Variable chlorophyll fluorescence in response to water plus heat stress treatments in three coniferous tree seedlings

Effects of water and heat stress treatments on chlorophyll fluorescence of Chinese fir (Cunninghamia lanceolata), Masson pine (Pinus massoniana) and western redcedar (Thuja plicata D. Don)_seedlings were monitored during a three-cycle stress period. It was shown that ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of these three species responded differently to water stress treatments. The Fv/Fm ratio of western redcedar decreased dramatically after water stress, while that of Chinese fir had only a slight reduction and that of Masson pine had no significant change. The experiment also showed that the Fv/Fm ratio of all three species differed significantly under heat stress treatments. Concerning three different water plus heat stress cycles, it was found that the Fv/Fm ratios of Chinese fir and Masson pine measured at the end of each water plus heat stress cycle were not significantly different. However, the Fv/Fm ratio of western redcedar was diminished significantly in response to an increase of stress time. Keywords Chinese fir - Chlorophyll fluorescence - Heat stress - Masson pine - Water stress - Western redcedar CLC number Q945.17 - S791.248 Document code A Biography: Yu Fang-yuan (1965-), male, Ph. Doctor. Associate professor in College of Forest Resources and Environment, Nanjing, Forestry University, Nanjing 210037, P. R. China.Responsible editor: Zhu Hong

铅笔柏种子休眠及快速催芽条件的研究

铅笔柏种子具有胚生理后熟现象。层积温度5－8℃时．后熟作用最快，高于或低于5－8℃时．后熟作用减慢。层积期间如于高温可诱导二次休眠。铅笔柏种子在最佳后熟条件下，层积60天，种子可以解除休眠，分别比秋季层积和隔年埋藏缩短90天和300天，为当年进口种子和当年育苗赢得了时间。