Nano-fertilizers for Balanced Crop Nutrition - Nanotechnologies in Food and Agriculture - page 73

Table 3.1 (continued)

Nutrient
release (h) References Nutrients Adsorbent Approach Size

Zn Zeolite Physical 25-30 1,176 Subramanian and

Sharmila Rahale
( 2013 )

Montmorillonite,
bentonite

Physical 35-

40 nm

312

Nano-Zn Chemical 35 nm - Nair et al. ( 2010 )

Nano-ZnO Chemical 20 nm - Mahajan

et al. ( 2011 )

B Zeolite Physical 60 nm 1,500 Selva Preetha

( 2011 )

wall can be weakened or broken by a critical amount of stress enzymes present.
Plant cell stress enzymes are activated by mechanical, thermal, chemical, or
biological stress. This stress sensitizes the plant during an attack and infection
from fungi and bacteria. These polymer-based CPA nanocapsules sprays are able to
prevent this infection: in this case, the plant cell stress enzymes are the stimuli
triggering the CPA release (Uzu et al. 2010 ).

3.5.2 Microelements Enter Plant Through Root Hairs
and Deliver Nutrients

The step-by-step method includes the following: the microelements, such as Ca,
Mg, Fe, S, and Zn, are encapsulated into microspheres, and these polymer micro-
capsules are, with time, incorporated and dissolved into the soil. Once close to the
root, the chemical bonds of the microcapsule

s wall polymer are broken down by
the organic acids or phenolic substances from the root exudates. These root exudates
are typically released to enhance plant feeding during the plant growth process and
represent the stimuli activating CPA release (Corredor et al . 2009 ). The possibility
of targeting the movement of nanoparticles to specific sites of an organism paves
way for the use of nano-biotechnology in the treatment of plant diseases that affect
specific parts of the plant. Different procedures have made use of nanoparticles in
plants, such as the controlled release of bioactive substances in solid wood and plant
transformation through bombardment with gold or tungsten particles coated with
DNA. In recent years, a breakthrough has been made as a result of the work by
Torney et al. ( 2007 ) who were able to control the intracellular release of substances
into protoplasts using mesoporous silica nanoparticles. Despite these advances, the
delivery of nanoparticles into plant tissues has been limited to methods involving
bombardment, a methodology that does not allowmassive application of particles in
large number of plants, thus being less exploited in crop improvement programs till
date (Gonz ´ lez-Melendi et al. 2008 ). Copper biomineralization with some wetland
plants that transform copper into metallic nanoparticles at soil-root interface with

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