1. Introduction
In intensive and sustainable agriculture, it is not enough to use plant protection products and fertilizers; it is also important to control plant physiological processes. For this purpose, growth stimulants are frequently used [
1]. According to Wadas and Kalinowski [
2], Tytanit is a liquid mineral growth biostimulant and contains 8.5 g Ti per liter in the form of titanium ascorbate. Hrubý et al. [
3] and Samadi [
4] demonstrate that titanium positively affects the content of chlorophyll and carotenoids in plants. Additionally, Michalski [
5] and Borkowski et al. [
6] confirm that this chemical element increases the activity of iron ions, pollen vigor and positively affects the growth and nutrition of plants. According to Hussain et al. [
7], it also improves the root architecture of
Glycine max L. However, Auriga et al. [
1] observed a lack of its significant effect on water balance in
Fragaria vesca L. growing in saline conditions, which indicates that stress might affect the effect of Tytanit. However, according to many studies [
2,
8,
9,
10,
11,
12], it positively affects not only the yield and quality of agricultural crops, but also those of fruit and vegetable plants.
The most common symptom of improper functioning of the metabolism in the plant is growth inhibition resulting from a decrease in respiration or from photosynthetic dysfunctions. Solar radiation in the range of 400–700 nm is called Photosynthetically Active Radiation (PAR). Located in the light-harvesting complex (LHC), photosynthetic pigments (chlorophyll and carotenoids) are responsible for radiation absorption. This antenna complex consists of many chlorophyll and carotenoid molecules linked to proteins. According to Maxwell and Johnson [
13], energy from this complex is transferred to the reaction centers of photosystem II and photosystem I (PSII and PSI).
The purpose of chlorophyll fluorescence is to remove excess light energy, and its mechanism is similar to the dissipation of energy as heat. It is therefore a kind of fuse-protecting photosynthetic system component that is sensitive to damage [
14]. Although fluorescence is emitted by chloroplasts, it is connected to all life processes occurring inside of the plant. That is why any change in the plant environment causing changes in these processes affects photosynthesis [
15]. Any disturbance of its intensity may decrease the yield and quality of plants. The result of chlorophyll fluorescence suggests the possible yield of plants; therefore, in practice it is used instead of the more popular level of photosynthesis and is a highly sensitive indicator of plant reaction [
16]. Chlorophyll fluorescence is used in eco physiology and in monitoring plant and ecosystem tolerance to toxins and various stress factors [
17]. According to Lyu et al. [
18], providing Ti to the plant through leaves or roots in an absorbable form has a positive effect on the yield. This is due to the stimulation of the plant by selected enzymes which stimulate the production of chlorophyll and intensify the photosynthesis process.
The parameter characterizing photosynthetic apparatus in terms of photochemical activity is the maximum photochemical efficiency of PSII (Fv/Fm). For most plants in the stage of full development and in optimal conditions, the value of this parameter can be up to 0.83 [
15,
19]. In addition, according to Angelini et al. [
20], the value of the Fv/Fm parameter depends on the processes occurring in the life of the plant and on varietal characteristics. The literature indicates the possibility of using the maximum photochemical efficiency of PSII as a measure of the impact of stimulants on the physiological condition of crops [
1,
21,
22,
23,
24,
25,
26].
The aim of the present research was to determine the effect of various doses of Tytanit applied to leaves on Festulolium braunii (K. Richt.) A. Camus dry matter production and composition, photosynthetic activity and chlorophyll a and b content in leaf blades. In particular, the weight of aboveground plants and roots, the maximum and actual efficiency of the leaf photosystem, the coefficients of non-photochemical and photochemical quenching, and the content of total protein, crude fiber, monosaccharides, crude fat, crude ash, Ca, Mg, P and K in the dry matter of Festulolium braunii (K. Richt.) A. Camus were determined.
3. Results and Discussion
The results (
Figure 1) indicated that Tytanit foliar application significantly affected
Festulolium braunii (K. Richt.) A. Camus dry matter production. The highest value, on average 24.2% higher than for control units, was recorded for plants treated with 0.04 and 0.06% stimulant concentrations. Compared to the control, the concentration of 0.02% also resulted in a statistically significant increase of 9.91%. The highest amounts of root dry matter (
Figure 2) were recorded in plants treated with the lowest concentration of Tytanit, i.e., 0.02%. In response to this amount, dry matter production was on average 12.8% higher than that in units with higher Tytanit concentrations and 23.8% higher than in control units.
