Study On Some Biological Characteristics Of Taraxacum Kok-saghyz

As an important strategic resource,rubber is mainly from Hevea brasiliensis,which grows in tropical and subtropical regions.However,due to the restriction of its geographical environment,rubber production was in short supply,which causes people eagerly looked for alternative sources of Hevea brasiliensis.The Taraxacum kok-saghyz Rodin was a plant of the genus compositae,and it was the preferred alternative plant resource due to its high rubber content in the root and the closest molecular structure the Hevea brasiliensis.As the wild T.kok-saghyz were often mixed in the same area with a variety of Taraxacum,the phenomenon of hybridization between plants was common,maked it difficult to determine the biological species of this genus,resulting in more difficult identification between species.Therefore,this dissertation mainly studies the comparison of leaf anatomical characteristics,flowering biology,breeding system,and germination characteristics of seeds in salt and alkaloid conditions of T.kok-saghyz and its genus,understands and grasps the morphological and structural characteristics of T.kok-saghyz,and further explores its reproductive strategy for the environment provides biological evidence and taxonomic basis for the further study of T.kok-saghyz and its other species.The main results are as follows:（1）The peel epidermis method was used to observe the leaf epidermis of T.kok-saghyz and five species of Taraxacum in the same region.The results showed that the upper and lower epidermal cells of the test material were irregular,and the upper epidermal wall was shallow or deep,but the lower epidermis was deep.The patterns are all deep waveforms;stomatal apparatus was randomly distributed in the upper and lower epidermis,and the types were irregular;the stomatal density,stomatal index,epidermal cell density and other indicators have significant differences among species.Leaf epidermal micromorphology has certain taxonomic significance for distinguishing Taraxacum plants（2）The paraffin section method was used to study the leaf structure of six species of dandelion plants.The results showed that the leaf anatomy of the test material consisted of three parts:epidermis,leaf mesophyll and leaf vein.The monolayer of epidermis cells was distributed in the upper and lower epidermis.In addition to the T.kok-saghyz,the other test materials have epidermal hair;the mesophyll tissue was well developed,and the palisade tissue was composed of a layer of closely packed cells;the space between the spongy tissue cells was large and the cells were irregular and scattered;T.erythrospermum different from other species in the number of vascular bundles;T.kok-saghyz is significantly different from other species in vascular bundle diameter.（3）In order to explore the reproductive biology characteristics of T.kok-saghyz,the species flower syndrome and breeding system of this species were studied through field observation,artificial pollination test and indoor observation.The results were as follows:the order of flowering of T.kok-saghyz capitulumwas the outer flower opening firstly and central flower later.,The single inflorescence lasts for 3to 4 days,and the male firstly mature,which was beneficial to the species reproduction.In the process of single flower opening,the filaments become shorter,the pollen matures and scatteres into the barrel of the anther,the style gradually elongates and pushes pollen out of the cartridge through the stigma and the style hair to form a secondary representation of the pollen.The shape of the stigma was rod-shaped,gradually cracking to form a small Y-shape,eventually rewinding into a hornlike shape,and carrying a large amount of pollen on the stigma;the pollen vitality of T.kok-saghyz was highest when it was dispersed,reached95%,pollen had decreased to 50%on the 17th day and was completely lost on the 35th day;the single flower pollen of T.kok-saghyz was（1742±108）granules,the number of ovules was 1,and the pollen ovule ratio was 1742±108,which was facultative heterogenous;the hybridization index was 4,belong to outcrossing,part of self-intergrity,need to pollinator type;artificial control test showed that T.kok-saghyz did not exist apomixis,self-incompatibility and cross-pollination can be solid,and the outcrossing rate was high,its breeding system was mainly based on outcrossings;as a result of its observation of flower-visiting insects,because of the low temperature of the morning and evening,no activity was observed on the flowering insects in their inflorescences.As the temperature rose at noon,a small number of butterflies,bees and fly insects were observed and active here,but they did not perform flowering behavior on T.kok-saghyz flower.（4）In order to clarify the germination characteristics of T.kok-saghyz seed under mixed salt and alkali conditions,neutral salt Na Cl,Na₂SO₄and alkaline salt Na HCO₃,Na₂CO₃were selected and mixed in different proportion.The results showed that the indicators such as germination rate,germination potential and seed vigor of T.kok-saghyz showed a downward trend with the increase of salt concentration,and the effect of alkaline salt on the seed index was greater than that of neutral salt;Based on the analysis of various stress factors and germination index of the regression equation,salt concentration plays a leading role in various stress factors.The resistance of T.kok-saghyz seed to different proportions of salt,alkali and concentration was different.The order of inhibition of seed germination by different saline treatments was Na Cl+Na₂SO₄<Na Cl+Na HCO₃<Na Cl+Na₂SO₄+Na HCO₃+Na₂CO₃<Na₂SO₄+Na₂CO₃<Na HCO₃+Na₂CO₃.