Impact of potassium nutrition on postharvest fruit quality: Melon (Cucumis melo L) case study

Abstract

Among the many plant mineral nutrients, potassium (K) stands out as a cation having the strongest influence on quality attributes that determine fruit marketability, consumer preference, and the concentration of critically important human-health associated phytonutrients. However, many plant, soil, and environmental factors often limit adequate uptake of K from the soil in sufficient amounts to satisfy fruit K requirements during development to optimize the aforementioned quality attributes. The objectives of this review are 1) to summarize published study abstracts on the effects of soil and/or foliar K fertilization as well as diverse K forms, on fruit phytonutrient concentrations; and 2) to illustrate the important role of K forms on fruit quality with a case study of Cucumis melo L (muskmelon) fruit produced with optimal soil applied K . The muskmelon studies will compare commercial sources (forms) of K applied to examine seasonal effects (spring vs. autumn) and the number of foliar K applications during fruit development on fruit marketability (maturity, yield, firmness, soluble solids, sugars, relative sweetness), consumer preference attributes (sugar content, sweetness, texture), and phytochemical concentrations (K, ascorbic acid, and β-carotene concentrations). Numerous studies have consistently demonstrated that specific K fertilizer forms, in combination with specific application regimes, can improve fruit quality attributes. Potassium fertilizer forms in order of effectiveness (Glycine (Gly)-complexed K=K 2 SO 4 ≥KCl>no K> KNO 3 ) when applied wet (foliar or hydroponic) vs. dry (soil) were generally superior in improving fruit marketability attributes, along with many humanhealth nutrients. The muskmelon case study demonstrated that two K forms: Gly-complexed K and K 2 SO 4 , combined with a silicone-based surfactant, applied weekly, as a foliar spray, during fruit development, from both autumn and spring-grown plants, had the greatest impact on improving fruit marketability attributes (maturity, yield, firmness, and sugars), as well as fruit quality attributes (human-health bioactive compounds K, ascorbic acid, and β-carotene). Among several foliar applied K salts studied under field conditions so far, salts with relatively low salt indices appeared to have the greatest impacts on fruit quality when applied during the mid-to late-season fruit development periods.

Macronutrientes na cultura da melancia cultivada em Neossolo com esterco bovino

“…O teor de cálcio observado no solo, antes do experimento (Tabela 1), é considerado bom e o esterco apresentava teores consideráveis desse elemento. Isso pode indicar que o alto teor de K (0,4 cmol c dm -3 ) existente no solo tenha inibido competitivamente a absorção de Ca pelas plantas (Lester et al, 2010), como observado por Grangeiro & Cecílio Filho (2004) em plantas de melancia submetidas à doses de K. No entanto, se faz necessário relatar que visualmente não foram observados sintomas de deficiência desse elemento nas plantas até porque o valor máximo registrado 22,5 g kg -1 está próximo ao limite inferior (25 g kg -1 ) estabelecido. Não se pode deixar de considerar também que a amplitude adotada como adequada pelos autores supracitados para a cultura no Estado de São Paulo seja superior à necessária para plantas cultivadas nas condições em que o experimento foi instalado.…”

Partição de nutrientes na parte aérea do meloeiro ‘Goldex’ fertirrigado

“…Como já mencionado, esse fato pode refletir numa maior demanda metabólica pelo fruto por esses nutrientes, a exemplo do Ca, que é componente de parede celular, sendo necessário para a firmeza do fruto (PEREIRA et al, 2002), do K, que participa do transporte de açúcares, estando associado ao teor de sólidos solúveis no fruto (LESTER et al, 2010), e do Zn, que atua na síntese do triptofano, precursor de vários hormônios na planta (EPSTEIN; BLOOM, 2006). Ressalta-se, ainda, que a extração do nutriente no fruto também é dependente da sua taxa de redistribuição, que por sua vez depende da mobilidade de cada nutriente (MAILLARD et al, 2015), assim como da sua taxa de fornecimento via solo ou via fertilização (MOREIRA et al, 2007).…”

The Effect of Potassium Biofortification Over Yield and Nutritional Quality of Cherry Tomato Fruits

“…In the sampling at 24 and 29 WAT, this relation did not appear, presumably due to the more adverse environmental conditions for the tomato crop (Table 3). K is considered the cation that has the greatest influence on the quality parameters that determine the commercial quality of fruits, according to consumer preferences, and on the concentration of essential phytonutrients for human health (Lester et al, 2010). In addition, with respect to the tomato fruit, this macronutrient significantly affects the concentration of pigments such as lycopene and β-carotene, which can be used as indicators of intrinsic quality, based on analytic and sensorial qualities (Ramí rez et al, 2012).…”

“…K is involved in numerous biochemical and physiological processes crucial to growth, performance, quality, and stress tolerance (Epstein and Bloom, 2005). Notably, this cation exerts the greatest influence on the parameters determining the market quality of fruit, consumer preferences, and the concentration of phytonutrients of vital importance for human health (Lester et al, 2010). In this sense, and although there are very few studies on the subject, an adequate K nutrition is also associated with greater crop yield and fruit size, increases in soluble solids and AsA concentrations, and improved fruit colour (Kanai et al, 2007).…”