Greenhouse conditions

The research was carried out in a greenhouse of the Campus-SLP, of the Postgraduate School in Salinas de Hidalgo, San Luis Potosí. With a surface of 120 m² chapel type, metallic with a glass covering, zenithal vents and side windows, with orientation of the Northeast greenhouse, to the Southwest. At coordinates 22° 35” north latitude and 101° 45” west longitude, at an average altitude of 2 200 m (^{Flores, 1985}).

Weather

The climate belongs to the BS1KW class corresponding to the least dry of the dry ones (BS1), average rainfall from May to October of 300 to 400 mm, according to the DGTN cartography (cited by ^{Flores, 1985}), this time is where it occurs from 82.75 to 84.88% of the annual total. The rainiest month is September and follow in decreasing order June, July, August, May and October. The warmest month is May and the coldest January (climate office Detenal, cited by ^{Fortanelli, 1981}).

Sowing and planting chili

For the preparation of the seedling, the variety pepper ‘Ancho Magno’ (HYB, Caloro Seeds) was used, which was germinated in peat moss substrate in trays of unicel (May 15, 2011) seedling height is 10 to 15 cm. These were placed in a substrate of black tezontle with particles of 0.3 to 0.7 cm from the region of Cerritos of San Luis Potosí, the container consisted of black polyethylene bags or containers of a volume of 4 L and were placed vertically and horizontal. A total of 48 vertical containers and 48 horizontal containers were placed with 16 containers per line with a total of 96 containers, placing one plant for each container. During the cultivation, the plants were guided vertically by a thread (polypropylene raffia).

Irrigation and nutritive solution

The irrigation system consisted of drippers (2 l h), which were connected to a secondary hose of 16 mm and a spaghetti that ended in a bayonet which was fixed to the south side of each container. Additionally, control drippers were established in the line, placing a container with a dropper (at the end) to determine the total amount of water used, draining 25%, the input pH was measured and the CE that the solution had. It used the nutritive solution recommended by Hewit and Smith, modified by ^{Gómez, (1995)} which was administered in two concentrations according to the phenological stage of the crop, as indicated in Table 1.

Temperature sensors

Four sensors (two centimeters deep) were placed in the containers, located according to the cardinal points and were connected to a Dataloger, which recorded the behavior of temperature and relative humidity during the critical period of the crop.

Variables analyzed

For the data analysis, 20 repetitions (10 horizontal and 10 vertical) were randomly used, from the following variables to: plant height, was measured from the base of the stem to the tip of the furthest leaf using a metal tape measure three meters long. For the fresh/dry weight of the plant the plant was cut from the base of the stem, the fruits were harvested and the fresh weight of the plant was determined by placing it in a stove at a temperature of 60 °C until constant weight for its dehydration and by difference the weight was determined. For the foliar area, the leaves of the plants were cut to draw in contour of the paper sheet, the leaf was taken to a foliar area integrator and the square centimeters of each plant sampled were obtained.

Fruit yield

The harvest began in August until November, where it is more abundant and with representative size to market it, therefore, the fruits were cut and weighed (digital scale). To determine fresh and dry weight, the fruits were subjected to 55 °C in a greenhouse adapted by heat convection by means of solar energy.

Root behavior

At the root of each plant the fresh weight was determined by means of dehydration in the oven at 60 °C until constant weight and to determine the volume of the root, it was taken in a 500 ml test tube and placed 200 ml of water.

Analysis of data

Some data of the morphological variables were submitted to the Anova, using the Statistical Analysys System (SAS) program. Comparisons of means were also made; through, of the Tukey test, with the probability of error of 5%. In the end, all the variables were correlated.

Solar radiation and effect in the greenhouse

The climate (Table 2) outside the greenhouse (during the experiment), prevailed a temperature of 20.90 to 37.96 °C, with a rainy period from June to September (average precipitation of 300 mm), a solar radiation between 246.91 (9:00 h) to 642 (12:00 h) W m^-2. During cultivation, a greater presence of CO₂ was observed at 9:00 h (853 ppm) inside the greenhouse and decreased as the hours of the day progressed, with the lowest concentration at 12:00 h. The above is possibly due to the moving air that is generated by the difference of a temperature effect ^{Marier (2012)} between the outside and inside of the greenhouse.

As the temperature, the resting time and the size of the plant increased, it also occurred in the accumulated time in seconds of irrigation during the crop, being the highest of up to 853.08 s (necessary for irrigation application). Regarding the temperature, at 3:00 pm, the highest temperature was reached, reaching 37.96 in the month of October, probably due to lack of rainfall compared to the month of August-September.

Temperature of the containers with respect to orientation

On the south side, the containers showed a difference in temperature starting at 11:00 in the morning when temperatures begin to be distant, and it is greater in vertical containers. The temperature for the vertical containers on the south face was 43 °C and the horizontal ones were 33 °C, the difference was 10 °C at the same time. ^{Abbott and Gouth (1987)}; ^{Spiers (1995)}, indicate that the growth of the root in the blueberry is controlled by the temperature of the soil, for this they mention that the radical system of the bilberry develops better when the temperatures of the ground are between 14 to 18 °C, which may be similar in the cultivation of chile ancho pepper. Considering five readings (starting at 6:00 and ending at 6:00 and ending at 6:00 pm), the containers showed differences in temperature (Table 3).

The side with respect to the south and east in both positions (vertical and horizontal) reach the highest temperature, projecting the horizontal container facing south with 49.66 °C at 12:00 h (followed by vertical containers in the same location with 46.04 °C). Averaging the temperatures during the day, the vertical containers to the south reached a higher average (34.27 °C), data almost similar to the horizontal containers to the south (33.94). The lowest average temperature during the day was presented by both containers facing north and east, with the vertical container being slightly lower, facing north (26.34 °C).

Morphological behavior of wide chili plants

In growth and yield of the chili plant (Table 4), the plants cultivated in horizontal containers stood out the plant height (98.88 cm) in dry weight of the plant (34.08 g plant), which represented an additional 24% to the containers vertical in the foliar area with almost double (2 958 cm²), in number of fruits (30% additional) and obviously in yield with an additional 15%. ^{Lorenzo (2000)}, mentions that when we use plastic container, the temperatures of the radical environment, affects the metabolism and affects the growth and development of the crops, since different processes intervene (cell division expansion, carbon assimilation, respiration, distribution of assimilated) and each one of them has a certain optimal temperature interval, according to species, phenological phase and previous growth conditions. In tomato plants with staircase arrangement (scalariform containers) blunted to three clusters yielded significantly more per unit area, compared to tomato plants in commercial arrangement also to three clusters, which accommodating the containers in the greenhouse it is very important for any crop (^{Bastida, 2012}).

The horizontal containers showed a greater correlation between the variables of fresh root weight and volume of 99% (Table 5). The lowest correlation was found between foliar area and yield, it is shown that the chili plants, even having more leaves, is not a guarantee that they produce more fruit. The vertical containers, in general, showed less correlation between their variables, possibly due to the temperature in the container. The above, coincides with ^{López et al. (2000)} to demonstrate high temperatures in Spain in greenhouse for crops without soil, due to its low thermal inertia, the temperature in the root zone is close to the air temperature, can in cold periods, limit the development of crops.