effect of supplemental light quality and season on growth and photosynthesis of two cultivars of greenhouse sweet pepper (capsicum annuum l.)

In the past decade, light-emitting diodes (leds) have been increasingly regarded as a suitable replacement for many other types of light source. they have attracted lots of attention. supplemental lighting improves growth and yield of greenhouse vegetables such as sweet pepper, cucumber and tomato all-year round. in the present study, the growth and photosynthetic functionality of two greenhouse sweet pepper cultivars, i.e. ‘padra’ and ‘shadleen’, were evaluated in response to the quality of led lighting on sweet pepper seedlings. for this purpose, three combinations of red (r) and blue (b) leds (r90b10, r80b20, and r70b30 were used, with a light intensity of 200 μmol m-2 s-1 in all led light treatments. evaluations were done in two growing seasons, winter and summer, in rasht, iran. seedlings exposed to supplemental light had thicker stems, wider leaf area, higher biomass, and greater photosynthetic functionality. we observed an increase in the ratio of b-light led to the positive effects on the growth and photosynthesis functionality of the seedlings. however, no significant difference was observed between the cultivars. the effect of supplemental light was more emphasized in the winter. thus, the control seedlings were weak and pale, while strong seedlings with dark green leaves were produced under the supplemental light. in conclusion, supplemental led lighting appeared as a practical tool for the commercial production of greenhouse seedlings.