The nonchlorophyllous (albino) tissue of matureC. blumeileaves is a sink for photoassimilate. Transport from the green to the albino region of the same leaf was inhibited by cold and anoxia. When the green tissue of mature leaves was removed, the remaining albino portion imported labeled translocate from other mature leaves in the phloem. Photoassimilate unloading in the albino region of mature leaves was studied by quantitative autoradiography. The unloading was inhibited by cold but not by anoxia. No labeled photoassimilate could be detected in the free space of mature albino tissue by compartmental efflux analysis as phloem unloading proceeded in a N2atmosphere, indicating that unloading, may occur by a symplastic pathway as it apparently does in sink leaves of other species. The minor veins of mature albino leaf tissue did not accumulate exogenous 14Csucrose. Minor veins of green tissue in the same leaves accumulated 14Csucrose but, in contrast to other species studied to date, this accumulation was insensitive to the inhibitorp-chloromercuribenzensulfonic acid (PCMBS).
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