Abstract
Silicon (Si) it is a beneficial element that relieves biotic and abiotic stresses in plants. However, cotton plants are not considered Si accumulators, with low potential for uptake the element by roots. The objective of this study was to evaluate the effect of combinations of Si rates applied by leaf spray and soil on the physiology, growth and yield of cotton (Gossypium hirsutum L. r. latifolium Hutch). The experimental design was a randomized complete block in a 3 x 4 factorial scheme with four replications. Leaf spraying consisted of three Si concentrations (0, 500, and 1000 mL ha-1) corresponding to 0, 100, and 200 ml ha-1 of monosilicic acid, with spraying split into three applications at stages V4, V6 and V8. Soil-based fertilization consisted of four Si rates in (0, 2.5, 5.0, and 10.0 kg ha-1) corresponding to 0, 0.5, 1.0, and 2.0 kg ha-1 of SiO2. At flowering, photosynthesis, green color index (GCI), plant height, and NDVI were evaluated. The application of Si in the planting furrow near the rhizosphere increased the green color index, reflecting a gain in photosynthesis and plant height, which positively increased NDVI. The use of high solubility Si in the planting furrow can increase the concentration of monosilicic acid in the area with the highest root distribution, enhancing the effect of this element in a non-accumulator crop such as cotton, by improving the green color index, photosynthesis and hence reflecting on gains in plant height and plant leaf area demonstrated by NDVI.
Highlights
Silicon (Si) is a beneficial element that relieves multi-stresses, both biotic and abiotic (Vasanthi et al, 2014)
The green color index (GCI) showed a linear response to Si application by soil in the planting furrow, increasing 0.37 units per 1 kg ha-1 of Si applied to the soil (Figure 2a)
The improved plant mass demonstrated by normalized difference vegetation index (NDVI) is resulting from the Si effects on increasing green color index, photosynthesis and plant height, since NDVI variability is related to several phenological variables in cotton crop, among them the leaf area index, photosynthetic rate and plant leaf mass (Silva et al, 2017)
Summary
Silicon (Si) is a beneficial element that relieves multi-stresses, both biotic and abiotic (Vasanthi et al, 2014). Si is absorbed by plants as monosilicic acid and deposited on the leaf epidermis as amorphous silica, increasing its rigidity through interaction with pectin and polyphenols (Pilon-Smits et al, 2009). Vasinfectum (Whan et al, 2016), increased CO2 assimilation (Curvêlo et al, 2013) and photosyntetic rate (Barros et al, 2019; Ferraz et al, 2014), provided by increased concentration of phenolics and Si accumulation below the cuticle of the leaves forming a cuticle-silica bilayer (Schoelynck et al, 2010). Si accumulation below the cuticle improves leaf architecture by increasing plant height of cotton, providing a higher incidence of light on the leaf surface (Ferraz et al, 2014), increasing the light stimulus to photosynthetic pigments and increasing the green color index (GCI) and the normalized difference vegetation index (NDVI). NDVI is a variable that strongly correlates with several phenological variables in cotton crops, including leaf area
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