Introduction

The ornamental horticulture in Mexico plays an important role in the diversification of agriculture, so currently the production of species with high productive and economic potential is sought. The lisianthus (Eustoma grandiflorum [Raf.] Shinn) is a good choice; as it is a flower for its beauty, its bright colors and long vase life, every day becomes more important in the market (^{Mazuela et al., 2007}); this ornamental is practically new in the national market, with great potential of commercialization, so much for internal consumption as for export; as well as for plant pot or cutting.

The cultivated area that is reported in the country is approximately 4 ha, producing areas are Arteaga, Coahuila; Zacatepec, Morelos; Villa Guerrero, State of Mexico; Tecamachalco, Puebla and Guadalajara, Jalisco (^{SAGARPA-SICDE, 2010}).

The current fertilization programs should be based on the nutrient demand of each crop during its phenological stages. This demand is given by its biomass production and total nutrient concentrations in plant tissues (^{Rodríguez et al., 2001}). The nutrition extraction curves determine the amount of elements extracted by a plant during its life cycle. With this information it is possible to know the periods of greatest absorption of each nutrient and a specific fertilization program can be defined to cover the needs of each of the species, considering both the quantity and the appropriate phenological phase (^{Bertsch, 2003}); which reduces the use of agrochemicals and improves the efficiency of utilization of nutrients and water, with a very low environmental impact.

So recent crop lisianthus, are unaware of their nutritional needs and consequently the nutritional management is incomplete and sometimes contradictory, based mainly in fertilization with nitrogen, phosphorus and potassium (^{Gill et al., 2003}; ^{Dole and Wilkins, 2005}), in addition to the fact that this management is proposed for conditions very different from those of the national producers.

Therefore in the present research had as objectives: to evaluate the accumulation and distribution of biomass, the extraction and nutritional distribution and to determine the stage of higher nutritional demand in lisianthus cv. Mariachi Pink.

Materials and methods

Location. The present work was carried out in a greenhouse with glass cover of the Autonomous University Chapingo, which is located at an altitude of 2 240 m and 19 °29’ north latitude and 38° 53’ west longitude.

Vegetal material. The plants of lisianthus cv. Mariachi Pink were used, obtained in seedlings of the company Plántulas de Tetela S. de R. L. de C. V. The crop was established in soil, whose physical, chemical and fertility characteristics are presented in Table 1. When the seedlings presented 3 to 4 pairs of leaves was transplanted into a low bed of 1 x 3.8 x 0.4 m, distributed as follows: 17 cm between rows and 12 cm between plants, resulting in a density of 186 plants in an area of 4 m² (46.5 plants m^-2). The plants were not fertilized because the soil had good fertility. The average temperature in the greenhouse was 23 °C and 62% of relative humidity.

Table 1 Characteristics of the soil used in the cultivation of lisianthus cv. Mariachi Pink in greenhouse.  

*= ^{Castellanos et al. (2000)}.

Sampling. Each sampling consisted of 25 randomly selected plants (with complete competition, which were not on the banks), in each of the four phenological stages identified throughout the crop cycle. The first sampling was performed 45 days after transplant (ddt), end of the rosetting stage, with little elongation of the stem; the second at 60 ddt, end of the stage of elongation of the stems and formation of secondary shoots; the third at 90 ddt, formation of flower buds and elongation of peduncles, and the fourth at 140 ddt, opening of the first flower (harvest point).

Handling of samples. The plants were separated into aerial part (stem and leaves), flowers and roots, separately dried to constant weight in an oven with circulating air at 65 °C in an oven Binder^®.

Variables evaluated. Once the samples were dry, the dry weight (biomass accumulation) of each organ of the plant was recorded on an Ohaus^® digital balance in the 25 replicates of each sample. The samples were then ground in a Wiley mill of stainless steel model 4 with a mesh sieve number 20 and the determination of N, P, K, Ca, Mg, Fe, Cu, Zn, Mn and B. For this, three replicates were formed by mixing the ground biomass of each organ from eight plants per sample. The digestion of the biomass is made with 4 mL of a mixture of sulfuric acid (H₂SO₄) and perchloric acid (HClO₄) in 2:1 (v/v) and 2 mL of hydrogen peroxide (H₂O₂) at 30%; At the end it was vented to 50 mL with deionized water. The nitrogen determination was performed by the microkjeldahl method and the additional elements with a plasma atomic emission spectrophotometer by induction coupled ICP-AES from Varian (Australia). In all cases was followed the methodology described by ^{Alcántar and Sandoval (1999)}.

The experimental unit consisted of a plant for recording dry weight, with a total of 25 repetitions per organ and sampling. For nutritional determination, three replications were done, also by organ and sampling; the experimental unit was a composite sample which was formed as indicated above.

