チューリップの生育障害(色抜け•首折れなど)の発生原因究明とその防止に関する研究

Abstract

The relationships between the occurrence of boron deficiency of tulips, characters of cultivated soils and boron contents in tulip plants were investigated at tulip bulb growing areas in Niigata and Toyama prefectures, at the time of flowering.It became clear through our investigation in the tulip fields that characteristic symptoms of boron deficiency of tulips such as disappearance of flower pigment (“Ironuke”) and transverse break of stem (“Kubiore”) occurred widely and strikingly in the field tulips of Niigata and Toyama.At the same time, the basis of diagnosis on boron deficiency in field tulips was established by using soil testing and plant analysis. The main results are summarized as follows.1) Tulips raised on sand and sandy loam soils and on highly water-permeable loam soil were inclined to develop boron deficiency.2) On sand dunes tulips were inclined to develop boron deficiency on their tops and slopes.3) Tulip fields in which hot-water-soluble born in soils was lower than about 0.2ppm engendered tulip boron deficiency.4) Boron deficiency of tulips occured easily on strongly acid soils, though hot-water-soluble boron in soils was more than 0.2ppm.5) The critical concentrations of total boron in tulip plant tissues were considered as follows; flower: 14-15ppm, upper stem : 12-13ppm, new main bulb: about 5ppm. But it was difficult to accurately diagnose the boron deficiency of the tulip plant only on the basis of levels of total boron concentration in plant tissues.6) Calcium-boron molar ratio in boron deficient tulip flowers was more than 25, but the ratio in healthy ones was less than 20. Therefore boron deficiency in tulips may be effectively diagnosed by the level of calcium-boron molar ratio in flowers at the blooming time.