Nano silicon application improves salinity tolerance of sweet pepper plants

Abstract

Salinity is a major limiting factor for crop growth and productivity especially in arid and semi arid areas. Therefore this study was conducted in order to compare the effect of applying silicon in the standard form versus the nano form on mitigating salinity negative effects on sweet pepper plants (Capsicum annumn L.) cv. California Wonder. Seedlings were transplanted in March 2013 and 2014 in North Delta, Egypt and were irrigated with saline water with an EC of 5.47 dS/m. Silicon in two forms (regular 25%) and nano silicon (25%) were supplied through irrigation systems at concentrations of 4.0 and 5.0 cm3/l for regular silicon and 1.0 and 2.0 cm3/l for nano silicon. Application took place at 3, 6 and 9 weeks after transplanting. Data showed that all plant growth aspects such as plant height, number of branches and leaves fresh and dry weights were improved under all silicon treatments compared to non treated plants. Yield parameters followed also the same trend. Among silicon treatments, concentration of 1.0 cm3/l of nano silicon recorded the highest significant effect in mitigating salinity negative effects. It could be concluded that nano silicon is more effective and efficient in mitigating salinity stress on sweet pepper plants.

Full text

Nano Silicon Application Improves Salinity Tolerance of
Sweet pepper Plants
Tantawy A.S.1*; Salama Y.A.M.2;El-Nemr M.A.1
and Abdel-Mawgoud A.M.R.1
1Vegetable Research Department, National Research Center, Dokki, Giza, Egypt
2 Plant Adaptation Unit, Genetic Resource Department, Desert Research Center, Cairo,
Egypt
Abstract: Salinity is a major limiting factor for crop growth and productivity especially in arid and semi arid
areas. Therefore this study was conduct ed in order to compare the effect of applying silicon in the standard form
versus the nano form on mitigating salinity negative effects on sweet pepper plants (Capsicum annumn L.) cv.
California Wonder. Seedlings were transplanted in March 2013 and 2014 in North Delta, Egypt and wer e
irrigated with saline water with an EC of 5.47 dS/m. Silicon in two forms (regular 25%) and nano silicon (25%)
were supplied through irrigation systems at concentrations of 4.0 and 5.0 cm3/l for regular silicon and 1.0 and
2.0 cm3/l for nano silicon. Application took place at 3, 6 and 9 weeks after transplanting.
Data showed that all plant growth aspects such as plant height, number of branches and leaves fresh and
dry weights were improved under all silicon treatments compared to non treated plants. Yield parameters
followed also the same trend. Among silicon treatments, concentration of 1.0 cm3/l of nano silicon recorded the
highest significant effect in mitigating salinity negative effects. It could be concluded that nano silicon is more
effective and efficient in mitigating salinity stress on sweet pepper plants.
Key words: Sweet pepper, Salinity, Nano Silicon, Total chlorophyll, N, P, K and Total Yield.
Introduction:
Nowadays, salinity is became one of the most serious environmental problems that caused great
reduction ongrowth and development of plant species. In fact Salinity is one of the major yield limiting factors
for crop plants mainly in arid and semiarid regions of the world1. In Egypt the problem is aggregated due to
overuse of fertilizers and shortage of good irrigation water. Therefore, many trails and approaches have been
attempted to mitigate the well-known negative effects of salinity on plant growth and production2,3,4,5,6. Among
those approaches is the improvement of plant nutritional status via external supplements to ameliorate salinity
damages with exogenous application of K+ in wheat7, N in Phaseolus vulgaris8 and Ca in snap bean9.10reported
an improvement of tomato crop growth and production under saline conditions as a result of application of nano
calcium. Furthermore, some beneficial mineral nutrients have been studied that can counteract adverse effects
of salt stress. Silicon, being a beneficial element provides significant benefits to plants at various ionic
compositions. Also, 11proved that nono silicon application can improve seed germination and seedling growth
of tomato. Earlier, 12showed that soyabean plants supplied with silicon had higher salinity tolerance compared
to non-supplied plants. Silicon deposition in the tissues help to alleviate water stress by reducing transpiration
rate, improve light interception characteristics by keeping the leaf erect, increase resistances to diseases pests
and lodging, remediate nutrient imbalances, and there are other documented beneficial effects 13,1 4,15. Silicon
International Journal of ChemTech Research
CODEN (USA): IJCRGG ISSN: 0974-4290
Vol.8, No.10 pp 11-17, 2015

