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Some structural characteristics of the flowers of apple cultivars with different susceptibilty to fire blight
Published May 10, 2004
21-23.

Several morphological characters of the hypanthium (size and form of the surface, the shape of the hypanthium) and anatomical traits (number and pattern of stomata) of apple cultivars (Malus domestica L.) with different susceptibility to fire blight were studied. The size of hypantium surface was calculated by modelling the hypanthium ...with a truncated cone. Three types of hypanthium surface form have been revealed: straight, convex and a complex "shouldered" one. The angle between the style and the wall of the hypanthium was narrow or wide. The stomata on the hypanthium surface can be arranged in a zone in the middle third of the hypanthium or dispersed more or less evenly. The number of stomata/flower substantially differed among the cultivars examined. The highest stomata number was detected in the flowers of the tolerant cultivar (Freedom)

No single characteristics of the hypanthium could convincingly be correlated with susceptibility to fire blight. We suggest, however, that combination of morphological properties that sustain moist environment in the hypanthium contribute to susceptibility.

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Study of Erwinia amylovora colonization and migration on blossoms of susceptible and tolerant apple cultivars
Published May 10, 2004
15-19.

The stigmata of detached flowers of susceptible and tolerant apple cultivars were inoculated with about 104 gfp labeled Erwinia amylovora . There were no apparent differences in the colonization, multiplication and survival of the bacteria on the stigmatic surface of the culivars. Bacteria were washed down to the hy...panthium surface 24 hours after inoculation. The visual symptoms of the infection were the discoloration and shrinkage of the floral parts. The gradual browning associated with the infection appeared first on the surface of the hypanthium followed by the discoloration of the style. The color of the filaments turned into brown only 120 hours after the inoculation. Bacterial cells were not detected in the tissues of the styles and filaments. The traits of the hypanthium surface are of prominent importance in the progression of the infection. The wrinkled surface, the convex shape of the outer epidermal cell walls with thin cuticle and the sunken stomata helped to preserve a water film for a longer period providing medium for the motility of the bacteria in the susceptible cultivar. Bacteria were restricted to small water droplets on the flat and waxy surface of the hypanthium of the tolerant cultivar and only a few were able to enter the tissues.

Large bacterium aggregations were detected in the intercellular spaces of the parenchyma of the susceptible cultivar 48 hours after the inoculation. In the next period the Erwinia amylovora cells gradually invaded the intercellulars of the hypanthium wall, the wall of the ovary and the pedicel. Low level of bacterium aggregation was found in the intercellulars of the tolerant cultivars. It is suggested that the progression of the infection was inhibited also by physiological factors.

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Studies on some seed traits of Iris pumila L., Adonis vernalis L., Primula veris Huds. and Alkanna tinctoria (L.) Tausch.
Published June 6, 2001
36-40.

In this study we summarize the results of a five-years period concerning seed traits examinations on Iris pumila, Adonis vernalis, Primula veris and Alkanna tinctoria, with special attention to seed dimensions, seed mass and other traits concerning plant fitness, to their variability and the relationship among them. We found t...ight correlation between seed weight and seed dimensions in Adonis and Primula, at the same time no correlation exists among the same characters in Alkanna tinctoria. Consequently, the seed weight and seed dimensions can be used as synonyms in the form of „seed size" only after preliminary detection of correlations among them.

The variability of seed traits is higher in natural categories (individuals, morphs) than in seed mass categories as speculative groups. When we need homogeneous plant stand (e.g. for an introduction experiment) it is suggested to use seeds pre-selected in this way. For ex situ conservation, where the central goal is to maintain the genetic variability, seeds originated from different individuals are preferred.

 

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