Figure 4.

Induction of cell death and generation of hydrogen peroxide by polyamines. A, Infiltration of chemicals. Indicated polyamines at the concentration of 10 mm were infiltrated into a healthy tobacco leaf. As the control, water was also infiltrated (Water). Tested samples were putrescine (Put), spermidine (Spd), and spermine (Spm). B, Cell collapse at infiltration sites. Photograph was taken 48 h after infiltration. C, Detection of hydrogen peroxide. 3,3′-Diaminobenzidine (DAB) solution was infiltrated 6 h after the first infiltration and incubated for further 6 h. Sample leaf was briefly boiled in ethanol and observed for hydrogen peroxide, which is seen as reddish-brown color.