EFFECTS OF TEMPERATURE ON YIELDS AND HYDROLYZABLE CARBOHYDRATE CONTENT OF ALFALFA AND TIMOTHY SEEDLINGS

Abstract

Alfalfa and timothy seedlings were exposed to four temperature treatments, simulating conditions in an average growing season in northern Ontario. Highest yields were recorded under continuous warm temperature (26.7 °C day, 15.6 °C night) and the lowest under continuous cold temperature (15.6 °C day, 4.4 °C night). Warm temperature conditions followed by a cold period decreased growth rate, the effect being more severe on alfalfa than on timothy. Growth was slower at first for timothy than for alfalfa, but timothy growth rate eventually exceeded that of alfalfa.Alfalfa root weights showed a strong dependence on temperature and were closely related to herbage yields. Timothy root weights demonstrated a smaller reaction to temperature and little relationship with herbage production. Shoot: root ratios were higher in timothy than in alfalfa but showed no consistent relationship with temperature.Timothy had a higher hydrolyzable-sugar content than alfalfa. Continuous low temperature resulted in the lowest sugar content in both species, but exposure to low temperature following a warm period gave the highest content.