Investigating foliar application of bulk and nanoparticles titanium dioxide on fennel productivity to mitigate the negative effects of saline irrigation water

Fennel essential oils are fragrance compounds used in food and pharmaceutical sectors. One of the major impediments to expansion of fennel farming in Egypt's reclamation areas is saline water. Titanium dioxide (TiO₂) or TiO₂ nano particles (TiO₂NP) can be utilized to boost the yield of aromatic plants cultivated under saline irrigation water. Saline water, particularly which contains sodium chloride can harm fennel plant; consequently, it was predicted that fennel production would fail in Egypt's reclaimed area, where the primary source of irrigation is groundwater consisting sodium chloride. This study sought to help fennel respond to sodium chloride by applying Ti forms to their leaves in order to reduce the detrimental effects of sodium chloride on them for expanding their production in the newly reclamation areas as a natural source of essential oil. Ti forms were applied as foliar application at 0, 0.1, 0.2 TiO₂, 0.1 TiO₂NP, and 0.2 TiO₂NP, mM under irrigation with fresh water (0.4 dS m⁻¹), or saline water (51.3 mM or 4.7 dS m⁻¹).

Plants exposed to 0.1 mM TiO₂NP under fresh water resulted in the maximum values of morphological characters, estragole, oxygenated monoterpenes and photosynthetic pigments; while those subjected to 0.1 mM TiO₂NP under saline water gave the greatest values of essential oil, proline, antioxidant enzymes and phenols. The greatest amounts of soluble sugars were recorded with 0.2 mM TiO₂NP irrigated with saline water. Plants subjected to 0 mM TiO₂ under saline water produced the greatest values of flavonoids, hydrogen peroxide and malondialdehyde.

To mitigate the negative effects of salty irrigation water on fennel plant production, TiO₂NP application is suggested as a potential strategy.