The objectives of this survey were to determine the effect of temperature on germination and seedling growth of Hyssop (Hyssopus officinalis L.), Sweet basil (Ocimum basilicum L.) and Oregano (Origanum vulgare L.) (Lamiaceae family) as well as comparing species regarding germination behavior and growth characteristics. Seeds were germinated on a temperature-gradient bar varying between 5 and 40 °C (with 5 °C intervals). Results indicated that the highest germination percentage of hyssop (92-98%), sweet basil (86-90%) and oregano (74-77%) occurred at 20-30 °C, 25-30 °C and 20-30 °C, respectively; therefore, moderate and warm temperatures are proper for germination of all species. In all species the maximum germination rate obtained at 30 °C. Among all species, Day 10 % of Sweet basil Germination had the lowest value, which indicates faster germination. The cardinal temperatures (base, optimum and ceiling or maximum) were estimated by the segmented model. Base temperature (Tb) was calculated for hyssop, sweet basil and oregano as 3.42, 5.70 and 5.46 °C, respectively. Optimal temperature (To) calculated for all species was approximately 30°C, So warmer temperatures are much more proper for them. The species showed different maximum temperatures (Tm) from 42.91 (Oregano) to 48.05 °C (Hyssop). In Hyssop and Sweet basil optimum growth of seedlings were observed at 30°C while Oregano reached its best growth at 25°C. The difference between maximum and minimum temperatures of germination knowing as temperature range (TR) index could show adaptation capability to broad sites for planting and domestication. Regarding this index Hyssop stood in the first place.

Temperature is the most critical factor determining success or failure of plant establishment. Seed germination response of five medicinal species include three seed-propagated perennial species, Cichorium intybus, cynara scolymus and Echinacea purpurea and vegetative-reproduction perennial species, Achillea millefolium and annual species, Matricaria aurea were assessed at constant temperatures. The seeds were exposed to constant temperatures of 5, 10, 15, 20, 25, 30, 35, 40 and 45°C under total darkness. Germination percentage of all the species were significantly affected by various temperatures (p ≤ 0.001). A. millefolium did not germinate at 5-10 and 35-45°C, but showed noticeable germination percentage (73.3-100%) at temperatures ranged from 15-30° C. The highest total germination percentage was observed within the range of 15-35 °C for other species. Also, we calculated cardinal temperatures (the minimum, optimum and maximum temperature) for seed germination of species. The highest value for minimum temperature was 10.07ºC in A. millefolium followed by C. scolymus and M. aurea (5ºC) while the lowest was for E. purpurea and C. intybus (2.68 and 2.90ºC respectively). The lowest value for optimum temperature was detected in A. millefolium (22.72ºC) and M. aurea (23.88°C) while the maximum values were observed in E. purpurea and C. intybus (30.40ºC and 29.90ºC respectively). Based on results of present study we concluded that species with both vegetative and seed-propagated reproduction forms like A. millefolium had smaller temperature range rather those with just one way of reproduction (seed production).

No abstract

No abstract