Phycomolecule-Coated Zinc Oxide Nanoparticles with Phosphorus Supplementation Enhance Plant Growth in Cotton (Gossypium hirsutum L.) -

Phycomolecule-Coated Zinc Oxide Nanoparticles with Phosphorus Supplementation Enhance Plant Growth in Cotton (Gossypium hirsutum L.)

Introduction:

 Nanoparticles under 100 nm have various applications in agriculture, pharmaceuticals, food technology, and environmental protection. Agronanotechnology, including nanofertilizers, offers a solution to optimize soil nutrients like phosphorus and water, boosting crop productivity while reducing fertilizer use and ecosystem pollution. Biologically-engineered nanomaterials are promising for agricultural applications, as they can promote plant growth without causing phytotoxicity. Engineered nanomaterials such as ZnONPs, FeONPs, ZnCuFe-oxideNPs, CaPNPs, and AgNPs have demonstrated growth-promoting effects in various food crops when used as micronutrient fertilizers. Additionally, carbon-based graphene nanoparticles and natural growth-enhancing phyco-compounds from seaweeds have also been found to stimulate seed germination, photosynthetic pigment levels, seedling growth rate, and yield in agricultural crops. A study investigated the impact of ZnONPs with phycomolecule ligands on phosphorus use and growth responses in cotton seedlings. The study aimed to biologically synthesize and characterize ZnONPs, measure growth responses and biochemical parameters, and examine antioxidative enzyme activities and membrane peroxidation damage in cotton seedlings exposed to a range of ZnONPs concentrations with phosphorus for 21 days.

Methodology:

The study involved the biological synthesis and characterization of zinc oxide nanoparticles (ZnONPs) using Halimeda tuna green macroalga extract. Cotton (Gossypium hirsutum L.) seedlings were exposed to a range of ZnONPs concentrations with phosphorus (P) supplementation for 21 days. The growth responses, biochemical parameters, and antioxidative enzyme activities were measured. The synthesis of ZnONPs involved the use of algal extract and a 5 mM zinc oxide solution, followed by characterization using various techniques such as FTIR, XRD, and FESEM with EDX analysis. The study employed a completely randomized block design with triplicates for each treatment.

Result and Discussion:

Growth Parameters: The study evaluated various growth parameters such as shoot length, root length, fresh weight, dry weight, and growth tolerance index (GTI) of cotton seedlings exposed to different doses of ZnONPs and P augmentation. Results showed a significant increase in shoot and root tissue growth tolerance index with increasing concentrations of ZnONPs, indicating a positive effect on plant growth .

Biochemical Changes: The study observed changes in biochemical mechanisms in response to ZnONPs exposure. Decreased activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) enzymes at higher doses of ZnONPs exposure were noted, possibly due to low oxidative stress as evidenced by reduced lipid peroxidation activity (low MDA content) in cotton plants. The use of natural phycomolecules coated ZnONPs was suggested to release Zn ions into cells in a slow and sustainable manner without causing phytotoxicity.

Antioxidant Defense Enzymes: ZnONPs exposure significantly enhanced the activity of antioxidant defense enzymes, including SOD, CAT, and POX, in cotton plants. The up-regulation of isozyme expression patterns of these enzymes indicated a protective mechanism against nanomaterial-induced stress and toxicity. The increased levels of SOD and POX enzymes were suggested to act synergistically to decrease reactive oxygen species (ROS) generation .

Photosynthetic Pigments and Protein Contents: The study reported a significant increase in the levels of chlorophyll a, chlorophyll b, carotenoids, and total soluble protein contents in cotton leaves following exposure to ZnONPs with P supplementation. This enhancement in photosynthetic pigments and protein contents indicated a positive impact on the plant’s physiological processes and growth .

Conclusion:  The findings of the study highlighted the effective plant growth-promoting role of phycomolecules coated ZnONPs in cotton plants. The exposure to ZnONPs  led to changes in morphology and biochemical mechanisms, activating multiple antioxidant defense pathways to prevent nanomaterial-induced toxicity. The study suggested that engineered ZnONPs coated with phycomolecules hold promise for judicious application in agriculture to enhance plant growth and productivity.

Reference:

VENKATACHALAM, P., PRIYANKA, N., MANIKANDAN, K., GANESHBABU, I., INDIRAARULSELVI, P., GEETHA, N., MURALIKRISHNA, K., BHATTACHARYA, R.C., TIWARI, M., SHARMA, N.J.P.P. AND SAHI, S.V., 2017. Enhanced plant growth promoting role of phycomolecules coated zinc oxide nanoparticles with P supplementation in cotton (Gossypium hirsutum L.). Plant Physiology and Biochemistry, 110, pp.118-127.