PPG-1721 was investigated for physiological activity in cotton (Gossypium hirsutum L.) by using simple laboratory techniques. The technique determines if a specific chemical influences three important plant systems. The three related systems (basal ethylene biosynthesis, auxin-induced (stress) ethylene biosynthesis, and membrane integrity) are good indicators of a chemicals potential to influence flower or fruit abscission, mitigate environmental stress, or perhaps alter translocation rates. Since PPG-1721 exhibited activity when tested on these systems, it was included in our bioregulant field evaluation and yield trials in cotton.

The effect of PPG-1721 on the three plant systems was investigated by soaking excised main-stem leaf discs in increasing concentrations of PPG-1721 and in solutions of PPG-1721 plus 0.1 mM 2,4-D. After ethylene evolution was-quantified by gas chromatography on a basis of nL-g Fwt^-1ú24 h^-1, membrane integrity was determined by use of an ASA-610 Automatic Analyzer. Leakage of electrolytes from leaf discs was monitored periodically over 28 hours.