Studies on gas transport system in plants.

用扫描显微镜对莲花叶片中板进行了形态观察。中央板表面可见与气孔相似的结构。其大小约为叶片气孔的2倍，分布密度为叶片气孔的1/4。观察到细胞器内有卫兵样细胞结构。维管器正下方有陷窝，与叶片内的大陷窝有关。这些细胞之间的间隙白天大多很窄或关闭，而夜间大部分间隙很大且开放。结果表明，该装置主要负责控制腔隙内的气体压力，腔隙与大气温湿度差所引起的热渗透和湿压力的物理效应所产生的压力主要发生在白天。腔隙内压力的增加可能最有利于氧气通过扩散输送到根部。相反，较高的压力会导致通风组织的透气率降低，从而降低根系呼吸所需的氧气浓度。已知加压与曝气组织的泄漏量呈负相关。

The morphological observation of central plate of leaf blade of Nelumbo nucifera was conducted with a scanning microscope. The apparatus similar to stoma was found on the surface of the central plate. The size of the apparatus was around 2 limes larger than stoma found on the leaf blade, and the distribution density was one fourth of that of leaf stoma. There observed the guard-like cell structure in the apparatus. There found lacuna just under the apparatus, which was connected to large lacunae running in leaf blade. The most of the gaps between the guard-like cells in the apparatus were very narrow or closed in the daytime, on the other hand the most of the gaps were large and open in the nighttime. It was suggested that the apparatus is responsible for controlling the gas pressure in lacunae, where pressure was generated by physical effects of thermo-osmosis and hygrometric pressurization driven by the differences of temperature and humidity between lacunae and atmosphere mostly occurred in daytime. The increase of pressure in the lacunae may be most beneficial for transport of oxygen to roots by diffusion. The higher pressure, on the contrary, leads to the decrease of ventilation rate in aerenchyma, then concentration of oxygen available for root respiration may be lowered. The pressurization is known to be negatively correlated with leakiness of aerenchyma.