Studies On The Photosynthetic Physiological Characteristics And Secondary Metabolites Of Endangered Plant Species Torreya Jackii

The photosynthetic physiological characteristics and the secondarymetabolites of Torreya jackii in family Taxaceae, an endangered species endemic toChina, was studied in order to better develop and utilze this resource. The photosyntheticcharacteristics of T. jackii and its accompanying plants, the content of the flavonoids andvolatile oil of Torreya jackii collected from different populations and those in thedifferent organs of T. jackii were tested. The photosynthetic rates of Torreya jackii indifferent habitats collected in different seasons were compared and the effect of theenvironmental factors on the photosynthesis and the sedonary metabolites were analyzed.The endangered mechanism of T. jackii was elucidated based on the photosyntheticcharacteirstics and the rules of the synthesis and accumulation of the secondarymetabolites were concluded in this study.1. We used a portable photosynthesis measuring system （Li-6400XT） to determinethe photosynthesis characteirstics of T. jackii in three natural light habitats （gap, edgeand understory）. The results show that the diurnal vairation of the photosynthetic rate ofT.jackii in forest gap and edge habitats in the summer are typical curves with doublepeaks, while those in the other seasons and those at understory habitat in all four seasonsare shown in curves with single peak. The net photosynthetic rate (P_nmax), light saturationpoint （LSP）, the apparent quantum yield （AQY）, maxmium rate of carboxy lation （Fcmax）,maxmium rate of electron transport （Jmax）, and triose phosphate utilization rate （TPU）significantly differ in four different seasons ranking in the order:summer>autumn>spring>winter. The light compensation points （LCP） of T. jackii in theforest gap and edge habitats are the highest in the summer, while those of Torreya jackiiunder the forest is the lowest in the winter. The dark respiration rate （Rd） in three different habitats are the highest in the summer, which is significantly different from theother three seasons.P_nmax, LSP and TPU of T. jackii in four seasons differ significantly in three differenthabitats, ranking in the order: forest gap>forest edge>underforest./?d differ signiifcantlyamong three different habitats. Fcmax and./max of T. jackii in spring, autum and winterdiffer signiifcantly in three different habitats with the order: forest gap〉forestedge>underforest, while the order in the summer is forest edge>forest gap>underforest.AQY in four seasons in three different habites ranked in the order: underforest>forestedge>forest gap and that in underforcst habitat is significantly higher than those in forestgap and edge habitats. In conclusion, the photosynthetic efficiency of T. jackii is thehighest in the summer and that of T. jackii in forest gap habitat. This suggests that T.jackii is a typical sunny plant based on the photosynthetic characteristics and growsbetter in the habitat with enough light.In the spring and summer, the尸nmax、LSP、AQY of T. jackii in forest gap aresignificantly lower than its acompanying plants, and the AQY of T. jackii in autumn issignificantly lower than its acompanying plants, and in winter, the LSP of T. jackii isalso significantly lower kythan its acompanying plants. The LCP and Rd of T. jackii inspring are significantly lower than four acompanying plants, but are signiifcantly higherthan the other four acompanying plants. Rd of T. jackii in spring is significantly lowerthat its accompanying plants，while that in summer is signficanlty higher than itsaccompanying plants. In spring and winter, the Fcmax、Jmax> TPU of T. jackii aresigniifcantly lower than its companying plants except Mach i I us leptophylla, and inautumn and winter, those are signiifcantly lower than Cyclobal anopsisglauca.Compared with the accompanying plants, the monthly Pn of T. jackii is under theaveraged level and the photosynthetic efficiency is low limited by the strong light andhigh temperature with the longest lasting period of the declination of midday Pn. Thissuggests that T, jackii takes adisadvantage place in the interspeciifc competition in thecommunity.2. The content of chlorophyll a. chlorophyll b and chlorophyll a+b of T. jackii indifferent habitats differ signiifcantly among four seasons, ranking in the order:summer>autum>spring>winter. The content of chlorophyll b in summer is significantly higher than the other three seasons. In spring, summer and autumn, the content ofchlorophyll a and chlorophyll a+b differ significantly in different habitats, ranking in theorder: underforest>forest edge〉gap，while the content of chlorophyll b of T. jackii in theunderforest habitat is significantly