Pectin esterase in relation to leaf abscission in coleus and phaseolus

Area of Science:

• Plant physiology
• Biochemistry

Background:

• Pectin esterase (PE) plays a role in plant cell wall modification.
• Understanding PE activity in abscission zones is crucial for plant development studies.

Purpose of the Study:

• To compare pectin esterase (PE) activities in abscission zones and surrounding tissues of attached and abscissing petioles in Coleus and bean.
• To investigate the effect of auxin treatment on PE activity during abscission in Coleus.

Main Methods:

• Enzyme assays were performed on tissue samples from Coleus blumei and Phaseolus vulgaris.
• Abscission was induced by deblading petioles, with some treated with auxin.
• PE activity was measured across different pH ranges and tissue locations.

Main Results:

• PE activity was lower in the distal abscission zones of abscissing petioles compared to attached leaves in both species, though less pronounced in Coleus.
• Coleus exhibited lower overall PE activity and smaller changes during abscission than bean.
• Auxin treatment in Coleus prevented abscission and increased PE activity in various tissues, notably adjacent stem tissue.

Conclusions:

• PE activity changes are associated with leaf abscission in both Coleus and bean, with variations in magnitude and clarity between species.
• Auxin's role in preventing abscission is linked to alterations in PE activity.
• Coleus PE functions optimally at a neutral to slightly alkaline pH (7.3-7.6), and tissue pH decreases during abscission.