Study On Plant Growth Regulating Effects Of Ailanthone

Quassiniods are highly oxidized picrasane-type nortriterpenes unique to the secondary metabolites of Simaroubaceae plants.They have excellent pharmacological and biological activities such as herbicidal,insecticidal,antiparasitic,antimalarial,anti-inflammatory and anti-tumor.Ailanthone is a representative C₂₀ quassiniods isolated and identified from the secondary metabolites of Ailanthus altissima（Mill.）Swingle.It has been widely concerned as a lead compound of biological herbicides due to its efficient herbicidal and allelopathic effects.As a characteristic secondary metabolite of Simaroubaceae plants,the significance of quassiniods on plant growth and life process has not been revealed.In this paper,the dicotyledonous plant Arabidopsis thaliana L.Heynh and the monocotyledonous plant Oryza sativa L.japonica.cv.Nipponbare were used as test plants to study the regulation of Ailanthone on plant growth and development.The following results were obtained:（1）AIL has a regulatory effect on plant growth and development.At high concentrations,AIL can inhibit plant growth and development,mainly manifested as delayed seed germination time,inhibition of plant root elongation,lateral root occurrence and aboveground growth and development;However,low concentration treatment in a specific range can promote or activate plant growth and development,which is manifested by accelerated seed germination,improved seed germination uniformity,and significantly promoted plant root elongation and lateral root occurrence.In addition,it has a very significant effect on the internode elongation of monocotyledonous plant A.thaliana and the development of rosette plant type.（2）Indole acetic acid（IAA）and Gibberellin（GA）could weaken the inhibitory effect of high concentration of AIL on primary root elongation of A.thaliana.By adding various exogenous growth regulators including gibberellin and cytokinin,indole acetic acid,etc.,together with high concentrations of AIL to treat A.thaliana,it was found that exogenous addition of 10 n M IAA or 1000 n M GA treatment can significantly reduce the inhibition of 500 and 1000 n M AIL on root growth and development of A.thaliana.This indicates that the high concentration of AIL may inhibit plant growth and development by affecting endogenous hormone levels.（3）AIL could activate the activities of NADH oxidase,glutamate synthase（GOGAT）and glutamate dehydrogenase（GDH）in rice roots at a certain range of low concentration application,and low concentration AIL treatment could significantly increase the content of NH₃-N and NO₃-N in roots.This indicates that low concentration of AIL may promote the absorption of nitrogen by roots by affecting the nitrogen assimilation process,thereby promoting plant growth and development.（4）The 16 kinds of C₂₀ quassiniods from A.thaliana can promote or activate root growth and development in a specific concentration range.The effects of 16 kinds of C₂₀ quassiniods from A.thaliana on the elongation of primary roots of A.thaliana were determined by 10μM,1μM and 10 n M three different initial concentrations.The results showed that the five kinds of quassiniods,including AIL,showed a very strong inhibitory effect on the primary root elongation of A.thaliana at 10 M concentration,while the concentration decreased to 10 n M showed a promoting or stimulating effect.When the initial concentration was as low as 10 n M,all of the 16 quassiniods substances tested showed a significant effect on promoting or activating the primary root elongation of A.thaliana.This paper is the first to confirm that Ailanthone can promote plant growth and development.It is preliminarily proved that low concentration of Ailanthone can activate GOGAT and GDH activities,promote root absorption of nitrogen,and promote plant growth and development.