摘要
研究种子在原生境休眠状态的变化,有助于了解种子萌发时机和休眠解除在自然条件下是如何被控制的。泡果沙拐枣(Calligonum junceum)是蓼科沙拐枣属的超旱生灌木,是达坂城荒漠的优势种,是荒漠地区植被恢复重要的候选植物种。于2015年7月,将鲜种子埋放在达坂城自然群落的地表和土中(3~5 cm),定期取回(第1年每6周取一次,第2年每8周取一次,直至2017年9月),在模拟原生境生长季4个变温(15/5、20/10、25/15、30/15℃)下培养萌发。结果表明:成熟的鲜种子在4个温度下萌发率很低,说明种子具有初生休眠;大部分种子具有非深度和中度两种水平的生理休眠;种子的休眠在晚秋和冬季以及来年春季得以解除;3月取出的种子萌发率较高;在夏季高温时节,大部分种子(70%)再次进入次生休眠;在达坂城原生境,泡果沙拐枣的种子处于休眠/非休眠循环,这与达坂城季节性水、热条件的变化及长期大风有关;埋放于土中种子的萌发率高于地表,冬季降雪时地表种子的萌发率高于土中,这与不同部位土壤温度和湿度的波动幅度不同有关。
Research in germination responses and dormancy of buried seeds contributes to a better understanding of how the timing of germination and dormancy breaking is controlled in nature. Calligonum junceum,a super-xerophilous shrub,is a candidate species for revegetation of the cold deserts of northwest China. Fresh seeds were placed on the surface and buried in soil( 3-5 cm) in its natural habitat in July 2015,and exhumed( every six weeks in first year,and every eight weeks in second year,up to September 2017) and tested for germination over a range of temperature( 15/5,20/10,25/15,30/15 ℃,respectively). The germination percentage of exhumed seeds was very low at four varying temperatures,indicating the existence of primary dormancy. Most seeds were characterized by both non-deep and intermediate physiological dormancy. Seed dormancy was broken in late autumn,winter or next spring. Seeds exhumed in March had a higher germination percentage. Most seeds( 70%) reentered secondary dormancy during summer due to high temperature. Most seeds exhibited annual dormancy/non-dormancy cycles in the natural habitat of Dabancheng,due to seasonal changes of temperature,rainfall and chronic wind. Seeds buried in soil had higher germination rate than that on soil surface,whereas seeds on soil surface had higher germination rate than that buried in soil when there was snowing in winter,which was related to different seasonal fluctuations of soil temperature and humidity.
引文
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