Roles of Polyamines in Growth and Development of the Solanaceous Crops Under Normal and Stressful Conditions

Polyamines (PAs) namely putrescine, spermidine, spermine and cadaverine are low molecular weight polycations found in all living organisms. In plants, considerable progress has been made on PA metabolism. As evident from the multiple research articles and reviews, PAs are known to stimulate various aspects of growth and development such as seed germination, organogenesis, pollination, flower and fruit development and senescence. In these processes, they could exhibit mostly synergistic and in some cases antagonistic effects with the phytohormone-mediated interactions. Various PAs are also closely related to both abiotic and biotic stress responses in plants. Currently, PAs are significantly gaining importance as substitutes of the plant growth regulators, and being used as media supplements for plant tissue culture. Both endogenous levels of PAs and their exogenous applications are known to influence various stages of plant life cycle under both normal and stressful conditions. The major objective of this review is to highlight the demonstrated effects of PAs, particularly on the commercially important solanaceous crops. Relationships between PAs and various stress responses are exceedingly complex in terms of involvement of the multiple processes. In-depth understanding of such biological processes would help to develop useful designer crops.