Laurenţiu FilipescuDepartment of Technology of Inorganic Substances and Environmental Protection, Faculty of Applied Chemistry and Material Science, University Politehnica of Bucharest, Phone: (021)4023885, e-mail: laurentiu_filipescu@yahoo.co.uk

A NEW CONCEPT CONCERNING THE FOLIAR

FLUID FORMULATIONS

International Conference On Chemistry And Chemical Engineering, Timisoara, 2008

1.1. FOLIAR FLUIDSFOLIAR FLUIDS

Composition Composition

Foliar nutritive products are concentrated fluids containing particular components of the following classes of

chemical compounds:

• macronutrients (N+P+K),

• mezonutrients (Ca+Mg),

• micronutrients (B+Mo+Zn+Cu+Fe+Mn),

• biostimulants (organic substances promoting growth in crop size and quality)

• Fungicides (inorganic and organic substances providing protection against fungi and other fruit

diseases both during vegetative growth and post harvesting storage).

Required properties

1. complete solubility and chemical stability at higher concentrations as commercial product,

2. compatible in mixture with diluting hard waters as sprinkling solutions,

3. hiding power,

4. adherence,

5. penetration power through waxy cuticles, cell walls and plasma cell membrane,

6. moderate pH,

7. low saline and contact stress,

8. environmental friendliness.

DestinationDestination

Complementary nutrient sources associated with growth enhancers or pesticides available

and used in the most simple and efficient ways to handle crop control during any vegetative

development stage.

Formulation pitfalls Formulation pitfalls

Refining quality of foliar products according to the plant transient demands is confined to

restrictive limits due to objectionable changes in physical properties required for foliar application.

Most of the researches in the field of foliar fertilizers/foliar growth enhancers and pesticide were

focusing on active formulas in term of nutrient ratios and concentrations or biological active

components availability and phytotoxicity. The problems of foliar product penetration and uptake

yields, or formula efficiency were chiefly treated in terms of adjuvant adding to improve foliage

distribution or to ease application.

2. NEW FORMULATION APPROACH2. NEW FORMULATION APPROACH

This paper brings about a new concept for approaching foliar nutrition, taking the leaf cuticle

penetration mechanism as a keystone in formula design and product properties assessment. According

to this concept the new foliar fluids are concentrated emulsions containing two distinctive phases:

•an organic phase which is the carrier of growth enhancing and fungicide functions,

•an aqueous phase yielding all the mineral constituents of usual NPK liquid/foliar fertilizers with or

without micronutrients.

Both phases after dilution and hydrolysis are dispatching all the mineral/organic plant

nutritive/enhancing entities at a prerequisite level.

Original approach of the hydrolyzing emulsion application and leaf born nutritive species was

fulfilled with high regard to the permeation of the biological active entities through cuticle by both lipophilic

and polar paths of diffusion.

Consequently, the emulsion components selection has been made in good agreement with the

mass transport mechanism of lipophilic species through cutin wax domains (Buchholz and Schonherr

2000), as well as with high humidity/hydrolysis promotion at leaf surface in order to activate the cuticular

permeability to water and non lipophilic species (Schreiber 2005).

Reliable correlations composition – property were searched for finding adequate balances in

chemical formulation and foliar products required properties.

3. 3. CUTICULAR PENETRATION OF THE NUTRIENTCUTICULAR PENETRATION OF THE NUTRIENT

The foliar fluids applied on the aerial organs of plants have to penetrate three barriers:

a) waxy cuticle covering the epidermal cells or stomata walls;

b) epidermal cell walls; and

c) the epidermal cells plasma membrane.

Permeation of the active entities through cuticle occurs by the lipophilic and polar paths of

diffusion.

Permeation through the cell wall and plasma membrane occurs by active enzyme transport

and takes place only if cuticle resistance is subdued.

Both processes are highly dependent on fluid composition and on particular properties of the

properly applied diluted solutions (Schreiber 2005).

