Growth and Development of Basil Species in Response to Temperature

Abstract

Basil (Ocimum sp.) is the most popular fresh culinary herb, but the effects of air temperature on growth and development of basil have not been well characterized. Our objective was to quantify the effects of air temperature on growth and development of three basil species. Seedlings of sweet basil (Ocimum basilicum ‘Nufar’), holy basil (O. tenuiflorum), and lemon basil (O. ×citriodorum ‘Lime’ and O. basilicum ‘Sweet Dani’) were placed in five different growth chambers with target air temperatures of 11, 17, 23, 29, or 35 °C. After 3 weeks, chlorophyll fluorescence (Fv/Fm), plant height, node and branch number, fresh and dry weight, and flowering data were recorded. For all species, Fv/Fm increased as temperature increased to 17 or 23 °C, then plateaued, whereas height increased with temperature to 23 or 29 °C. Also, the percentage of plants with flowers or flower buds increased with temperature to 17 or 23 °C for all species, with the exception of sweet basil, of which all plants were vegetative and node appearance rate was calculated. Sweet basil node appearance increased from 0.03 to 0.30 node/day as the temperature increased from 11 to 29 °C. Fresh weight gain increased with increasing temperature to 29 °C, but then decreased at 35 °C. Data from plants grown within the linear air temperature range were used to develop models for calculating the base temperature (Tb) and predicting growth in response to air temperature. These models can be applied by commercial producers to schedule crops and predict yields.