Hanley M E, Fenner M, Whibley H, Darvill B
School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK.
New Phytol. 2004 Jul;163(1):61-66. doi: 10.1111/j.1469-8137.2004.01094.x.
• Despite the importance of seedling establishment in plant biology, there is no consensus on what constitutes a 'seedling'. Here we examined aspects of early plant development that could be used to mark the transition from the seedling to the postseedling phase. • Using a hypogeal species (pea, Pisum sativum) and an epigeal species (sunflower, Helianthus annuus), we investigated whether the utilization of cotyledon-stored mineral nutrients coincides with any changes in relative growth rate (RGR). We also examined how the timing of cotyledon removal at different points during early development affected subsequent growth. • For both species, the timing of RGR , the exhaustion of cotyledon reserves, and the attainment of independence from cotyledons all roughly coincided (though exhaustion of seed reserves was not observed in the epigeal species because the cotyledons absorbed external nutrients). • We conclude that because the point of attainment of RGR is a distinctly identifiable event, it is a more reliable marker for defining the end of the seedling stage than either the exhaustion of mineral reserves, or the cessation of dependence on cotyledon reserves.
• 尽管幼苗建立在植物生物学中很重要，但对于什么构成“幼苗”尚无共识。在这里，我们研究了早期植物发育的各个方面，这些方面可用于标记从幼苗阶段到幼苗后阶段的转变。
• 我们使用一种地下生长的物种（豌豆，Pisum sativum）和一种地上生长的物种（向日葵，Helianthus annuus），研究了子叶储存的矿质营养的利用是否与相对生长速率（RGR）的任何变化同时发生。我们还研究了在早期发育的不同时间去除子叶的时间如何影响后续生长。
• 对于这两个物种，RGR的时间、子叶储备的耗尽以及从子叶独立的实现都大致同时发生（尽管在地上生长的物种中未观察到种子储备的耗尽，因为子叶吸收了外部养分）。
• 我们得出结论，由于RGR达到的点是一个明显可识别的事件，因此它比矿质储备的耗尽或对子叶储备的依赖停止更可靠地标记幼苗阶段的结束。
