Physiological Response Of Mulberry And Broussonetia Papyrifera To Drought Stress Simulated By Polyethylene Glycol And Phosphorus Deficiency

The Karst environment is a brittle environment. In the area, there is much environment adversity, of which Karst drought and low phosphorous is the two largest model adversity. They inhibited the absorption of nutrition elements by foliage, and incumbered the normal growth of the plants which were inclined of acid, wet, and fertile can't grow normally, finally resulted in the simple community structure, the ecosystem would be destroyed easily. And for the repair of southwest degenerate Karst entironment, the pioneer plants select and cultivate played a very important role, first we should study the stress resistance of these selected plants and it could provide a credible scientific gist for the father of the brittle Karst environment.Took a woody plant Broussonetia papyrifera the study material, for it adapted to the Karst area, and took the Morus alba L as the counterpart, then simulated the Karst environment such as Karst drought and low phosphorous. Finally under the treatment by different concentration of polyethylene glycol (PEG 6000) and different phosphorus levels, the carbonic anhydrase activity, responses of leaf net photosynthetic rate to light and CO2, chlorophyll fluorescence characteristics and content of Fe, Mn, Cu, Zn of leaves of two species woody plants, Broussonetia papyrifera and Morus alba L were determined, which provides more convincing evidence for the adaptability of Broussonetia papyrifera to Karst environment.From the experiment, we got the result as following:1) The carbonic anhydrase's activity of Broussonetia papyrifera is higher than it of Morus alba L.The carbonic anhydrase's activity of Broussonetia papyrifera had no significant variation with different effects of drought stress, it of Mulberry had lot of it, among which the maximum is four times as large as the minimum. The activity of carbonic anhydrase of Morus alba L. when the concentration of polyethylene glycol is 5,10,20 g·L-1 is obviously less than controls and it when the concentration of polyethylene glycol is 40,60 g·L-1.The activity of carbonic anhydrase of Broussonetia papyrifera mainly keep invariable when phosphorus deficiency is low but it of Morus alba L. continually drop down. So that in the dry or low phosphorus environment, Broussonetia papyrifera all has stronger adaptability than Morus alba L. 2) The net photosynthetic rate, maximum quantum yield of photo systemⅡ(Fv/Fm) and actual photosynthetic efficiency of PSⅡ(OPSⅡ) of paper mulberry had little influence by PEG 6000, and those of mulberry had large inhibition by PEG. And the maximum quantum yield of photo systemⅡ(Fv/Fm), actual photosynthetic efficiency of PSⅡ(ΦPSⅡ), photochemical quenching coefficient (qP) and electron transport rate (ETR) of paper mulberry was significantly higher than those of mulberry. The result indicated that in arid environment the light efficiency of Broussonetia papyrifera is higher than it of Morus alba L.3) The net photosynthetic rate, Fv/Fm and OPSⅡof mulberry prompt lessening with the degree of phosphorus deficiency, but the downtrend of it of Broussonetia papyrifera is slow. And Fv/Fm, OPSⅡ, qP; ETR of paper mulberry was also significantly more higher than those of mulberry in the low phosphorus. The result indicated that under phosphorus deficiency stress, the light efficiency of Broussonetia papyrifera is also higher than it of Morus alba L.4) Effects of PEG stress on Fe Mn Cu Zn absorbed and accumulated in the leaf of Broussonetia papyrifera is lower than the leaf of Morus alba L. Fe Mn Cu Zn accumulated in the leaf of Broussonetia papyrifera will slowly decrease as the phosphorus deficiency,but it in the leaf of Morus alba L changes much. The result indicated that absorption low of the element of Broussonetia papyrifera is more suitable than it of Morus alba L for drought and phosphorus deficiency stress.5) Above all, grown under the Karst's flimsy condition with drought conditions and low phosphorus levels, paper mulberry can grow normally, and maintain the normal metabolism, show a strong adaptability to the environment with drought conditions and low phosphorus levels. Meanwhile when did the ecology repair of Karst area by Broussonetia papyrifera,we could fertilize the soil so as to improve the environment, then we could plant Broussonetia papyrifera far and wide, finally, expired the destroyed brittle environment in Karst area through plant growing.