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Growth and yield responses of `New Mexico 6-4' and `NuMex R Naky' chile pepper [Capsicum annuum L. var. annuum (Longum Group)] to four Fe levels were studied under sand culture. A balanced nutrient solution (total nutrient concentration <2 mmol·L-1) was recirculated continuously to plants potted in acid-washed sand from the seedling stage to red fruit harvest. Plants received 1, 3, 10 or 30 μm Fe as ferric ethylenediamine di-(o-hydroxyphenyl-acetate). Plant growth was determined by leaf area, specific leaf area [(SLA), leaf area per unit dry weight of leaves], instantaneous leaf photosynthetic rates, and dry matter partitioning. Low Fe (1 or 3 μm Fe) in the nutrient solution was associated with lower relative growth rates (RGR), increased SLA, and higher root to shoot ratios (3 μm Fe plants only) at final harvest. High Fe levels (10 or 30 μm Fe) in the nutrient solution were associated with an increased yield of red fruit and total plant dry matter. RGR of low-Fe young chile plants was reduced before any chlorotic symptoms appeared.
Pigment and micronutrient concentrations of New Mexico 6-4 and NuMex R Naky chile pepper (Capsicum annuum L.) cultivars as affected by low Fe levels were studied under soilless culture. A custom-designed, balanced nutrient solution (total concentration <2 mm) was continuously recirculated to the plants potted in acid-washed sand (pot volume 15.6 L). Each set of plants from each cultivar received iron concentrations at 1, 3, 10, and 30 μm Fe as Fe-EDDHA. The pigments of leaves, green fruit, and red fruit were extracted with acetone and measured with a spectrophotometer. Surface color of green and red fruit was measured with a chromameter. Total concentrations of Fe, Cu, Zn, Mn, P, and K of leaf blades and red fruit were measured by inductively coupled plasma emission spectroscopy (ICP). Ferrous iron in leaf blades, and NO3-N in petioles also were determined. Iron nutrition level affected total leaf chlorophyll and carotenoid content at early season, and the level of these pigments in green fruit at second harvest. No differences in extractable or surface color of red fruit were found among iron treatments in the nutrient solution, despite variations in red fruit iron content, total foliar iron, and foliar ferrous iron. Higher levels of iron in the nutrient solution increased both ferrous and total iron of the leaves, but depressed foliar Cu and P. High iron supply also increased fruit iron, and decreased fruit Cu content. High iron levels in the nutrient solution were associated with higher concentrations of leaf pigments at early season and higher pigment concentration in green fruit.