Figure 2. The overlapping interactions of polyamines (PA), jasmonic acid (JA), salicylic acid (SA), auxin (Aux), cytokinins (Cyt), abscisic acid (ABA) and gibberellic acid (GA) that are responsive to ethylene stimuli and their plausible relations with NO during ripening. Although NO's relation with phytohormones (Aux and GA) and signal molecule (JA) are yet to be established, the possible link between the ethylene biosynthesis inhibition (┴) by former and enhancement (→) by the latter can be hypothesized. The reciprocal interactions (↔) of NO with Cyt and SA affect the ethylene turnover during fruit ripening. NO's direct interaction with PA and ABA is known to negatively modulate ethylene biosynthesis. (Straight arrows indicate established phenomena; dotted arrows indicate phenomena of unidentified mechanisms).