| Abstract: | A measuring device is described with which it is possible torecord the elongation rate (in mm h-1) of monocotyledonous leavesduring the whole growing period. By means of inductive displacementtransducers connected to a computer, the elongation rate isdetermined every 10 min during day and night for 3–8 d.A time period of 30 min proved to be suitable for calculatingthe elongation rate at any given moment. Shorter periods emphasizethe experimental error and longer time periods tend to concealsudden changes in the elongation rate. Elongation rate curvesof wheat leaves are presented. They revealed that the elongationrate. Elongation rate curves of wheat leaves are presented.They revealed that the elongation rates during the night periodwere significantly lower than during the day (approximately60–70% of the rates by day). This reduction is not causedby a reduction of the plant temperature. If the night periodwas extended, the elongation rate decreased almost to zero after14 h darkness. The length of this dark period until decreasebegins was dependent on the previous day's light intensity.The elongation rates of the 3rd wheat leaf under the given conditionswere for 5 d about 3 mm h-1, and during the nights about 2 mmh-1. During the 7th day, the elongation rate decreased and remainedzero from the 8th day onwards. |
