Boron ranging from 13 to 800 ppm was applied (100 ml per 15 cm pot) to the media of the Chrysanthemum morifolium Ramat. cvs. Improved Albatross and CF No. 2 Good News. Seasonal variation was observed in injury time and foliar toxic levels. Boron toxicity symptoms were observed at foliar levels of 136 ppm in ‘Improved Albatross’ and 350 ppm in ‘CF No. 2 Good News’ 4 days after B application in an April to May experiment, while 7 to 28 days were required to produce symptoms at foliar levels of 158 ppm in ‘Improved Albatross’ and 144 ppm in ‘CF No. 2 Good News’ in a December to March experiment. Stem length and flower diameter decreased with increases in B concentration applied. Foliar B levels exceeding 100 ppm reduced growth.
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Gogue et al. (1973) studied this question.
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