Optimal Light Intensity for Lettuce Growth, Quality, and Photosynthesis in Plant Factories

Area of Science:

• Agricultural Science
• Plant Physiology
• Horticulture

Background:

• Light is essential for plant growth and nutrition in agriculture.
• Artificial lighting offers control over plant light environments.
• Balancing plant growth with nutritional quality under artificial light is challenging.

Purpose of the Study:

• To investigate the effects of different light intensities on lettuce growth and nutritional quality.
• To determine the optimal light intensity for enhanced lettuce yield and nutrient content.
• To provide insights into environmental factor optimization for sustainable agriculture.

Main Methods:

• Lettuce was subjected to three light intensity treatments: 180 μmol m⁻² s⁻¹ (L1), 210 μmol m⁻² s⁻¹ (L2), and 240 μmol m⁻² s⁻¹ (L3).
• Plant growth parameters (height, weight, leaf area, canopy diameter) and nutritional components (soluble sugar, vitamin C, nitrate, amino acid) were measured.
• Transpiration rate, stomatal conductance, membership function values, and heatmap analysis were used for comprehensive evaluation.

Main Results:

• Light intensity L2 (210 μmol m⁻² s⁻¹) significantly improved plant height, fresh weight, dry weight, and leaf area.
• L2 treatment also led to significant increases in total soluble sugar, vitamin C, nitrate, and free amino acid content.
• L3 treatment primarily affected canopy diameter and root-shoot ratio, while L1 showed minimal impact.
• Lettuce exhibited the highest membership function value, indicating optimal yield and quality under L2 conditions.

Conclusions:

• Light intensity significantly influences lettuce growth and nutritional profiles.
• A light intensity of 210 μmol m⁻² s⁻¹ is optimal for achieving a balance between high yield and superior nutritional quality in lettuce.
• Findings offer valuable guidance for optimizing artificial lighting strategies in controlled agricultural environments.