4. PENETRATION MECHANISM

The plant cuticle membrane has a composite structure made of (Stark and Tian 2006):

a) cutan, a non-saponifiable non-depolymerizable hydrocarbon polymer;

b) cutin, an easy solvent depolymerizable biopolymer;

c) waxes which are soluble lipids predominantly linear with different functionalities

(alkanes, alcohols, aldehydes, acids, etc.).

Figures 1 and 2 show the a leaf crossing section and respectively the the fine structure of

cuticle.

Figure 1. Leaf section Figure 2. Fine structure of the cuticle (Koch et al., 2006)

Figure 3. Schematic drawing of a solubility membrane traversed by an aqueous pore(Schonherr, J. 2006)

There are 3 criteria to match emulsified foliar nutritive fluid formula to cuticle pentration mechanism

First criterionFirst criterion

Due to their lipophilicity and mobility, organic compounds can easily cross the lipophilic

pathways opened in liphophilic domains which cover randomly the waxy cuticle surface. This

process is strongly depending on the size of diffusing molecules and the presence of liphophilic

accelerators. Accordingly, the first criterion in the formulation of emulsified foliar nutritive fluids is

the low molecular mass of the selected lipophilic organic carrier phase or lipophilic species of

growth enhancers and fungicides.

Second criterionSecond criterion

Polar and not charged water molecules can diffuse under high mobility conditions across the plant

cuticle using lipophilic cutin and wax domains as transport pathway. Actually, the water molecules are

absorbed into lipophilic cuticle producing swelling and promoting cuticular transpiration, and giving birth

of polar islands inside the lipophylic domains. Significant increase in the cuticular permeability of the

non lipophilic/ionic species was observed when larger amounts of water are absorbed in these newly

substantiated polar domains. This process is rather affected by relative humidity than the molecular

mass of transported ionic or charged molecules. Hence, the second criterion in the formulation of

emulsified foliar nutritive fluids is the relative humidity inside the mass transport limiting layer, which can

be hold at highest values by promoting hydrolysis of the organic components in the thinly layer

dispersed on the foliage surface.

Third criterionThird criterion

Stomatal penetration and foliar uptake yield of the ionic components is governed by three

parameters: relative humidity, stomatal area and number of wetting cycles. In addition, some applied

fluid properties as the surface tension, viscosity, contact angle as well as the use of additives

stimulating the stomatal opening are certainly factors of leverage in upsurging foliar absorption of the

ionic species. Therefore the third criterion in the formulation of emulsified foliar nutritive fluids is linked

to the development of reliable correlations composition – property and the matching applied fluid

properties to the compulsory terms of the stomata opening and foliar uptake mechanism.

5. SELECTION OF THE PARTICULAR COMPONENTS OF 5. SELECTION OF THE PARTICULAR COMPONENTS OF FOLIAR NUTRITIVE FLUIDSFOLIAR NUTRITIVE FLUIDS

From the above overview on foliar absorption mechanism and the presumed matching properties

of emulsified nutritive fluids, we figure out the following mandatory features for both aqueous and

organic phase of these fluids: Organic phase:

- low molecular mass organic acids and appropriate overbasic salts which may hydrolyze

over pH interval 7.0 - 9.0 by dilution with hard waters and prone to quick reaction with atmospheric

carbon dioxide and calcium/magnesium ions from hard waters,

- generation of stabile hydrolizates emulsions with high solubility and mobility through waxy

cuticle barrier,

- capacity to dissolve growth enhancers and fungicide;

Aqueous phase:

-high soluble saline components carrying macro and micronutrients,

-additives promoting the stomata opening,

-low density, viscosity and surface tension,

-capacity of wetting and spreading as thinly layers over the leaves.

All these properties must be associated with typical NPK formulas in foliar nutritive fluids

containing growth enhancers and fungicide components.

