*5.3.2 Quantity of fruit harvest and marketable fruit quality*

The number of fruits harvested from the eight variants and the control was higher on average when the biostimulators were applied to the rhizosphere directly at the roots (**Figure 6**). The fresh weight of all cucumbers with market quality was about 500 g, therefore the number of fruits is representative for the cucumber yield. In particular, the treatment with biostimulators on the substrate that means to the root system, resulted in a higher yield at the first harvest. The number of fruits finally harvested was considerably higher after treatment of roots with Lactate and *B. subtilis* (FZB24®). The number of marketable fruits was higher than in the control in most variants treated with biostimulators.

For future experiments should include more applications also during the fruit set because these additional applications could enhance the yield further, this could be especially important in long time cultivation.

The different application methods with Biostimulators on the leafs and to the roots have not only an influence on cucumber plant growth and yield, but also on the amount of marketable and non-marketable fruits (**Figure 7**). The percentage of non-marketable fruits (C class) was more than 25% in the control and could be reduced by leaf application of each Biostimulator investigated until 20% and even until 10% if substances were applied over the roots.

mechanisms including stimulation of plants'self-defense mechanisms, as it was demonstrated in chapter 5.2.1 and 5.2.2 in case of suboptimal pH, EC values. Furthermore, *Bacillus subtilis* can accelerate plant growth and stimulate the process of formation of plant organs. Furthermore, *B. subtilis* can increase the unspecific resistances of plants against stress conditions, such as extreme high temperatures,

*Effect of application biostimulators (lactate, K-Humate, FZB24®) on leaves and roots respectively on the percentage on non-marketable fruits. Different letters indicate significant differences (chi-square-test,*

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation…*

*DOI: http://dx.doi.org/10.5772/intechopen.96536*

frost, drought, strong radiation, and deficiency of plant nutrients [18, 19].

lactates have been used as foliar fertilizers and as well as bioregulators.

on the growth of cucumber. The aim was to investigate the photosynthetic reactions to clarify first stress responses in the cucumber plants. Measuring of Chlorophyll Fluorescence is a very useful method for evaluation of plants' photosynthetic conditions and a tool in non-invasive stress detection and its

subsequent evaluation [12].

*5.4.1 Experimental design*

**81**

**Figure 7.**

*P = 0.05).*

Application of lactates in the form of LACTOFOL (**Table 2**) tends to reduce plant stress under suboptimal pH levels of nutrient solution (chapter 5.2.2) [6, 14, 16]. Introduction of Lactate as LACTOFOL into the growing system increases availability of micro- and macro-nutrients for plants. Investigations have shown that lactates have more stable bonds with several metal ions than other chelates do. Therefore,

In greenhouse cultivation of cucumbers in soilless culture systems, two stress situations are of importance, the pH and the temperature stress. In an experiment was the aim to investigate the physiological effect of a biostimulating complex consisting of *B. subtilis* (FZB24®), K-Humate and Lactate as LACTOFOL (**Table 2**)

(*Cucumis sativus* L.) cv. Jessica was cultivated in 'Mitscherlich' container volume

One half of the cucumber plants were not treated with the Biostimulator solution. The substrate of the other half of the plants was treated once a week with 300 ml of biostimulator solution (*B. subtilis* (0.2%) + K-humate (0.01%) + lactate (0.1%) per container. Treatments coincided with the following plant developmental

8 L filled with perlite with a physical and chemical properties as described in **Table 3**. The same nutrient solution was used as described in chapter 5.3. The cucumber plants were cultivated in a climatic chamber at 25°C and 80% RH.

## **5.4 Use of biostimulators to reduce abiotic stress in cucumber plants**

Different bacteria and in particular *Bacillus subtilis* are well known for their effects against soil-born fungal and bacterial diseases. There are selected strains in this regard with good effects in the field of plant protection. The strain *Bacillus subtilis* FZB24 is in addition capable of evolving different kinds of stress protective

#### **Figure 6.**

*Effect of application biostimulators (lactate, K-Humate, FZB24®) on leaves and roots respectively on number of marketable fruits in four harvesting periods of 9 days each. No significant differences.*

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation… DOI: http://dx.doi.org/10.5772/intechopen.96536*

