Translocation ofRadioactive Carbonafter theApplication of'4C-Alanine and14CO2 toSunflower Leaves1

C- (UL)-L-Alanine wasapplied tothesurface ofmature leaves atthesecondnodeofsunflower (Helianthus annuusL. cvCommander) plants, underillumination. Thealanine was absorbed during a4-hourperiod, andsomeofitwasmetabo- lized bytheabsorbing tissue. Aftera lagperiod ofabout15 minutesfromfirst application, distribution of"4Cthrough the plantproceeded inmuch thesamepattern aswhen"CO2is assimilated bysimilar leaves. Most, ifnotall, ofthe"4Cex- ported fromtheabsorbing regions wasinsucrose. Onlyminute amountsappeared inalanine orother aminoacids insurround- ingpartsoftheleafbladeorinthepetiole, although these werestrongly labeled inthetissue absorbing '4C-alanine. When "CO2wassupplied for15minutestoleaves ofdif- ferent ages, aminoacids werelightly labeled intheleafblade. Maturegreenleavesexported onlysucrose. Yellowing leaves on 60-day-old plants exported a variety ofsubstances includ- ingaminoacids.