Enhancing greenhouse pepper production using pre-transplant LED treatments

Pepper (Capsicum annuum L.) is a widely cultivated vegetable whose growth and development are significantly modulated by light quality. This study aimed to evaluate the effects of different LED light treatments during the seedling stage on pepper subsequent development and yield after transplanting into a greenhouse. Commercial sweet pepper variety Morava was used as the plant material. At the phenological stage of first true leaf formation, the plants were placed in closed plant growth chambers under four light treatments: multispectral white light-emitting diodes (W LEDs), monochromatic blue LEDs (B LEDs), red LEDs (R LEDs), and a mixed (50:50% ratio) red and blue LEDs (RB LEDs). The seedlings were cultivated for either 20 or 27 days under a 12/12 h (light/dark) photoperiod at a controlled temperature of 23 ± 2 °C. After 20 and 27-day exposure periods, five uniform seedlings per treatment were transplanted into larger plastic pots and transferred to a greenhouse, where they were grown under natural daylight for an additional 51 and 44 days, respectively. At the full maturity stage, the number of fruits and yield per plant, chlorophyll content, and total soluble sugar content were recorded. The results show that the number of pepper fruits per plant was significantly influenced by both the light treatment and its interaction with the duration of light exposure. In contrast, the fruit weight, total soluble sugar content, and chlorophyll content depended exclusively on the duration of exposure to the light treatments. A 27-day red light treatment applied at the first true leaf stage significantly increased fruit number and weight while proving statistically equivalent to other leading treatments in optimizing sugar and chlorophyll accumulation.