Dekker Jack, Hargrove Mark
Weed Biology Laboratory, Agronomy Department, Iowa State University, Ames, Iowa 50011 USA;
Am J Bot. 2002 Mar;89(3):410-6. doi: 10.3732/ajb.89.3.410.
The effects that naturally occurring gases (oxygen, nitrogen, carbon monoxide) may cause in dormant giant foxtail (Setaria faberii) seed germination under favorable temperature and moisture conditions were investigated. The germination responses to gas mixtures supported the hypothesis that S. faberii germination behavior is regulated by the amount of oxygen taken into hydrated seed over time. Setaria faberii seed germination was markedly affected by O(2) concentration (in N(2)) above and below that of air (20% O(2)): the largest increase in germination (from 37 to 60%) occurred between 20-25% O(2); between 0-10% O(2), germination increased from 0-30%; and surprisingly germination at 10 and 20% O(2) was similar. These observations reveal an asymmetrical response to incremental changes in O(2) above and below that typically found in agricultural soils. Carbon monoxide had opposite effects on S. faberii germination in air depending on concentration, stimulation, and inhibition: germination increased from 37 to 56% with the addition of 1% CO, but decreased from 37 to 14% with 75% added CO. An explanation may be that there are two separate effects of CO, each occurring in different physiological systems of dormant seeds at the same time. At high concentrations (75%) in air CO inhibited seed germination, probably by inhibiting mitochondrial respiration. But low CO concentrations (0.1 or 1%) in air stimulated seed germination. It was not apparent which physiological system(s) CO and O(2) affected. It seems unlikely that CO-stimulated germination arises from effects on the respiratory apparatus, but may be a consequence of CO interactions with an as yet unknown physiological factor in the seed. We provide a model of Setaria spp. dormancy consistent with its seed morphology, the gas-germination data, and the hypothesized second physiological factor that may be involved in CO stimulated germination.
研究了自然存在的气体（氧气、氮气、一氧化碳）在适宜的温度和湿度条件下对休眠大狗尾草（Setaria faberii）种子萌发可能产生的影响。对气体混合物的萌发反应支持了这样一种假设，即大狗尾草的萌发行为受随着时间进入水合种子的氧气量的调节。大狗尾草种子萌发受到高于和低于空气中氧气浓度（20%氧气）的氧气浓度（在氮气中）的显著影响：萌发率最大增幅（从37%增至60%）出现在20%-25%氧气浓度之间；在0%-10%氧气浓度之间，萌发率从0%增至30%；令人惊讶的是，10%和20%氧气浓度下的萌发率相似。这些观察结果揭示了对农业土壤中常见氧气浓度上下增量变化的不对称反应。一氧化碳根据浓度、刺激和抑制作用，对空气中大狗尾草种子萌发产生相反影响：添加1%一氧化碳时，萌发率从37%增至56%，但添加75%一氧化碳时，萌发率从37%降至14%。一种解释可能是一氧化碳有两种不同的作用，每种作用同时发生在休眠种子的不同生理系统中。空气中高浓度（75%）的一氧化碳抑制种子萌发，可能是通过抑制线粒体呼吸。但空气中低浓度（0.1%或1%）的一氧化碳刺激种子萌发。一氧化碳和氧气影响哪些生理系统尚不明确。一氧化碳刺激萌发似乎不太可能源于对呼吸器官的影响，而可能是一氧化碳与种子中一个未知生理因素相互作用的结果。我们提供了一个与大狗尾草种子形态、气体萌发数据以及可能参与一氧化碳刺激萌发的假设第二个生理因素相一致的大狗尾草休眠模型。
