中文摘要：

以向日葵品种白葵杂6号为试验材料,中性盐NaCl和Na2SO4混合模拟盐胁迫、碱性盐NaHCO3和Na2CO3混合模拟碱胁迫（两者摩尔比均为9∶1）,设计各6种处理。研究盐、碱胁迫下种子萌发及幼苗形成的相关生理表现。结果表明,种子能够萌发并成苗的最高盐胁迫强度是pH6.98,电导率为1.311dS m^-1（培养介质的pH和电导率）;碱胁迫强度是pH9.71,电导率为0.360dS m^-1。在能够成苗的盐碱条件下,随着盐胁迫强度的增强出苗率、成苗率下降,出苗时间明显延迟;而随着碱胁迫强度的增加,成苗率下降,出苗时间并不延迟。同时随着盐碱胁迫强度的增强,幼苗的各项生理指标均下降,下降幅度以碱胁迫明显大于盐胁迫。试验结果证明,盐胁迫和碱胁迫对白葵杂6号种子萌发及幼苗形成的影响机制不同,向日葵在这两个阶段对盐碱两种胁迫的耐受能力及响应特点也不同。这一结论进一步证实了盐、碱胁迫是两种性质不同的胁迫。

英文摘要：

Salinization and alkalization of soil are a widespread environmental problem, including salt-stress and alkali-stress in terms of the salt characteristics. In fact, the destructive effects caused by alkali-stress are more serious than that by salt-stress. The resistance to salt- and alkali-stress of sunflower （Helianthus annuus L.） is stronger than that of the other crops, as some sunflowers are able to grow on alkalinized soil. The stress conditions of 6 salinities and 6 alkalinities were simulated by mixing two neutral salts （NaCl and Na2SO4） and two alkaline salts （NaHCO3 and Na2CO3） both in the molar ratio of 9：1 respectively. The concentration range of treatments was from 40 to 240 mmol L-1 for the salt-stress, and 10 to 60 mmol L-1 for the alkali-stress. A sunflower cultivar Baikuiza 6 with higher resistance to salt-alkaline stresses, was used to determine emergence time, emergence rate, survival seedling rate, and physiological indexes including leaf area, water content, biomass of seedlings, and content of Na^＋ and K^＋ under salt- and alkali-stresses. The results showed that the maximum intensity of salt-stress for baikuiza 6 germination and seed- ling growth was pH 6.98 and electric conductivity of 1.311 dS m^-1 in the culture medium, and alkali-stress was pH 9.71 and electric conductivity of 0.360 dS m^-1. Under the salt or alkali conditions that seedlings could be able to grow, not only the emergence rate and survival seedling rate decreased, but also the time of emergence delayed significantly with the increasing intensity of salt-stress. Whereas the survival seedling rate decreased and the emergence time didn＇t delay with the increasing of alkali-stress intensity. Moreover, various growth indexes of seedling decreased with increasing intensity of salt- or alkali-stress, and the extent of decrease was greater under alkali-stress than under salt-stress. In conclusion, the mechanisms of salt- and alkali-stresses effects on germination and seedling growth of sunflower are different, a