THE GROWTH AND DEVELOPMENT OF HIPPEASTRUM IN RESPONSE TO TEMPERATURE AND CO_2

Flowering time of Hippeastrum can be controlled by applying specific thermal regime to large sized bulbs. Due to high-energy costs, the aim of this study was to examine the possibility to reduce soil heating and keep high bulb growth rate by increasing the CO_2 concentration. Two sets of experiments were carried out in a controlled greenhouse at the North-Western Israeli Negev Desert. In both experiments, bulbs of different initial sizes were grown under two levels of CO_2 concentrations (ambient, 350ppm and elevated, 1000ppm) combined with different minimum soil temperature regimes. In the first experiment three temperature regimes (16℃, 22℃ and 24℃) were tested, while in the second experiment only one minimum soil temperature regime (22℃) was investigated. In both experiments, raising CO_2 concentration from the ambient level to elevated one, or increasing soil temperature resulted in a higher bulb growth rate. Temperatures, CO_2 concentration and initial bulb size significantly influenced the final diameter of the bulbs. A significant difference in final bulb diameter was obtained only between the 16℃ treatment and the 22℃ and 24℃ treatments, but not between the two high temperatures tested. The area of the largest leaf was significantly affected only by the soil temperature treatments. No effect of CO_2 concentration on leaf area development was detected. The number of leaves, however, was affected by the CO_2 but not by the temperatures. Bulbs grown under elevated CO_2 had a higher flowering rate compared to ambient CO_2. This was effective both in shortening the period of time from replanting until flowering and by the significant high number of flowers compared to the ambient CO_2 conditions

THE GROWTH AND DEVELOPMENT OF HIPPEASTRUM IN RESPONSE TO TEMPERATURE AND CO_2

Flowering time of Hippeastrum can be controlled by applying specific thermal regime to large sized bulbs. Due to high-energy costs, the aim of this study was to examine the possibility to reduce soil heating and keep high bulb growth rate by increasing the CO_2 concentration. Two sets of experiments were carried out in a controlled greenhouse at the North-Western Israeli Negev Desert. In both experiments, bulbs of different initial sizes were grown under two levels of CO_2 concentrations (ambient, 350ppm and elevated, 1000ppm) combined with different minimum soil temperature regimes. In the first experiment three temperature regimes (16℃, 22℃ and 24℃) were tested, while in the second experiment only one minimum soil temperature regime (22℃) was investigated. In both experiments, raising CO_2 concentration from the ambient level to elevated one, or increasing soil temperature resulted in a higher bulb growth rate. Temperatures, CO_2 concentration and initial bulb size significantly influenced the final diameter of the bulbs. A significant difference in final bulb diameter was obtained only between the 16℃ treatment and the 22℃ and 24℃ treatments, but not between the two high temperatures tested. The area of the largest leaf was significantly affected only by the soil temperature treatments. No effect of CO_2 concentration on leaf area development was detected. The number of leaves, however, was affected by the CO_2 but not by the temperatures. Bulbs grown under elevated CO_2 had a higher flowering rate compared to ambient CO_2. This was effective both in shortening the period of time from replanting until flowering and by the significant high number of flowers compared to the ambient CO_2 conditions

VARIOUS CUTTING METHODS FOR THE PROPAGATION OF HIPPEASTRUM BULBS

One of the major problems of Hippeastrum is the large amount of labor involved in its production. There are three common methods for the propagation of the Hippeastrum: Seeds, offset bulblets and twin scaling. Study on various cutting methods for the propagation of Hippeastrum was conducted in the Northern Israeli Negev Desert during two consecutive years. Fewer bulblets were developed when the mother bulb was divided into un-separated sections, compared to twin scales. Increasing the number of sections into which the bulb was divided resulted in larger number of bulblets. No correlation between the number of sections and the average weight of bulblets was found. The total weight of all the bulblets derived from one bulb, doubled after one growing year. Propagation coefficient, defined as the ratio between the bulblets number to the number of section into which the bulb was divided, was larger than one unit when the bulbs were cut into un-separated sections and smaller than one unit when the twin scaling method was used. Higher economic profit was found when the bulbs were divided into un-separated sections. By using the un-separated section method, it was possible to receive bulbs ready for marketing one year sooner, when compared to the twin scaling method. The greatest economical profit is expected when the mother bulb was divided into eight un-separated sections