3. Relationship between Important Ecological Factors Characteritics of Cultivars and Introduction 1. Temperature factors Response of crops to temperatures Higher temperature----fastercrop growth----shorter duration Upper limit, lower limit, critical temp. optimum temp Vernalization(春化作用) in winter crops 2. Light factors Length of day: long day >12h; short day 12h Response to light: long-day crops: Wheat, Barley short-day crops: Rice; maize Intensity of Light: Depending on the altitude 3. Precipitation and humidity Yearly amount Yearly distribution and seasonal distribution vS requirement of crops for water Air humidity3. Relationship between Important Ecological Factors, Characteritics of Cultivars and Introduction 1. Temperature factors Response of crops to temperatures: Higher temperature----faster crop growth----shorter duration Upper limit, lower limit, critical temp., optimum temp. Vernalization (春化作用）in winter crops 2. Light factors Length of day：long day >12h; short day < 12h Response to light: long-day crops: Wheat, Barley short-day crops: Rice; Maize Intensity of Light: Depending on the altitude 3. Precipitation and Humidity Yearly amount Yearly distribution and seasonal distribution vs. requirement of crops for water Air humidity