The values of chlorophyll fluorescence parameters and chlorophyll content (
Figure 3 and
Figure 4 and
Table 4) indicated a various effect of Tytanit on the photosynthetic activity of
Festulolium braunii (K. Richt.) A. Camus leaves. In response to the stimulant, the content of chlorophyll a and b statistically significantly increased in relation to the control. In response to higher doses of the product (0.04 and 0.06%), chlorophyll a content in leaf blades was on average 29.2% and 16.2% higher than in plants treated with a 0.02% concentration. For chlorophyll b, an increase was not statistically significant, but its content in plants treated with the stimulant was 25.6% higher than in
Festulolium braunii from the control unit. Chlorophyll a and b are responsible for collecting light and transferring it to photosynthetic reaction centers, and higher content of these pigments might contribute to an increase in photosynthetic activity [
29,
30]. Likewise, in the present experiment Tytanit increased the amounts of
Festulolium braunii (K. Richt.) A. Camus chlorophyll pigments and its photosynthetic activity. Studying the effect of Tytanit on chlorophyll content in very early potato cultivars, Wadas and Kalinowski [
2] also recorded increased chlorophyll content in the leaves of plants treated with Tytanit. In turn, after triple application of a foliar fertilizer containing titanium ions, Tan and Wang [
31] found that potato leaves were dark green, shiny and dense, which was also confirmed in the present research on
Festulolium braunii (K. Richt.) A. Camus. In addition, according to Radkowski [
32] and Kováčik et al. [
33], Tytanit increased chlorophyll concentration in the leaves of
Phleum pratense L.,
Triticum aestivum L. and
Brassica napus var.
napus.
Chlorophyll fluorescence removes excess light energy in a way that is similar to energy dissipation in the form of heat. Thus, it protects photosynthetic apparatus components sensitive to damage. Although fluorescence is emitted by chloroplasts, all life processes in the plant cell are also affected. Therefore, changing environmental conditions will result in changes in the plant’s phenology [
14]. Fluorescence measurements of
Festulolium braunii (K. Richt.) A. Camus leaves indicated (
Table 4) that Tytanit application affected the maximum and actual efficiency of PSII in a statistically significant way. According to Khaleghi et al. [
34] and Laisk et al. [
35], increasing the maximum photosystem II efficiency means it activates after dark adaptation, resulting from a lack of photoinhibition in nitrogen-deficient plant cells. Thus, the energy used to transport electrons is not reduced. At the same time, as Nishiyama et al. [
36] and Cetner et al. [
15] argue, by providing the optimal dose of nitrogen, it is possible to increase the activity of reaction centers in dark-adapted cells. As a result of these activities, the activity of the photosynthetic apparatus and the efficiency of light energy processing can be increased.
According to Chen et al. [
37], temperature change is a limiting factor in photosynthesis. Depending on the difference between the optimal and current temperature, different changes happen in photosynthetic machinery. Based on chlorophyll fluorescence measurements, it was found that plants respond to high temperature by decreasing the ratio of reduced electron acceptors to reaction centers, reducing the maximum efficiency of PSII. Similarly, low temperatures affect the efficiency of the photosynthetic apparatus [
38].
Drought strongly inhibits the process of photosynthesis. Water deficiency is becoming a growing problem in agriculture, leading to a significant reduction in yields. It hinders the effective use of the absorbed light energy, which is increasingly dissipated through heat and increased fluorescence. These changes result in visible signs of plant wilting. Hence, the method of measuring chlorophyll fluorescence is used to monitor plants for drought stress [
15]. The harmful effect of salts consists in reducing the osmotic potential in soil solution. This leads to difficulties in water uptake and to changes in nutrient uptake. During salt stress, chlorophyll fluorescence monitoring indicates changes in the functioning of PSII, whose ability to capture energy becomes lower. Additionally, an increase in non-photochemical quenching has been found [
39]. It can be assumed that, in the present experiment, an increase in photosynthetic parameters such as the maximum (Fv/Fm) and actual (Fv′/Fm′) efficiency of the
Festulolium braunii leaf photosystem resulted from better nutrition of plant cells with nitrogen after Tytanit application. The maximum efficiency of PSII is an indicator of photochemical activity of the photosynthetic apparatus. During optimal conditions for plant growth, its value should be about 0.85 units [
20]. A decrease in this parameter indicates that the plant is undergoing stress, manifested in the form of photoinhibition, while very low values of PSII (0.2–0.3) indicate irreversible changes in its structure. However, according to Maxwell and Johnson [
13], this parameter value is not proportional to the intensity of photosynthesis, expressed by CO
2 assimilation or O
2 release. Additionally, Kalajii et al. [
40] emphasize that the value of PSII is not sensitive to certain kinds of stress (e.g., drought).