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presence in the cell wall fiber makes the cell wall tough and resistant to pest and pathogens attacks. Naturally,
plants contain Si in appreciable concentrations, ranging from 1% to 10% or even higher of the dry matter. This
difference of Si levels in different plant species have been attributed to the Si uptake ability of the roots16,17.
Despite of the prominence of Si as a mineral constituent of plants, Si is not considered as "essential" nutrient,
for any terrestrial higher plants except members of the Equisitaceae and is thus not included in the formulation
of any of the commonly used nutrient solutions13. As the beneficial effect of silicon has been proved as shown
above, the application of non silicon can be mor e effective than the large applied particles which means a more
efficient input use. 10showed that application of nano calcium to saline stress tomato plants ha d more efficient
and effective impact on mitigating the negative effect of salinity compared to the application of chleated
calcium. The use of the new science, nanotechnology in agriculture has begun and will continue to have a
significant effect in the main areas of breeding new crop varieties, development of new functional materials and
smart delivery systems for agrochemicals like herbicides, fertilizers and pesticides, smart systems integration
for food processing, packaging and other areas like remediation of herbicide and pesticide residues from plant
and soil, effluent water treatment, etc.18.Nano-technology can present solution to increasing the value of
agricultural products and environmental problems. Nanomaterials because of their tiny size show unique
characteristics. They can change physic–chemical properties compared totheir bulk materials, they have a great
surface area than bulk materials. Because of these larger surface areas, their solubility and surface reactivity
was higher19. By manufacturingthe preparation ways of nanomaterials can change their characteristics, for
example, the addition of nanoparticlesin liquid changes their chemical, physiological and transport
characteristics compared to their base fluids such as enhancement of thermal conductivity20.
Yet no studies were found on the effect of nano silicon application on the growth and production of
sweet pepper plants. In Egypt, sweet pepper is a major vegetable crop for local consumption and export.For
these reasons, this study was conducted to compare the effectiveness of applying silicon in the nano or regular
forms in reducing the negative effects of salinity on tomato plants growth and production.
Materials and methods:
Seeds of sweet pepper plants (Capsicum annumn L.) cv. California Wonder were sown on 15
th of
January 2013 and 2014 and seedlings were transplanted on the 15th of March in the two seasons of 2013 and
2014 in a sandy soil in a private farm in the area of Wadi El-Natron, Bahaira governorate, Egypt. The soil
physical and chemical analysis are shown in tables 1 and 2. Individual transplants were grown at the bottom of
ridges 100 cm width at 50 cm apart. Plot area was 1X12= 12 m2. The drip irrigation system of GR 16 was used
and plants were irrigated daily using saline-well water with an EC value 5.47 dS/m and pH of 7.8. The complete
chemical analysis of the irrigation water is shown in table (3).
All standard agricultural practices other than experimental treatments were applied according to the
recommendations of the ministry of agriculture, Egypt.
Experimental treatments:
After three weeks from transplanting, plants were supplied through the irrigation system with two types
of siliconforms namely Nano Silicon (Nano-Si 25%) or regular silicon (Si 25%). Each form was supplied to the
plants in two concentrations as follow: Nano-Si : 0.0 (control), 1.0 or 2.0 cm
3
/l. Meanwhile Si (25%) was
applied as 0.0 (control), 4.0 or 5.0 cm3/l.
Applications of silicon treatments were at 3, 6 and 9 weeks after transplanting.
Experimental design and statistical analysis:
The treatments were arranged in a complete randomized block design with three replicates and analysis
of variance was carried out at probabilit y level of 0.05. Least Significant Differ ence LSD was calculated to
differentiate between the treatments.
Measurements:
After 70 days from transplanting the following measurements were carried out:

