Departamento de Biologia, Universidade Federal de Lavras, Lavras, 37200-000, Brazil.
Instituto de Ciências da Natureza, Universidade Federal de Alfenas, Alfenas, 37130-001, Brazil.
Protoplasma. 2021 Jul;258(4):765-777. doi: 10.1007/s00709-020-01597-8. Epub 2021 Jan 6.
Radial oxygen loss is a physical phenomenon that occurs naturally in aquatic plants. Typha domingensis was chosen as a model plant because it possesses basic morphological characteristics, such as a stem (rhizome) that produces leaves and adventitious roots, which are present in many aquatic plants. This study aimed to evaluate the following: the relevance of the anatomy of T. domingensis on gas diffusion among organs; the influence of plant parts on radial oxygen loss; the role of catalase in radial oxygen loss; and the proposition of a novel explanation for the downward diffusion of oxygen through the organs of this aquatic macrophyte and into the environment. Typha domingensis plants were cultivated in a greenhouse under different conditions: plants with intact leaves, plants with leaves cut in half, and plants without leaves. Furthermore, we evaluated the percentage of aerenchyma in different vegetative organs, the minimum pressure required for radial oxygen loss, the daily variations of dissolved oxygen, and the roots' catalase activity. The results demonstrated that certain cellular features contributed to decreased oxygen diffusion among the organs, specifically, those found in the leaf-rhizome and root-rhizome interfaces as well as the suberin and lignin layers in these regions. Additionally, our experiments with a catalase activator and inhibitor validated that a significant amount of the oxygen released in radial oxygen loss could not, in fact, be exclusively supplied by the atmosphere. Thus, a complementary model is proposed in which catalase activity is an important component of radial oxygen loss.
径向氧气损失是一种自然发生在水生植物中的物理现象。选择香蒲作为模式植物，是因为它具有基本的形态特征，如产生叶片和不定根的茎（根茎），这在许多水生植物中都存在。本研究旨在评估以下几个方面：香蒲解剖结构对器官间气体扩散的相关性；植物部分对径向氧气损失的影响；过氧化氢酶在径向氧气损失中的作用；以及对这种水生大型植物器官中氧气向下扩散到环境中的新的解释。香蒲植物在温室中在不同条件下进行了培养：有完整叶片的植物、叶片切成两半的植物和没有叶片的植物。此外，我们评估了不同营养器官中通气组织的比例、径向氧气损失所需的最小压力、溶解氧的日变化以及根的过氧化氢酶活性。结果表明，某些细胞特征有助于减少器官间的氧气扩散，特别是在叶片-根茎和根-根茎界面以及这些区域的栓质和木质素层中发现的特征。此外，我们对过氧化氢酶激活剂和抑制剂的实验验证了，在径向氧气损失中释放的大量氧气实际上不能完全由大气供应。因此，提出了一个补充模型，其中过氧化氢酶活性是径向氧气损失的一个重要组成部分。