#### **Figure 7.**

However, the leaf treatment with the combination of all substances led to a reduction in leaf growth. After application of biostimulators via roots more or less the same ratio was found as in the control indicating the shoot and leaf growth was

The number of fruits harvested from the eight variants and the control was higher on average when the biostimulators were applied to the rhizosphere directly at the roots (**Figure 6**). The fresh weight of all cucumbers with market quality was about 500 g, therefore the number of fruits is representative for the cucumber yield. In particular, the treatment with biostimulators on the substrate that means to the root system, resulted in a higher yield at the first harvest. The number of fruits finally harvested was considerably higher after treatment of roots with Lactate and *B. subtilis* (FZB24®). The number of marketable fruits was higher than in the

For future experiments should include more applications also during the fruit set because these additional applications could enhance the yield further, this could be

The different application methods with Biostimulators on the leafs and to the roots have not only an influence on cucumber plant growth and yield, but also on the amount of marketable and non-marketable fruits (**Figure 7**). The percentage of non-marketable fruits (C class) was more than 25% in the control and could be reduced by leaf application of each Biostimulator investigated until 20% and even

**5.4 Use of biostimulators to reduce abiotic stress in cucumber plants**

Different bacteria and in particular *Bacillus subtilis* are well known for their effects against soil-born fungal and bacterial diseases. There are selected strains in this regard with good effects in the field of plant protection. The strain *Bacillus subtilis* FZB24 is in addition capable of evolving different kinds of stress protective

*Effect of application biostimulators (lactate, K-Humate, FZB24®) on leaves and roots respectively on number*

*of marketable fruits in four harvesting periods of 9 days each. No significant differences.*

stimulated in the same manner.

*5.3.2 Quantity of fruit harvest and marketable fruit quality*

*Cucumber Economic Values and Its Cultivation and Breeding*

control in most variants treated with biostimulators.

until 10% if substances were applied over the roots.

**Figure 6.**

**80**

especially important in long time cultivation.

*Effect of application biostimulators (lactate, K-Humate, FZB24®) on leaves and roots respectively on the percentage on non-marketable fruits. Different letters indicate significant differences (chi-square-test, P = 0.05).*

mechanisms including stimulation of plants'self-defense mechanisms, as it was demonstrated in chapter 5.2.1 and 5.2.2 in case of suboptimal pH, EC values. Furthermore, *Bacillus subtilis* can accelerate plant growth and stimulate the process of formation of plant organs. Furthermore, *B. subtilis* can increase the unspecific resistances of plants against stress conditions, such as extreme high temperatures, frost, drought, strong radiation, and deficiency of plant nutrients [18, 19].

Application of lactates in the form of LACTOFOL (**Table 2**) tends to reduce plant stress under suboptimal pH levels of nutrient solution (chapter 5.2.2) [6, 14, 16]. Introduction of Lactate as LACTOFOL into the growing system increases availability of micro- and macro-nutrients for plants. Investigations have shown that lactates have more stable bonds with several metal ions than other chelates do. Therefore, lactates have been used as foliar fertilizers and as well as bioregulators.

In greenhouse cultivation of cucumbers in soilless culture systems, two stress situations are of importance, the pH and the temperature stress. In an experiment was the aim to investigate the physiological effect of a biostimulating complex consisting of *B. subtilis* (FZB24®), K-Humate and Lactate as LACTOFOL (**Table 2**) on the growth of cucumber. The aim was to investigate the photosynthetic reactions to clarify first stress responses in the cucumber plants. Measuring of Chlorophyll Fluorescence is a very useful method for evaluation of plants' photosynthetic conditions and a tool in non-invasive stress detection and its subsequent evaluation [12].

#### *5.4.1 Experimental design*

(*Cucumis sativus* L.) cv. Jessica was cultivated in 'Mitscherlich' container volume 8 L filled with perlite with a physical and chemical properties as described in **Table 3**. The same nutrient solution was used as described in chapter 5.3. The cucumber plants were cultivated in a climatic chamber at 25°C and 80% RH.

