Applications of Nanobiotechnology in Plant Sciences

Nanobiotechnology is a hybrid new discipline collaborating the aspects of both nanotechnology and biotechnology. Many of its applications are there in the field of plant sciences which are briefly discussed in this work. Nanoparticles are its basic tools which are used for the manipulation of plants. Many types of nanoparticles do exist. The applications of these particles are dynamical from plant to plant. Many kinds of nano-genetic modifications are made in plants which render improvements and resilience in them. Agricultural developments by this nanobiotechnology are also very significant. Besides all the positive developments, there also exist some harmful impacts of these nanoparticles. Overall, this technology has a lot of potential and depth for the future development and progress.


Introduction
Nanotechnology is regarded as the science of manipulation of atomic and subatomic particles for developing new machinery and products which are beneficial to the human beings, whereas, biotechnology is the practical application of living things for synthesizing new products useful to humans. After the combination of these two grand approaches, we came up with a new classical discipline of science being termed as nanobiotechnology. More precisely, it can be referred as the hybrid of nanotechnology and biotechnology. The term nanobiotechnology was first coined by a biophysicist Lynn W. Jelinski, of Cornell University, USA.
Nanobiotechnology is also termed as the eco-friendly technology for the synthesis of nano materials. A very wide scope of this promising new technology has been found in the field of agriculture and plant sciences. Moreover, over the last few decades nanobiotechnology has been exploited immensely in other disciplines like engineering, food technology, medical sciences and biotechnology as well. Nanoparticles which are the practical application tools of this technology, have a size between 1 to 100 nm. All the biological entities are organized on this nanoscale and nanobiotechnology, with new insights and tools is employed to transform the biosystems of many plants.

Types of Nanoparticles Used in Plants
Nanoparticles used in this field are of the two types, i.e., metal based, and carbon based. Carbon based nanoparticles are further of two types, carbon nanotubes and fullerenes, while the metalbased nanoparticles are divided into metal oxides, quantum dots and simple metals [1]. The most widely employed metal-based nanoparticles are Titanium dioxide (TiO2), Silver, Gold, Zinc oxide (ZnO) and Copper [2]. Based on the type of nanoparticles used, they cause many physiological and morphological changes in the plants.
The type, chemical composition, reactivity and most significantly the effective dose of nanoparticles are vital in this regard.

Nanoparticles Utilization in Plants
Silicon Dioxide Nanoparticles tomato, maize etc. Along with the improvement of germination percentages, these nanoparticles also enhanced root length, root diameter and the number of lateral roots in the seedlings [3].

Zinc Oxide Nanoparticles
Many studies suggest that these nanoparticles increase the rate of development and growth in the plants like soybean, peanut, wheat etc. [4][5][6].

Carbon Nanotubes
These nanoparticles have distinct mechanical, thermal, electrical and chemical properties. They can penetrate easily in the cell membrane and cell wall of the plant cell making the process of nanoparticles relatively easier. Increased germination rates by using carbon nanotubes has been observed in Brassica juncea, rice, tomato and Bt cotton [7]. It is being observed that carbon nanotubes also contributes to the flowering, fruit yield, biomass and medicinal attributes of some plants [8].

Gold Nanoparticles
Relatively few studies have been performed to analyses the effects of gold nanoparticles in plants. However, these studies indicate that these nanoparticles significantly improve the seed germination rates in lettuce, cucumber, Brassica juncea, Boswellia ovalifoliolata and Gloriosa superba [9][10][11][12].

Silver Nanoparticles
A great research work has been documented on the effects of silver nanoparticles in microbial and animal cells. However, research work on plants is limited in this case. Biologically synthesized silver nanoparticles increase the seed germination and growth of Boswellia ovaliofoliolata trees [11], along with the enhancement of some biochemical attributes and plant growth profile (PGP) of maize, common bean and Brassica juncea [13,14].

Titanium Dioxide Nanoparticles
These nanoparticles have been observed to increase the seed germination and length of radicle and plumule in canola [15].

Genetically Modified Plants through Nanobiotechnology
Many companies worldwide are now launching genetically modified crops with better combinations of desired traits. All these efforts are done by scientists to increase the production of the crops to feed the ever-growing population of the world. All the companies previously were employing Agrobacterium tumefaciens mediated method for this purpose or in few crops gene gun was also employed [16,17]. Although now these technologies for DNA

Nanobiotechnology and Agricultural Development
Nanobiotechnology has played a prominent role in agricultural development mainly by the better control of plant nutrients, improved disease resistance and pesticides development for sustainable agriculture. Applications of nanobiotechnology in the form of as nano-pesticides and nano-fertilizers is discussed below.

Nano-Pesticides
Besides the wide usage of synthetic pesticides by the farmers, bio-pesticides have their own distinct status in the control of insects and pests. A new technology has been introduced in the field of bio-pesticides, that is the use of nanobiotechnology. In this regard, synthesis of non-toxic and eco-friendly nano-pesticides is of great importance. Metallic nanoparticles exhibiting relatively superior anti-pathogenic, anti-fungal and anti-bacterial qualities are being used in these nano-pesticides. But for the usage of these nano-pesticides in the field, their ecotoxicological aspects on the environment should be considered wisely as these nano pesticides also kill the soil harbouring microorganisms [18,19].
The soil microbes are mandatory for the plants as they serve many ecological and biological purposes.

Nano-Fertilizers
Nano-fertilizers are made these days which contain silica, iron and titanium dioxide, zinc and gold nano-rods. Nanoparticles and are beneficial too for the ecosystems are more preferred than the conventional ones because the world is moving towards smart agriculture like the organic farming which protects the environment from all the hazards of chemicals [20,21].

Nanobiotechnology Application for Mitigating Abiotic Stresses in Plants
Abiotic stress affects adversely plant growth and productivity.
Out of all the abiotic stresses, the two-salinity and drought are the most prevalent in all plant [22,23]. Realizing this fact, scientists and researchers from decades are working to find out new

Future Generation Stress Tolerant Transgenic Plants
In today's agriculture, abiotic stress tolerant plus transgenic plants are highly desirable on commercial scales. With this realization, the scientists are working on newer methods to achieve more milestones in this field. By means of this new method, many more species of plants can be transformed and sole reliance on Agrobacterium method for genetic transformation will be reduced as the Agrobacterium method is limited and not feasible in all plant species [22]. So, by the combination of biotechnological and nanotechnological aspects, it is possible now that many new plants can be transformed to tolerate abiotic stress in more advanced ways with improved and desired combination of agronomic traits as well [22].  [29] Usually, the nanoparticles utilized in plants have a level of toxicity as well which is harmful for the plants to some extent but are more harmful for the microbial life or microflora existing in the soil. Nanoparticles and free radicles which usually generate toxicity, ultimately leads to DNA damage and peroxidation of lipids in plants [24]. Moreover, heavy metals have a toxicological mechanism in the form of reactive oxygen species in plants and it has been observed that if a plant is under some biotic or abiotic stress then the generation of these reactive oxygen species increases and results in necrosis and oxidative damages in plants. The production of reactive oxygen species is a very serious and dangerous effect of nanoparticles which must be overcome necessarily for the more frequent and efficient utilization of this technology in plants [25][26][27][28][29] (Table 1).

Author Contributions
AS and T came up with the idea and wrote the manuscript while WMB and SQ critically reviewed and proofread the manuscript.