02-absorcion-foliar 2 (1)

Principios dePrincipios de

Fertilización Fertilización FoliarFoliar

1- Epidermal cells

2 - Mesophyl

3- Transportation vessels

3 systems composing leaves

Plasma membrane

Scheme of the outer wall of a leaf epidermal cell

Wax

Cuticle proper

Pectin layer (negative charge)

Cuticle layer (capa)

Primary wall

Secondary wall

Cytoplasm

Penetration through cuticle and epidermal cell wall

SURFACE WAX Hydrophobic layer

+CUTIN + WAX

PectinCELLULOSE

EXTERNAL LAYER Cutin (weak negative charge) - Semi-hydrophilic

Cutin + Wax + Polysaccharides Pectin (negative charge) Cellulose

CUTIN + WAX Cuticle

can absorb water

Penetration through cuticle and epidermal cell wall by diffusion

Wax - Hydrophobic layerExternal layer - Cutin (weak negative charge) - Semi-hydrophilicCuticle - Pectin (negative charge) and cellulose - can absorb water

SURFACE WAXCUTIN + WAX

CUTIN + WAX + POLYSACCHARIDES

PECTINCELLULOSE

EPIDERMALEPIDERMALCELLCELL

SU

RF

AC

E

HA

IR +

Uptake preference to cation +

in direction toward cells membranes (low concentration)

Anions only small quantity penetrates, due to rejected by cell’s membranes (negatively charged)

-

Passive diffusion is responsible

for most of the penetration

The rate of diffusion across a membrane is

proportional to the concentration gradient across it

The higher concentration of solute

which can be applied to leaf surface

without causing damage

and the longer the time it remains

active state on the leaf surface

Schematic representation ofcell-to-cell

type transport processes

DIFFUSION OR MASS FLOW DIFFUSSION

ACTIVE TRANSPORTINVOLVING ATP

DIFFUSION VIA PLASMODESMATA

Penetration through cuticle and epidermal cell wall by diffusion

1) Uptake preference to cation (Cutin - negative charge) +

3) Movement in direction toward cells membranes (low concentration)

2) Anions only small quantity penetrates, because rejected by cell’s membranes (negatively charged)

-

The plant’s cuticle

is

nonliving, noncellular, lipoidal biopolymer cutin

with embedded wax

3) Active penetration into protoplast requires energy. Energy is supplied by metabolic respiration or photosynthesis process of the plant

Uptake steps by Leaves

1) Penetration through cuticle and epidermal cell wall by

passive diffusion:

Influenced by temperature and gradient of concentration

2) Absorption of ions by the cytoplasm’s membrane surface

Leaf surface

Cuticle

Cell wall

Guardcell

Guardcell

STOMATA

Solute penetration across the cuticular layer of leaf epidermal cells

Ion uptake is higher at night (closed stomata)

than during day-time

Most solutes do not penetrate through open stomata

EC

TO

DE

SM

AT

A

Passive diffusion is responsible for most of the penetration

The rate of diffusion across a membrane

is proportional to the concentration gradient across it

1) the higher the concentration of solute without causing

damage

The higher KNO3 spray concentrationthe higher the uptake

2) as longer the time it remains active on the leaf surface

Achieve better uptake

1. Production of insoluble precipitates

2. Irreversible fixation onto soil particles

3. Leaching by rain or irrigation below plant root network

4. The physical and chemical heterogeneity of the soil makes

it unsuitable pathway for supplying low dosages

5. Competitive (antagonistic) uptake

Disadvantages of soil pathway

Ventajas de la

Fertilizacion Foliar

4. Many problems associated with soil applications are

avoided.

1. Uptake commences within hours after application

and can continue for several days thereafter

2. Effectiveness of the uptake of applied solution can be

very high (in trials recovery reached > 70%)

3. Several compounds can be applied in single spray

MgMg - foliar spray

KK - foliar spray

To prevent and To prevent and cure deficienciescure deficiencies

Effective foliar feeding when the roots are unable to provide the plant with adequate nutrients at critical stages of growth

as a result of sink competition for

carbohydrates. Thus, nutrient

uptake by the roots decline.

Decrease in root activity during the

reproductive stage

UNDER CERTAIN CIRCUMSTANCES FOLIAR

FEEDING CAN LARGELY

REPLACE SOIL APPLICATION

FOLIAR SPRAY CAN BE USED TO

SUPPLEMENT

SOIL APPLIED FERTILIZERS

5. Wetting (rain, dew, irrigation) may leach applied spray

Possible disadvantages with leaf application pathway

1. Spray drift on non-targeted sites (deriva)

2. Limited available leaf area (seedlings)

3. Sensitivity to burn damage limit the amount applied - costly and time consuming repeat applications

4. Penetrability of leaf cuticles may vary considerably with leaf age, environment and plant variety

PROBLEMS & SOLUTIONS AFFECTING

EFFICIENT UPTAKE OF FOLIAR FEEDING


EFFICIENT UPTAKE OF FOLIAR FEEDING

Spray drifts away from target plants

Poor coverage of leaves inside plant canopy

Poor wetting of individual leaves

Spray when wind speeds are low. Increase droplet size

Optimize spray technology: Use larger spray volumes and higher pressure

Add surfactant adjuvants

Adding a suitable surfactant to the spray solution, may improve the uptake by the plant in the following ways:

* Increasing the penetration capacity of nutrients through the cuticle

* pH control of the solution.

