Analysis On Seed Germination Characteristics And Seedling Drought Resistance Of Helianthemum Songaricum Schrenk

Helianthemum songaricum Schrenk plays an important role in keeping the fragile ecological balance in arid and semi-rid regions of inner mongolia. H. songaricum is reproduced by seed, Nevertheless,also the expert thinks, H. songaricum can be asexual reproduction by slitting.The seed-originated seedings and population regeneration of H. songaricum mainly depends on sexual reproduction under natural conditiongs.Althoug a great deal of research has been conducted about H. songaricum,but its seeds germination characteristics and drought resistance of seedlings has not been studied at present. The research on the seeds germination characteristics and drought resistance of seedlings has very important scientific significance to deeply understand the mechanism of plants adapted to a wide range of environmental conditions.In this study, the seeds of H. songaricum were collected from their mother plant in the core of the H. songaricum of West Erdos National Nature Reserve, which is one of the typical arid and semi-rid regions of northwest China. Through the research on the morphological structure of seed of H. songaricum,seed dormancy and dormancy breakin, seed germination responses to temperature and water limitation. Aims to verify the proposed hypotheses of seeds germination characteristics and drought resistance of seedlings,and to provide a theoretic guide for reproduce、cultvation ofH.songaricum.The main results and conclusions were listed as followings:(1) The seeds of H. songaricum. have non deep physiological dormancy.There were significant differences in seed germination responses to precooling, preheating, GA3, CaCO3and soaking. Specifically, soaking+alternating temperature is the optimal method for dormancy breakin ofH. songaricum. Precooling, preheating and GA3can all enhance the germination rate of H. songaricum,yet the effect take second place. CaCO3has no discernible effect on the germination rate ofH. songaricum. (2)The optimum temperature of seed germination for H. songaricum were25/35℃alternating temperature. Under the condition of30℃constant temperature,the germination rate,germination index, vigor index can all increase.This demonstrates that the germinationof H. songaricum seed needs higher temperature.In contrast with constant temperature,alternating temperature can inprove germination rate efficiently. with the water limitation was intensified,the germination rate、germination index、vigor index of H.soongoricum seeds declined In10%、20%concentrations, seeds were less affected.25%concentration have inhibition effect on seeds.30%concentration, seeds could hardly germinate. The cubic curve model fitted the relationship between drought stress and seed gemination rate better than did of quadratic model or linear model.(3) As the stress of drought was intensified and last,the relative water content of leaves has trended down,the chlorophyll concentration was up and then descended, the proline content、soluble protein content and malondialdehyde (MDA) content have increased, and the variation was evidently at the mid-late drought stress stage.