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Physical measurements: Plant height, number of branches, fresh and dry weights of leaves; total yiel d
(ton/fed.); and average weight of individual fruits (g).
Chemical measurements: Total chlorophyll content (SPAD); total contents of N, P and K (%).
Table (1): Soil physical analysis and soil properties of the experimental farm.
Soil depth (cm3)Total sand (%) Silt (%) Clay (%) Texture
0-15 58.0 11.5 30.5 Sandy
30 – 60 57.0 13.0 30.0 Sandy
Table (2): Soil chemical analysis of the experimental farm.
Soluble anions (ppm) Soluble cations (ppm)
Soil depth (cm3) EC (dS/m) pH
CO3
-- Cl- SO4
-- Ca++ Mg++ Na+K+
0-30 4.77 7.7 55.85 31.20 10.50 24 11 10.52 2.18
30-60 4.16 7.4 51.21 22.50 16.10 16.83 6 17.80 0.097
Table (3): Chemical analysis of irrigation water (underground well) of the experimental farm.
Soluble anions (ppm) Soluble cations (ppm)
Water sample EC (dS/m) pH
HCO3
-Cl-SO4
-- Ca++ Mg++ Na+K+
Average 5.47 7.8 2.50 81.08 16.24 25.29 19.43 54.83 0.45
Results:
Data in Table (4) show that plant height was significantly reduced under salinity treatment. Meanwhile
all silicon treatments mitigated these negative effects and plant height was improved with superior effects
recorded with Nano-Si treatments which were not s ignificantly different between each ot her. Although Si
treatments significantly improved plant height under salinity conditions, they were significantly lower in their
effects compared to Nano-Si treatments. Similar trends were obser ved in the number of branches where all
silicon treatments improved this parameter compared to the untreated plants. The Nano-Si treated plants showed
the highest mitigated effects compared to Si treatments. The effectiveness of each Si treatment was clear in
leaves fresh weight (Table 4). With significant differences among all treatments, Nano-Si treatment of 1 cm3/l
showed the highest effectiveness in mitigating salinity effect on that parameter followed by Nano-Si 2.0 cm3/l
then Si 4.0 cm3/l and finally Si 5.0 cm3/l treatment. All silicon treatments showed a significant improvement in
leaves fresh weight compared to untreated plants. Dry weight of the leaves showed also a similar trend that all
silicon treatments improved that parameter compared to untreated plants grown under saline conditions.
However Nano-Si treated plants showed higher significant positive responses compared to regular silicon
supplied plants with superiority effect for 1 cm3/l treatment.
Fruit yield data are shown in Table (5). Average fruit weight of individual fruits was also improved by
all silicon treatments compared to untreated plants grown under salinity conditions. The lower concentration of
Nano-Si had the highest significant mitigating effect regarding this parameter compared to all other silicon
treatments. There was no significant difference between the highest applied concentration of Nano-Si (2 cm3/l)
and the lowest concentration of regular silicon (4 cm3/l) treatments. Also there was no significant difference
between the two concentration treatments of regular silicon. Total fruit yield (Table 5) showed also an
improvement as a result of all silicon treatments compared to untreated plants grown under saline conditions.
The Nano-Si treatment of 1.0 cm
3
/l concentration showed the highest significant mitigating effects on total
yield of sweet pepper plants compared to all other silicon treatments. There was no significant difference
between the two concentrations of r egular silicon treatments.

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Chemical analysis data as shown in Table (6) showed that all silicon treated plants showed an
improvement in total chlorophyll content compared to control plants grown under salinity conditions. However,
only the lowest concentration of Nano-Si treatment that was significantly higher than all other silicon
treatments. Nitrogen total content showed also an improvement as a result of all silicon treatments compared to
control plants. In addition the only significant difference among silicon treatments was between the lowest
Nano-Si treatment and the rest of s ilicon treatments. Similar trend was observed also in phosphorus total
content where all silicon treatments improved that content compared to control treatment. Among silicon
treatments, only the highest concentration of regular silicon treatment showed a significant difference compared
to other silicon treatments. Potassium total content followed the same observed trend of improvement in all
parameters as a result of silicon treatments. There was a significant differences among the treatments wit h
superiority to the lowest concentration of Nano-Si treatment.
Table (4): Effect of different silicon treatments on plant height, leaf fresh and dry weights, and number of
branches of sweet pepper plants.
2013 Season 2014 Season
Treatments Plant
height
(cm)
Leaves
fresh
weight
(g)
Leaves
dry
weight
(g)
No. of
branches
/ plant
Plant
height
(cm)
Leaves
fresh
weight
(g)
Leaves
dry
weight
(g)
No. of
branches
/ plant
Control 30.45 61.45 14.67 4.32 28.64 59.34 12.40 4.11
Nano Si ( 25% ) 1 cm / Lit. 46.32 98.28 26.49 7.86 44.51 96.50 23.69 7.68
Nano Si ( 25% ) 2 cm / Lit. 44.91 81.19 23.51 7.02 43.27 80.73 21.38 6.93
Si ( 25% ) 4 cm / Lit. 40.23 73.61 19.92 6.57 39.34 71.02 18.43 6.48
Si ( 25% ) 5 cm / Lit. 38.21 69.37 18.23 6.01 35.45 67.47 15.57 5.98
L.S.D. at 5 % 2.09 3.01 1.93 0.92 1.91 1.79 1.57 0.71
Table (5): Effect of different silicon treatments on individual fruit weight and total fruit yield sweet
pepper plants.
2013 Season 2014 Season
Treatments Fruit weight
(g)
Total Yield ton /
fed.
Fruit weight
(g) Total Yield ton / fed.
Control 62.23 5.32 63.11 5.11
Nano Si ( 25% ) 1 cm / Lit. 96.12 7.86 98.42 7.72
Nano Si ( 25% ) 2 cm / Lit. 85.23 7.32 82.55 7.02
Si ( 25% ) 4 cm / Lit. 79.56 6.62 78.72 6.30
Si ( 25% ) 5 cm / Lit. 74.38 6.21 70.22 6.09
L.S.D. at 5 % 5.78 0.42 5.44 0.35
Table (6): Effect of different silicon treatments on chlorophyll content and chemical composition of sweet
pepper leaves.
2013 Season 2014 Season
Treatments Total
chlorophyll
(SPAD)
N
(%)
P
(%)
K
(%)
Total
chlorophyll
(SPAD)
N
(%)
P
(%)
K
(%)
Control 38.45 0.98 0.42 1.10 37.33 0.93 0.43 1.09
Nano Si ( 25% ) 1 cm / Lit. 49.23 1.73 0.72 2.01 47.54 1.70 0.75 1.99
Nano Si ( 25% ) 2 cm / Lit. 47.12 1.56 0.70 1.82 45.32 1.51 0.73 1.78
Si ( 25% ) 4 cm / Lit. 44.07 1.48 0.66 1.71 44.09 1.46 0.68 1.60
Si ( 25% ) 5 cm / Lit. 43.67 1.42 0.50 1.52 42.11 1.39 0.55 1.43
L.S.D. at 5 % 4.12 0.21 0.07 0.08 3.84 0.19 0.09 0.06

