Gloxinia is native to Brazil and is grown as flowering potted plants (Dole and Wilkins, 2005). Growers who wish to produce gloxinia must understand its cultural needs, including fertility requirements. Limited information regarding nutritional requirements of gloxinia is available. Overall recommendations suggest that gloxinia has a low fertility requirement and excessive electrical conductivity (EC) levels should be avoided (Hollis, 1997). Dole and Wilkins (2005) recommend supplying the plants with 150 mg·L−1 nitrogen (N), while maintaining the substrate EC between 1.0 and 1.2 mS·cm−1. Kimmins (1992) recommended applying 200 mg·L−1 N, but only on a 7 to 10-d interval. The reported optimal substrate pH range is reported to be between 5.5 and 6.0 (Dole and Wilkins, 2005; Hamrick, 2003; Kimmins, 1992), and high substrate pH induced iron (Fe) deficiencies have been observed by the authors when the substrate pH exceeded 6.5. Growers are also cautioned to avoid excessive levels of ammoniacal-nitrogen, especially during winter production, as ammonium toxicity can occur (Hamrick, 2003; Hollis, 1997). Avoiding excessive levels of phosphorus (P) is also recommended (Hamrick, 2003; Hollis, 1997). Reported boron (B) deficiency symptoms include the loss of the apical meristem and development of thicker, distorted younger leaves (Love, 1985). Symptomology of other gloxinia nutrient disorders have not been published.
Growers producing gloxinia can encounter problems if nutritional disorders manifest because they lack the resources to accurately identify specific disorders. Tissue nutrient sufficiency ranges for gloxinia are available (Bryson and Mills, 2014; Cresswell and Weir, 1997; Dole and Wilkins, 2005), but there are not specific guidelines for critical tissue nutrient values when an element is deficient. To evaluate crops for the unique symptoms of gloxinia nutrient disorders, it is important that plants be grown under nutrient-stress conditions. The information gleaned from such species-specific studies adds information to the grower’s toolbox of diagnostic criterion. These diagnostic tools include symptomology descriptions, images of the disorders, and critical tissue nutrient concentrations. The objective of this study was to characterize the symptomology of gloxinia nutritional disorders and to determine critical nutrient levels of the crop.
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