HIGHLIGHTS:
Zinc concentration of 15 mg kg-1 in leaf tissue does not meet the needs of dwarf green coconut in the seedling phase.
Dwarf green coconut seedlings develop better with a zinc concentration of 82 mg kg-1 in leaf tissue.
Fertilization with up to 16 g of zinc per plant improves the metabolism of dwarf green coconut seedlings.
ABSTRACT
Zinc is an essential micronutrient for plant metabolism and has been studied in several crops of economic interest. However, there is no evidence of its use in coconut crops. The objective of this study was to evaluate the influence of foliar zinc fertilization with doses of zinc on dwarf green coconut seedlings based on their nutritional status, growth attributes, and gas exchange. The experimental design consisted of randomized blocks, and the treatments consisted of different zinc doses (0, 5, 10, 15, 20, and 25 g per plant) with five replicates. Seedlings were positively influenced by zinc dose, mainly in terms of growth variables and gas exchange. Zinc fertilization reduced iron and manganese content and increased zinc concentrations in the leaf tissue. Zinc fertilization promoted an increase in leaf area, height, shoot dry mass, and total dry mass. Furthermore, zinc fertilization improved photosynthesis, transpiration, stomatal conductance, internal CO2 concentration, instantaneous water use efficiency, and intrinsic water use efficiency. The improvement in these growth indices and gas exchange, in most variables, was up to an estimated dose of approximately 16 g of zinc per plant and decreased with increasing doses.
Key words:
Cocos nucifera L.; micronutrient; fertilization management; best dose of zinc; seedlings
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ns - Not significant by the F test; R2 - Coefficient of determination; CV - Coefficient of variation. Vertical bars indicate standard error of the mean (n = 5)
ns - Not significant; ** - Significant at p ≤ 0.01 by the F test; R2 - Coefficient of determination; CV - Coefficient of variation; Vertical bars indicate standard error of the means (n = 5)
*, ** - Significant at p ≤ 0.05 and p ≤ 0.01 by the F test, respectively; R2 - Coefficient of determination; CV - Coefficient of variation; Vertical bars indicate standard error of the means (n = 5)
*, ** - Significant at p ≤ 0.05 p ≤ 0.01 by the F test, respectively; R2 - Coefficient of determination; CV - Coefficient of variation; Vertical bars indicate standard error of the means (n = 5)
Leaf area (LA), height (H), shoot dry mass (SDM), root dry mass (RDM), total dry mass (TDM), photosynthesis (A), transpiration (E), stomatal conductance (gs), internal CO2 concentration (Ci), instantaneous water use efficiency (WUE) and intrinsic water use efficiency (iWUE)
*, ** - Significant at p ≤ 0.05 at p ≤ 0.01, by Pearson’s. The slope of the circles and the degree of coloring are proportional to Pearson’s correlation, according to the legend at the bottom of the figure