Baskin Carol C, Zackrisson Olle, Baskin Jerry M
School of Biological Sciences, University of Kentucky, Lexington, Kentucky 40506-0225 USA;
Am J Bot. 2002 Mar;89(3):486-93. doi: 10.3732/ajb.89.3.486.
The broad objective of this research was to define the role of warm (≥15°C) stratification in breaking dormancy in seeds with stony endocarps that require warm-plus-cold (∼0°-10°C) stratification for germination. This question was addressed using seeds (true seed + endocarp, hereafter called seeds) of Empetrum hermaphroditum. Only 2-5% of freshly matured seeds collected in September and October at five sites in Sweden germinated in light at daily alternating temperature regimes of 15°/6°, 20°/10°, and 25°/15°C. Dormancy was not due to impermeability of the stony endocarp surrounding each seed, and embryos did not grow prior to radicle emergence. Thus, seeds did not have physical, morphological, or morphophysiological dormancy. Long periods of either cold stratification (20 or 32 wk) or warm stratification (16 wk) resulted in a maximum of 22-38 and 10% germination, respectively, in light at 25°/15°C. After 12 wk warm stratification plus 20 wk cold stratification, 83-93% of the seeds germinated in light at the three temperature regimes. For a cold stratification period of 20 wk, germination increased with increase in length of the preceding warm stratification treatment. Gibberellic acid (GA(3)) promoted germination of 77-87% of the seeds. Based on dormancy-breaking requirements and response to GA(3), 62-78% of the seeds had intermediate physiological dormancy; the others had nondeep physiological dormancy. Contrary to suggestions of several other investigators that warm stratification is required to make the endocarp permeable to water via its breakdown by microorganisms, our results with E. hermaphroditum show that this is not the case. In this species, warm stratification is part of the dormancy-breaking requirement of embryos in seeds with intermediate physiological dormancy.
本研究的总体目标是确定温暖（≥15°C）层积在打破具石质内果皮种子休眠中的作用，这类种子需要温暖加寒冷（约0°-10°C）层积才能萌发。使用雌雄同株岩高兰的种子（真种子+内果皮，以下简称种子）来解决这个问题。9月和10月在瑞典五个地点采集的新鲜成熟种子，在15°/6°、20°/10°和25°/15°C的日交替温度光照条件下，只有2%-5%的种子萌发。休眠并非由于围绕每粒种子的石质内果皮不透水，并且胚在胚根出现之前不生长。因此，种子不具有物理、形态或形态生理休眠。长时间的冷层积（20或32周）或暖层积（16周），分别在25°/15°C光照条件下，最多导致22%-38%和10%的种子萌发。经过12周暖层积加20周冷层积后，83%-93%的种子在三种温度光照条件下萌发。对于20周的冷层积期，萌发率随着之前暖层积处理时间的延长而增加。赤霉素（GA₃）促进了77%-87%的种子萌发。基于打破休眠的需求和对GA₃的反应，62%-78%的种子具有中间生理休眠；其他种子具有非深度生理休眠。与其他几位研究者认为暖层积是使内果皮通过微生物分解而透水所必需的观点相反，我们对雌雄同株岩高兰的研究结果表明并非如此。在这个物种中，暖层积是具有中间生理休眠种子中胚打破休眠需求的一部分。
