Fogliani Bruno, Gâteblé Gildas, Villegente Matthieu, Fabre Isabelle, Klein Nicolas, Anger Nicolas, Baskin Carol C, Scutt Charlie P
Institut Agronomique néo-Calédonien (IAC), BP 73 Port Laguerre, 98890 Païta, New Caledonia.
Laboratoire Insulaire du Vivant et de l'Environnement (LIVE)-EA 4243, University of New Caledonia (UNC), BP R4, 98851 Noumea, New Caledonia.
Ann Bot. 2017 Mar 1;119(4):581-590. doi: 10.1093/aob/mcw244.
Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda , the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade.
Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms.
Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp-mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth.
Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp-mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed.
近期基于简约法的系统发育重建表明，早期被子植物的种子具有形态生理休眠或生理休眠，前者被认为更有可能。本研究的目的是确定最基部被子植物谱系无油樟目唯一现存代表物种无油樟（Amborella trichopoda）种子的休眠类型，以期全面解析被子植物分支基部存在的休眠类型。
将无油樟去除肉质部分的核果进行萌发和解剖，以观察其结构和胚的生长。测试了包括酸蚀、赤霉素处理和种子切除在内的预处理方法对休眠破除和萌发的影响。然后采用最大简约法进行性状状态图谱分析，纳入本研究及已发表文献的数据，以确定早期被子植物可能存在的休眠类型。
无油樟种子萌发需要至少约90天的暖温层积期，之后胚乳膨胀，使具有透水性的果皮 - 中果皮包膜裂开。然后胚在种子内迅速生长，约17天后胚根伸出，再过24天后子叶伸出。赤霉素处理、酸蚀以及从周围核果组织中切除种子均通过缩短休眠初始阶段（在胚生长之前）来促进萌发。
无油樟种子具有非深度简单形态生理休眠，其中果皮 - 中果皮包膜的机械阻力在初始生理阶段起关键作用。包括本研究获得的数据在内的最大简约法分析表明，形态生理休眠可能是开花植物的一个祖征性状。讨论了这一结论对早期被子植物进化研究的意义。
