TULIP BULBS PREPARATION BY HEAT TREATMENT FOR FORCED CULTURE IN GREEN HOUSE

Tulip can be grown in parks as ornamental plant and cut flowers, or possibly in protected areas for cut flowers during winter and early spring. An important condition for the successful cultivation of tulips is the quality of the bulbs that are going to be planted and their biological preparation. Under the quality aspect bulbs have to be uniform and large, preferably with circumference greater than 11 cm and must have good phytosanitarical status. Preparation of organic bulbs for ensuring the continuation of the differentiation process of germs (floral), is made during the storage. It is known that the preparation of organic bulbs are made in interaction with environmental factors, among which temperature plays an important role. At the beginning and throughout the process of biological preparation, temperature is maintained at a higher level then the temperature must be low until planting. The temperature level and the duration of treatment varies by followed objective respectively early or late flowering and staggered flowers production over a longer period of time.


INTRODUCTION
Tulip is a perennial flower plant, with bulbs originary from Central Asia and introduced in Europe in 1554, and in Romania in 1559. The plant has large bulbs with brown tunic, linear or linear-broad leaves, with straight or wavy edge. Large colored flowers are held erect on long sticks of 30-50 cm, depending on the variety.
The morphological specificity of the tulips is the type of flower constitution -3 -that sepals are processed into colored tepals. Are blooming at the beginning of spring to early summer in the open and can be made to bloom in winter or summer in the greenhouse scheduled (forced) crops. Tulips are light-lowers but they are good in little shadow. Tulips are growing well on heavier soils, requires moderate water, change of culture place and returning on it only after four years.
Harvesting the flowers is made in the morning when the flower buds reached the maximum size of variety and are well colored.

MATERIALS AND METHODS
Have been used the variety of Apeldoorn, from Darwin hybrid group which has large flowers red orange color with black base and vigorous floral rod.
Treatments performed on bulbs included two variants, namely: V1 -bulbs maintained for two weeks at 30 ° C up to the state G (distinct trilobite gynoecia) made on 18 July.
V2 -bulbs maintained at 20 ° C, achieving the state G on July 30. The workload was 600 bulbs / variant and 300 bulbs per variant.
Thereafter half of bulbs were kept at 5 ° C for 12 weeks (immediately after reaching the state G) and those in the second half (variant) were kept on for 11 weeks at 5 ° C and one week at 27 ° C. Planting in the greenhouse was made on 12 October in V1 and October 23 at V2.
After planting the bulbs in the greenhouse, the minimum temperature in air at ground level was maintained on three different levels at 13-14 ° C, 8-9 ° C, 3-4 ° C.

RESULTS AND DISCUSSIONS
As shown in Table 1 the percentage of bloomed plants shows values close when bulbs were maintained in the initial phase at a temperature of 30° C and 20 ° C.
After going through the phase of differentiation of germs at temperatures of 30° C and 20 ° C and maintain temperature above 5 ° C, raising the temperature to 27 ° C for one week reduce the period of restraint. The influence of threshold temperature of the biological preparation period, storage and after bulbs planting in greenhouse on plants growth and flowering The time from bulbs planting to achieve a proportion of 50% bloomed plants shows values from 42 days when the temperature in the greenhouse was maintained at a higher level (13-14 ° C) until 75 days when was kept at 8-9 ° C and above that bulbs were treated by keeping the temperature at 20 ° C for 12 weeks. Under this last aspect detaches the idea that the temperature in the greenhouse should be maintained at least in the first period at a lower level. A relatively similar conclusion can be the positive influence of lower temperatures on improving the quality factors by length of the floral stick.
The heat treatment on tulip bulbs exercise positive influence on their rooting. As shown in Table 2, bulbs treated at the initial stage at 30 ° C and kept at 5 ° C root after only 7 days. As the temperature decreases with the initial treatment of bulbs and the resumption of the final treatment at 27 ° C the rooting period may be extended up to 17 days. Economic efficiency is favorable for both variants, but at top parameters to the variant which bulbs were kept 11 weeks at 5 ° C + a week at 27 ° C after reaching the G state that the profit was 248,700 lei / ha. Higher profits obtained here is due to reducing the period of restraint and reducing the heating and maintenance expenses up to 25 days.

CONCLUSIONS
Preparation of organic tulip bulbs in favor of differentiating the flower germs can be stimulated by heat treatment, at different periods and temperatures Repetition in the final stage of heat treatment at a temperature of 27 ° C for one week entails a reduction in the duration of restraint, and thereby a reduction of production costs Heat treatment exercise positive influence on bulbs of tulips rooting too, if they are treated in the initial phase at 30 ° C and below at 5 ° C. Under these conditions the rooting occurs after only 7 days, reducing the duration of restraint and its costs.