Responses Of Chemical Defense Substances Of Three Taxus Plants To Light Environment And Kinship Levels Of Neighboring Plants

In recent years,the effects of light signals on plant chemical defense strategies has attracted the attentions of ecologists.Plants may adjust their chemical defense strategies through detecting the proximity of surrounding plants by means of light signals.Taxus plants has been listed as protected endangered species by many countries due to their slow growth rates,weak population regeneration ability and scarce number of existing individuals.As a type of woody plant with high chemical defense ability against insects,in the natural conditions,it usually distributed in the middle or lower layers of the forest community.It usually showed inferior in the competition for resources such as light and space and competition with neighboring plants,and often scattered,rarely forming the forest dominated by itself.Therefore,it is of great ecological significance to study the effects of light environment and neighboring plants on the chemical defense strategies of Taxus plants,based on which,the effects of light environment in terms of light intensity,UV-B radiation and R/FR gradients,and neighboring plants on the responses of the chemical defensive substances of three Taxus plants,Taxus X media,Taxus cuspidata and Taxus chinensis var.Mairei,were studied.In addition,the relative plants of the three Taxus plants,Torreya grandi and Metasequoia glyptostroboides were used as neighboring plants with different kinship levels aiming to test the effects of different neighboring plants on the chemical defense substances of Taxus plants.The main results were as follows:(1)Low light significantly inhibited the phenolic levels of the three Taxus plants,and promoted their photochemical efficiency and paclitaxel contents,and significantly improved the induction effect of MeJA on paclitaxel production in Taxus X media and Taxus chinensis var.mairei,whereas the effect on Taxus cuspidata was not obvious.(2)The photochemical efficiency and chemical defense substances of the three Taxus plants differently responded to UV-B radiation,which indicated that their photosynthesis efficiency and chemical defense level responding to UV-B radiation were not monotonous,and might be affected by specific UV-B radiation dose and time.Lower UV-B radiation significantly promoted the accumulation of paclitaxel in Taxus X media and Taxus chinensis var.mairei,but not obvious in Taxus cuspidata.(3)The response curves of photochemical efficiencies,phenolic defensive substances and paclitaxel content to R/FR from 0.5 to 6.5 in three Taxus plants were obtained,which would be helpful for analyzing the mechanism for Taxus plants to detect the neighboring plants through light signals and take chemical defense strategies.(4)The chemical defensive level of three Taxus plants did not show a consistent response to the kinship levels of neighboring plants,indicating that kinship levels of neighboring plants might not affect the chemical defense strategies of Taxus plants.