Development of a Simple Method for Observing Crop Plant Root System Using a Fiber Scope

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For observing roots of crop plants growing in the field, a fiber scope and a portable video recorder were employed in the minirhizotron system. The acrylic tube of 60 mm outer diameter and 54 mm inner diameter was used as the minirhizotron observation tube. The accuracy and the utility of the system were examined.(1) The length of copper wire and all branch roots of soybean on the acrylic tube was measured accurately with this minirhizotron system.(2) All branch roots intersected the face of the acrylic tube in the soil could be distinguished and the length of the roots on the face was measured accurately with the system.(3) It seemed that the minirhizotron tube did not affect significantly the manner of soybean root penetration in the soil.(4) There was significant linear correlation between the length of roots on the face of the minirhizotron tube and the root length density measured with soil-core sampling method in soybean growing in the field.(5) The coefficients of variation with … More the minirhizotron method and with soil-core sampling method were large, which means that many individual measurements should be taken for accurate measurements of root systems. The minirhizotron method is easier to take many measurements than the soil-core sampling method.(6) It was shown by using the system in the field that the roots penetrated deeper and the root length was larger in soybean plants grown under deficient soil moisture than in plants grown under sufficient soil moisture.(7) It was observed that the amount of water extracted from soil by the plants was larger in the soybean with well-developed root system than in poor root system and therefore the degrees of midday reduction in leaf xylem water potential, diffusive conductance and photosynthetic rate were smaller in the former than in the latter.From the results mentioned above, it could be concluded that the minirhizotron system developed in this study is a simple and useful method for measuring root systems of soybean plants growing in the field accurately. Less