NaCl或PEG胁迫对裸果木种子萌发的影响

Effect of NaCl or PEG stress on seed germination of Gymnocarpos przewalskii

为保护亚洲中部荒漠区比较稀少的第三纪孑遗濒危物种裸果木,模拟不同程度的盐分和干旱胁迫,研究裸果木种子萌发的抗旱抗盐机理。采用不同浓度的NaCl溶液(50、100、150、200、250和300 mmol/L)、不同渗透势的PEG-6000(-0.1、-0.3、-0.5、-0.7和-0.9 MPa)溶液,分别模拟盐胁迫和干旱胁迫,以蒸馏水为对照,测定裸果木种子的发芽率和发芽天数,计算发芽势、发芽指数和活力指数,分析裸果木萌发特性,以及对盐胁迫、干旱胁迫的响应特性。结果表明:在低浓度的NaCl溶液(50 mmol/L)中,种子的发芽率和活力指数较对照提高,表现出促进种子萌发的作用;较低浓度的NaCl溶液(100和150 mmol/L)或较高渗透势的PEG溶液(≥-0.3 MPa)中,对种子的发芽能力和发芽整齐度的影响不显著;在高浓度的NaCl溶液(≥250 mmol/L)或低渗透势的PEG溶液(≤-0.7MPa)中,发芽率、发芽势、发芽指数和活力指数降低极显著,发芽进程明显延长,由于渗透作用和毒害作用增强,种子萌发被明显抑制和延缓。裸果木种子萌发对盐胁迫或干旱胁迫具有一定的耐受性,当胁迫超过该范围(NaCl溶液浓度≥250 mmol/L或PEG渗透势≤-0.7 MPa)时,萌发能力受到显著抑制。研究裸果木种子萌发特性,为干旱荒漠区裸果木的人工培育和荒漠化防治提供依据。

[Background] Gymnocarpos przewalskii is the rare relic of tertiary and endangered species of desert area in central Asia,and one of the oldest groups in saline environment. It is mainly distributed in the desert area in our country being one of the main constructive species in stony desert area where rainfall is small but evaporation is strong,which results in the salt accumulation in soil,subsequently drought and soil salt affect its seed germination and further its population establishment and regeneration.To protect G. przewalskii,salt and drought stress was respectively stimulated to research salt and drought resistance mechanism in seed germination. [Methods] Seeds of G. przewalskii were collected from botanic garden of Anxi Extra-arid Desert National Nature Reserve with the mean annual rainfall of 45. 3 mm and the salt content more than 2% in the soil depth of 30 cm. Using the different concentration ofNaCl（ 50,100,150,200,250,and 300 mmol/L） and the different potential of PEG-6000（-0. 1,-0. 3,-0. 5,-0. 7,and-0. 9 MPa） to stimulate salt stress and drought stress respectively,taking the distilled water as the control to measure the germinated seeds and time,germination rate,germination energy,germination index vigor index and average germination days were calculated and the germination characteristics and the response to salt stress and drought stress were analyzed. [Results] The results showed that the germination rate and the vigor index increased at low concentration of NaCl（ 50 mmol/L）compared with the control. The germination rate,germination energy and average germination days were not significantly affected at the concentration of 100 and 150 mmol/L NaCl,and the germination rate,germination energy and vigor index decreased insignificantly at the osmotic potential of-0. 3 MPa,which indicated that germination ability and uniformity was not significantly affected by relatively low concentration of NaCl（ 100 and 150 mmol/L） or relatively high osmotic potential of PEG（ ≥-0. 3 MPa）. At high concentration of NaCl（ ≥250 mmol/L） or low osmotic potential of PEG（ ≤-0. 7 MPa）, the germination rate, germination energy, germination index and vigor index extremely significantly decreased and the germination process was markedly prolonged,the seed germination of G.przewalskii was significantly inhibited and delayed due to the intensified osmosis and toxic action.Regression analysis indicated that the critical and limited value of NaCl stress on seed germination was337. 4 mmol/L and 628. 6 mmol/L,respectively and the critical and limited value of PEG stress on seed germination was-0. 70 MPa and-1. 01 MPa,respectively. [Conculsions]The seed germination of G.przewalskii was improved at the concentration of 50 mmol/L NaCl and showed some tolerance to salt and drought stress,beyond the range（ more than NaCl concentration of 250 mmol/L or less than PEG osmotic potential of-0. 7 MPa）, its seed germination was significantly inhibited. Researching the seed germination characteristics of G. przewalskii can provide some basis for the cultivation of G. przewalskii and combating desertification in desert area.