TRANSLOCATION OF INDOLE-3-ACETIC ACID-1'-14C AND TRYPTOPHAN-1-14C IN SEEDLINGS OF PHASEOLUS COCCINEUS L AND ZEA MAYS L

Indole-3-acetic acid-l[image]-14c (IAA-14C) and trypto-phan-l-14c injected in small amounts into cotyledons of Phaseolus coccineus L. seedlings were found to be translocated acropetally into the epicotyls and young shoots. Similarly IAA-14C was translocated acropetally into coleoptiles of Zea mays following injection into the endosperms. Labeled metabolites of the injected compounds were also extractable from shoot tissue. However, evidence that IAA-14C itself was translocated acropetally was obtained by collection in agar blocks applied to cut surfaces of coleoptiles of injected seedlings. The acropetal translocation in Phaseolus was shown not to occur in the transpiration stream but in living tissue. Cotyledons of P. coccineus and P. vulgaris contain extensive vascular tissue. Tryptophan- 14C was not actively translocated through excised segments of P. coccineus epicotyl and Z. mays coleoptile when supplied from donor agar blocks in concentrations as high as 100 [mu][image]. The small amount of tryptophan-14C which did reach receiver blocks when high concentrations were used may be accounted for by passive diffusion through the fluid-filled xylem vessels. Translocation of a non-toxic dye, Light Green SF Yellowish, through xylem vessels was found to occur when supplied from donor blocks placed acropetally or basipetally. Metabolism of the supplied tryptophan- 14C by the tissue segments was shown to occur during the 3 to 6 hr. translocation experiments. IAA-14C was transported in a strictly basipetal manner in both tissues. Only 1 labeled compound with an RF value of IAA was found in receiver blocks. Composition of a simple green safelight suitable for work in plant physiology is described.