One half of the cucumber plants were not treated with the Biostimulator solution. The substrate of the other half of the plants was treated once a week with 300 ml of biostimulator solution (*B. subtilis* (0.2%) + K-humate (0.01%) + lactate (0.1%) per container. Treatments coincided with the following plant developmental stages, first treatment at 5–6 leaf stage (week 1); second at 7–8 leaf stage (2 weeks) and the third at 9–10 leaf stage (3 weeks).

After the last treatment with the biostimulator solution (4 weeks), the stress factor was applied. For the pH stress experiment, pH values were adjusted to a suboptimal level (pH 3.2) by adding H3PO4 to the nutrient solution. This pH stress was maintained for 1 week. For temperature stress, temperature in the growth chamber was lowered from 25 to 6°C for 3 h.

#### *5.4.2 pH stress for cucumber plants*

One week after transplanting the cucumber plants the chlorophyll fluorescence Fv/Fm-value increased from 0.760 (**Figure 8**) to 0.790 in plants treated with biostimulating complex and 0.770 in plants without treatment. A drastic decrease in electron efficiency was observed after imposition of a strong lowering the pH value. Between the 4th and 5th measurements, Fv/Fm of treated plants decreased to 0.747 and that of the non-treated ones even to 0.654.

given for a short time from three hours and the lowest temperature was 6°C. This stress was applied by lowering the air temperature in the climate chamber right

*Growth parameters of cucumber plants treated with biostimulators mixture prior to pH- stress (pH 3.2) for*

**Leaf weight (g/plant)**

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation…*

Not-treated 325.75 b 230,25 b 460 ns 7002.3 ns 275.75 ns 45.08 ns

315.25 a 350 a 477.75 ns 7105.2 ns 265.5 ns 52.93 ns

**Leaf area (cm2**

**/plant)**

**Root weight (g/plant)**

**Root length (m/plant)**

Fm development showed its peculiarities (**Figure 9**). Measurement 1 to 4 gave equal electron efficiency levels. After temperature stress, Fv/Fm values decreased considerably indicating a reduction in photosystem II efficiency. Only the treated plants were able to reach higher levels of Fv/Fm after stress and could recover much

The Fv/Fm parameter had the same pattern as in case of pH stress. However, Fv/

At the end of this temperature stress experiment, the plant growth parameters were also determined (**Table 11**). The effect of the biostimulator mixture led to a

*Electron efficiency in photosystem II of cucumber plants treated with biostimulators mixture before and after*

**Leaf weight (g/plant)**

Not-treated 341,75 b 244,5 b 477,75 ns 7333,7 b 206 b 4,86 b

*Growth parameters of cucumber plants treated with biostimulator mix prior to temperature - stress at 6°C for*

**Leaf area (cm<sup>2</sup>**

390 a 358,5 a 548,25 ns 9637,4 a 321,25 a 6,98 a

**/plant)**

**Root weight (g/plant)**

**Root length (m/plant)**

after the third treatment with the biostimulating mixture.

**Shoot weight (g/ plant)**

*Different letters indicate significant differences (LSD, p = 0.05); and ns = non-significant).*

better than non-treated plants.

*low temperature treatment with 6°C for 3 h. [12].*

**length (cm)**

**Shoot weight (g/plant)**

*Different letters indicate significant differences (LSD, p = 0.05); and ns = non-significant.*

**Variants Shoot**

Treated with biostimulator

**Table 11.**

*3 h [12].*

**83**

**Variants Shoot**

Treated with biostimulator

**Table 10.**

**Figure 9.**

*one week [12].*

**length (cm)**

*DOI: http://dx.doi.org/10.5772/intechopen.96536*

Whereas without biostimulator treatment, the fluorescence Fv/Fm-value was slightly decreasing after second and third week. In the time of the pH stress influence in the fifths week, it is visible, the stress effect was much stronger (**Figure 8**), where the lowest Fv/Fm value was 0.620. Four weeks later the plants treated with the biostimulator treatment recovered completely from the stress, but the plants without Biostimulator were still in weak condition. The plants treated with biostimulator mixture showed a higher electron efficiency of photosystem II (0.765 Fv/Fm-value) at the end of the experiment as compared to the plants without treatment (0.670 Fv/Fm-value).

The final evaluation of cucumber plants showed that this plants treated with biostimulators had significant shorter shoot length and but heavier weight than non-treated plants (**Table 10**). The roots were longer than non-treated plants and treated plants also yielded some marketable fruits (data not shown). Obviously, the biostimulators mixture was effective for reduction of the pH-stress.

