| The study is about a kind of 3-year-old pharmaceutical plant T.media cv.Hicksii. We set up 3 kinds of different illumination handles using the black sunshade net shading in the pharmaceutical plant garden of the southwestern normal university (elevation is 250 meters) of Chongqing. The natural light intensity (passing through light rate is 100%) is the contrast, consequently the passing through light rates of one-layer shading and two-layer shading are 50.0%, 12.5% respectively. We have carried on comparing research on the changes of photosynthetic physiological characteristics, water metabolism, membrane protective system, material metabolism, cold resistance and the content of endogenous hormone of T.media cv.Hicksii grown at different light intensity conditions.The light saturation points, compensation points and dark respiration rates of T.media cv.Hicksii seedlings go down while the contents of chlorophyll and the ratios of chlorophyll a and b increase along with the weakening of light intensity of the growing environment, but their CO2 compensation points and photorespiration rates go up. T.media cv.Hicksii seedling' s total leaf area, specific leaf area, biomass, blade's thickness, apparent quantum efficiency (AQY) and the activity of Hill reaction in one-layer shading are biggest. It shows that the ability using weak light is the strongest, which is favour of the accumulation of assimilating outgrown, and that it grows suitably at the place in shading.T.media cv.Hicksii seedling hi natural light has higher content of bound-water and water saturation deficit, bigger transpiration rate, and lower relative water content,stronger ability of fighting loss water than that in shading light intensity conditions. Shading decreases transpiration rate and content of bound-water, but raises relative water content. So it weakens the resisting contrary ability.Light intensity effects on the ability of membrane protective system scavenging free radical. The seedling grown at one-layer shading shows the changes in activities of anti-oxidation enzyne such as SOD, POD and Vc content increase, leading to increasing of ability of scavenging free radical. Consequently, the level of O2 and the MDA content decrease. It shows the ability of scavenging free radical is the strongest. The seedling in natural light intensity condition has lower activity of SOD, POD, CAT and Vc content, but the difference is not significant between them, so it also possesses the stronger ability to scavenge free radical. The seedling in two-layer shading has lowest activity of SOD, POD and Vc content, but it enhances CAT activity dramatically, Which retards the harm of free radical to the membrane.The light intensity effects on the content of endogenous hormone of T.media cv.Hicksii leaves ,too. In natural light intensity condition, the content of ABA is the highest, but the contents of GA, IAA, ZRs reduce, which is adaptive to the state of its higher transpiration rate, lower content of relative water and bigger water saturation deficit. One-layer shading enhances the contents of IAA, GA and ZRs, which is consistent to its growth condition.Material metabolites of T.media cv.Hicksii leaves change correspondly with light conditions variation. Shading increases contents of Star and Spro, but reduces contents of Fpro and Ssug. In following change from the autumn to winter, The seedlings in different light intensity conditions all reduce the content of Star to the difference level, while the contents of Ssug and Fpro increase 1-2.5 times. Since the contents of protein also increase 1-1.5 times universally, it indicates that the main cause of increasing Fpro content is not the content of protein falling, but is low temperature guide, which leads to the increasing of composing Fpro. Consequently the seedlings enhance the leaf cold resistance through improving Fpro, Spro, Ssug contents and declining Sta content with temperature falling, Which can reduce the organisation osmosis power and improve the capacity of water-keeping. The taxol, t...
|
PDF Full Text Request