Surfactants

* Lowering surface tension. The addition of wetting agent is necessary to ensure the adherence of droplets on difficult-to-wet leaves +

Usually, at pH below 4 -5, damage is noted.

Better penetration of P fertilizers at low pH, related

mainly to improved solubility, moisture retention and

degree of crystallization of salts on leaf surface.

When tank mixed with pesticides is prepared, to avoid

alkaline hydrolysis of pesticides, it is recommended to

prepare a spray solution of pH: 5.5 -6.5.

pH

pH - less leaf damage when spray solution is low no alkaline hydrolysis

Surfactant - silicon-based decreases leaf damage and increases efficiency of sprays

Decrease in root activity during the reproductive stageAs a result of sink competition for carbohydrates, root and thus nutrient uptake by the roots decline with the onset of the reproductive stage.

Poor retention of spray by leaf surfaces


EFFICIENT UPTAKE OF FOLIAR SPRAY



Rapid drying of solution on leaf surfaceinitially increases effective concentrations and accelerate penetration, subsequent: drying (inactivated) inhibits further penetration

Decrease spray droplet size (desprendimiento gotas)Increase solution viscosity by adding polymeric stickers

Spray when lowered temperature, windspeed, and high relative humidity are prevalent Add oils to spray solution in order to inhibit drying

Poor cuticular penetration





Effective concentration causes unacceptable

burn damage

Add low surface tension surfactant to encourage penetration via stomatal openings

(increased run-off, more rapid drying and increased penetration leading to burn damage - such as: L77)

Pretest to determine threshold concentration of burn damage.Apply lower concentration at frequent intervals

500 1000concentration ( mM )

Uptake ( % )

20

10

Effect of concentration on the foliar uptake of potassium from KNO3 by lettuce over 20 hr.*Effect of concentration on the foliar uptake of potassium from KNO3 by lettuce over 20 hr.*

* - Peter M. Neumann - 1988

(g )

Translocation of K

Potassium applied to leaves is quickly translocated to young parts of the plant

TYPICAL DISTRIBUTION OF 42K IN YOUNG MAIZE PLANT

24 h AFTER KNO3 APPLICATION TO THE SECOND LEAF

Same leaf can both export and import

Distribution %

Treated leaf

Middle (vaina)

Top (treated) Base Sheath

5.1 39.0 11.3 12.2

Aerial

parts Roots

23.0 9.3

Flux through the xylem is regulated by root

output and driven by water potential differences

between soil, leaf, and

atmosphere.

Ligninreinforcement

Xylem vessel

Xylem

Little importance to the

transport of foliar

applied plant nutrients

from sprayed leaves to

growing organs with low

transpiration rates

(buds, flowers, fruits).

Phloem

Phloemsievetube

Companioncell

Sieveplate

Composed of living cells with plasma membranes and cytoplasm

Phloem transport is

extremely important

for distribution from

mature leaves to

growing regions in

the roots and

shoots.

The export of 42K from treated leaf decreases when grown without K in the soil.

Potassium Translocation with and without soil supply

Foliar translocation depends on the condition of the roots and nutritive status of the plant

42KNO3 applied at

7 days

Days without potassium 0 7

% 42K translocated in 22 hr

Influence of potassium nutrition of the roots on translocation of 42KNO3 ( 3rd leaf of maize plants)

14 days

0 5 9 14

32.2 9.1 27.3 21.2 13.3 7.0

Mobility of plant nutrients within the phloem

Divided into three groups*

* Bukovac & Wittwer (1957), Kunnan (1980)

Mobile K P S Cl Na

Partially mobile Zn Cu Mn Fe Mo

Not mobile Ca Mg

Guardcell

Guardcell

STOMATA

Cuticle

Cell wall

Summary

SURFACE WAX Hydrophobic layer

Cutin (Semi-hydrophilic)Pectin (negative charge) - - -Cellulose

passive diffusion

+

K+-

only small quantity penetrates

Movement toward cells membranes (from high to low concentration)

Absorption by cytoplasm’s membrane

penetration into protoplast: ACTIVE = energy involved

1. Uptake commences within hours of application

and can continue for several days thereafter

Decrease in root activity during the reproductive

stag as a result of sink competition for

carbohydrates.

Thus, nutrient uptake by the roots decline.

* Foliar applied plant nutrients move within phloem system

02-absorcion-foliar 2 (1)

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