With data were calculated the dry weight of total biomass accumulation per organ, the percentage representing the total per plant per m². With the total nutritional data was calculated of each nutrient extraction by organ, plant, the percentage and total m². The graphs were made with the SigmaPlot 12.5 package.

Results and discussion

The accumulation of biomass in the plant was increasing through the study stages, the total registered at 45 ddt (0.32 g plant^-1, 6.5%) increased 15 times to 140 ddt, where it reached a total of 4.97 g plant^-1. During the formation of flower buds (90 ddt), the plant accumulated 28% of its biomass; the remaining 72% was formed during thickening of the buds and elongation of the stalks, with a biomass accumulation rate of 70.8 mg per day. The biomass of the aerial part (stem and leaves), increased with growth, but from 90 to 140 ddt, during the formation and thickening of flower buds and elongation of peduncles, accumulation increased 71%, which was achieved with a rate of 55.4 mg of biomass per day. In this last stage, the roots accumulated 95% less biomass than the aerial part; while the flowers accumulated up to three times more biomass than the roots (Table 2).

Table 2 Biomass accumulation by organ and total in plants of lisianthus cv. Mariachi Pink.  

Donde: ddt= días después del trasplante; 45 ddt= fin de la etapa de arrosetamiento; 60 ddt= fin de la etapa de alargamiento de los tallos y formación de brotes secundarios; 90 ddt= formación de botones florales y alargamiento de pedúnculos; 140 ddt= apertura de la primera flor, punto de corte. Los valores son el promedio de 25 observaciones.

The aerial part presented the highest percentage of accumulation of biomass in the plant, in the four stages of evaluation; of the 45 to 90 ddt, the percentage step from 88 to 93%, with decrease to 140 ddt to 82.7%. The root was the organ with the lowest biomass accumulated, its greatest accumulation (12.5%) was presented at 45 ddt, from 60 ddt the percentage decreased to 140 ddt, where it represented only 4.2% of the total. In this same stage the flowers represented 13.2% (Figure 1). The order of distribution of biomass in the organs of the plant was: aerial part˃ flowers˃ root.

Figure 1 Relative distribution of total biomass in lisianthus cv. Mariachi Pink. Values are the average of 25 observations.  

The decrease in accumulation of biomass recorded in aerial part and root in the last stage evaluated, is due to the remobilization of photosynthates towards the developing floral buds. The root is the structure with less demand force in the plant, during the phase of vegetative growth and flowering can store little carbon in it (^{Patrick, 1990}). However, in the first stage evaluated (40 ddt) that is when the vegetative growth is very slow, is when the radical system develops (^{Melgares de Aguilar, 1996}). In this investigation it was found that the greatest accumulation of biomass was submitted after vegetative growth, which is consistent with observations in various cultivars of poinsettia (^{Whipker and Hammer, 1997}; ^{Galindo-García et al., 2015}).

During the crop cycle, the plant increased the accumulation of biomass; so that in this research, a m² a density of 46.5 plants, the total accumulation was 231 g; of which 30.69 g corresponded to flowers, 9.77 g roots and 190.65 g stems with their ramifications (Table 3).

Table 3 Organ biomass accumulation and total m² in lisianthus cv. Mariachi Pink.  

Donde: ddt= días después del trasplante; 45 ddt= fin de la etapa de arrosetamiento; 60 ddt= fin de la etapa de alargamiento de los tallos y formación de brotes secundarios; 90 ddt= formación de botones florales y alargamiento de pedúnculos; 140 ddt= apertura de la primera flor, punto de corte.

The nutritional extraction by the aerial part (stem and leaves) and root was increased with the development of the plant, but at 90 ddt the increase was very remarkable. This tendency of increase continued towards the 140 ddt, stage in which the greatest nutritional accumulation was observed, since the plant almost doubled or even tripled, in the case of Fe, the amount of elements extracted in the previous stage. The flower exceeded the root extraction, for most of the elements, with the exception of Ca, Fe, Cu and Mn (Table 4).

Table 4 Extraction of macro and micronutrients (mg plant^-1) of lisianthus cv. Mariachi Pink cultivated in soil under greenhouse conditions.  

Donde: ddt= días después del trasplante; 45 ddt= fin de la etapa de arrosetamiento; 60 ddt= fin de la etapa de alargamiento de los tallos y formación de brotes secundarios; 90 ddt= formación de botones florales y alargamiento de pedúnculos; 140 ddt= apertura de la primera flor, punto de corte. Los valores son el promedio de tres observaciones.

