Putrescine (Put), spermidine (Spd), and spermine
(Spm), the most common aliphatic polyamines (PAs)
in plants, are implicated in many growth and developmental
processes and have thus been proposed as a
new class of plant growth regulators. This is because
altered levels of PAs and activities of their biosynthetic
enzymes have been associated with changes in growth
and development in numerous plants