RELATIONSHIPS BETWEEN BULB FORMATION AND DORMANCY IN RESPECT TO THE ENDOGENOUS PLANT HORMONE LEVELS.

Dutch Iris begins to form a bulb just after sprouting buds are introduced to the pre-dormancy period. For this experiment, bulbs were introduced into pre-dormancy at a temperature below 15°C and in natural short day conditions. The bulb developing aspect of scale growth and its swelling for daughter bulb formation was observed. At the same time, it was observed that, in the meristem region of the shoot, a significant increase of both auxin and abscisic acid activities took place with a slight time lag. By contrast, iris plants grown in 25°C did not form any bulb and only a rise of endogenous auxin activity was recognized. A similar situation was noted in the bulb formation of Lilium and Allium.

Furthermore, it was recognized that the bulb forming aspect was controlled by stages of the growth cycle in bulbous plants. In the scaling propagation process in the lily, two distinctive bulb forming phenomena were ascertained: firstly, a bulbil without leaf was formed in both the pre-dormancy and true-dormancy stages of the mother plant, and, secondly, a small seedling with leaves or a bolting stem developed in the post-dormancy period and later. This was synchronized with the changes of plant hormones, as with iris.

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