Evidence for Flowering Hormones • 71 



when grafted to any of several LDP members of its family, the 

 composites, such as species of Erigeron or Rudbeckia (Okuda, 

 1953). Using members of the family Crassulaceae, Zeevaart (1958) 

 found that the LDP Sedum ellacombianum or Sedum spectabile 



Fig. 5-1. Transfer of flowering stimulus between LDP and SDP by grafting, 

 showing role of leaves. (/I) Induction of flowering in an LDP (Sedum spectabile) in 

 short days by grafting onto an SDP (Kalanchoe' blossfeldiana) . In the graft to the right, 

 the Kalanchoe (below) was kept defoliated. Photograph made 96 days after grafting. 

 (B) Induction of flowering in an SDP (Kalanchoe) in long days by grafting onto an 

 LDP (Sedum) — the reciprocal of the experiment in (.4). Again, in the graft to the 

 right, the Sedum was kept defoliated. Photograph made 130 days after grafting. 

 (Photographs from Zeevaart [1958], courtesy of Dr. J. A. D. Zeevaart, Agricultural 

 Institute, Wageningen.) 



could flower under short days when grafted onto the SDP Kalan- 

 choe blossfeldiana, whereas the latter would flower under long days 

 when grafted to the Sedians (see^ Fig. 5-1). Such effects can be 

 turned to practical use. Many varieties of the cultivated sweet 

 potato, Ipomoea batatas, flower irregularly if at all, no matter 

 what the environmental conditions, which is a distinct hindrance 

 to breeding programs. This recalcitrance can be overcome by 

 grafting shoots to any of several free-flowering (SDP) genera of the 



