Dynamics of mineral nutrient element concentrations in developing cotton leaves,bracts, and floral buds in relation to position in the canopy

Plant mineral nutrient element status is an important factor influencing cotton (Gossypium hirsutum L.) growth, development, metabolism, and yield. A field study was conducted to determine changes in mineral nutrient element concentrations in leaves, bracts, and floral buds of field‐grown cotton plants during development of squares (floral bud with three bracts) as affected by fruiting position within the plant canopy. During square ontogeny, the nitrogen (N), phosphorous (P) and potassium (K) concentrations of sympodial leaves and floral bracts decreased, whereas the calcium (Ca) and magnesium (Mg) increased, and sulfur (S) concentration exhibited little change (leaves) or increased (bracts) with increasing square age. The N, P, Ca, and S concentrations in floral buds declined synchronously; K and Mg concentrations showed an increasing trend within the first 20 days, peaked at about 25‐day square age, and then sharply decreased three to five days before flowering. During square development, the effect of main‐stem node (MSN) and sympodial branch fruiting position in the plant canopy on mineral nutrient element concentrations of bracts was greater than on those of floral buds. Differences in the mineral nutrient element concentrations existed among the sympodial leaves, bracts, and floral buds. This study provides the patterns of mineral nutrient element concentrations in these plant tissues during the square development phase in relation to MSNs and branch fruiting positions in the cotton plant canopy.