Growth of cucumber plants (Cucumis sativus L.) under diurnal control of air temperature

Growth of cucumber plants (Cucumis sativus L.) was analyzed under three different control regimes of air temperature (i.e., constant-value, two-value and variable-value controls): Desired values were set at 20°C under the constant-value control, at 15°C (night) and 25°C (day) under the two-value control and in a sinusoidal pattern between 15°C and 25°C under the variable-value control. Stem length, leaf area and shoot fresh weight under the two-value control were smaller than those under the constant-value control and the variable-value control, and however percent of dry matter became largest under the two-value control. The largest stem length and leaf area were found under the variable-value control. Thus, it is suggested that the shoot growth can be modified by the control regimes of air temperature, and the variable-value control of air temperature can promote the plant growth.