Thermal-biological aspects on seed germination of hairy bird's-foot trefoil under different temperatures

The objective of this research was to determine the minimal, optimal and maximal temperatures for seed germination of Lotus subbiflorus Lag., using germination percentage, speed, frequency, informational entropy and enthalpy of activation of germination. The experiment was carried out in two lots with four replicates of 100 seeds each. The data were submitted to variance analysis and means were compared by Tukey's test. Eight constant temperatures (0, 5, 10, 15, 20, 25, 30 and 35 degrees C) and light exposition (darkness and 8 h of light plus 16 h of darkness) were used. This species of seed germinates in a temperature range of minimal values between 0 and 5 degrees C, optimal values between 15 and 20 degrees C and maximal values between 30 and 35 degrees C. Germination rate was temperature dependent. The highest values of speed germination, occurring between 15 and 20 degrees C below and above this range germination speed had a significant reduction. The lowest values of informational entropy occurred between 15 and 20 degrees C, showing a higher synchronization of germination process in these temperatures. The enthalpy value of the system was calculated, reaching its minimum point at 278 K, and its maximum, at 303 K; the point at which the curve crossed the absciss axis was 290.5 K.