Figure 3.1 Outline of different methods used for the treatment of seeds with Zn NPs and their effects.
Table 3.1 Effects of Zn NPs on germination and seedling growth after application through different modes.
| Size and coatings (nm) | Crop | Concentrations | Mode of application | Effects | References | ||
|---|---|---|---|---|---|---|---|
| Root growth | Shoot growth | Germination percent | |||||
| 21.3 | Lupine | 20, 40, and 60 mg/L | Seed priming (12 hours) under salt stress (150 mM NaCl) | + | + | + | Latef et al. (2017) |
| 20 | Onion | 10 and 20 mg/L | Seed treatment in petri‐plate for 10 days | + | + | + | Raskar and Laware (2014) |
| 30 and 40 mg/L | Seed treatment in petri‐plate for 10 days | − | − | − | |||
| 25 | Peanut | 400 and 1000 mg/L | Seed treatment (3 hours) | + | + | + | Prasad et al. (2012) |
| 2000 mg/L | Seed treatment (3 hours) | − | − | − | |||
| 25 | Maize | 50–2000 mg/L | Seed soaking (3 hours) | + | + | + | Subbaiah et al. (2016) |
| <100 | Brassica | 500–1500 mg/L | Seed allowed to grow in treated plain agar for 12 days | − | − | − | Zafar et al. (2016) |
| <100 | Wheat | 500 mg/L | Seed treatment (24 hours) | + | + | + | Elhaj Baddar and Unrine (2018) |
| n/a | Rice | 500 and 750 mg/L | Seed treatment till germination | − | − | − | Sheteiwy et al. (2017) |
| 30–60 | Rice | 5, 10, 15, 20, and 50 mg/L | Seed soaking (1 hour) | + | + | + | Panda (2017) |
| 34 | Wheat | 25, 50, 75, and 100 mg/L | Seed priming (24 hours) | + | + | + | Munir et al. (2018) |
| 13 | Wheat | 10, 20, and 50 mg/L | Hydroponic supplement (14 days) | + | + | + | Awasthi et al. (2017) |
| 100 mg/L | − | + | − | ||||
| 20, 40, and 60 | Common Bean | 1, 10, 100, and 1000 mg/L | Seed priming (20 minutes) | + | + | o | Savassa et al. (2018) |
| 5000 mg/L | − | − | − | ||||
| 18 | Capsicum | 100, 200, and 300 mg/L | Applied during imbibition (72 hours) | + | + | + | Israel García‐López et al. (2018) |
| 400 and 500 mg/L | − | − | − |
3.2.3 Effects of Seed Treatment on Plant Growth
Seed treated with ZnO NPs not only protects seeds from microbial infections but also provides Zn to the crops after germination in the easily available form (Masuthi et al. 2009; Farooq et al. 2012). Seed priming with Zn NPs (34 nm) for 24 hours at 100 mg/L increased photosynthetic pigment content by 58% and stomatal conductance by 102% after 65 days of treatment. Moreover, the same treatment increased wheat plant height, tillers per plant, spike length, biomass yield, and grain yield by 16, 69, 87, 58, 36, and 185% respectively (Munir et al. 2018).
3.2.4 Molecular Mechanisms Involved in Effects of Zn NPs on Seed
Compare to salt‐based Zn, ZnO NPs can enhance Zn delivery to seeds through the particle‐specific mechanisms. Zhang et al. (2015a) suggested