Plant root function under the gaseous environmental condition of medium in hydroponics.

为了研究水培基质气体环境对植物根系功能的影响，采用在线传感器探头和气相色谱仪系统，对砂、浮石和岩棉板等水培基质中气体浓度进行了测定。氧分压和游离无机碳浓度（气态CO_2分压）能够在线测量。隔热传感器盖实现了在光照条件下对介质中氧气和二氧化碳的准确测量。即使在介质中的水含量波动的情况下，也能够准确地测量气体分压。试验结果表明，在一定的基质中，水分含量会影响根系气生条件。但是，即使在灌溉后，岩棉板中的氧分压仍然很高。这可能是种植在岩棉板上的园艺作物根系和新梢生长旺盛的原因。对于介质中的一些极微量气体，我们重点研究了烃类气体、乙烯，并尝试使用气相色谱系统进行测定。但是，我们无法获得定量分析培养基中积累的乙烯所需的准确度。研究结果表明，水培基质中气体的分析方法可用于植物根系环境因子的精确控制，为植物水培生产环境的优化提供依据。

For a study on effects of gaseous environment in medium of hydroponics on plant root function, gas concentration in root media, such as sand, pumice stone and rockwool slab, was measured by using online sensor probes and a gas chromatograph system. Oxygen partial pressure and concentration of free inorganic carbon (gaseous CO_2 partial pressure) was able to be measured online. The thermal insulating sensor cover brought about accurate measurement of oxygen and carbon dioxide in the medium under the light condition. Even in the case of fluctuated water content in the medium, the gas partial pressure was able to be measured accurately. From the result of the experiment, it was found that water content in a certain medium could affect root aerial condition. But, very high oxygen partial pressure in the rockwool slab was maintained even after irrigation. It could be the reason that vigorous root and shoot growth was found in the horticultural crop planted in the rockwool slab.For some kinds of a very small amount of gases in the medium, we focused on the hydrocarbon gas, ethylene, and tried to measure using a gas chromatograph system. But, we were not able to obtain the accuracy necessary for quantitative analysis of ethylene accumulated in the medium. More effective method for sampling the very small amount of gases was necessary.From the results, methods of gas analysis on hydroponic medium could be useful for exact control of root environmental factors for optimization of environment for plant production in hydroponics.