Paweł Szot
The influence of growth regulators on the quality and the postharvest longevity of tulip flower stem
In the years 2002–2005 two experiments were performed that differed in the method of application of growth regulators. In the first experiment tulips were sprayed in the green bud stage, and in the second tulips were conditioned in solutions of growth regulators after harvest for cut flowers. Measurements of morphological features and mechanical properties of tulip stems in the first experiment were performed immediately after the cutting and after 7 days of keeping them in vessels with water at room temperature, and in the second – after 24 hours of conditioning and after 7 days of keeping them in water. Following the conditioning, estimation was made of the quality and the post-harvest durability of flower shoots kept in water (at room temperature). The ornamental value (quality) was assessed visually, using a 5 step scale, and the post-harvest durability was estimated in terms of a number of days. 
The research material were tulip cultivars ‘Ballade’, Ile de France’, ‘Yokohama’ and ‘Libretto Parrot’. The growth regulators applied in the study were benzyladenine, gibberellic acid, daminozyde and flurprimidol, and the conditioning preparations were Chrysal BVB and Chrysal BVB plus. The following morphological features were determined – the length of perianth leaves, length of the flower shoot and of the upper internode, and its diameter. Certain anatomical features of the stem were also determined. Measurements of the mechanical properties of tulip stems under static conditions were made with the help of the Instron strength tester. Based on the tests applied, the following were determined: the force within limits of elasticity, the maximum force destroying the stem structure, maximum stem deflection, energy at that force value, and the modulus of elasticity and maximum bending stress were calculated. Analysis of the morphological and mechanical traits under study revealed considerable differentiation among the cultivars. The study showed that flurprimidol inhibited the growth of the shoot and of the upper internode of tulips ‘Ballade’, ‘Ile de France’ and ‘Yokohama’, whereas daminozyde limited primarily the length of the upper internode of tulips ‘Yokohama’, ‘Ile de France’ and ‘Ballade’. Increase in the thickness and in the number of layers of the sclerenchyma was observed after the application of daminozyde and flurprimidol in the case of tulips ‘Ile de France’. Gibberellic acid caused an increase in the number of vascular bundles in ‘Ballade’ and ‘Ile de France’. In the case of cultivar ‘Yokohama’ daminozyde at concentration 8500 mg×dm-3 caused an increase in the thickness and in the number of layers of the sclerenchyma, which was reflected in the highest values of the modulus of elasticity and of the maximum bending stress among all the treatments for that cultivar.

The preparations applied caused an extension of the utility life of the flowers after their cutting. The most durable were the flowers of tulips conditioned in BVB plus 
(average of 9.8 days) and in gibberellic acid solution with concentration of 50 mg×dm-3 (average of 9.0 days). Plants conditioned in solutions of benzyloadenine and gibberellic acid with the highest concentrations (150 mg×dm-3) were characterised by the shortest durability (average of 7.8 days).