#### *5.4.3 Temperature stress for cucumber plants*

Temperature stress can be happens in greenhouses if the heating system is not working or the ventilation is not proper functioning. Therefore, this stress was

#### **Figure 8.**

*Electron efficiency in photosystem II of cucumber plants treated with biostimulators mixture before and after pH-stress (pH 3.2) for one week. [12].*

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation… DOI: http://dx.doi.org/10.5772/intechopen.96536*


#### **Table 10.**

stages, first treatment at 5–6 leaf stage (week 1); second at 7–8 leaf stage (2 weeks)

After the last treatment with the biostimulator solution (4 weeks), the stress factor was applied. For the pH stress experiment, pH values were adjusted to a suboptimal level (pH 3.2) by adding H3PO4 to the nutrient solution. This pH stress was maintained for 1 week. For temperature stress, temperature in the growth

One week after transplanting the cucumber plants the chlorophyll fluorescence

Whereas without biostimulator treatment, the fluorescence Fv/Fm-value was slightly decreasing after second and third week. In the time of the pH stress influence in the fifths week, it is visible, the stress effect was much stronger (**Figure 8**), where the lowest Fv/Fm value was 0.620. Four weeks later the plants treated with the biostimulator treatment recovered completely from the stress, but the plants without Biostimulator were still in weak condition. The plants treated with

biostimulator mixture showed a higher electron efficiency of photosystem II (0.765 Fv/Fm-value) at the end of the experiment as compared to the plants without

The final evaluation of cucumber plants showed that this plants treated with biostimulators had significant shorter shoot length and but heavier weight than non-treated plants (**Table 10**). The roots were longer than non-treated plants and treated plants also yielded some marketable fruits (data not shown). Obviously, the

Temperature stress can be happens in greenhouses if the heating system is not working or the ventilation is not proper functioning. Therefore, this stress was

*Electron efficiency in photosystem II of cucumber plants treated with biostimulators mixture before and after*

biostimulators mixture was effective for reduction of the pH-stress.

Fv/Fm-value increased from 0.760 (**Figure 8**) to 0.790 in plants treated with biostimulating complex and 0.770 in plants without treatment. A drastic decrease in electron efficiency was observed after imposition of a strong lowering the pH value. Between the 4th and 5th measurements, Fv/Fm of treated plants decreased to 0.747

and the third at 9–10 leaf stage (3 weeks).

*Cucumber Economic Values and Its Cultivation and Breeding*

chamber was lowered from 25 to 6°C for 3 h.

and that of the non-treated ones even to 0.654.

*5.4.2 pH stress for cucumber plants*

treatment (0.670 Fv/Fm-value).

**Figure 8.**

**82**

*pH-stress (pH 3.2) for one week. [12].*

*5.4.3 Temperature stress for cucumber plants*

*Growth parameters of cucumber plants treated with biostimulators mixture prior to pH- stress (pH 3.2) for one week [12].*

given for a short time from three hours and the lowest temperature was 6°C. This stress was applied by lowering the air temperature in the climate chamber right after the third treatment with the biostimulating mixture.

The Fv/Fm parameter had the same pattern as in case of pH stress. However, Fv/ Fm development showed its peculiarities (**Figure 9**). Measurement 1 to 4 gave equal electron efficiency levels. After temperature stress, Fv/Fm values decreased considerably indicating a reduction in photosystem II efficiency. Only the treated plants were able to reach higher levels of Fv/Fm after stress and could recover much better than non-treated plants.

At the end of this temperature stress experiment, the plant growth parameters were also determined (**Table 11**). The effect of the biostimulator mixture led to a

**Figure 9.**

*Electron efficiency in photosystem II of cucumber plants treated with biostimulators mixture before and after low temperature treatment with 6°C for 3 h. [12].*


#### **Table 11.**

*Growth parameters of cucumber plants treated with biostimulator mix prior to temperature - stress at 6°C for 3 h [12].*

#### *Cucumber Economic Values and Its Cultivation and Breeding*

significant difference in all parameters as compared to the non-treated plants, except for the leaf area.

