Blue light inhibits stomatal development in soybean isolines containing kaempferol‐3‐O‐2G‐glycosyl‐gentiobioside (K9), a unique flavonoid glycoside

Abstract

ABSTRACTStomata have a fundamental role in controlling plant photosynthesis and transpiration, but very little is known about factors controlling stomatal differentiation and development. Lines of soybean that contain a specific flavonol glycoside, kaempferol‐3‐O‐2‐glycosyl‐gentiobioside (K9), as well as greatly reduced stomatal density, especially on the adaxial epidermis, have been identified. The specific effects of blue light photoreceptors on stomatal development in K9 lines and their isoline pairs containing no K9 were studied. Low irradiances of blue light (7% of total photosynthetically active radiation) added to high irradiances from low‐pressure sodium lamps strongly inhibited stomatal development on the adaxial epidermis of K9 lines, but not in isoline pairs differing putatively in only one gene and lacking K9. Overall, blue light slightly increased stomatal density on the abaxial epidermis in all isolines, demonstrating differential regulation of stomatal development in the upper and lower epidermis. Blue light also caused an increase in leaf area in all isolines, indicating that changes in stomatal density were not the non‐specific result of alterations in leaf area. Morphological studies revealed that the blue light‐induced reduction in stomatal density in K9 lines was due to reduced stomatal initiation as well as aborted or abnormal stomatal development. As the phytochrome photostationary state was kept constant, the results indicate that one or more blue light receptors are involved in the control of stomatal development. This system should be useful for the study of mechanisms controlling stomatal development, even if the photo‐inhibitory response is unique to K9 lines.