**6.1 Nanoparticles' effect on plants**

*Smart Nanosystems for Biomedicine, Optoelectronics and Catalysis*

UV tests could detect changes in absorption.

**5.4 Silver nitrate (AgNO3) concentration**

**5.5 Reaction stirring time**

**6. Fate of nanoparticles in plants**

stirring time for up to which reaction mixture is stirred.

**5.3 Effect of pH**

to the reduction of Ag++ ions to the formation of stable Ag atoms in nanoscale, making it the main parameter during optimization for nanoparticle manufacturing.

of biomolecules, which may affect their ability to cap and stabilize and, consequently, the growth of nanoparticles [21]. In general, in the course of research work experimentation, our observations suggest that, if the pH of the reactant is acidic, the transition from light green to dark brown will take a much longer time, indicating that the acidic medium is not appropriate for nanoparticle synthesis. The size of nanoparticles is expected to be higher in the acidic medium than in the basic media, which is also reported in different studies. It was our observation that particle sizes at pH 3 were greater than those at pH 8 with regular spherical shape, both of which were observed in the TEM analysis. The alkaline pH condition facilitated the reduction and stabilizing capacity of antioxidants in the leaf extract. During optimization, the pH spectrum could be tested from 3 to 11 pH and potential spectroscopic

A major influence of the reaction (pH) is its ability to change the electrical loads

The concentration of AgNO3 is measured in a range of 0.1–1 mM or even more concentrations, such as 10, 50 and 100 mM [22]. However, 1 mM concentration is best studied and suggested as we are actually synthesizing nanoparticles that are very minute and cannot be seen with naked eyes. Therefore, a very small quantity of the reactant is required for the reaction to occur. If the concentration of the reactant is increased, the reduction of Ag++ will not be successful and the accumulation could be noticeable. Actually, it does not make sense to use higher concentration for synthesis of nanoscale particles. Another factor vital for synthesis is the reaction

The reaction stirring time is the time required for silver nanoparticle synthesis starting from the reactant is added in the beaker to occur reaction. The stirring time will enable the proper interaction of silver salt with the reducing complex components present in test leaf extract. The plant containing the more secondary metabolites or phytochemicals will reduce the silver salt in less time, in other terms the plant containing fewer reduced compounds will take longer time for reducing silver salt. However, the less number of secondary metabolites reduces silver salt and nanoparticles formed quickly in very less time. The stirring time will be dependent on reaction mixture acidity, basicity, temperature, reducing power of extract, light intensity, enzyme and secondary metabolites of the test plant extract. Ref. [23] concluded that the stability of silver nanoparticle synthesis using glutathione as a reducing agent increases at 72 h and confirms the visible UV absorbance at 344–354 nm. Thus stirring time affects the synthesis of nanoparticles, the duration of the synthesis of nanoparticles, the time allowed for the interaction of silver nitrate and leaf extract.

Targeted application nanoparticles have led to their use in many areas, including medical, pharmacological, chemical, paint, fertilizer, geosensing, agriculture, etc.

**106**

Plants are faced with nanoparticles due to application in the field of plant protection. These nanoparticles are absorbed or collected or absorbed through the cell wall, the leaf surfaces, and the stomata or through the root from the soil. Once entry into the plant through the leaf surfaces, cell cytoplasm, mitochondria, ribosome, plant proteins, and enzymes radically alter their normal functions that cause cell death. They also interact with different processes in cells that cause alteration in phytohormones, metabolites, photosynthesis, transport and apoptosisinducing metabolism. In addition, nanoparticles binding induce oxidative stress leading to degradation of proteins, lipids, nucleic acid, stress-related genes and increased antioxidant development for ROS activity, effects cell function and leads the oxidation of proteins, lipids and nucleic acid [24]. The nanoparticles could activate certain cells that activate apoptosis by intrinsic pathway or necrosis. Thus, while formulating the nanoparticles or the nanoparticles-based products for various applications, it is very important to keep the track of nanoparticle products side effect into environment. These nanoparticles interact through an unknown mechanism and sometimes act in support of and increase the growth of seeds and plants. Nanoparticles, on the other hand, could inhibit seed and plant growth without any clues. Nanobiopesticide (NBP) products must therefore be organic and nontoxic and their final deposition in plants must be studied exclusively. There are several studies that use nanoparticles or nanobiopesticides to combat pests; on the other hand, these nanobiopesticides are being purged into healthy plant cells. Therefore, the pesticide in nanoform or nanomaterial must be eco-friendly to plants and, at the same time, the NBP must act selectively to suppress pests or insects.
