Red and blue light ratio affects the growth and quality of edible cactus (Nopalea cochenillifera)

Abstract

This study investigated the effects of light of different wavelengths on the growth and quality of daughter cladodes in the edible cactus Nopalea cochenillifera. Mother cladodes were cultivated under a deep-flow hydroponic culture system and irradiated with red or blue light alone or in combination (in the ratio 1:3 or 3:1) in an enclosed-type plant factory. Daughter cladodes developed from mother cladodes in all treatments. The rate of elongation of first cladodes was lower under blue light and the combination of red and blue light (in the ratio 1:3) compared with other treatments. The number of daughter cladodes was also low under blue light. Thus, compared with red light, blue light appears to suppress daughter cladode development. However, the width of daughter cladodes was higher under blue light and the combination of red and blue light (in the ratio 1:3) compared with other treatments. Total fresh weight (FW) of daughter cladodes emerging from one mother cladode was lowest under blue light and high under combined red and blue light (1:3 and 3:1). The number of spines, an undesirable characteristic of edible cacti, was significantly higher under both combinations of red and blue light (1:3 and 3:1) compared to other treatments. On the other hand, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of extracts of the daughter cladodes was highest under blue light or under combined red and blue light (1:3). Our results show that light wavelength strongly affects daughter cladode growth and development. Thus, controlling the lighting environment is effective for improving growth and quality in edible cacti.