The Effect of Air Temperature on Growth of Eight Herb Species

Abstract

The effect of different constant air temperatures (18˚C, 21˚C, 24˚C and 27˚C) and variable temperatures (24˚C/18˚C and 27˚C/15˚C in 12 h/12 h periods) on basil, sage, thyme, lemon balm, cilantro, rosemary, oregano and rocket was studied. Supplementary lighting was given 16 h·day −1 at a photon flux density (PFD) of 150 µmol·m −2 ·s −1 (corresponding to 8.6 mol·m −2 ·day −1 photosynthetic active radiation [PAR]). Including daylight the PAR was 29.6 ± 6.9 mol·m −2 ·day −1 as a mean during the experimental period. Increasing the temperature from 18˚C to 27˚C increased the fresh weight in basil (106%), sage (95%), rosemary (126%) and rocket (62%), while an increase from 18˚C to 24˚C increased the weight in lemon balm (78%), cilantro (41%), oregano (40%) and thyme (58%). For the last four species the fresh weight was unaffected by a further increase to 27˚C. No significant difference was found between the 24˚C/18˚C and 27˚C/15˚C treatments. These treatments gave a mean temperature of about 21˚C, and no significant differences were found between these treatments and the constant 21˚C treatment. The plant height generally increased in the same proportion as the fresh weight increased in the different species. No differences were visually observed between the treatments after two weeks under indoor conditions. All species remained green except cilantro and rocket, for which some leaf yellowing took place. A simple test indicated that the flavour increased with increasing temperature (from 18˚C to 27˚C) in all species except cilantro.

Growth and Development of Basil Species in Response to Temperature

“…Our models showed increases of 272% and 276%, respectively, after 3 weeks of growth. Mortensen (2014) reported the fresh weight of sweet basil increased by 106% as temperature increased from 18 to 26°C, whereas our models predicted a 120%, 124%, 135%, and 112% increase in sweet basil, lemon basil 'Sweet Dani', lemon basil 'Lime', and holy basil, respectively, across the same temperature range. In contrast, Chang et al (2005) found no differences in weight between plants grown at 25 and 30°C and, although the air temperatures were different, our results showed a 51% and 52% increase in fresh and dry weight of sweet basil, respectively, as temperatures increased from 23 to 29°C, followed by a decrease as temperature increased to 35°C.…”

“…The results presented here provide a comprehensive evaluation on the effects of air temperature on growth and development of four basil species. Our sweet basil results have a similar trend as those from Chang et al (2005) and Mortensen (2014), although they differ in respect to magnitude. In the work by Chang et al (2005), after 1 week of temperature treatments, the fresh and dry weight of sweet basil increased by 27% and 29%, respectively, as temperature increased from 15 to 25°C.…”

“…Similarly, in our study, the node appearance rate of sweet basil increased as temperature increased up to 29°C, then decreased as temperature increased to 35°C, whereas the predicted increase from 15 to 25°C was 151%. Mortensen (2014) highlighted a 125% increase and Chang et al (2005) reported a 27% increase in sweet basil height as temperature increased from 18 to 26°C or from 15 to 25°C, respectively. Similarly, our results predicted an increase in height of 51% and 114% as temperature increased from 18 to 26°C and from 15 to 25°C, respectively.…”

“…Although Chang et al (2005) evaluated the growth of sweet basil at different temperatures, the study evaluated three temperatures only, which was insufficient to model growth. Mortensen (2014) grew sweet basil at constant air temperatures from 18 to 26°C. However, with no supraoptimal air temperatures, T opt could not be determined, nor was T b or the slope of the linear range calculated.…”

Effects of irrigation management and seasonal stages on essential oil content and biomass of Origanum vulgare L.

“…They also found that these plants produced thick epidermis and mesophyll in the leaves when they met the evapotranspirometric demand of the season; therefore, water storage by leaves has helped cell turgor and, thereby, increased the leaf area. Thus, radiation absorption is expanded to positively boost biomass accumulation during the warmest seasons (Mortensen, 2014).…”