The question is what could be the reason, that the temperature stress was less disturbing the cucumber plant if the plants were several time treated with Biostimulator. The biostimulators used in this experiment had shown also in previous experiments a positive reaction on the root growth [14]. It can be assumed plants with well-developed root systems have higher resistance against different stress situations. Therefore, a correlation between the green biomass of the cucumber plants and the root mass were calculated. In the experiments without treatments with biostimulators, no correlation could be found (**Figure 10**).

**6. Conclusions**

*DOI: http://dx.doi.org/10.5772/intechopen.96536*

(EC) at about a value of 2 EC.

root growth.

**85**

In general can be stated, intensively in greenhouses cultivated crops such as cucumbers, suffer often from inadequate abiotic or biotic growth conditions in particular in the rhizosphere. Many studies were done to find growth promoters or biostimulators to stabilize the production process or to enhance plant growth of cucumbers under these conditions. One task was to find substrates with appropriate physical and chemical properties for root growth of cucumbers desirable from organic materials. Sheep wool slabs, peat slabs and coconut fiber slabs were therefore successful tested with and without Biostimulator treatments and compared with perlite and rockwool slabs. It was to decide which of the biostimulators and their modifications should be tested and could be recommended. Based on the research with different Humates the K-Humate was selected. From the different lactates the LACTOFOL"O" (CO. ECOFOL) a foliar fertilizer was chosen after many previous experiments. From the different strains of Bacillus subtilis the strain FZB24® was successful tested and can be recommended. Under the growing conditions in soilless culture, using different substrates a buffer is missing completely or partly for regulation of the nutrient availability and regulation of the sorption capacity as in the natural soil. Therefore, different stress situations can occur, the Biostimulators used in all investigations as single component or in treatments combined in order to reduce such stress situation. Very successful was used for cucumber plants growing in substrate with a high EC value the application of K-Humate and *B. subtilis* (FZB24®) as single component and combined the salt concentration could be stabilized convenient for cucumbers. The mixture of all three components, however, was as effective as Humate alone and stabilized the salt concentration

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation…*

In general, pH values affect the nutrient availability and uptake, in particular of micronutrients. The pH of substrates in soilless culture systems, changed with the duration of cultivation. Application of Lactate (LACTOFOL) and *B. subtilis* (FZB24®) stimulated root growth and shoot development even at pH 7.5 and the

Application of the biostimulators solution with all three components BS-FZB24® (0.2%), K-Humate (0.01%), and LACTOFOL "O" (0.1%) were tested regarding their effects in case of strong but short time pH and temperature stress the growth of cucumber plants. The chlorophyll fluorescence Fv/Fm value showed a positive effect of the curative biostimulator treatments under the stress counteraction in plants. Results showed that there was strong correlation between green biomass of treated cucumber plants and their root mass. It can be assumed that the effect of stress prevention by the biostimulator was based mainly on enhancing the

In the experiments using the biostimulator for stabilization of cucumber plant growth, the biostimulators were applicate only in the rhizosphere that means direct to the roots. Lactate was originally developed and used as foliar-fertilizer. Therefore, it came to the thought to use the biostimulators to the root zone and on the leaves. Following the experimental results, it can be assumed, the application of the combined biostimulators with all substances if applied over the roots was a stimulating effect visible, whereas if applied over the leaves an inhibiting effect for cucumber plant growth. The number of fruits harvested from all variants and the control was higher on average when the biostimulators were applied to the

rhizosphere directly at the roots in comparison to the leaf application.

pH of the substrates treated with biostimulators was more stable.

On the other hand, those cucumber plants treated with biostimulators showed a very close correlation (R<sup>2</sup> linear =0.949) between green biomass and mass of roots (**Figure 11**). This close relationship confirms the hypothesis that increases in root mass lead to formation of larger shoots and leaf mass even under stress conditions if treated with some biostimulators.

**Figure 10.**

*Correlation between green biomass and root mass of cucumbers in plants exposed to pH and temperature stress condition, without biostimulators treatment [12].*

#### **Figure 11.**

*Correlation between green biomass and root mass of cucumbers in the experiment with pH and temperature stress condition, with biostimulators treatments [12].*

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation… DOI: http://dx.doi.org/10.5772/intechopen.96536*
