Abstract

Nanotechnology has become one of the several approaches attempting to ameliorate the severe effect of drought on plant's production and to increase the plants tolerance against water deficit for the water economy. In this research, the effect of foliar application of TiO2, nanoparticles or ordinary TiO2, on Helianthus annuus subjected to different levels of water deficit was studied. Cell membrane injury increased by increasing the level of water deficit and TiO2 concentration, and both types of TiO2 affected the leaves in analogous manner. Ord-TiO2 increased H2O2 generation by 67–240% and lipid peroxidation by 4–67% in leaves. These increases were more than that induced by Nano-TiO2 and the effect was concentration dependent. Proline significantly increased in leaves by water deficit stress, reaching at 25% field capacity (FC) to more than fivefold compared to that in plants grown on full FC. Spraying plants with water significantly decreased the activities of enzymes in the water deficit stressed roots. The water deficit stress exerted the highest magnitude of effect on the changes of cell membrane injury, MDA, proline content, and activities of CAT and GPX. Nano-TiO2 was having the highest effect on contents of H2O2 and GPX activity. In roots, the level of water deficit causes highest effect on enzyme activities, but TiO2 influenced more on the changes of MDA and H2O2 contents. GPX activity increased by 283% in leaves of plants treated with 50 and 150 ppm Nano-TiO2, while increased by 170% in those treated with Ord-TiO2, but APX and CAT activities increased by 17–197%, in average, with Ord-TiO2. This study concluded that Nano-TiO2 didn’t ameliorate the effects of drought stress on H. annuus but additively increased the stress, so its use in nano-phytotechnology mustn’t be expanded without extensive studies.

Highlights

  • The response of plants to water deficit stress is complex and involves changes in their macro- and micro-morphology and all physiological processes

  • Does the foliar application of Nano-TiO2 exert the same effect as Ord-TiO2 on sunflower plants? Second, how increasing concentrations of TiO2 affect the cell membranes and some enzyme activity? Third, can Nano-TiO2 ameliorate the effect of drought to some extent? Fourth, does Nano-TiO2 have a combined effect with drought as abiotic stressor on plants? As the TiO2 is applied by foliar spraying, whether or not the root will be affected as the shoot under different levels of water availability was another objective for this study

  • In plants grown on 25% field capacity (FC) and sprayed with 150 ppm Nano-TiO2, the membrane injury was magnified to 11-fold of that at full FC

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Summary

Introduction

The response of plants to water deficit stress is complex and involves changes in their macro- and micro-morphology and all physiological processes. Properties, concentration, method of application, uptake by plants, reactivity and translocation of nanoparticles into different plant tissues could determine their interference with various physiological activities that lead to toxic impacts (Mattiello et al 2015; Rastogi et al 2017; Paramo et al 2020). Sompornpailin et al (2020) showed that application of titanium nanoparticles increased the cell membrane stability, photosynthetic pigments, and antioxidant activities in Nicotiana tabacum. Hong et al (2005) and Liu et al (2021) reported an increase in the activities of SOD, CAT, POD and a decrease in accumulation of ROS when plants were exposed to TiO2 nanoparticles. Mohammadi et al (2016) concluded that foliar treatment of dragonhead plant with high concentrations of Nano-TiO2 increased injurious effects of water deficit stress on physiological processes due to increasing the levels of lipid peroxidation and H2O2 generation, and decreasing the stability of photosynthetic pigments. Does the foliar application of Nano-TiO2 exert the same effect as Ord-TiO2 on sunflower plants? Second, how increasing concentrations of TiO2 affect the cell membranes and some enzyme activity? Third, can Nano-TiO2 ameliorate the effect of drought to some extent? Fourth, does Nano-TiO2 have a combined effect with drought as abiotic stressor on plants? As the TiO2 is applied by foliar spraying, whether or not the root will be affected as the shoot under different levels of water availability was another objective for this study

Materials and methods
Results
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Discussion and conclusion
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