Photosynthetic Characteristics In Different Growth Phases Of Potaninia Mongolica Maxim In Western Ordos

Potaninia mongolica Maxim,desert shrub of Rosaceae.P.mongolica is endangered plant under state protection.With unique three leaves morphology,P.mongolica is different from Rosaceae.It relies strongly on water especially in semi arid area,if late spring or early summer,water is deficit,its leaves,flowers,fruits will all fall off,and enter a dromant state in“suspended animation” escape from high temperature and drought environment stress.If having certain precipitation it can quickly turned green,then flowering again.The research of P.mongolica is mainly focused on bioecology,and more and more attention has been paid to its especial physio-ecological characteristic.We want to show the physiological adjustment mechanism of old Mediterranean relict under drought stress and make sure their protective policy.In order to reveal the correlativity between habitat physical factor and the physiological response.This paper has choose P.mongolica as experimental material,combing with the local meteorological data to measured the gas exchange photosynthetic characteristic parameters,soil moisture,water physiological characteristics,compare with Tetraena mongolica Maxim under the same natural condition.These plants have different property on morphological adaptation.The main results are as follows:(1)There was midday depression of photosynthesis in growing and dormant period of P.mongolica.But there was no midday depression of photosynthesis at different growth stages of T.mongolica.Photosynthetic available radiation and moisture factor have great influence of P.mongolica.Other factors also have an effect on it.(2)P.mongolica have evident differences among Pn at different growthstages.Dormant period declined obviously.Different growth stages have same change trend of T.mongolica.(3)At different growth stages,it all reflect dependents on moisture.Just days before the drought stress,it can finish life history in time.If the top soil moisture content as low as 3.5%,the major reason is that leaf lacked water,entered dormancy.When there is precipitation effectively,measured the top soil moisture content can up to 8.8%,significantly higher than the growing and dormant period,at the same time,the leaf water content of P.mongolica significantly higher than the dormant period could up to 48.2%.P.mongolica recovery.At the same water conditions,T.mongolica will not enter the dormant.The result show that the two plants adapted to different strategies under the same water condition.(4)From the perspective of habitat adaptability,taking the sensitive response and evading strategy to adapt to environment stress,P.mongolica is a successful species which lived through the long term evolution,it can form a special ability to adapt the environment changes.The type of dormant-resurrect shows its natural habitation,P.mongolica belong to adept using the opportunity for opportunistic growth mechanism.