The best choice for the main components of emulsified nutritive fluids are:The best choice for the main components of emulsified nutritive fluids are:

- Low molecular organic carrier or growth enhancers and fungicide: naphthenic and oleic acids

option due to the following reasons: stability of their emulsions with saline solutions, solubility of their neutral and

overbasic ammonium/potassium salts (as mineral nutrients) in aqueous solutions, fast reaction of their overbasic

ammonium/potassium salts with carbon dioxide, miscibility with many classes of organic compounds, low

surface tension of their emulsions or aqueous salt solutions. Also, the naphthenic ammonium and potassium

salts, as well as naphthenic acids copper, zinc and manganese overbasic salts act as plant growth enhancers

(Wort et all. 1973, Wort 1976, Shulian Zhou et al. 1991, Hoque et al. 1992, Begum et al. 2002,), and oleic acid

overbasic salts exhibit antimicrobial and fungistatic action (Lack and Heiden 2006, Harry and Rajamannan 2006,

Colleman 2004). Naphthenic and oleic overbasic salts diluted solutions are hydrolyzing by air carbonation. Both

naphthenic and oleic acids are environmentally safe products completely biodegradable aerobic and anaerobic

in soils and waters (Biryukova and all. 2007, Scott 2005, Clemente 2004).

- Macronutrients:

* potassium option as the overbasic salts of both naphthenic and oleic acids is based on two factual

observations: stomata opening stimulation by potassium ions (Willmer et all.1983) and fungicide performances

of the potassium bicarbonates (Zitter and Drennan 1995, Ziv and Zitter TA 1992), coupled with its contribution as

macronutrient in any common fertilizer;

* nitrogen option as urea, due to this compound contribution to stability of the overbasic sals in saline

solutions (Calogrea and al. 2003, Chitu and al. 2004)

* phosphorus option as monohydrogen and dihydrogen orthophosphates, due to their buffering capacity in

diluted emulsified nutritive fluids (Cirjaliu-Murgea and al. 2005);

* micronutrients option for any soluble salt which do not interfere with organic acid overbasic salts.

6. FOLIAR NUTRITIVE FLUIDS DISTINGUISHED 6. FOLIAR NUTRITIVE FLUIDS DISTINGUISHED

PROPERTIESPROPERTIES

- Composition – property diagrams. - Composition – property diagrams.

Overbasic potassium salts of the naphthenic and oleic acids, picked up as intermediaries

bearing the physical and chemical properties matching the above selection criterion, are non-

crystalline materials with poor solubility in water. Meaningful overbasicity and additives choice may

produce aqueous emulsions/solutions of these salts bearing mandatory properties for foliar applied

fluids.

The use of ethanol as the third component in the pseudoternary system overbasic salts of

the naphthenic and oleic acids – water - ethanol is a good replacement for the random and mostly

insecure choice of other compatibility additives, because the miscibility water – ethanol and

ethanol – organic acids provides a convenient weight in handling the mixture properties and

shifting them to worthwhile values.

Pseudoternary liquid – liquid diagrams in systems overbasic naphthenate/oleate – water –

ethanol isotherms subsuming overbasicities from 2/1 to 6/1 are providing valuable information

about the balanced compositions which may carry demanded properties in both concentrated

emulsified fluids and diluted hydrolyzing solutions (figure 4).

Figure 4. Pseudo ternary systems overbasic potassium naphthenate – water – ethanol (a) and overbasic potassium oleate – water – ethanol (b) at 30ºC; Overbasicity 2/1, 4/1 and

6/1; Composition – surface tension diagrams.

Composition - property diagrams like these from figures 4 yield new data and leverage prospects due to

ethanol share in properties adjustment and control. Some other properties linked to fluids foliar

application may be disclosed by similar composition-properties diagrams as those presented in figure 4.

Intermediaries hydrolysis. Intermediaries hydrolysis.

The initial assumptions on hydrolysis process originate from the workable step by step reaction

of carbonation with free air carbon dioxide, able to push the pH beyond a certain hydrolyzing point

and help adherent layers precipitation, while other species of nutritive compounds are nucleated from

diluted emulsion over hydrolyzing mass and grew as amorphous or poor crystallized phases.

