Hydroxycinnamic amide (HCA) conjugates of polyamines accumulate markedly in the floral apex during flower development, and are implicated in the development of competence to flower; certain mutants of tobacco which are deficient in HCAs are unable to flower, and male sterile mutants of maize lack HCA accumulation in anthers (Flores et al, 1989). A novel polyamine conjugate, N⁴-hexanoylspermidine, has been identified in senescing pea ovaries and petals (Perez-Amador et al, 1996).

Flores HE, Protacio CM, Signs MW 1989 Primary and secondary metabolism of polyamines in plants. In "Plant Nitrogen Metabolism" (JE Poulton, JT Romeo, EE Conn eds), Rec. Adv. Phytochem, Vol 23, Plenum Press, New York, pp. 329-393.

Perez-Amador MA, Carbonell J, Navarro JL, Moritz T, Beale MH, Lewis MJ, Hedden P 1996 N⁴-Hexanoylspermidine, a new polyamine-related compound that accumulates during ovary and petal senescence in pea. Plant Physiol. 110: 1177-1186.