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Mandarin accounts for a significant part of the Colombian citrus fruit production, the postharvest degreening of these products to attain pigmentation being a common practice when they are harvested in the tropics. The endogenous signaling molecules such as methyl jasmonate and ethylene are produced during fruit formation, and they play a key role in postharvest and stress responses. The latter is commonly used to degreen mandarin, which, however, exhibits low sensitivity to this compound. It is therefore important to establish degreening alternatives to ethylene. Thus, the aim of this study was to determine the effect of methyl jasmonate on the degreening of Arrayana mandarin (Citrus reticulata L.). For such purpose, respiration rate, weight loss, color index, total chlorophyll, total soluble solids, firmness and total acidity were determined. The treatments applied were: methyl jasmonate (MeJA) 1 µM 24h, Ethylene (ET) 1000 ppm 20 min, 1-methylcyclopropene (1-MCP) 0.5 µL L -1 2h; and the combinations 1-MCP + MeJA, 1-MCP + ET. Generally obtained with the MeJA and 1-MCP + MeJA treatments, the most significant results took place at 14 days after treatment implementation (DATI) for total titratable acidity, and at 4 DATI for total chlorophyll and color index. The TSS/acid ratio (maturity ratio) became constant since 7 DATI under the MeJA treatment. Thus, the use of MeJA after 1-MCP pretreatment comes to be an interesting degreening option, all the more when considering that these physiological responses have not been reported in previous studies.

Una alternativa a la lixiviación de nitrógeno en el cultivo de flores de corte es la optimización de la fórmula de fertirriego. Con el objetivo de estudiar la reducción de nitrógeno y el aumento de la proporción de amonio en la relación NH4+:NO3-, se evaluaron en condiciones de invernadero dos concentraciones de nitrógeno total (200-140 mg L-1 en fase vegetativa y 160-112 mg L-1 en fase productiva) y tres relaciones de NH4:NO3- (5:95, 15:85 y 25:75) en clavel estándar cv. Don Pedro sembrado en sustrato. Se determinaron en tres momentos de cultivo los contenidos elementales del tejido vegetal, el pH y la concentración de nitrato en los lixiviados. Se observó mayores concentraciones de Zn y Cu en el tejido vegetal con la disminución de N total; así mismo, se obtuvieron incrementos de N y Zn y disminución de Mg con el incremento NH4+, que, a su vez, disminuyó el pH en el sustrato. La disminución de N total no afectó significativamente el contenido de N en el tejido de la planta, pero si el contenido de NO3- y N total en el lixiviado.

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Although nitrogen is the most widely used fertilizer in agriculture, it contaminates the surface and groundwater through leaching. A decrease in the concentration of total nitrogen and changes in the ammonium:nitrate ratio can provide information for a better use of this nutrient. The objective of this study was to evaluate the effect of a decrease in total nitrogen and an increase in the percentage of N-NH4+ on indicators of growth, productivity, quality and nitrogen use efficiency (NUE) in carnation cultivation. In the Centro Agropecuario Marengo at the Universidad Nacional de Colombia, two concentrations of total nitrogen were evaluated (200-140 mg L-1 in the vegetative phase and 160-112 mg L-1 in the productive phase) with three ratios of N-NH4:N-NO3 (5:95, 15:85 and 25:75) in standard carnation plants cv. Don Pedro grown in substrate. In both fertigation formulas, similar productivity and qualities were obtained, and the formula with less total N provided better NUE, mitigating the negative impact of this nutrient on the environment. Likewise, the ammoniacal component played a preponderant role: the number of floral stems per plant decreased as the ammoniacal component increased, similar to that observed with the percentage of flowering stems in the ‘Select’ quality grade.

One of the most important physiological disorders of red rose cultivars is blackening of petals, it affects outer and inner ones and results in flowers of poor quality. The goal of this review is to make an approach to the blackening disorder, determining the main possible causes in order to make available to growers, academics, scientifics as well as stakeholders, the inputs that allows to unveil its origin and to optimize its handling. Symptoms of blackening are showed especially when the flowers have been harvested and stored under cold room conditions; due to high accumulation of pigments, such as anthocyanins, also could be due to stress conditions, such as high or low UV radiation, low temperatures or a nutrient imbalance in the affected tissues.The following subjects will be treated: i) calcium and boron and their interaction, ii) calcium and physiological disorders, iii) pigments involved in the petals red color, iv) role of the phenolic compounds, particularly the anthocyanins, which are responsible for most of the red, pink, purple and blue colors observed in plant parts; as well as the environmental factors that can influence the blackening on red rose.

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