Blue Light Enhances Salt Tolerance in the Model Fern Ceratopteris richardii through Cryptochrome-Mediated Signaling

Global soil salinization is increasing at an annual rate of approximately 10%, threatening to claim 50% of arable land by 2050. High salinity adversely affects crop production by inducing osmotic and ionic stress, which leads to the formation of reactive oxygen species (ROS) that damage cellular structures. Beyond soil quality, light is a critical regulator of plant development and influences how plants respond to environmental stressors. This study investigated how specific light wavelengths affect the salt stress response in the model fern Ceratopteris richardii. It was hypothesized that blue light would mitigate the inhibitory effects of salinity by activating cryptochrome-signaling stress response pathways. Gametophytes were grown under white, blue, red, and green light in both 0 mM and 150 mM NaCl environments. Growth was quantified by measuring the surface area of prothalli and the total number of prothallus cells. In non-saline conditions, white light promoted the greatest growth. However, under 150 mM NaCl stress, blue light exposure resulted in the highest prothallus area and cell counts, while red light resulted in the lowest growth. Despite the improved vegetative growth under blue light, sporophyte development remained completely inhibited regardless of the light treatments in saline conditions. These results suggest that blue light enhances salt tolerance, likely through cryptochrome signaling that stabilizes development against ionic stress. These findings provide evidence that managing spectral light quality could improve crop resilience in salt-affected regions.