Studies on Effect of Light Spectrum and Photoperiod on Days to 50% Flowering and Fruit Morphology of Chilli (Capsicum annuum L.) in Indoor Vertical Systems

Abstract

The present investigation was conducted to evaluate the influence of different LED light spectra and photoperiod combinations on flowering behaviour and fruit morphological characteristics of chilli under controlled indoor vertical farming conditions. The experiment comprised two chilli varieties, Thai chilli and Bullet chilli, subjected to five light treatments consisting of different red and blue LED light ratios under varying photoperiods. Significant differences were observed among the treatments and varieties for days to 50% flowering and fruit morphology. The Bullet chilli variety exhibited superior performance over Thai chilli by attaining 50% flowering earlier and producing fruits with greater length, diameter, and individual fruit weight under favourable light conditions. Among the light treatments, the 2R:1B LED spectrum combined with a 16-hour photoperiod effectively reduced the number of days to 50% flowering, indicating an enhanced flowering response under extended light exposure. In contrast, the 1R:2B LED spectrum with a 14-hour photoperiod improved fruit morphological traits, resulting in better fruit size and weight compared with the control. The findings indicate that the optimisation of LED light quality and photoperiod can effectively regulate flowering time and improve fruit morphology in chilli. These results highlight the potential application of LED-based lighting strategies for accelerating flowering and enhancing fruit quality in indoor vertical farming and speed-breeding programmes.