Seed Polymorphism And Its Ecological Adaptive Strategy Of Halogeton Glomeratus In Xinjiang

In this paper, we observed and compared the characteristics of germination, salt stress, seedling desiccation tolerance of two types seeds of Halogeton glomeratus, and discussed their survival strategies in the extreme environment of Junggar desert. The main results were as follow:(1) Seed dimorphism and germination: The two types of seeds of Halogeton glomeratus are different in shape, size, color and external structure. The green seeds have lignified tepals with long wings can be easily dispersed far distance from the mother plant. The yellow seeds have tepals without wings, and dispersed near by wind to the mother plant. The seeds of Halogeton glomeratus germinated in incubators with thermoperiods of 5/15℃, 5/25℃and 15/25℃(dark 12 h / light 12 h) for 30 d. The germination percentages of freshly matured dimorphism seeds are low (<50%). Cold stratification and extending the storage time can significantly increase germination percentage of green seeds, but have no significant effect on yellow seeds. Scarification on covering layers can significantly increase the germination percentage of these dimorphism seeds. Results indicated that green seeds have non-deep physiological dormancy and yellow seeds have deep physiological dormancy.(2) Salt stress on seed germination: The seeds of Halogeton glomeratus were treated with different concentration of NaCl. The results indicated that concentrations below 0.05 mol/L NaCl solution have little impact on the germination. However, the germination rate decreased with the concentration increased from 0.10 mol/L. And there was a strong negative relationship between germination percentage and salt concentrations. After 20 days, all non-germinated seeds from all the salinity treatments were transferred to distilled water, the finial rate of germination was more than 85% of that of original distilled water control. The results showed that salinity was a reversible osmotic inhibition to seed germination and has no much effect on seed germination ability .The rate of germination recovery increased with an increase of the salt concentration.(3) Seedling desiccation tolerance: In natural habitats, the germinated seedlings may be wholly exposed to the air and undergo drought stress. However, the young seedlings have the ability to resist drought and start to recover after rehydration. The root length at dehydration and drying periods from 10 to120 days influenced seedling revival ability. The later the stage of seedling development, the longer is the root and the lower is the percentages of recovery. Further field observations need to be done in order to study the importance of the present findings on the ecological adaptations of this species to its natural habitats.