利用影像技术在线追踪测量植物生长速率及其对二氧化碳的响应

Tracking of plant growth and its dependence on indoor carbon dioxide level with a webcam

二氧化碳(CO_2)是室内空气质量的重要监测指标之一,同时又是植物光合作用的原材料,与植物生长有着密切的联系.考虑植物生长速率与CO_2浓度之间的关联,利用影像技术发展在线追踪测量植物生长速率的方法,并探索利用该方法实时监测CO_2浓度的可能性,建立基于植物的低成本、简单、灵敏的气体传感平台.使用普通的网络摄像头,开发了基于matlab的、极其灵敏的光学边界跟踪方法,实时测量了活体黄豆幼苗的生长速率(下胚轴茎高增长率)及其与二氧化碳浓度(400~1700ppm)之间的关系.结果显示,随着二氧化碳浓度的增加,植物生长速率从400ppm时的6μm·min^(-1)增加到800ppm时的22μm·min^(-1),但当浓度超过900ppm时,生长速率却随之降低.该方法所观察到的这种现象与文献中使用其他方法得到的结果大致相符,进一步验证了该方法的可信性.另外,此方法成本低、简单、灵敏、无污染,无需化学药品和专门仪器,未来不仅可能应用于空气质量监测,还可以用于植物生理学和农业科学研究.

Plant growth relies on the conversion of carbon dioxide in air to carbohydrates.Naturally,one expects that the plant growth rate depends on carbon dioxide concentration in air.Indoor air quality is of paramount importance to human health.Motivated by the possibility of monitoring indoor carbon dioxide level with potted plants,wedeveloped a sensitive optical tracking method with a webcam to measure the growth rate(height increase in the stem)of soybean(Glycine max L.)in real time over a broad carbon dioxide concentration range,from 400 ppm to1700 ppm.An imaging processing algorithm was developed to track the growth rate from captured images.A paper label was stuck to the stem of plant.The algorithm first plotted the image intensity profile along the hypocotyl,identified a position where the intensity profile of the marker had the largest gradient(e.g.,the edge of the paper label),and determined the vertical shift in the position(growth)from the time sequence images.Result shows the growth rate increases with carbon dioxide concentration from 6μm·min^(-1) at 400 ppm to 22μm·min^(-1) around800 ppm,but decreases when the concentration exceeds 900 ppm.Our optical tracking method has the following advantages:(1)plants are cheap and available everywhere,(2)a camera can achieve real-time measurement without additional equipment,(3)this method produces no pollution and chemical reagents are not necessary.