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Discussion:
It is evident that Si is beneficial for growth of many plants under various abiotic (e.g. salt, drought and
metal toxicity) and biotic (plant diseases and pests) stresses21,22. Some authors reported that Si could ameliorate
salt stress depression on plant species23,24,25,26. Indeed our results showed that the application of silicon
improved all plant growth aspects under saline conditions. 27observed that Si application leaded to balance
growth reduction of Phaseolus vulgaris L. caused by salinity like decrease stomatal conductance, drop of leaf
RWC, decrease K+ tissues contentand etc. Our results on leaf fresh and dry weights as well as potassium
contents confirm these results. Among the possible mechanisms of Si mitigation to stress is that it maintains the
plant water Status under saline conditions which resulted in higher cell expansion and leaf area compared to Si-
untreated plants grown under saline conditions27. This may explain the increment in plant height of Si treated
plants compared to untreated one under salinity conditions. 29found that plants treated with NaCl in the presence
of Si showed values of turgor potential 42% higher than those plants treated only with NaCl. This may result
also in higher stomatal conductance hence higher photosynthesis which may lead to higher dr y matter
production. In fact this may explain our result of the dry weight of the leaves. 28reported that leafturgor potential
and net photosynthesis rates were found 42 and 20% higher respectively in salt-stress ed plants treated with Si in
comparison to plants grown in Si fr ee solution. Higher chlorophyll content reported in this study contribute
further in improving photosynthesis rate and dry matter production for Si treated plants compared to control.
Improvement in water content and net photosynthesis rates must be reflected on fruit yield and this is exactly
what was found in this study with Si treated pla nts grown in saline media compared to untreated plants.
Increment in nutrient contents such as N, P and K in plant tissue is another mechanism of Si mitigation to
salinity stress. Si reduces uptake of Na+
by improving K+: Na+ and also alleviates the toxicity of other heavy
metals29,30.
The effects of Si treatments on saline stress plants have been confirmed in our study on sweet pepper
plants. However, the nano silicon form has proved a stronger mitigating effects compared to regu lar silicon
form. Nano silicon was used earlier by31 who found that it could enhance the gr owth of soybean. They observed
that soybean seeds which treated by a mixture of Nano SiO2 and Nano TiO
2
had more germination and the
activity of nitrate reductase, superoxide dismutase, catalase and peroxidase of germinating seeds were increased
significantly. 10reported a more beneficial effects of nano Ca compared to chleated Ca on mitigation of salinity
stress on tomato plants. This has been also noticed in this study with the superiority of nano silicon effects
compared to regular silicon on mitigation of stress damages. This may be due to the fact that changing the
particles to nano form can change physic–chemical properties compared to their bulk materials, they have a
great surface area than bulk materials. Because of these larger surface areas, their solubility and surface
reactivity was higher20. By manufacturingthe preparation ways of nanomaterials can change their
characteristics, for example, the addition of nanoparticlesin liquid changes their chemical, physiological and
transport characteristics compared to their base fluids such as enhancement of thermal conductivity21. This may
mean mor e availability to plant absorption and higher reactivity wit hin plant tissue.
Conclusion:
It could be concluded that application of silicon can mitigate salt stress damages on sweet pepper
plants. However, the application of nano silicon is more effective and efficient compared to regular silicon
application.
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