In Vitro Culture Of Solidago Canadensis L. And The Effect Of Glyphosate On Its Physiological And Biochemical Indices

Solidago canadensis L.,Asteraceae,is a long-lived perennial herbaceous species native to North America.It is an aggressive invader of abandoned fields,river banks,and reafforestations(Capek,1971;Voser-Huber,1992),and achieves a large range within a short time after their introduction because of its great reproductive capacity(both seed production and clonal growth) and high variation(Dong mei,2006).As an invasive specie,S.canadensis poses a serious threat to the ecosystems and the biodiversity,and causes considerable economic loss to the regions they invade.Physical control is not effective but human and money cost.Burning also increases the environmental pollution. Chemical controls of S.canadensis are still in need of an effective method.Further study should be done to guarantee for feasibility of the biological controls of this weed.This study was to determine how the glyphosate influence this plant by evaluating the effect of glyphosate damage on physiological and biochemical indexes of S.canadensis which were obtained via the tissue culture systerm.Important findings:1) The optimum culture medium for leaf section producing callus was MS+1.0 BA+1.0 NAA.And the optimum culture medium for stem section was MS+1.0 BA+1.0 NAA.The optimum successive transfer medium for callus was MS+0.5 BA+1.5 NAA.The optimum differential culture medium was MS+1.0 BA+0.5 NAA.The optimum culture medium for stem producing axillary shoots was MS+0.05 NAA+1.0 BA,while for rhizome was MS+0.5 NAA.The MS without hormone was the best medium for root induction.The percentage survival of plantlets was nearly 97%after transfer to soil.2) Leaf segments showed higher callus formation capacity,regarding the callus fresh weight and callus browning frequencies.PGR requirements for callus induction vary depending on the source of the explant.The optimal concentrations of PGRs for callus induction varied between the two explant types. 3) The rhizome could produce axillary shoots when cultured in the hormone-free medium while the stem couldn't.The rhizome also could produce axillary shoots when cultured in the MS with NAA more than 0.1mg/L while 0.1 mg/L NAA will inhibit the axillary shoots induced from stem.And the induction of axillary shoots from rhizome increased with the concentration of NAA.It showed the rhizome of S. canadensis had a strong adaptive capacity.4) The plants obtained by this plant regeneration system showed no morphological malformations compared with the donor plant.Chl fluorescence data also showed no significant differences of photosynthetic characteristics between the plantlets obtained by this plant regeneration system and the wild plantlets.These phenomenon suggested this plant regeneration system is efficient to produce high yielding and high quality plants of S.canadensis and it could be used as materials for further study.5) All of the aboveground parts of S.canadensis died 18d after A,B,C,and D times liquid glyphosate processing.And the bud rates of the three concentrations are 100%, 89%,71%and 2%respectively.D times liquid glyphosate will be effective for control of this weed.6) Glyphosate resulted in significant influence of the physiological indexes in the plantlets of S.canadensis.The fresh/dry weight value decreased with increased concentration of glyphosate and increased processing period.It showed the contents of dry matter were significantly reduced because of the glyphosate.7) The contents of chl a and chl b decreased significantly with the concentration and timing of treatment increased.The value of chl a/b increased at the first period after glyphosate treatment and decreased significantly with the increased processing period.8) The contents of the reducing sugar in leaf and rhizome segments were increased significantly with the concentration of glyphosate and increased processing period.9) The glyphosate reduced the light saturation point(LSP),net photosynthetic rate(Pn) and transpiration rate(E) of leaves of Solidago Canadensis L.and increased the respiration rate,light compensation rate(LCR),and intercellular CO₂ concentration (C_i) of leaves of S.canadensis.Quantum yield(yield) declined after damage by glyphosate and similar trends also were observed for apparent electron transport rate (ETR),photochemical quenching(qP),and nonphotochemical quenching(NPQ) response to photon flux density(PPFD).These results showed that with increased concentration of glyphosate and increased processing period,PSII reaction centers gradually closed resulting in a decline of electron transport rate and quantum yield, and even damage of thylakoid membrane integrity.At the same time,the capacity to utilize high light intensity was weakened.The most obvious variation we can observe was in the third period(18d after treatment).The values of net photosynthetic rate (Pn),transpiration rate(E),quantum yield(yield),apparent electron transport rate (ETR),photochemical quenching(qP),and nonphotochemical quenching(NPQ) of S. canadensis were lowest,and all of them almost tends to naught as photon flux density (PPFD) increased.The integrity of thylakoid membrane was severely damaged,the PSII reaction centers almost completely closed and electron transport was disappeared.10) The different concentrations of glyphosate and the processing periods had no significant influence on the chemical substances and structures of S.canadensis.But the contents of chemical substances in leaf,stem and rhizome of S.canadensis were different with the different concentrations of glyphosate and the processing periods. As the results of thermogravimetric analysis shows that cellulose,hemicellulose and lignin degraded and the content of reducing sugar increased with the increased concentrations of glyphosate and increased processing periods.At the first period after glyphosate B and C times liquid processing,the thermal properties of aboveground parts of S.canadensis transfered to the underground parts for storing it in the underground parts of plantlets and pulling through the adverse conditions. Thermal properties of rhizome treated with glyphosate D times liquid decreased significantly at the first period.And its values decreased to be the lowest ones at the third periods,glyphosate D times liquid glyphosate will be the effective to kill the cell of rhizome and the whole plants and degraded its hemicellulose and lignin.11) The morphological and anatomical characteristics showed that glyphosate can injure the leaf epidermis and the polysacchardes of leaf,stem and rhizome.Significant differences in cell shape and amount of spongy tissue were observed between healthy and glyphosate-damaged leaves.The degradation of polysacchardes in leaves was increased with the timing of treatment.In stem and rhizome segments,epidermis was crimpled and polysacchardes contents were decreased with timing of treatment increased.In this study,we developed a tissue culture system for callus induction and plantlet regeneration of S.canadensis.Chlorophyll fluorescence was conducted to examine the quality of the plantlets of S.Canadensis via our tissue culture system.The physiological and biochemical indices of this plant after treated with glyphosate were determined by fresh/dry weight,chl contents,reducing sugar contents,photosynthetic capability,chl fluorescence,thermogravimetric analysis and morphological and anatomical characteristics.It could be obtained that D times liquid glyphosate will be effective for control of this weed.