Variation of phenotypic responses to lighting using a combination of red and blue light-emitting diodes versus darkness in seedlings of 18 vegetable genotypes

Abstract

The objectives of this study were to identify traits and screen genotypes sensitive to narrow-waveband light-emitting diode light in 18 vegetable genotypes. Their phenotypic plasticity responses were examined under a combination of red (85%) and blue (15%) light-emitting diodes relative to darkness from seed germination to cotyledon unfolding. The photosynthetic photon flux density was around 316 μmol m−2 s−1 and the photoperiod was 17 h. Generally, light vs. dark delayed germination by reducing germination rate and increasing spread time of germination; inhibited shoot growth by reducing shoot length and fresh mass; promoted root growth by increasing root length, diameter, branching, and fresh mass; and promoted genotype-inherent colouring in leaves and stems. Shoot colour, shoot length, and (or) root branching showed higher plasticity indices than other plant traits in response to light, suggesting that some or all of these plant traits are more sensitive to lighting across the tested genotypes. Using cluster analysis based on the plasticity index, the 18 genotypes were separated into six groups that expressed response sensitivity to part or all of the above-mentioned traits. Based on the average plasticity index of all the tested plant traits, the 18 genotypes were graded into four groups using the Fisher optimal partition. Small- vs. large-seed species and the red- vs. green-leaf/root cultivars within the same species showed higher phenotypic plasticity indices in most cases, suggesting that they are more sensitive to lighting.