**3. The impact of iodine, selenium, and silicon on the antioxidant system of plants**

The energy metabolism of aerobic organisms inevitably produces reactive oxygen species (ROS), which are free radicals that react with the different biomolecules in the cell causing damage. Additionally, when there is some stress, both biotic and abiotic, a substantial increase in ROS content is induced. As an adaptive response to neutralize these species, the synthesis of enzymatic and nonenzymatic antioxidants is used, granting tolerance to stress [30]. A partial explanation of the beneficial effect provided by I, Se, and Si is the stimulation of the increase in antioxidants. **Table 2** shows results obtained with the application of different chemical species and concentrations of I, Se, and Si on the antioxidant content in soilless crops.


**4. Proposed mechanisms of action of iodine, selenium, and silicon as** 

**Table 2.** Impact of I, Si, and Se on the antioxidants of various crop species grown in soilless cultivation systems.

Iodine is considered the first inorganic antioxidant used by ancestral organisms when the

mechanism is widely elucidated in algae, where the direct neutralization of species such as

has been proven, mainly due to iodine oxidation–reduction power. **Figure 1** illustrates the

O2

), singlet oxygen (<sup>1</sup>

increased as a result of oxygenic photosynthesis [6]. This

**Effect Reference**

[36]

159

http://dx.doi.org/10.5772/intechopen.75069

[37]

[38]

[39]

[42]

[43]

[44]

[45]

[46]

Increase in vitamin C content of 80 and 30%,

Increase in vitamin C and phenylpropanoids by 50 and

The Use of Iodine, Selenium, and Silicon in Plant Nutrition for the Increase of Antioxidants…

three times, respectively, in the leaves of the plants

5 mg L−1 Increase in total antioxidant capacity by 38% in fruits [40]

1 mg L−1 Increase of seven times the quercetin content in fruits [41]

 25 μM Increase of three times the glutathione in leaves during 5 days of exposure to the treatment

 1 mM Increase of 28% in the concentration of glutathione in leaves sensitive and resistant to salinity

1 mM Increase cysteine content by 78% in plants subjected to

1 μM Increase in the activity of APX and GPX of four and

two times in leaves relieving the stress by salinity in

glutathione to double, at 7 and 3 days of treatment, respectively, in the roots of tomato plants subjected to

arsenic stress

water stress

*super dominus* cultivar

2.5 mM Increase in the concentration of ascorbate and

**Effect Reference**

**Effect Reference**

respectively, in fruits

reduction in total acidity

14%, respectively, in the leaves

40 μM Increase in glutathione and ascorbic acid by 38% and

Pepper KI 1 mg L−1 Increase in ascorbic acid by 35% in fruits and 50%

), and hydrogen peroxide (H<sup>2</sup>

O2 ) [47]

**inducers of the accumulation of antioxidants**

possible mechanisms of reaction proposed by Luther et al. [48].

), hydroxyl (OH−

concentration of atmospheric O2

**Plant species Chemical species and concentration**

− ≤0.50 mg L−1

 40 μM and salicylic acid 40 μM

Strawberry I− ≤0.25 mgL−1 or IO3

**Selenium application in soilless crops Plant species Chemical species and concentration**

SeO4

SeO<sup>3</sup>

SeO4

SeO4

SiO<sup>3</sup>

SiO4

SiO<sup>3</sup>

SiO<sup>3</sup>

**Silicon application in soilless crops Plant species Chemical species and concentration**

Lettuce KIO3

Lettuce Na2

Tomato Na2

Tomato Na2

Tomato Na2

Wheat Na2

Rice H<sup>4</sup>

Cucumber Na2

Tomato K2

−

superoxide (O2


In regard to the concentration of I, Se, and Si, the use of soilless crops results in plants with a lower level of these elements than in soil crops. Hydroponic production of crops for human consumption has increased substantially in recent years, mainly due to the efficient use of water and nutrients from the crop. However, as far as commercial production is concerned, nutrition only considers the application of the elements deemed essential for plants [29], leaving aside those that are beneficial as I, Se and Si. These beneficial elements raise the antioxidant content in plants, giving an advantage against oxidative stress, in addition to its use allows obtaining biofortified crops with high nutritional value for human consumption.

**Concentration in soils (mg kg−1) Concentration in plants (mg kg−1) Reference**

500 (rice fields in Chiba, Japan) 15.6 mg g−1 leaves of rice plants [27]

**3. The impact of iodine, selenium, and silicon on the antioxidant** 

and concentrations of I, Se, and Si on the antioxidant content in soilless crops.

Lettuce KI ≤40 μM Increase of 6, 2, 1.5, 1.2, and 1.2 times, respectively, in

plants

Lettuce IO3 < 40 μM Increases the antioxidant potential by double in the leaves of plants

and antioxidant potential

80 μM Increase of ascorbic acid by 1.2 times in the leaves of

85% in the leaves of seedlings

 7.88 μM Increase of 8% in the concentration of ascorbic acid and 6% in total phenols in tomato fruits

The energy metabolism of aerobic organisms inevitably produces reactive oxygen species (ROS), which are free radicals that react with the different biomolecules in the cell causing damage. Additionally, when there is some stress, both biotic and abiotic, a substantial increase in ROS content is induced. As an adaptive response to neutralize these species, the synthesis of enzymatic and nonenzymatic antioxidants is used, granting tolerance to stress [30]. A partial explanation of the beneficial effect provided by I, Se, and Si is the stimulation of the increase in antioxidants. **Table 2** shows results obtained with the application of different chemical species

**Effect Reference**

*Themeda triandra* 36.9 mg g−1 [28]

[31]

[32]

[33]

[34]

[35]

the total phenols, flavonoids, anthocyanins, ascorbate,

Increase of ascorbic acid by 22% and glutathione by

**system of plants**

**Silicon concentration in soils and agricultural plants**

North of Tanzania, and South of Kenia)

158 Antioxidants in Foods and Its Applications

7.3 mg kg−1 amorphous Si, 0.092 mg kg−1 dissolved Si (Serengeti,

**Table 1.** Concentration of I, Se, and Si in soils, irrigation waters, and crop plants.

**Plant species Chemical species and concentration**

**Iodine application in soilless crops**

Tomato KI 1 μM daily foliar application

Lettuce IO3

Tomato KIO3

**Table 2.** Impact of I, Si, and Se on the antioxidants of various crop species grown in soilless cultivation systems.
