Study Onanatomical Structure Of Vegetative Organs And Physiological Characteristics Of The Typicalalpine Cold Hardy Plant In Hedinia Tibetica (Thoms.) Ostenf

In order to insight into the cold-resistant adaptability characteristics of the extremenviroment, the anatomical structure of nutritive organs, leaf, stem and root, of thewild Hedinia tibetica (Thoms.) Ostenf was firstly studied by paraffin section methodand in the same time,the change of the7physiological and biochemical indexes ofthe leaf in the wild Hedinia tibetica (Thoms.) Ostenf were also discussed with thenatural cooling,which included the content of soluble sugar and protein, proline,MDA,photosynthetic pigment and root activity. Objective is to make clear of theanatomy and physiology of cold resistance about the wild Hedinia tibetica (Thoms.)Ostenf.The main results were as follows:1.Research on anatomical and morphological structure of nutritive organs inHedinia tibetica (Thoms.) Ostenf and its adaptation to ecological environment.This species evolved the obviously morphological and anatomical characteristicsto adapt to gale, frozen and drought stress in the alpine region.The principal characterwere as follows:(1)Leaf:there were apparent wax layer and cuticle spur on the leavesurface and upper and lower epidermal cells were monolayer cell. And the lowerepidermis stomatal number more than upper epidermis.In addition,2～4layers of thepalisade tissue were observed and were obviously thicker than the sponge tissue.Lastbut not the end,There were plenty of aerenchyma in the the mesophyll.（2）Stem：The study found that stem color was purple and there were apparentcuticle spur on the stem surface. Epidermal cells only had one layer which wascomposed by rectangular parenchyma cells. And the Cuticle covered above the cellwall.The most obvious feature was that the epidermal and cortical cells of stem hadthe apparent plasmolysis phenomenon and There were a lot of pith and cortexaerenchyma.Besides,the cortex were comprised by7～9layers of parenchymacell.The Phloem cells was small and tight and the cell wall had undergone secondarythickening.Thus,the sclerenchyma is formed.Fascicular cambium have fissionability.Moreover,there was only one type catheter——spiral vessel.The xylemof vascular bundle arranged in a ring which was generally consiste by20. There hadbeen found the cambium between the xylem and phloem and had secondary growth.（3）Root:The transaction of root showed “wheel” shape and there were somebranch roots and only one layer of the epidermal cell which outside covered thethicker wax layer.But not found the root hair.Particularly noteworthy was thedeveloped periderm that were formed of cork layer(4～7layer rectangularcells),phellogen(1～2layer pavement cells) and cork cortex(2～5layer flatrectangular cell).In addition, cortical cells of root had the apparent plasmolysisphenomenon.There was only one type catheter——spiral vessel.The primary xylem inthe middle of the root still exsited,which was considered to be2or3prototype root.2.The change of physiological indexes with the natural cooling(1)The change of root activity with the natural cooling:It was at2℃(17:00) thatthe root activity achieved zenith rather than at15℃(14:00,The highest temperaturewithin a day).When the outside temperature dropped qickly during a short period oftime,the root activity had gone up5times.In contrast, after the long period lowtemperature stress,the root activity had considerably reduced.(2)The change of the content of photosynthetic pigment with the natural cooling:By and large,there had a higher content of chlorophyll.The intensity of illuminationwas the dicisive factor to the Chlorophyll content instead of fast cooling.Underconditions of no Illumination,Chlorophyll content was positively correlated withlong-term low temperature stress.It was at15℃(14:00) that the content of carotenoidsrun up to minimum value.The content of carotenoids wound increase4times incondition of fast cooling.compared with long-term low temperature stresssituation,the content of carotenoids obviously declined.And this penomenon show thatthe carotenoids is the one of major factor to antioxidant effect when responding to thelow temperature stress.(3)The change of the content of proline with the natural cooling:There was very closed relationships between the proline and the Hedinia tibetica (Thoms.)Ostenf.The experiment proved that all the three factors of flooding injury,short-termrapid cooling and long time low temperature stress could lead to substantialaccumulation of proline.(4)The change of the content of soluble sugar with the natural cooling:TheHedinia tibetica (Thoms.) Ostenf could synthetize the soluble sugar when the Opticalradiation and ultraviolet radiation was the most Severe.When the outside temperaturedropped qickly during a short period of time,the soluble sugar could be rapidlyaccumulated;Yet,long time low temperature stress make the very content declined.(5)The change of the content of soluble protien with the natural cooling:On thewhole,there had a higher content of soluble protien.When the outside temperaturedropped qickly during a short period of time,the soluble protien could be rapidlyaccumulated;Yet,long time low temperature stress made the very content declined.(6)The change of the content of MDA with the natural cooling:The strongradiation was a decisive factor for the MDA content of the Hedinia tibetica (Thoms.)Ostenf,rather than low temperature stress.We found that short-term rapid cooling andlong time low temperature stress could not make the MDA content increasedsignificantly.