studies show allelopathy is one of the prime reasons which lead to continuous cropping obstacle of ginseng, therefore, the study core was screening of allelochemicals and its mechanism for preliminary study the effects of ginseng allelochemicals on its continuous cropping obstacle,and it could provide highly important theory for resolving continuous cropping obstacle .the main research contents as follows:1 The study on active constituent screening of extracts from cultivation ginseng soil and its effects of allelopathyThe study applied two methods that used different chemical reagents to extract aquatic extracts from cultivation ginseng soil and directly used different chemical reagents to extract cultivation ginseng soil, and each constituent was done determination of activity with ginseng seeds, and then we researched the effects of higher activity constituents on ginseng seedling.The results showed that extracts from cultivation ginseng soil had effects on radicle growth of ginseng seeds in various degrees,and the allelopathic effects were strengthened with concentration increasing.Both aquatic extracts ethyl acetate phase and ethyl acetate extracts from cultivation ginseng soil manifested stronger inhibition effects,and used them whose concentration were about 50% inhibition effects to culture ginseng seedling .The results indicated both constituents could promote root cell membrane lipid peroxidation and increase membrane permeability, and reduced significantly root activity of ginseng seedling.2 The study on the effects of allelochemical constituent on ginseng root callusGinseng root callus were cultured with allelochemicals.The results showed the inhibition effects were strengthened with concentration increasing.Ginseng allelochemicals could increased remarkably MDA content of ginseng root callus and decreased DNA content,and DNA content of callus between treatment and control groups were significantly different (p<0.01)at the 24th hours after cultivation. We could know from ginseng root callus anatomical structure observation that randomness of cell wall increased and cell nuclear gradually disintegrated and disappeared with prolongation of culture time, and then cell division and growth was inhibited.3 The study on the effects of allelochemical constituent on ginseng seedling root endogenous hormonesWe studied the effects of ginseng allelochemicals on its seedling root endogenous hormones, and used them whose concentration were about 50% inhibition effects to culture ginseng seedling, and sampled at the 12th hours, 24th hours, 48th hours and 96th hours respectively and determined the content of seedling root endogenous hormones (ZT, IAA, GA3 and ABA) by HPLC.The results indicated the effects of ginseng allelochemicals on seedling root endogenous hormones were remarkable,and they significantly reduced the content of endogenous hormones (ZT, IAA and GA3) which were favorable to plant growth, however, they increased the content of ABA which inhibited plant growth and promoted senescence,and then metabolism regulation system was unbalanced and the growth and development of ginseng seedling were influenced.4 The study on the effects of ginseng allelochemicals on anatomical structure of ginseng seedling root tipGinseng allelochemicals could lead to its seedling root cell membrane lipid peroxidation and hormone disequilibrium, and they also could decrease root activity of seedling.They must induce cell morphological structural change due to the effects of allelochemicals on physiological and biochemical aspects of seedling. We used allelochemicals to culture ginseng seedling and sampled at the 96th hours, and made paraffin section with root tip of seedling.The results showed that the treatment seedling cells of several functional regions took place obvious changes in size and arrangement.The seedling root tip became coarse obviously and intercellular space increased, a part of epidermal cells dropped off and the cells of apical meristem and root cap became unordered. The allelopathic effects were strengthened with culture concentration increasing, and some cell walls of apical meristem became abnormal morphology and even fractured in treatment groups with culture concentration of 40g/ml, and the cells of pericycle were also expansive obviously.