Influence of Multiple Factors on the Wettability and Surface Free Energy of Leaf Surface

Abstract

The wettability of plant leaves directly reflects leaf hydrophilicity, which is the key factor that influences the adhesion of liquid pesticide as well as affects plant protection products (PPP) efficacy. Generally, the wettability of leaf surface is quantified by the contact angle and surface free energy (SFE), which are mainly dependent on leaf surface properties, liquid properties and other spraying parameters. Therefore, the aim of this paper was to investigate the SFE of rice and rape leaves with the variation of leaf status, leaf surface, and probe liquid as well as the influence of droplet falling height, solid surface, and PPP concentration on the wettability. The results showed that: (1) the dispersive components of SFE of rice and rape account for a large proportion which are closely related to their hydrophobicity—the abaxial of rape new leaf and the adaxial of rape old leaf are easier to wet comparing with rice and rape leaves in other statuses; (2) the increase of droplet falling height had a significant effect on improving the wettability between wax surface and adjuvant solution, while it had little improving effect on the wettability between wax surface and water; (3) the wettability of different solid surface varied greatly, and the order of wettability from good to bad is water-sensitive paper (WSP), wax, rape leaf, and rice leaf; (4) the effect of PPP concentration on the leaf surface wettability is significant, the contact angle decreased with the increase of PPP concentration, and the wettability of microemulsion is better than that of suspending agent and wettable powder. In conclusion, the SFE and wettability of crop leaf surface determine the suitable type of PPP, studying the influence of multiple factors on leaf surface wettability can provide a reliable reference for providing scientific guidance as well as improving the effective utilization of PPP.

Effect of Adjuvant on Glyphosate Effectiveness, Retention, Absorption and Translocation in Lolium rigidum and Conyza canadensis

“…Droplet contact angles which range between 600 and 800 could be characterized as moderate wetting [27,28]. In this research, contact angle measurements showed that, for C. canadensis and L. rigidum, the ranges were between 650 and 740 and 680 and 740, respectively.…”

Influence of Glyphosate Concentrations on Spray Solution Physicochemical Characteristics and Drift Potential

“…The contact angle showed a significant interaction (p>0.01) between glyphosate concentrations and surfaces (U. ruziziensis leaves, paraffin film, and glass) at the four analyzed times (Table 3). The interactions indicate that contact angle is dependent on target surface characteristics, such as polarity and physicochemical characteristics of spray solutions, such as surface tension (Kissmann, 1998;Behring et al, 2004;He et al, 2019;Iost & Raetano, 2010;Decaro Junior et al, 2015;Barreto et al, 2017;Oliveira et al, 2019). The values of contact angle as a function of glyphosate concentrations in the spray solution on the adaxial surface of the U. ruziziensis leaf, paraffin film, and glass coverslips were adjusted to hyperbolic, quadratic inverse, and exponential models, respectively.…”

“…2020 Droplets of spray solutions sprayed on hydrophilic surfaces provide their higher spreading, with lower contact angle and, consequently, higher interfacial contact, which may result in a higher spray solution absorption and evaporation rate than hydrophobic surfaces. Both the rate of absorption and evaporation are naturally dependent on the specific characteristics of the leaf surface, liquid, and weather conditions (Iost & Raetano, 2010;Decaro Junior et al, 2015;Barreto et al, 2017;Oliveira et al, 2019;He et al, 2019). Because of the high contact angle, U. ruziziensis leaf surface may have small areas wetted by droplets (Decaro Junior et al, 2015), thus reducing the evaporation rate under the weather at application time and after it (Yu et al, 2009a;Yu et al, 2009b;Xu et al, 2010;Xu et al, 2011).…”

“…However, the surface characteristics must be taken into account, as spreading is also a function of interfacial characteristics (liquid and surface component substances), as well as surface tension (Iost & Raetano, 2010;Oliveira et al, 2019). Thus, spray solution spreading on plants depends on both surface tension of the liquid and anatomical constituents and biochemical composition of the epidermis (Kissmann, 1998;Behring et al, 2004;Barreto et al, 2017;He et al, 2019), which may also interfere with the differential penetration of products deposited on plants (Marques et al, 2012).…”

Image analysis of shatter and pinning events on hard‐to‐wet leaf surfaces by drops containing surfactant

“…There are very many experimental studies of droplets impacting on synthetic surfaces, [6][7][8][9][10][11] but there are far fewer studies of droplets impacting on leaf surfaces over very short time scales. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] This study contributes to this research by reporting on droplet impaction experiments on leaves from two plant species, one artificial surface, and three aqueous formulations.…”