School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
New Phytol. 2011 Apr;190(2):311-9. doi: 10.1111/j.1469-8137.2010.03524.x. Epub 2010 Nov 9.
• Many wetland plants produce aquatic adventitious roots from submerged stems. Aquatic roots can form chloroplasts, potentially producing endogenous carbon and oxygen. Here, aquatic root photosynthesis was evaluated in the wetland plant Meionectes brownii, which grows extensive stem-borne aquatic roots during submergence. • Underwater photosynthetic light and CO(2) response curves were determined for aquatic-adapted leaves, stems and aquatic roots of M. brownii. Oxygen microelectrode and (14)CO(2)-uptake experiments determined shoot inputs of O(2) and photosynthate into aquatic roots. • Aquatic adventitious roots contain a complete photosynthetic pathway. Underwater photosynthetic rates are similar to those of stems, with a maximum net photosynthetic rate (P(max)) of 0.38 μmol O(2) m(-2) s(-1); however, this is c. 30-fold lower than that of aquatic-adapted leaves. Under saturating light with 300 mmol m(-3) dissolved CO(2), aquatic roots fix carbon at 0.016 μmol CO(2) g(-1) DM s(-1). Illuminated aquatic roots do not rely on exogenous inputs of O(2). • The photosynthetic ability of aquatic roots presumably offers an advantage to submerged M. brownii as aquatic roots, unlike sediment roots, need little O(2) and carbohydrate inputs from the shoot when illuminated.
• 许多湿地植物从水下茎中产生水生不定根。水生根可以形成叶绿体，潜在地产生内源性碳和氧。在这里，对湿地植物弯梗水蕨（Meionectes brownii）的水生根光合作用进行了评估，该植物在淹没时会产生广泛的茎生水生根。• 为适应水生环境的叶片、茎和弯梗水蕨的水生根确定了水下光合作用的光和 CO₂响应曲线。氧微电极和（14）CO₂吸收实验确定了 shoots 将 O₂和光合作用产物输入到水生根中的情况。• 水生不定根含有完整的光合作用途径。水下光合作用速率与茎相似，最大净光合速率（P(max)）为 0.38 μmol O₂ m⁻² s⁻¹；然而，这比适应水生环境的叶片低约 30 倍。在 300 mmol m⁻³溶解 CO₂的饱和光下，水生根以 0.016 μmol CO₂ g⁻¹ DM s⁻¹的速度固定碳。受光的水生根不依赖于外源 O₂的输入。• 水生根的光合作用能力可能为淹没状态下的弯梗水蕨提供了优势，因为与沉水根不同，受光时水生根几乎不需要来自 shoots 的 O₂和碳水化合物输入。
