55:	Differential temporal sensitivity to control of leaf development by blue light in soybean lines with an unusual kaempferol triglucoside (K9).

Authors:	Liu, Lan(A)Britz, Steven, J.(A)
Affiliations:	(A): USDA, ARS, NRI, Climate Stress Laboratory, Beltsville MD
Presenter:	Liu, Lan , lliu@asrr.arsusda.gov

Little is known of the specific cellular and molecular processes that underlie formation of stomatal guard cell complexes. We reported earlier that blue light inhibits the formation of stomata in the upper epidermis of soybean lines competent to make an unusual kaempferol triglucoside (K9). It has been suggested that expression of K9 chemically inhibits guard cell development. While this scenario may not represent "normal" control, it should nonetheless be an valuable approach to an important problem. Since blue light also stimulates the synthesis of phenolic compounds, including K9, we asked the question whether an increase in K9 was obligatorily coupled to altered stomatal formation. It might be possible to separate these processes if they have a different temporal sensitivity to blue light. Plants (OX922 & OX921) were raised under high irradiance light from blue-deficient low pressure sodium lamps (LPS). Large numbers of stomates form on the upper epidermis of leaves under these conditions. At successive stages of first trifoliolate leaf development, plants were transferred to a LPS + blue light chamber at similar total irradiance. Blue light inhibited adaxial stomatal formation largely at the guard mother cell stage of development, although some inhibition was found at later stages of development. Blue light induced flavonol synthesis at early stages of leaf development. Thus, it was not possible to separate the presence of K9 from inhibition of stomatal formation or rule out a causative role for this compound. Our experiments showed that supplemental blue light under these conditions increased photosynthetic pigmentation, comparable to effects on phenolic content, at all stages of leaf development.