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Photosynthetic light curve, chlorophyll (Chl) content, Chl fluorescence parameters, malondialdehyde (MDA) content, phosphoenolpyruvate carboxylase (PEPC) activity and reactive oxygen metabolism were studied under drought stress in two autotetraploid rice lines and corresponding diploid rice lines. Net photosynthetic rate decreased dramatically, especially under severe drought stress and under high photosynthetic active radiation in diploid rice, while it declined less under the same conditions in autotetraploid lines. Compared with the corresponding diploid lines, the Chl content, maximum photochemical efficiency of photosystem (PS) II, and actual photochemical efficiency of PSII were reduced less in autotetraploid lines. PEPC activities were higher in autotetraploid rice lines. PEPC could alleviate inhibition of photosynthesis caused by drought stress. The chromosome-doubling enhanced rice photoinhibition tolerance under drought stress. The lower MDA content and superoxide anion production rate was found in the autotetraploid rice indicating low peroxidation level of cell membranes. At the same time, the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were higher in autotetraploid rice lines. SOD, POD, and CAT could effectively diminish the reactive oxygen species and reduced the membrane lipid peroxidation.

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Because of its relatively high water solubility and mobility, 2,4-dichlorophenoxy acetic acid (2,4-D) has a high leaching potential threatening the surface water and groundwater. Controlled release formulations of 2,4-D could alleviate the adverse effects on the environment. In the present study, positive-charge functionalized mesoporous silica nanoparticles (MSNs) were facilely synthesized by incorporating trimethylammonium (TA) groups onto MSNs via a postgrafting method. 2,4-D sodium salt, the anionic form of 2,4-D, was effectively loaded into these positively charged MSN-TA nanoparticles. The loading content can be greatly improved to 21.7% compared to using bare MSNs as a single encapsulant (1.5%). Pesticide loading and release patterns were pH, ionic strength and temperature responsive, which were mainly dominated by the electrostatic interactions. Soil column experiments clearly demonstrated that MSN-TA can decrease the soil leaching of 2, 4-D sodium salt. Moreover, this novel nanoformulation showed good bioactivity on target plant without adverse effects on the growth of nontarget plant. This strategy based on electrostatic interactions could be widely applied to charge carrying agrochemicals using carriers bearing opposite charges to alleviate the potential adverse effects on the environment.

Nanotechnology-based pesticide formulations would ensure effective utilization of agricultural inputs. In the present work, mesoporous silica nanoparticles (MSNs) with particle diameters of ~110 nm and pore sizes of ~3.7 nm were synthesized via a liquid crystal templating mechanism. A water-soluble chitosan (CS) derivative (N-(2-hydroxyl)propyl-3-trimethyl ammonium CS chloride, HTCC) was successfully capped on the surface of pyraclostrobin-loaded MSNs. The physicochemical and structural analyses showed that the electrostatic interactions and hydrogen bonding were the major forces responsible for the formation of HTCC-capped MSNs. HTCC coating greatly improved the loading efficiency (LC) (to 40.3%) compared to using bare MSNs as a single encapsulant (26.7%). The microstructure of the nanoparticles was revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The pyraclostrobin-loaded nanoparticles showed an initial burst and subsequent sustained release behavior. HTCC-capped MSNs released faster than bare MSNs in the initial stage. Pyraclostrobin-loaded HTCC-capped MSNs with half doses of pyraclostrobin technical demonstrated almost the same fungicidal activity against Phomopsis asparagi (Sacc.), which obviously reduced the applied pesticide and enhanced the utilization efficiency. Therefore, HTCC-decorated MSNs demonstrated great potential as nanocarriers in agrochemical applications.

The application of nanotechnology in pesticide loading can improve the uptake and transportation behavior in plants, which helps to increase the utilization efficiency of pesticides. In this work, prochloraz-loading mesoporous silica nanoparticles were prepared to study the translocation, distribution and degradation of the target pesticide in cucumber plants. Fluorescein isothiocyanate labeled nanoparticles were used to track the distribution of the carriers in plants. Four hours after the treatment on the leaves, the nanoparticles could be found in the leaves, stem, petioles and roots. Fourteen days later the concentration levels of prochloraz and its metabolite were measured in different parts of cucumber using high performance liquid chromatography tandem mass spectrometry. Compared to the conventional suspension concentrate, prochloraz-loaded mesoporous silica nanoparticles had almost the same fungicidal activity, and they tend to be absorbed by cucumber plants with a better deposition performance. The final residue levels of prochloraz in cucumbers were lower than the maximum residue levels, which indicated the low risk of p-MSN application on the plant.

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Pesticide spray droplets can damage ecological environments and negatively affect biodiversity if they reach nontarget areas. Effective retention of pesticide droplets on plant surfaces is an important challenge. In this study, a high-speed camera was utilized to visualize the bounce behavior of droplets of different pesticide solutions on rice leaf surfaces. We explored the addition of surfactants (SAAs) to different pesticide solutions and altered a pesticide solution system to prevent or regulate droplet bounce behavior. Experimental results indicate that the addition of SAAs to a pesticide solution can inhibit the bouncing of droplets on rice leaf surfaces. Additionally, a water-in-oil (EO) emulsion not only can significantly inhibit droplet rebound on a superhydrophobic surface, but also can quickly and automatically spread pesticide droplets to maximize the wetting area. Therefore, this work effectively improves the utilization of pesticides and reduces environmental pollution.