Time lapse analysis of root elongation rates of rice and sorghum during the day and night

This paper describes a technique to monitor the root elongation rate (RER) per hour for several days, and variation in RER during the day and night. Rice (Oryza sativa L.) and sorghum (Sorghum bicolor Moench) were grown in root boxes placed inside a growth chamber set at 25 degrees C with a 12 h photoperiod. Seminal root axes were sandwiched between a transparent acrylic board and filter paper placed on a loamy sand soil. The roots were photographed under dim green light using a CCD camera connected to a time lapse video recorder. The environment of the root, including temperature, light, nutrient, water and air supply, was controlled precisely and maintained constant. RER fluctuated hourly in sorghum and to a greater extent in rice. Maximum RERs were 1.4 to 4.4 limes faster than minimum rates. RERs during the day and night did not differ statistically when temperatures were the same. (C) 1998 Annals of Botany Company.