Contrasting interactions between photon spectra and temperature in cold-sensitive basil and cold-tolerant lettuce

Area of Science:

• Plant Physiology
• Environmental Plant Science
• Horticultural Lighting

Background:

• Blue (B) light, far-red (FR) light, and temperature are critical environmental factors influencing plant growth.
• While individual effects are known, the interactive impacts of these signals on plant development remain unclear.
• Understanding these interactions is crucial for optimizing controlled environment agriculture.

Purpose of the Study:

• To investigate the interactive effects of blue light photon flux density (PFD), far-red light fraction, and temperature on lettuce and basil.
• To determine if the effects of far-red light and temperature are modulated by blue light PFD.
• To elucidate species-specific responses to combined light and temperature cues.

Main Methods:

• Lettuce and basil were grown at two temperatures (19°C and 24°C).
• Lighting treatments varied in blue light PFD (40 or 100 µmol m⁻² s⁻¹) and far-red fraction (0.01, 0.19, or 0.32).
• Total PFD and photoperiod were kept constant across all treatments.

Main Results:

• Increasing far-red light fraction promoted shoot expansion in lettuce and internode elongation in basil.
• Lettuce shoot expansion was enhanced by higher temperatures and reduced by higher blue light PFD.
• Far-red light effects on basil internodes were independent of temperature and blue light PFD.
• Increased shoot expansion in lettuce led to decreased foliage coloration, with minimal impact on basil.

Conclusions:

• Plant responses to light and temperature are highly species-dependent, with implications for shade-avoidant vs. shade-tolerant strategies.
• Complex integration of environmental signals, rather than isolated effects, governs plant growth regulation.
• Findings highlight the need for tailored lighting and temperature strategies in horticulture based on crop species.