Hornwort stomata do not respond actively to exogenous and environmental cues
Hornwort stomata do not respond actively to exogenous and environmental cues
复制标题
DOI：
10.1093/aob/mcy045
复制
发表时间：
2018-06
期刊：
影响因子：
4.2
通讯作者：
S. Pressel;K. Renzaglia;Richard S Dicky Clymo;J. Duckett
中科院分区：
文献类型：
--
作者：
S. Pressel;K. Renzaglia;Richard S Dicky Clymo;J. Duckett
背景与目的由于苔藓植物的气孔发生在孢子囊上，它们受到不同于维管植物叶片上的发育和进化的限制。目前还没有确凿的实验证据证明金鱼藻气孔对外界刺激的反应。方法比较金鱼藻气孔对脱落酸(ABA)、干燥、黑暗和质壁溶解的反应，并与维管植物叶片进行比较。用X射线微区分析了保卫细胞和相邻细胞中的钾离子浓度，用低温扫描电子显微镜比较了孢子体细胞间隙和管状植物细胞间隙的个体发育。关键结果：金鱼草气孔在发育早期开放，此后保持开放。在角藻中，实验处理基于对9000个气孔的测量，在干燥和质壁分离后仅产生轻微的孔尺寸减小，而在ABA处理和黑暗处理后没有变化。在维管植物中，所有这些处理都导致气孔完全关闭。在所有处理下，角菜保卫细胞和表皮细胞中的钾浓度在所有时间都是相似的。角豆草气孔大小对干燥和质壁分离的响应可能是所有表皮细胞和海绵状叶绿素细胞的机械和/或胁迫反应，影响保卫细胞。与横跨管状植物的新生充满气体的对应物种不同，角藻中的孢子体细胞间空间最初是充满液体的。结论与维管植物相比，角藻缺乏气孔开闭的生理调节，支持角藻气孔主要参与孢子体的干燥和孢子排出，而不是光合作用相关的气体交换的调节。我们的结果与苔藓植物早期获得主动控制气孔运动的概念背道而驰，这是从以前的苔藓实验中提出的。
Backgrounds and Aims Because stomata in bryophytes occur on sporangia, they are subject to different developmental and evolutionary constraints from those on leaves of tracheophytes. No conclusive experimental evidence exists on the responses of hornwort stomata to exogenous stimulation. Methods Responses of hornwort stomata to abscisic acid (ABA), desiccation, darkness and plasmolysis were compared with those in tracheophyte leaves. Potassium ion concentrations in the guard cells and adjacent cells were analysed by X-ray microanalysis, and the ontogeny of the sporophytic intercellular spaces was compared with those of tracheophytes by cryo-scanning electron microscopy. Key Results The apertures in hornwort stomata open early in development and thereafter remain open. In hornworts, the experimental treatments, based on measurements of >9000 stomata, produced only a slight reduction in aperture dimensions after desiccation and plasmolysis, and no changes following ABA treatments and darkness. In tracheophytes, all these treatments resulted in complete stomatal closure. Potassium concentrations are similar in hornwort guard cells and epidermal cells under all treatments at all times. The small changes in hornwort stomatal dimensions in response to desiccation and plasmolysis are probably mechanical and/or stress responses of all the epidermal and spongy chlorophyllose cells, affecting the guard cells. In contrast to their nascent gas-filled counterparts across tracheophytes, sporophytic intercellular spaces in hornworts are initially liquid filled. Conclusions Our experiments demonstrate a lack of physiological regulation of opening and closing of stomata in hornworts compared with tracheophytes, and support accumulating developmental and structural evidence that stomata in hornworts are primarily involved in sporophyte desiccation and spore discharge rather than the regulation of photosynthesis-related gaseous exchange. Our results run counter to the notion of the early acquisition of active control of stomatal movements in bryophytes as proposed from previous experiments on mosses.