• Stomata exert control on fluxes of CO₂ and water (H₂O) in the majority of vascular plants and thus are pivotal for planetary fluxes of carbon and H₂O. However, in mosses, the significance and possible function of the sporophytic stomata are not well understood, hindering understanding of the ancestral function and evolution of these key structures of land plants.
• Infrared gas analysis and ¹³CO₂ labelling, with supporting data from gravimetry and optical and scanning electron microscopy, were used to measure CO₂ assimilation and water exchange on young, green, ± fully expanded capsules of 11 moss species with a range of stomatal numbers, distributions, and aperture sizes.
• Moss sporophytes are effectively homoiohydric. In line with their open fixed apertures, moss stomata, contrary to those in tracheophytes, do not respond to light and CO₂ concentration. Whereas the sporophyte cuticle is highly impermeable to gases, stomata are the predominant sites of ¹³CO₂ entry and H₂O loss in moss sporophytes, and CO₂ assimilation is closely linked to total stomatal surface areas.
• Higher photosynthetic autonomy of moss sporophytes, consequent on the presence of numerous stomata, may have been the key to our understanding of evolution of large, gametophyte‐independent sporophytes at the onset of plant terrestrialization.

中文翻译：

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苔藓气孔不响应光和二氧化碳浓度，但促进孢子体吸收碳：气体交换、气孔孔径和 13C 标记研究

• 在大多数维管植物中，气孔控制 CO ₂和水 (H ₂ O) 的通量，因此对碳和 H ₂ O 的行星通量至关重要。然而，在苔藓中，孢子体气孔的重要性和可能的​​功能是不太了解，阻碍了对这些陆生植物关键结构的祖先功能和进化的理解。
• 红外气体分析和¹³ CO ₂标记，以及来自重量分析和光学和扫描电子显微镜的支持数据，用于测量具有一系列气孔数的 11 种苔藓物种的年轻、绿色、± 完全膨胀的胶囊上的CO ₂同化和水交换、分布和孔径大小。
• 苔藓孢子体实际上是同型的。与其开放的固定孔径一致，与气管植物中的气孔相反，苔藓气孔对光和 CO ₂浓度没有反应。虽然孢子体表皮高度不透气，但气孔是苔藓孢子体中¹³ CO ₂进入和 H ₂ O 损失的主要部位，并且 CO ₂同化与总气孔表面积密切相关。
• 由于存在大量气孔，苔藓孢子体具有更高的光合自主性，这可能是我们理解植物陆生化开始时大型、不依赖配子体的孢子体进化的关键。