ارزيابي خصوصيات جوانه زني بذر دو توده زراعي و طبيعي آويشن خراساني (Thymus transcasicus Klokov) با استفاده از مدلهاي رگرسيوني

Germination behaviour of cultivated and natural stand seeds of Khorasan thyme {Thymus transcaspicus Klokov) with application of regression models

In order to investigate the germination characteristics and cardinal temperatures of Thymus transcaspicus, a laboratory experiment was conducted with two different cultivated and natural seedlots at constant temperatures including 2, 5, 10, 15, 20, 25, 30, 35, 40 and 45 °C in a completely randomized design with four replications. Two seedlots were monitored for variability in germination criteria based on three regression models namely: Five-parameters Beta (FPB), Intersected-lines (ISL) and Quadratic Polynomial (QPN) models. The effect of temperature on rate and percentage of seed germination in both seedlots was significant. For both seedlots the highest germination percentage (GP) was within the range of 10-30 °C while the highest germination rate (GR) occurred in 30 °C. Although means of GP and GR for the field seedlot were higher than the natural seedlot, variability of GP and GR in response to temperature was higher for natural seedlot. Best model fit over the entire temperature range was obtained by the FPB and ISL models for both seedlots. However, FPB model showed most suitable fitness particularly in the case of natural seedlot. Based on the regression between germination rate and temperature in both seedlots, the cardinal temperatures (Tbase, Topt and Tmax) were: (1.2-3.84), (29.1-25.8) and (45-47) °C for field seedlot and (1.0-3.3), (24.9-29) and (45-46) °C for natural seedlot, respectively.