Laboratory of Plant Ecology, Katholieke Universiteit Leuven, Kasteelpark Arenberg, Leuven, Belgium.
Plant Biol (Stuttg). 2010 Sep 1;12(5):765-71. doi: 10.1111/j.1438-8677.2009.00290.x.
Temperate forest herbs with seeds exhibiting both a physical and a physiological dormancy mechanism are rare, and knowledge on the factors regulating germination of these species is fragmentary. The biennial Geranium robertianum L. grows mainly in temperate woodlands, but can also be found in exposed habitats. Seedlings of G. robertianum are known to emerge from spring until autumn, but little is known about the environmental factors regulating germination. In this study, phenology of seedling emergence and of physical dormancy loss was examined for seeds buried at shaded or sunny exposed locations. The role of temperature in regulating dormancy and germination was analysed by incubating seeds in temperature sequences simulating temperatures that seeds experience in nature. The results indicate that most seeds of G. robertianum buried in sunny conditions germinate immediately after physical dormancy loss in summer. Seeds buried in shaded conditions also lose physical dormancy mainly during summer, but remain physiologically dormant and do not germinate until late winter or early spring. Besides physical dormancy, seeds of G. robertianum also initially have a high level of physiological dormancy, which is reduced during dry storage. Physiological dormancy is reduced through chilling in winter, thus enabling the seeds to germinate at low temperatures. We conclude that a complex combination of physical and physiological dormancy ensures that G. robertianum seeds germinate in summer at exposed sites and in early spring at shaded sites.
温带森林草本植物的种子具有物理休眠和生理休眠机制，较为罕见，而关于这些物种发芽调控因素的知识则较为零散。二年生的老鹳草主要生长在温带林地，但也可以在暴露的栖息地中找到。已知老鹳草的幼苗可以从春季一直生长到秋季，但关于调节其发芽的环境因素却知之甚少。在这项研究中，对埋藏在遮荫或阳光充足位置的种子的幼苗出芽和物理休眠丧失的物候进行了研究。通过在模拟种子在自然界中经历的温度序列中孵育种子，分析了温度在调节休眠和发芽中的作用。结果表明，夏季阳光充足条件下埋藏的大多数老鹳草种子在失去物理休眠后立即发芽。遮荫条件下埋藏的种子也主要在夏季失去物理休眠，但仍处于生理休眠状态，直到冬末或早春才发芽。除了物理休眠外，老鹳草种子最初还具有高水平的生理休眠，这种休眠在干燥储存过程中会降低。生理休眠通过冬季的冷藏而降低，从而使种子能够在低温下发芽。我们得出结论，复杂的物理休眠和生理休眠的组合确保了老鹳草种子在夏季的暴露地点和早春的遮荫地点发芽。
