Elevated temperature affects axillary meristem development in Dendranthemaxgrandiflorum 'Improved mefo'

Effects of heat stress on viable and nonviable axillary meristem developmen t and subsequent lateral branching in 'Improved Mefo' chrysanthemum [Dendra nthema xgrandiflorum Ramat. (Kitamura)] were studied. Plants grown at 33 de greesC day/27 degreesC night produced more nonviable buds than did plants g rown at 23 degreesC day/18 degreesC night. A negative linear relationship { y = 28.7 + [-0.66 (x days)], r(2) = 0.70} between timing of exposure to hig h temperatures and the number of nonviable buds was observed. Histological examination 28 days after exposure to 33 degreesC/27 degreesC revealed that plants showed both normal and abnormal bud development. Abnormal bud devel opment occurred as a consequence of premature differentiation of axillary m eristematic tissue into nonmeristematic parenchyma tissue immediately after separation of axillary from apical meristems.