The Research On The Photosynthesis And Water Eco-physiological Characteristics Of Syringa Oblata Lindl. Sorbaria Sorbifolia (L.) A.Br. And Prunnus Triloba Lindl.

This article has studied the Photosynthesis and Water Eco-physiological Characteristics of Syringa oblate Lindl. Sorbaria sorbifolia(L.)A.Br. and Prunnus triloba Lindl. Under different moisture content owes lacks in semi-arid Huhhot area. The result is as follows:1 The re-saturated relatively saturation moisture content assumes drops the tendency of tested trees along with the re-saturated initial moisture content lack the degree enlargement. When the re-saturated initial moisture content owes lacks (WSD) to initial loses Swelling pressure point saturation deficit (SWDπp) if given re-saturated absorbing water, the trees can completely restore the moisture content which its owes lacks water. It indicates that the trees are not harmed by dehydration under the water condition of initial loses Swelling pressure point in the short-term .While the capacity of restoring water is zero, the order of the three trees to the adaptation of the low moisture content condition is Syringa oblata Lindl.> Prunnus triloba Lindl. > Sorbaria sorbifolia(L.)A.Br.2 The re-saturated relatively saturation moisture content (RSRWC) presents the drop trend of the tree trees with the reduction re-saturated initial water potential (ψr).The restoring water capacity of samples is lower with the degree of water lacks being bigger. The saturated deficit of initial loses Swelling pressure point is bigger the restoring water capacity is stronger. When the water lacks of Sorbaria sorbifolia(L.)A.Br.≤30%, it can recover capacity of absorbing water. Then the water lacks of Syringa oblata Lindl. and Prunnus triloba Lindl.≤20%, them can not restore to the saturatial moisture content.3 The water potential trend of the three trees appear single-peak in every day. Starting from the early morning (6:30) With the increase in solar radiation, warming, the rapid decline in the humidity of the air, water potential also quickly reduced, to about 14:00, the water potential drops to minimum point (Syringa oblata Lindl. -2.45 Mpa; Prunnus triloba Lindl. -2.2Mpa; Sorbaria sorbifolia(L.)A.Br. -1.88Mpa); And then with the weakening of solar radiation, the temperature dropped, raising the relative humidity of air, water potential is gradually rebound (Syringaoblata Lindl. -0.625Mpa ;Prunnus triloba Lindl. -0.425Mpa; Sorbaria sorbifolia(L.)A.Br. -0.25Mpa).4 Under different water conditions, the relative total photosynthetic rate, net photosynthetic rate, transpiration rate assume the declining trend, which owes along with the trees in vivo moisture content lacks, namely increases along with the appearance of the water potential. The water potential number which When net photosynthetic rate is equal to zero is water potential compensation point (ψnpc),its annual variation rule was more for the early growing season (April to May) and then reduces gradually, to the strong period of growth (July-August) reached the minimum. At the end of the growth (in September) gradually rebound. The net photosynthetic rate water potential compensation point is stronger, the adaptation of the plants becomes greater to water stress. The ability to endure arid patiently of Syringa oblata Lindl .is bigger than Prunnus triloba Lindl. and Sorbaria sorbifolia(L.)A.Br. The changes of the water potential compensation point (ψnpc) trends are the same with the initial loss swelling pressure point overall osmotic potential (πp) basically.5 The biggest water using efficiency of Syringa oblata Lindl is greater than Prunnus triloba Lindl. and Sorbaria sorbifolia(L.)A.Br.6 In the entire growing season (May-September) compositing all indexes to the drought, the order of the ability to drought-resistance is: Syringa oblata Lindl . > Prunnus triloba Lindl. > Sorbaria sorbifolia(L.)A.Br.