| 摘要 |
In the commercial cultivation of plants such as tomatoes in glass houses, their roots are oxygenated by supplying oxygen to oxygenation pipes (28) embedded in support medium for the roots. The rate of oxygenation is increased or decreased automatically in response respectively to increases or decreases in the number of quanta of photosynthetically active radiation incident per unit time on the glass house. Typically an oxygen flow rate control valve (14) responds to a sensor (8) comprising a photo-electric cell (18) having a filter (20) that transmits only chosen wave lengths. |
