Biochemical nutrient pathways in plants applied as foliar spray: Phosphorus and iron

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Bindraban, Prem S.
Renu Pandey
Vengavasi Krishnapriya
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In plants, the roots are traditionally the primary site for water and inorganic nutrient absorption from the soil. However, recent research has shown that foliage, including leaves, stems, inflorescence, and fruits, can also affect nutrient uptake. This study aims to review the general pathways of foliar nutrient absorption and investigate the specific mechanisms involved in the penetration, absorption, and translocation of phosphorus (P) and iron (Fe) into various cell organelles. The physico-chemical properties of the spray formulation used for foliar application, such as pH, surface tension, polarity, spreading, and fluid retention, influence the efficacy of nutrient uptake. Additionally, the molecular size, ionic charge, and solubility of nutrient elements in the spray fluid, along with environmental factors such as relative humidity, temperature, light, and wind, affect the rate of foliar uptake. Plant-related factors like phenological stage, leaf morphology (shape, presence of hairs, stomatal characteristics), leaf surface architecture, chemistry, and nutrient mobility within the plant also contribute to foliar nutrient uptake efficiency. Soil fertilization of P and Fe is often limited by their low bioavailability, primarily influenced by soil pH. Slow diffusion and P fixation in soil result in limited availability of P, with plants absorbing only 10-20% of applied P during the growing season. Similarly, Fe availability is reduced at higher pH levels, and its deficiency is more pronounced in growing plant tissues. Foliar application of nutrients can effectively address the low bioavailability of P and Fe in soil and provide immediate relief from nutrient stress. Although foliar application cannot completely replace soil fertilization, it can enhance plant growth. This paper reviews and synthesizes existing literature on the pathways of foliar nutrient absorption and explores the biochemical processes involved in P and Fe penetration, absorption, and translocation within plant cells. Understanding these processes can aid in identifying effective nutrient compositions and developing advanced foliar fertilizers. The findings contribute to the knowledge of foliar nutrient uptake mechanisms and support the development of sustainable agricultural practices.
Nutrients, Phosphorus, Iron, Foliage
Renu Pandey, Vengavasi Krishnapriya and Prem S. Bindraban. 2013. Biochemical nutrient pathways in plants applied as foliar spray: Phosphorus and iron. Washington, VFRC, VFRC Report 2013/1. 23 pp.; 6 figs.; 63 ref. nbsp;