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Moya, T.B.1, L. J. Wade1 and K. T. Ingram2
1:Agronomy, Plant Physiology and Agroecology Division, IRRI,
Philippines
2:University of Georgia, USA
Introduction
Generally, knowledge on plant root growth dynamics lags behind that of aboveground parts because current techniques for measuring root growth either do not permit repeated measurements on the same roots over time or are too laborious and time consuming. The minirhizotron system consists of three major components: (1) minirhizotron, (2) video recording subsystem, and (3) root image analysis and measurement subsystem.
Methods
We compared the performance of the minirhizotron system to that of soil core sampling in characterizing root length density (RLD) of upland rice cultivars in a greenhouse experiment in the 1992 dry season. The experiment was a 2 x 2 factorial in randomized complete block design with six replications. Two rice cultivars, Moroberekan and Lubang Red were grown under well-watered and drought-stressed conditions.
Results and Discussion
Previous studies have characterized rice rooting depth and RLD by the minirhizotron system (Samson and Sinclair 1994), but results from this study indicated problems associated with use of the minirhizotron system to determine RLD of upland rice cultivars. For both rice cultivars under both water conditions, the minirhizotron system's RLD in the upper 10 cm of the soil was negatively correlated with that of the soil core sampler (r2=0.50). At the soil depths deeper than 10cm, the correlation between the minirhizotron RLD and that of core sampler was positive, however, the minirhizotron system underestimated by about 30% the RLD obtained by soil core sampling. Poor soil tube contact, light penetration into rhizotron and accuracy of tracing root images account for the discrepancy in RLD between these two measurement techniques, (Moya et al,1997). To adapt minirhizotron to root studies on rice, further calibration and operation studies on the minirhizotron system have yet to be done. For repeated measurements of root turnover, however, minirhizotron is preferred.
References