Total nutritional extraction followed the same behavior as biomass accumulation; that is, it increased with the advance of the development of the plants; so that at the time of opening of the first flower (140 ddt), the plant presented the greatest accumulation of all the elements (Figure 2). From 90 to 140 ddt, stage of flower formation, the plant presented the highest rate of nutritional absorption, with an extraction of 60 to 70% of the total (Table 4). The order of extraction of macronutrients was: K˃ N˃ Mg˃ Ca˃ P; of the micronutrients were: Zn˃ Fe˃ Mn˃ B˃ Cu. This indicates that during the formation and thickening of floral buds and elongation of peduncles, the plant had the highest nutritional demand. Such behavior was also observed in two cultivars of poinsettia sun (^{Galindo-García et al., 2015}); in chrysanthemum (Chrysanthemum morifolium Ramat) (^{Valdez-Aguilar et al., 2015}) and strawberry (Fragaria x ananassa Duch.) (^{Avitia-García et al., 2014}).

Figure 2 Total extraction by plant of macro and micronutrients in lisianthus cv. Mariachi Pink.  

It should be noted that in this evaluated lisianthus cultivar, the extraction of Mg was superior to that of Ca, when in most species the Ca is required in greater quantity than the Mg. This behavior is also observed in other ornamentals as Calathea spp. and Schlumbergera (^{Dole and Wilkins, 2005}).

The K was the most extracted element in this cultivar of lisianthus; on poinsettia was the N (^{Galindo-García et al., 2015}); in chrysanthemum extraction of N and K it was similar (^{Valdez-Aguilar et al., 2015}). Lisianthus bears resemblance to fruit crops in terms of increased demand for K that of N (^{Tagliavini et al., 2000}), as noted in red raspberry (^{Pineda-Pineda et al., 2008}) and banana ‘Dominico’ (^{Castillo-González et al., 2011}).

The aerial part (stem and leaves) presented the highest percentage of accumulation of all nutrients in all stages, with 80% or more of the total accumulated by the plant, followed by the flower, with the exception of Ca; the root was the one that presented the lowest percentage of macronutrients, except the Ca whose percentage was equal to that of the flower (Figure 3).

Figure 3 Relative distribution of macronutrients in plants of lisianthus cv. Mariachi Pink.  

In the case of micronutrients (Figure 4), the highest percentage of Fe, Zn, B and Mn was recorded in the aerial part at all stages. The Cu at 45 ddt accumulated more in the root (56%) than in the aerial part (44%), a situation that was changing with the development of the crop.

Figure 4 Relative distribution of micronutrients in plants of lisianthus cv. Mariachi Pink.  

At the end of the cycle (140 ddt), the root had a higher percentage of Fe and Cu (17 and 23%, respectively) than the flower (11 and 19%); The flower presented 15% of the B, while the root only 5%. The Mn accumulated in very close percentages in root and flower (7 and 6%, respectively). The root presented a higher percentage of nutrients at the beginning of the cycle (45 ddt), than at the end (140 ddt), because in the first stage the aerial part does not grow because it is in the stage of rosetting and the growth of the stem is slow; while the root is in development (^{Melgares de Aguilar, 1996}).

The nutrient removal by m² is shown in Table 5, the K was, of macronutrients, the largest extraction cultivation; while P was the least required. Of the micronutriments the Zn was the most extracted and the Cu the least. So it is necessary to restore to the soil at least those amounts through fertilization. However, it should be considered that the stage of flower bud formation is the most demanding nutrient during phenological development.

Table 5 Total extraction of nutrients per m² in plants of lisianthus cv. Mariachi Pink.  

Donde: ddt= días después del trasplante; 45 ddt= fin de la etapa de arrosetamiento; 60 ddt= fin de la etapa de alargamiento de los tallos y formación de brotessecundarios; 90 ddt= formación de botones florales y alargamiento de pedúnculos; 140 ddt= apertura de la primera flor, punto de corte.

Conclussions

The stage of greater accumulation of biomass and nutritional extraction in lisianthus cv. Mariachi Pink, was during the formation and thickening of floral buttons; as well as elongation of stalks (90 to 140 dt). The order of extraction of macronutrients was: K˃ N˃ Mg˃ Ca ˃ P, the of micronutrients was: Zn˃ Fe˃ Mn˃ B˃ Cu. The structure of the plant that accumulated the highest biomass and consequently the highest amount of nutrients in the different phenological stages was the aerial part. The total extraction of macronutrients in g m^-2 was: 2.4 of N, 0.46 of P, 3.3 de K, 0.8 of Ca and 1.0 of Mg; of micronutrient in mg m^-2 was: 17.2 of Fe, 3.8 of Cu, 20.4 of Zn, 8.6 of B and 13.7 of Mn. So the fertilization proposal, under the conditions of this research, is to apply these amounts for the maintenance of soil fertility; 40% will be applied at the beginning of the vegetative growth stage and 60% at the beginning of flowering.