Functional stomata in non-photosynthetic, non-ABA accumulating leaves of aGymnocladus albino

Investigation of the white-leaf form of Gymnocladus dioicus (L.) K. Koch gr owing permanently as a part of a wild type plant showed that lack of carote noid biosynthesis causes the albinism. Under extremely low light conditions the growing leaf is able to synthesize chlorophyll. The defect has multipl e consequences regarding structural, functional and biochemical leaf charac teristics that have been investigated. Plastid proteins as well as plastid and nuclear encoded mRNAs are affected to a different extent. Both leaf typ es exhibit a characteristic daily course of transpiration with the albino r egularly exhibiting significantly higher transpiration rates. One reason fo r this behaviour may be the different structure of the leaf epidermis, espe cially the formation of "giant" pores towering above the surface level on c himney-like, structures in the albino. In contrast to the green wild-type l eaves, no accumulation of abscisic acid has been observed, either during le af differentiation or as a consequence of wilting.