higher than that in the forest edge and forest gaphabitat. In winter, the content of chlorophyll a, chlorophyll b and chlorophyll a+b of T.jackii differ significantly in different habitats, raking in the order: gap>forestedge>underforest. In spring, summer and autumn, the diurnal variation curves of FJFmof T. jackii and its acompanying plants are typical “V” type, which is the highest in themorning，then decreases gradually and reaches the lowest at12:00. and returns graduallyto the initial level in the atfernoon. In summer, FJFm of T. jackii at12:00in the forestgap is signiifcantly lower than its acompanying plants, suggesting the effects of the hightemperature and strong light on T. jackii were higher than those its acompanying plants.3. The activities of peroxidase and superoxide dismutase differ significantly in thefour seasons, ranking in the order: summer>autumn> winter>spring. In summer, theactivity of peroxidase and superoxide dismutase different significantly in three habitats，ranking in the order: forest gap>forest edge>underforest. In spring, the activity ofsuperoxide dismutase of T. jackii is significantly lower than its acompanying plantsexcept for Quercus fabric. In autumn and winter, that is significantly lower than itsacompanying plants. In spring, the activity of peroxidase is significantly lower than itsacompanying plants, but in summer and autumn, that is signiifcantly higher thanCyclobalartopsis glauca and Rhus chinensis, while in winter, that is significantly higherthan Cyclobalartopsis glauca. Tthe malonydialdehvde content of T. jackii and itscompanying plants in three habitats differ significantly among four different seasons,raking in the order: summer>winter>autumn>spring. In spring and summer, the contentof malonydialdehyde differs significantly among different habitats, ranking in the order:forest gap>forest edge>understory. The malonydialdehvde content of T. jackii in fourdifferent seaons are significantly lower than those in its companying plants. Themembrane permeability of T. jackii differs signiifcantly among four seasons, ranking inthe order: summer〉winter>autumn>spring. In summer and autumn, the membranepermeability of T. jackii in the forest gap are the highest followed by the forest edge,while that in the understory habitat is the lowest. In summer，there are significant difference among three different habitats. In spring, the membrane permeability of T.jackii is significantly higher than its companying plants, but is significantly lower thanits companying plants in summer.4.Flavonoids was extracted from T. jackii using the microwave-assisted extractionmethod. The optimal condition is:90%ethanol, solid-liquid ratio1:40, irradiation°temperature85C and the irradiation time5min. Flavonoids were detected in allthevegetative organs of T‘jackii, with the highest in the annual leaves and the second inthe old leaves followed by the twigs. The flavonoids content in the old branches，barkesand roots were relatively low. The flavonoids content of T. jackii differed significantlyamong three different habitats, ranking in the order: gap>edge>understory. The contentof flavonoids in annual leaves and the old leaves differed significantly among fourdifferent seasons, ranking in the order: summer>autumn>spring>winter.The volatile oil of T. jackii was extracted using the supercritical carbon dioxideextracted method. The optimal condition is: extraction pressure16Mpa，extractiontemperature45°C, extraction time5min. The volatile oil were detected in allthevegetative organs of T, jackii，with the highest in the annual leaves followed by theold leaves, while that in the old branches, barkes and roots were relatively low. Thevolatile oil content in the annual leaveas and old leaves of T. jackii differed significantlyamong four different seasons, ranking in the order: summer>autum>spring>winter.The total content of volatile oil of T. jackii differed signiifcantly among three differenthabitats, ranking in the order: forest edge>forest gap>underforest. The composition ofthe flavonoids and alkaloid extracted from different organs of T. jackii were analyzedusing HPLC method. The number of the components in the flavonoids and alkaloids of T.jackii in the annual leaves and the old leaves were the most followed by those in theroots, while those in the old branches and barkes were the lowest.5.The bacteria are lowly sensitive to the volatile oil of T. jackii while the fungi aremoderately sensitive*The bacteria and fungi are moderately sensitive to the ethanolextract of T. jackii. The ethanol extract of T. jackii showed strong DPPH-free radicalsclearance effect and the antioxidant capacity.1gram dry powder of the extrac had theDPPH^free radicals clearance ability similar with3.05mg of ascorbic acid.