Seed Germination and Early Growth Responses of Hyssop, Sweet Basil and Oregano to Temperature Levels

Abstract

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.