In this present research, the Tytanit stimulant also contributed to increasing the value of the non-photochemical quenching coefficient by 25.4% compared to the control. However, no statistically significant effect of its application on the photochemical quenching coefficient was found, which may be explained by the fact that fluorescence parameters are genetically conditioned [
41].
Tytanit had a significant effect on the content of
Festulolium braunii (K. Richt.) A. Camus organic components (
Table 5). The application of its higher concentrations resulted in an increase in total protein content (on average by 14.8%) compared to the control, but the lowest concentration did not affect it. However, higher concentrations of Tytanit decreased the amounts of fiber in the dry matter of plants (on average by 13.9%), and the concentration of 0.06% decreased it by 5.51%. Yet the stimulant did not affect crude fat and crude ash content. Tytanit has a positive effect on the chlorophyll content in the plant and, consequently, on the protein content. According to the literature [
42], the leaf greenness index (SPAD) and protein yield are correlated. The above results were confirmed by the research of other authors. Thus, other authors studying the effect of Tytanit doses on the content of organic compounds in the dry matter of meadow plants [
43,
44] also recorded an increase in protein and sugar amounts and a decrease in crude fiber content.
The highest calcium amounts (
Table 6) were in plants sprayed with 0.04 and 0.06% concentrations. These values were on average 16.4% higher than those on control units. Plants treated with the lowest dose of the stimulant contained 12.3% more calcium. An increase in calcium content in the dry matter of plants after Tytanit application was confirmed by other authors. Radkowski and Radkowska [
11] found that its various doses increased meadow hay calcium content. Its greatest amounts were recorded in plants sprayed with a 0.04% titanium concentration. In the first year, the increase was 79%, with a 133% increase in the second year and 63% in the third year. Wójcik [
45] and Skupień and Oszmiański [
46] argue that, under the influence of a biostimulator with titanium, the plant is able to accumulate more macro- and microelements in the vegetative and generative parts. The improved nutrition of the plant is caused by a more extensive root system, especially the elongation of the capillaries zone. As a result, the plant rapidly absorbs more nutrients from the soil environment.
Statistical analysis also showed a significant effect of the stimulant on magnesium and potassium content in
Festulolium braunii (K. Richt.) A. Camus. The magnesium content was significantly higher relative to the control (on average by 36.7%) in plants treated with 0.04 and 0.06% concentrations of the stimulant. The effect of Tytanit on an increase of magnesium accumulation in plants was also noted by Radkowski and Radkowska [
11] and Kleiber and Markiewicz [
47]. In tomato cultivation, the highest magnesium content was in leaves sprayed with a liquid containing 960 g Ti ha
−1. However, a low dose of 80 g Ti ha
−1 lowered magnesium content relative to the control. In turn, Kalembasa et al. [
48] recorded its highest content in the blades and petioles of celery treated with 1.0, 1.2 and 2.4% concentrations of Tytanit, but its concentration of 3.6% and very low amounts did not affect magnesium content relative to the control. In turn, potassium content in the dry matter of
Festulolium braunii (K. Richt.) A. Camus was the lowest on units treated with 0.04% stimulant solution. This increase averaged 13.4% relative to the control and to plants treated with other doses. In turn, Kleiber and Markiewicz [
47] found no significant effect of Tytanit doses on potassium content in tomato fruits. Radkowski and Radkowska [
11] reported that foliar application of Tytanit at a concentration of 0.04% resulted in the largest increase in the content of all macroelements in the dry matter of meadow plants. This difference compared to the control was 28% for phosphorus, 78% for potassium, 80% for calcium and 81% for magnesium. A higher concentration of the product (0.08%) reduced macronutrient content compared to a concentration of 0.04, and in some cases even compared to a concentration of 0.02%. In this present experiment, Tytanit doses did not affect phosphorus content, which remained typical (average 3.63 g kg
−1 DM). However, some authors [
47,
49] observed an increase in phosphorus content in vegetables treated with titanium.