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 an d night. Rice (Oryza sativa L.) and sorghum (Sorghum bicolor Moench) w ere grown in root boxes placed inside a growth chamber set at 25 degre es C with a 12 h photoperiod. Seminal root axes were sandwiched betwee n a transparent acrylic board and filter paper placed on a loamy sand soil. The roots were photographed under dim green light using a CCD ca mera connected to a time lapse video recorder. The environment of the root, including temperature, light, nutrient, water and air supply, wa s 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 Ann als of Botany Company.