Allelopathic effects of triacontanol on the growth of marine photosynthetic bacteria

We studied the effects of triacontanol (plant growth hormone) on the growth of photosynthetic bacteria (PSB). Triacontanol promoted the growth of PSB at an optimal concentration of 1.0 mg/L. In the presence of triacontanol, a deferred logarithmic growth phase appeared. At the optimal concentration 1.0 mg/L, both growth slope and growth rate reached maximum. The growth rates of the four treated samples were 0.45, 0.49, 0.61 and 0.33 AU/day. At the optimal concentration 1.0 mg/L, the growth rate was 0.61 AU/day, while the growth rate of the control sample was 0.38 AU/day. The slopes of the treated samples were 0.2460, 0.4245, 0.5675 and 0.1300 AU/day, while the slope of the control sample was 0.0766 AU/day. In the deferred logarithmic growth phase (5–9 days), especially at the optimal concentration 1.0 mg/L, the growth rate was 0.61 AU/day. The OD_660nm result of promoting the growth of PSB were statistically analysed with SPSS: the treated sample (6.4920±0.0466) at the optimal concentration 1.0 mg/L and the control sample (3.8140±0.1111), obviously the treated sample were higher than the control sample, so the difference was significant, indicating the most significant allelopathic effect. This is first report on the allelopathic effects of triacontanol on PSB.