Abstract: The daily cycle of ψWL and LER of corn, sorghum, eggplant, cowpea, poplar and paulownia, as well as air temperature, relative humidity and soil water content, are monitored in the field. The results from experiments show that ψWL of expanding leaf exhibits a sinusoidal curve with time, with minimum value around 1300–1500 and maximum value before dawn. The lower the soil water content and the lower ψWL at noon are, the lower the ψWL will be.There are close relations between temperature and LER of corn, sorghum, poplar and paulownia under well-watering. When temperature is limited, LER is rapid at daytime and slow at night. When ψWL is very low at noon, the LER of plant leaves exhibits two peaks, one in the forenoon and the other late in the afternoon. When the soil water content is limited, greater growth of plants occurs at night.Leaf growth of eggplant and cowpea is very sensitive to water deficit, so greater growth of them takes place at night. Leaves shrink at noon under soil water deficit for the drying process.