The figures 5(a) and 5(a) illustrate the hydrolysis onset process going on at a pH dependent

dilution ratio of the overbasic naphthenate (molar ratio 4/1 and 1M), respectively potassium overbasic

oleate (molar ratio 4/1 and 1M) emulsions.

a b

Figure 5. Hydrolysis of potassium overbasic naphthenate (4/1) 1M(K) non pre-carbonated (a) and pre-carbonated up to pH 10 (b) during dilution with deionized water

Figure 6. Hydrolysis of potassium overbasic oleate (4/1) 1M(K) non pre-carbonated (a) and pre-

carbonated up to pH 10 (b) during dilution with deionized water

a b

Working on overbasiciy, carbonation degree and ethanol concentration seems to be a fair

reasonable way for control diluted spaying fluid pH.

Hydrolysate layer precipitation.Hydrolysate layer precipitation.

Hydrolysate layer precipitation process was monitored through pH measurements over the entire duration

of applied liquid layer carbonation process accompanied by a partial water evaporation.

It was assumed that immediately after application the emulsified overbasic salts, hydrolysis advances due

to air free carbon dioxide absorption and the liquid film breaks out in a discontinuous micelle structured

fluid leaving on the leaf surface an adherent layer of organic hydrolysates.

While the hydrolysis and carbonation progress in extent, there is expected a significant decline in liquid

phase pH, because more and more hydroxyl ions are bound into hydrolysate complexes. Minimum value

of pH is reached when full hydrolysis is achieved and organic layer building up ceased.

Figure 7. a) Layered matrix precipitation in non pre-carbonatated naphthenate K4R(OH)3 1M. Diluted solutions 1/25 (▲), 1/50 (∆), 1/100 (●), 1/200 (○); b) Layered matrix precipitation in pre-carbonatated K4R(OH)3 1M, diluted 1/100 (●); K4R(CO3)3/2 , diluted 1/100 (▲) 1M; K4R(OH)3 1M +

urea, diluted 1/100 (○);K4R(CO3)3/2 1 M + urea, diluted 1/100 (∆)

Hydrolysates particle size distributionHydrolysates particle size distribution..

Hydrolysate particles have a relative mobility on the leaf surface within applied fluid layer, from where

they canpenetrate liphophilic or polar pathways inside cuticle. Sooner or lather, due to liquid phase

evaporation, hydrolysate particles are entrapped into semisolid matrix layer and released during daily

rewetting and transpiration. Both spontaneous freshly hydrolyzed and terminating released size particle

are critical facing the depth cross through cuticle. In other words as small is the hydrolysate particle size

as large is its probability to penetrate either liphophilic or polar pathways. We assume the unexpected

magnitude in stimulative performances of these hydrolysable products is originating from the hydrolysate

capacity to use both liphophilic and polar pathways through cuticle.

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50

Time, minutes

Mo

de,

nm K Naphthenate, dilution 1/25

K Naphthenate, dilution 1/200

K Oleate, dilution 1/25

K Oleate, dilution 1/200

Figure 5 shows that the one of the ranking feature of the

overbasic sold hydrolysates is the particle dominant dimension

(expressed by the mode of particle size distribution), which is

placed between 10 nm and 200 nm. Dominant particle size in

1/25 diluted overbasic oleate lays in the same interval as

dominant size in concentrated emulsions. For other dilutions this

significant parameters is displaced to higher dimensions and

eventually on higher dilutions hydrolysis products are flocculated.

Figure 8. Hydrolysate particle size in layered matrix

ExpectationsExpectations

The new class biological activities are extending over:

- dormant buds stimulation;

- ratio fruitlets/flowers;

- growth enhancing both in fruits and shoots;

- boosting crop and quality;

-promotion against fungi and other fruit diseases;

-extended protection against fungi and fruit diseases during the

long term storage.

