title: Effect of solution and leaf surface polarity on droplet spread area and contact angle.
abstract: BACKGROUND
  How much an agrochemical spray droplet spreads on a leaf surface can significantly influence efficacy. This study investigates the effect solution polarity has on droplet spreading on leaf surfaces and whether the relative leaf surface polarity, as quantified using the wetting tension dielectric (WTD) technique, influences the final spread area. Contact angles and spread areas were measured using four probe solutions on 17 species.
  
  
  RESULTS
  Probe solution polarity was found to affect the measured spread area and the contact angle of the droplets on non-hairy leaves. Leaf hairs skewed the spread area measurement, preventing investigation of the influence of surface polarity on hairy leaves. WTD-measured leaf surface polarity of non-hairy leaves was found to correlate strongly with the effect of solution polarity on spread area.
  
  
  CONCLUSIONS
  For non-polar leaf surfaces the spread area decreases with increasing solution polarity, for neutral surfaces polarity has no effect on spread area and for polar leaf surfaces the spread area increases with increasing solution polarity. These results attest to the use of the WTD technique as a means to quantify leaf surface polarity. © 2015 Society of Chemical Industry.
authors: Plant Protection Chemistry NZ Ltd, Rotorua, New Zealand.
authors: Justin J
authors: JJ
authors: Nairn
authors: Plant Protection Chemistry NZ Ltd, Rotorua, New Zealand.
authors: W Alison
authors: WA
authors: Forster
authors: Plant Protection Chemistry NZ Ltd, Rotorua, New Zealand.
authors: Rebecca M
authors: RM
authors: van Leeuwen
mesh_terms: D016573:Agrochemicals / Q000737:chemistry*; D001557:Benzenesulfonates / Q000737:chemistry; D018515:Plant Leaves / Q000033:anatomy & histology*; D013499:Surface Properties; D017155:Wettability
chemical_list: D016573:Agrochemicals; D001557:Benzenesulfonates; C414926:Blankophore P fluessig
keywords: adhesion; contact angle; dielectric constant; leaf surface; spreading; wetting