Finite dose diffusion studies: III. Effects of temperature, humidity and deposit manipulation on NAA penetration through isolated tomato fruit cuticles

Abstract

Effects of temperature, humidity, rewetting and removal of deposits on penetration of NAA [2-(1-naphthyl)acetic acid] through isolated tomato (Lycopersicon esculentum Mill) fruit cuticles were studied using a finite dose diffusion system. In this system, an aqueous 5-microliter droplet (0.1 mM NAA in 20 mM citric acid buffer) is applied to the outer surface of a cuticle, which is mounted in a glass diffusion half-cell. The cell wall surface is in contact with a receiver solution (20 mM citrate). Penetration is monitored by repeated sampling of the receiver solution. Droplets appeared dry on visual inspection within 1 h of application, but significant NAA penetration continued after droplet drying. Maximum rates of NAA penetration increased exponentially as temperature was increased (from 5 degrees to 35 degrees C), the energy of activation averaging 153 (+/- 11.6)kJ mol-1. At 35 degrees C, penetration reached a plateau within 10 h of application (at 91.1 (+/- 1.0)% of dose applied) while at 5 degrees C penetration after 800 h reached only 30.2 (+/- 7.5)%. Increasing relative humidity from 20 to 80% increased maximum rates [from 1.0 (+/- 0.21) to 2.7 (+/- 0.80)% h-1] and penetration at 120 h after application [from 36.8 (+/- 2.1) to 64.3 (+/- 3.7)%]. Rewetting deposits at 120, 240 and 360 h after application resulted in increased NAA penetration. However, amounts and rates of NAA penetration progressively decreased with each subsequent rewetting. Removal of deposits by cellulose acetate stripping at various times after droplet application resulted in a rapid decrease in NAA penetration. NAA penetration following deposit removal was always less than 6.1% of the amount of NAA applied and averaged 0.5 (+/- 0.2)% when deposits were removed immediately after droplet drying.

Organic Pollutant Penetration through Fruit Polyester Skin: A Modified Three-compartment Diffusion Model

“…Additionally, several approximations were required because of the lack of K d values for the cuticle components. K d,PC1 (48,880 L/Kg) was determined and employed to represent K d,EW because its sorption capability was equivalent to those of intact components after dewaxing 34 41 48 49 52 . This value was calculated through the regression of the sorption isotherm of intact green pepper fruit cuticle.…”

“…The superior organic pollutant-sorption capacities of EW and CP slowed the diffusion of organic pollutants but created sharp concentration gradients within the plant cuticular membrane, which likely supplied a stable driving force and eventually caused linear penetration. This endogenous driving force increased as the penetration rate of pollutants into CP, which mainly consisted cutin, a superior reservoir for organic pollutants, increased 49 52 .…”

“…Organic pollutants in the environment are well known to be dynamically transported among various environmental media, and this dynamic transport is temperature sensitive and could alter local pollution levels 46 47 48 . For example, during daytime in the summer, the organic pollutant concentrations of plants become diluted as the temperature decreases; conversely, during nighttime in the winter, the organic pollutant concentrations of plants increase as the temperature increases 49 50 . Similar phenomena are known, including the latitude effect 51 and grasshopper effect 52 .…”

Effects of relative humidity and substrate on the spatial association between glyphosate and ethoxylated seed oil adjuvants in the dried deposits of sessile droplets

“…Furthermore, the spatial separation between the AIs and the adjuvants might directly or indirectly influence the penetration of the compounds and their biological efficacy. For instance, several studies have shown the importance of the relative humidity for the penetration of the active ingredients 45–48. However, little or no attention has been paid to the deposit structure,49 and thus the hypothesis cannot be excluded that much of the unexplained variation in herbicide uptake arises from the differences in the physical form of the dry deposits 4.…”

Usefulness of Fluorescent Probe Prodan To Gain Insight into the Polarity of Plant Cuticles

“…In polymer science, hydrophobicity and surface hydration govern many applications . In agrochemistry, the efficacy of foliage-applied agrochemicals depends on the amount of active ingredients delivered into the target species and/or tissues across the cuticle layer, which forms a natural interface between the plant and the environment. , Plant cuticle is a thin (<0.1–10 μm) continuous layer or membrane of predominantly lipid material that covers the entire external surface of plants. This barrier is constituted of three cuticular hydrophobic components arranged as layers: the epicuticular wax, the cuticle proper, and the cuticular layer .…”