CONCLUSIONSCONCLUSIONS

There was demonstrated the viability of a new way to formulated emulsified foliar fluids

on the grounds of prominent attributes originating from the mechanism and kinetics of

foliar absorption. The two liquid phase emulsions enable the implementation of

multifunctional biological performances and best control of the foliar properties. Also, a

new mechanics in the waxy cuticle penetration was provided through reactive

components hydrolysis, pH control and particle size distribution.

Selectiv literature citedSelectiv literature citedBuchholz A, Schonherr J, Thermodynamic analysis of diffusion of non-electrolytes across plant cuticles in the

presence and absence of the plasticiser tributyl phosphate. Planta 212, 2000, 103–111;Calogrea M., Chitu V., Chitu E., Filipescu L. “A new class of multifunctional foliar nutritive products”, Proc. of

13th Romanian International Conference on Chemistry and Chemical Engineering, Bucuresti, 2003;C. Cristea, M. Calogrea, M. Murgea, V. Chitu, L. Filipescu, Nutrinaft products and their fungicide effects,

Analele Universitatii din Craiova, vol. IX (XLV), 2004, 103; Chitu V. , E. Chitu, A. Hororoi, M. Calogrea, M. Murgea, L. Filipescu, Researches concerning Nutrinaft

products effects on apple production and fruit quality, Analele Universitatii din Craiova, vol. IX (XLV), 2004, 123Cirjaliu – Murgea M, Chitu V, Chitu E, Isopescu R Filipescu L Sequential Foliar Nutritive Fluids Design And

Foliar Absorption Mechanism 14th International Conference On Chemistry And Chemical Engineerig Proceegings Bucharest, Romania, 2005;

Downer JD Ragoonanan D Non-phytotoxic micronutrient composition US 4125395, 14 November 1978.Filipescu L. “Designing ecological products for agricultural uses” invited lecture University Venice, 2004; Filipescu L., Pincovschi E., Echilibrul solid-lichid, Ed. Tehnica Bucuresti, 1981.Koch K., Barthlott W., Koch S., Hommes A., Wandelt K., Mamdouh W., De-Feyter S., Broekmann P. 2006.

Structural analysis of wheat wax ( Triticum aestivum, c.v. ‘Naturastar’ L.): from the molecular level to three dimensional crystals. Planta, 223: 258-270.

Schreiber L.() Polar paths of diffusion across plant cuticles: New evidence for an old hypothesis. Annals of Botany 95(7), 2005, 1069–1073;

Schreiber L. Copermeability of 3H-labelled water and 14C-labelled organic acids across isolated Prunus laurocerasus cuticles: effect of temperature on cuticular paths of diffusion. Plant, Cell and Environment 25, 2002, 1087–1094;

Schreiber L, Effect of temperature on cuticular transpiration of isolated cuticular membranes and intact leaf disks. Journal of Experimental Botany 52, 2001, 1893–1900;

Schonherr J, Schreiber L., Size selectivity of aqueous pores in a stomatous cuticular membranes isolated from Populus canescens (Aiton) Sm leaves. Planta 219, 2004, 405–411;

Schönherr J, Bukovac MJ, Penetration of Stomata by Liquids: dependence on surface tension, wettability, and stomatal morphology. Plant Physiol. 49, 1972, 813-819;

Schonherr J.2006. Characterization of aqueous pores in plant cuticles and permeation of ionic solutes. Journal of Experimental Botany, 57: 1-21.

Stark RE, Tian S, Biology of the Plant Cuticle, Blackwell Publishing, 2006.Petcu F, Tabara O, Lupu N, Ban I, Hodina V, Calogrea M, Filipescu L, Process for obtaining nutrient fluids

with sequential action containing macronutrients, micronutrients and biostimulators, RO 120064, August 2005.

Acknowledgment

The work was carried out with the financial support of CNCIS, Program Idei, project

1035/2007.