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Sensor in Controlled Environment Agriculture（CEA）: Measuring Growth and Development By Tadashi Takakura（1992） 報告人：張福祥 中華民國八十九年十二月八日

CONTENTS Introduction Classification Reading plants’ faces Problems to be solved Conclusions Reference

Introduction Sensor are essential to monitor and control non-destructively the change in plants and their environment. Direct measurement by sensor of plan growth and development is not easy. Sensor is still one of the most important tasks to be solved in research as well as in practical fields.

Introduction Another difficulty is measuring more than one plant, for example a plant canopy. Monitoring several plants from a canopy in a greenhouse, for example, as indicators of an average could be a practical solution, but the problem would be how to select such indicators.

Introduction Ideal sensing techniques have been connected with the 〝 speaking plant approach. 〞 The speaking plant approach was defined much more broadly by Udink Ten Cate  et al.﹙1978﹚, who again highlighted the direct measurement of plant growth.

Classification The characteristics of measurement methods are shown in Fig. 1 .

Classification The symbols in the figure are a fuzzy presentation based on over-all evaluation of each method. 〝Single 〞 means the measurement of single plant. 〝Canopy〞 to that of more than one plant and usually a canopy.

Classification Partial malfunction, such as disease-affected plant in a preliminary stage, cannot be detected by single method. One of the most important goals for the measurement of the canopy is to monitor and manage all individual plants based on the data for each one. A similar approach is now becoming popular in milk cow management.

Classification A more recent approach uses an electronic devices such as strain gauges. Image analysis has a very broad range. Computer vision is now very commonly used in mechanization and automatization of plant management.

Classification Growth can also be detected by CCD camera imaging. The cloud symbol means that the method can be applicable but has several shortcomings. The umbrella and rain mark means that the method cannot in principle be used for practical purposes.

Classification The sunshine symbol means the method has been successfully used. The snowman symbol means that it has some problems at the present time but may be promising in the future.

Classification

Reading plants’ faces Weight measurement can detect over-all change in growth, but it is sometime too late, after change has been detected, to modify the situation.  non-contact methods as gas balance and image processing will be the next approaches, supported by the recent development of electronic devices.

Reading plants’ faces Over-all detection for whole plants in an enclosure can be done with gas balance techniques,but it is not possible to detect change in individual plant in a canopy. Monitoring and management of individual plant can only be done by image processing with either computer vision or infrared thermometry, just as expert growers are doing every day in their greenhouse.

Reading plants’ faces This technique can be called a 〝reading plants’ faces〞 instead of a 〝speaking plant approach.〞

Problems to be solved To cover all plants in an enclosure, the problems to be solved involve the resolution of sensors such as CCD cameras and infrared thermometers, the speed of processing computers and the size of their memories.

Problems to be solved Software developments that can be used to analyze images are another research target. Overlapping of plant leaves and hidden fruits behind leaves . An air blow method  to move leaves from the view of  a CCD camera is one  of the attempts.

Conclusions Historically, the growth and development of plants were analyzed by destructive sampling methods. Non-destructive methods are becoming common and being applied in practice with the development of electronic devices.

Conclusions Non-destructive methods are used for the measurements of co2 uptake/release by plants, expansion of  leaves, increase of plan weight and elongation of  stems  and for the image processing of plant shapes.

Reference 1. Takakura, T. 1992. Sensor in controlled environment agriculture: measurement growth and development. Acta-Hortic. Wagenningen: International Society for Horticultural Science. (304) P.99-102.