Nanotechnology in Plant Growth Promotion and Protection. Группа авторов

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soil or other solid growth media (Kořenková et al. 2017). The type of soil also affects bioavailability. The higher concentration of clay and organic matter decreases the mobility and bioavailability of nanoparticles and thus may also affect the influence that nanoparticles have on plants (Larue et al. 2018).

TiO₂NPs are considered to be used as a coating additive to increase the germination of plant seeds. It was observed that certain concentrations have a positive effect on germination (Table 2.1). The selection of the appropriate concentration of TiO₂NPs to enhance the early stages of plant growth was found to be species‐specific. Zheng et al. (2005) studied the effect of TiO₂NPs at a various concentration between 250 and 8000 mg/L on spinach seeds (Spinacia oleracea). The treatments of seeds with as high as 4000 mg/L concentration had a positive effect on germination, germination index, seedling dry weight, and vigor index. However, not all studies showed a similar pattern of positive effects. A study in Vicia narbonensis and Zea mays by Ruffini Castiglione et al. (2011) showed growth inhibition at similar concentrations (200–4000 mg/L). Similarly, in another study, the germination of Cucumis sativus was found to inhibit at concentrations as low as 100 mg/L (Mushtaq 2011). However, there are several studies that report positive effects of TiO₂NPs at various concentrations between 50 and 400 mg/L (Gao et al. 2008; Clément et al. 2013; Haghighi and Teixeira da Silva 2014; Ruffini Castiglione et al. 2016) or 2–60 mg/L (Feizi et al. 2012; Feizi et al. 2013a,b). Andersen et al. (2016) tested the efficacy of TiO₂NPs in 10 plant species and found that concentrations between 250 and 1000 mg/L had a positive effect on germination and early plant development for some plant species, while in other plant species negative or no effect at all was observed. However, it was observed that the negative effect is most common in plants treated with concentrations higher than 1000 mg/L (Zheng et al. 2005; Frazier et al. 2014). However, enzymatic activity and water uptake were negatively affected in onion seeds (Allium) at concentrations as low as 40 and 50 mg/L (Laware and Raskar 2014).

Soil structure and chemical composition have a strong influence on the behavior of chemical compounds, including nanoparticles in soils (Šebesta et al. 2017; Šebesta et al. 2020; Urík et al. 2020). Hydroponic experiments are used to evaluate the behavior of chemical compounds without the added influence of soil. Hydroponic toxicity tests were also used in the evaluation of the influence of TiO₂NPs on plants (Table 2.2). In hydroponics, no negative effect was observed for TiO₂NPs at concentrations between 10 and 100 mg /L in lettuce (Lactuca sativa), however, at concentrations with 1000 mg/L they were found to affect the plant weight significantly but no organ interaction was detected (Larue et al. 2016). The significant toxic effect in barley (Hordeum vulgare) was observed only at concentrations higher than 150 mg/L and expressed by a reduction in root length (Kořenková et al. 2017). Seeger et al. (2009) demonstrated that concentrations of 1–100 mg/L did not induce any significant response in willow tree saplings (Salix schwerinii x viminalis). The experiment performed in petri dishes showed that suspension of TiO₂NPs with concentrations as low as 0.01 mg/L exert phytotoxic effects on flax (Linum usitatissimum) (Clément et al. 2013). Wheat (Triticum aestivum) was exposed to differently sized TiO₂NPs of two crystalline structures (anatase and rutile) at concentrations of 10, 50, and 100 mg/L. Only nanoparticles having a smaller size (14 nm anatase and 22 and 36 nm rutile) had a significant positive effect at concentrations higher than 50 mg/L (Larue et al. 2012a). However, in rapeseed (Brassica napus), TiO₂NPs did not induce any significant physiological response at the same concentrations as shown in wheat (Larue et al. 2012b). TiO₂NPs at concentrations 100, 250, 500, or 750 mg/L negatively affected the formation of nodules with symbiotic bacteria and nitrogen fixation in legumes (Fan et al. 2014). Inhibition in nutrient transport was also observed at a concentration higher than 100 mg/L (Asli and Neumann 2009; Fan et al. 2014). Damage from reactive oxygen species and genotoxicity were reported even at concentrations as low as 10 mg/L (Demir et al. 2014; Pakrashi et al. 2014; Okupnik and Pflugmacher 2016). During longer cultivations (20 days) wheat's photosynthesis and other associated parameters were negatively affected by concentrations as low as 5 mg/L (Dias et al. 2019). Similarly, a lower concentration (12.5 mg/L) of TiO₂NPs showed a negative effect on root growth of red clover (Trifolium pratense) in a 28‐day exposure experiment (Moll et al. 2016).

Table 2.1 Influence of TiO₂ nanoparticles on plants, seed treatment.

Size (diameter in nm)	Plant species, length of exposure	Effect of concentration	Impact	References
No effect	Positive	Negative
n.a.	Spinacia oleraces, 48 h	n.a.	250–4000 mg/L	4000−8000 mg/L	Increased germination, germination index, seedling dry weight, vigor indexDecreased germination, germination index, seedling dry weight, vigor index	Zheng et al. (2005)
5	Spinacia oleraces, 48 h	n.a.	300 mg/L	n.a.	Increase in plant fresh and dry weightIncrease in amount of Rubisco activase	Gao et al. (2008)
n.a.	Oryza sativa, 24–72 h	100, 500, 1000 mg/L	n.a.	n.a.	Slight decrease in root length at 2‐ and 3‐day exposure	Boonyanitipong et al. (2011)
<50	Cucumis sativus, 6 days	n.a.	n.a.	100–5000 mg/L	Decrease in germination, germination index	Mushtaq (2011)
<100	Vicia narbonensis, Zea mays 24 h	n.a.	n.a.	200–4000 mg/L	Decrease in root elongationDecrease in mitotic indexIncrease in aberration index	Ruffini Castiglione et al. (2011)
21	a Triticum aestivum, 8 days	1, 100, 500 mg/L	2, 10 mg/L	n.a.	Mean germination time loweredIncrease in shoot length	Feizi et al. (2012)
21	a Foeniculum vulgare, 14 days	80 mg/L	5, 20, 40, 60 mg/L	n.a.	Mean germination time loweredGermination percentage, germination value, vigor index and mean daily germination improved	Feizi et al. (2013b)
21	a Salvia officinalis, 21 days	5, 20, 40, 80 mg/L	60 mg/L	Скачать книгу В начало < 14 15 16 17 18 19 20 21 22 23 > В конец e-mail: [email protected]