Red and blue lights influence the development of pepper seedlings

Researchers investigated the effects of red and blue light on the leaf and stem development of pepper seedlings (Capsicum annuum L.), revealing significant opposite effects on plant growth.

Red light promoted an increase in leaf area and stem elongation, while blue light resulted in smaller leaves and shorter stems.

The study suggests that these results are related to the regulation of plant hormones and the expression of specific genes.

Leaf growth

Exposure to red light significantly increased leaf area and promoted petiole elongation. However, chlorophyll content was lower compared to plants exposed to blue light, which presented more compact leaves with higher chloroplast density and chlorophyll content. This indicates that blue light favors photosynthetic efficiency, although it limits leaf size.

Stem growth

Stem length was greater under red light, with more elongated cells and greater biomass deposition. Blue light inhibited cell elongation, resulting in shorter stems with greater cell density. These results show an antagonism between the two types of light in modulating the structural growth of plants.

Hormonal mechanisms

Levels of the hormones indole-3-acetic acid (IAA) and trans-zeatin riboside (TZR), which regulate cell growth and leaf expansion, were higher in plants under red light.

On the other hand, blue light reduced these hormones, inhibiting leaf expansion. Genes related to cell development, such as CaGRF and CaARF, were more expressed under red light, promoting cell proliferation.

In contrast, genes such as CaRAX, which limit leaf growth, were more expressed under blue light.

Practical applications

The results provide a theoretical basis for choosing light combinations in industrial seedling production. Red light can be used to maximize leaf area and vertical growth, while blue light can be strategic for controlling plant height and improving photosynthetic efficiency.

More information can be found at doi.org/10.1016/j.plantsci.2024.112338