Nanotechnology in Plant Growth Promotion and Protection. Группа авторов

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secondary lateral roots, diminished nutrient transportdisrupted Rhizobium–legume symbiosis system and nitrogen fixation Fan et al. (2014) 90–98 Allium cepa, 4 h n.a. n.a. 12.5, 25, 50, 100 mg/L Increased damage from reactive oxygen speciesIncrease in genotoxicity with concentration Pakrashi et al. (2014) 4 Lactuca sativa, 7 days 10–1000 mg/L n.a. n.a. Higher accumulation of Fe, P, S, and Ca in the root epidermisDecreased concentrations of Fe, P, S, and Ca in both the parenchyma and vascular cylinder Larue et al. (2016) 29, 92 Trifolium pratense, 7‐day old plants for 28 days n.a. n.a. 12.5, 25 mg/L Decrease in nodule formationDecrease in growth Moll et al. (2016) 10–30 Hydrilla verticillata, 24 h 0.01, 0.1, 1 mg/L n.a. 10 mg/L Increase in catalase and glutathione reductase activityIncrease in H₂O₂ at 10 mg/L Okupnik and Pflugmacher (2016) 25, 33, 41, 40 Oryza sativa, 35‐day old plants for 7 days n.a. 10, 1000 mg/L n.a. Reduced concentration of Pb in plantNo negative effect on plants Cai et al. (2017) 8 Hordeum vulgare, 7 days 100 mg/L n.a. 150–1000 mg/L Decrease in root length Kořenková et al. (2017) 21 Triticum aestivum, 20 days n.a. n.a. 5, 50, 150 mg/L Impaired light‐dependent and ‐independent phases of photosynthesisDecreased chlorophyll a content, maximal and effective efficiency of PSII, net photosynthetic rateDecreased transpiration rate, stomatal conductance, intercellular CO₂ concentration, and starch content Dias et al. (2019)

The experiments performed with plants grown in soil contaminated with nanoparticles, either in pots in laboratory, greenhouse, or in field conditions represent the realistic scenarios of exposure to nanoparticles in the environment to a greater degree. From these experiments, the right concentration of TiO₂NPs can be more objectively selected and later used to enhance plant growth in agriculture. Most of these experiments need to be performed for a longer duration than that of hydroponic growth and hence, it can help to get a better understanding of the effects of long‐term exposure of nanomaterials in plants (Table 2.3). Usually, two modes of nanoparticle application were preferred, (1) contamination of soil where plants were growing and (2) foliar application at the important stages of development of plants (Servin et al. 2013; Raliya et al. 2015b; Rezaei et al. 2015; Marchiol et al. 2016; Pošćić et al. 2016; Moll et al. 2017; Rafique et al. 2018; Giorgetti et al. 2019; Zahra et al. 2019; Bellani et al. 2020). In case of soil contamination, it was observed that the higher concentrations of TiO₂NPs in soil may have negative effects on the growth of plants (Du et al. 2011; Song et al. 2013; Marchiol et al. 2016; Pošćić et al. 2016; Tan et al. 2017; Rafique et al. 2018; Giorgetti et al. 2019; Bellani et al. 2020). However, the most concerning thing is that even concentrations as low as 100 mg/kg may have a negative long‐term effect on the growth and nutritional quality of crop plants (Du et al. 2011; Rafique et al. 2018; Bellani et al. 2020). The positive effects of TiO₂NPs applied to soil were recorded at concentrations between 25 and 500 mg/kg (Servin et al. 2013; Rafique et al. 2018; Zahra et al. 2019). The concentration range with positive effects for a plant species is narrower and the differences between studies may largely depend on the composition of the soil. Higher amounts of fine particles in the soil led to a higher concentration of TiO₂NPs needed to enhance plant growth (Zahra et al. 2019). In addition, it was reported that the concentrations of TiO₂NPs that enhance growth in plants may vary between plant species (Andersen et al. 2016). Moreover, foliar application of TiO₂NPs may become the preferred method of application on plants. A single application at the right growth stage may have a positive effect on the plant growth (Rezaei et al. 2015) and even concentrations as low as 10 mg/L in the form of a spray can improve the plant growth (Raliya et al. 2015b). Foliar application has the benefit of using lower amounts of nanoparticles that lead to lower contamination of soil and thus are more sustainable.

2.5 Benefits of Using TiO₂NPs Alone and in Complex Formulations on Plant Growth and Yield

At every stage of plant development, TiO₂NPs may have beneficial effects on the health of plants. On the other hand, there are some concerns, since their application led to the limited transport to fruits or other edible parts of the plant. However, literature has repeatedly shown that the overall uptake of TiO₂NPs is not increased compared to control and there are reports showing no major implication for food safety after whole plant life cycles (Bakshi et al. 2019). TiO₂NPs are, therefore, viable to use either alone or in composite form to increase the health, nutritional quality, and yield of plants or to protect them from diseases and adverse environmental conditions. Two main applications are considered:(1) seed coating to promote germination and (2) foliar or soil application to promote plant growth.

Table 2.3 A influence of TiO₂ nanoparticles on plants grown in soil.

Size (diameter in nm)	Plant species, length of exposure	Effect of concentration	Impact	References
No effect	Positive	Negative
<100	Triticum aestivum, 7 months in contaminated soil	n.a.	n.a.	91 mg/kg	Reduced biomassInhibition of soil protease, catalase, and peroxidase activities	Du et al. (2011)
27	Cucumis sativus, 150 days in contaminated soil	250, 750 mg/kg	500 mg/kg	n.a.	Enhanced metabolic activity in plant leavesIncreased K and P allocation in fruitNanoparticles transported to fruit	Servin et al. (2013)
27	Solanum lycopersicum, after 35 days Скачать книгу В начало < 16 17 18 19 20 21 22 23 24 25 > В конец e-mail: [email protected]