Screening of Positive Regulatory Stimuli for Stomatal Opening in Chinese Cabbage

Increasing the stomatal aperture is a crucial strategy for enhancing the rate of CO2 absorption, which ultimately contributes to increased plant yield through improved photosynthetic activity. The successful implementation of this strategy depends on the rapid identification of positive regulatory environmental stimuli that promote stomatal opening. However, current research on stomatal opening regulation has predominantly focused on Arabidopsis and other crops, with comparatively less attention given to leafy vegetables. In this study, Chinese cabbage was selected as the experimental material. A suitable method for isolating stomata from Chinese cabbage was developed by comparing the advantages and disadvantages of several commonly used stomatal isolation techniques. Subsequently, an effective method for observing stomatal aperture was established through an investigation of the time and concentration dependence on potassium-containing solutions. Utilizing this observation method, the stomatal aperture response to twelve environmental stimuli was examined to facilitate the rapid screening of a formula to enhance stomatal opening. The stomatal aperture observation protocol involved incubating the abaxial epidermis, obtained via the epidermal peeling method, in an opening solution containing 0.5% KCl (pH 6.0) under light for 5 h. The results indicated that stomatal opening is concentration dependent on external environmental stimuli. The exogenous application of 100 µM Ca2+ (33.5%), 50 µM brassinosteroid (43.5%), and 10 µM cytokinin (43.4%) resulted in an increase in stomatal aperture of over 30%. This research provides a foundation for manipulating the stomatal opening of Chinese cabbage to enhance production.