Seymour R S
Department of Environmental Biology, University of Adelaide, Adelaide, SA 5005, Australia.
J Exp Bot. 2001 Jul;52(360):1465-72. doi: 10.1093/jexbot/52.360.1465.
Thermogenic inflorescences of some arum lilies have the highest rates of respiration known among plants. Peak rates of oxygen consumption in the sterile male florets of Philodendron selloum Koch exceed 0.3 micromol x s(-1) x g(-1) when the inflorescence warms to 38 degrees C. This study describes the morphology of the oxygen diffusion pathway between the atmosphere and the parenchymal cells of the florets. Dimensions of the florets, stomata, interstitial gas network, and cells provide data for diffusion models of the PO2 profiles at each level of the 'oxygen cascade'. The lowest calculated PO2 of 4.7 kPa (35 mmHg) at the axis of the thickest part of the floret indicates that maximum respiration does not reach the point of diffusion-limitation, confirming earlier physiological measurements of the dependence of oxygen consumption rate on environmental PO2. Adequate aeration of all cells is achieved by appropriate floret size, despite a stomatal density less than 5%, and interstitial gas fraction less than 2%, of values commonly found in leaves.
一些海芋百合的产热花序具有植物中已知的最高呼吸速率。当海芋的不育雄小花花序升温至38摄氏度时，其耗氧峰值速率超过0.3微摩尔×秒⁻¹×克⁻¹。本研究描述了大气与小花实质细胞之间氧气扩散途径的形态。小花、气孔、间隙气体网络和细胞的尺寸为“氧气级联”各水平的PO₂分布扩散模型提供了数据。在小花最厚部分的轴处计算出的最低PO₂为4.7千帕（35毫米汞柱），这表明最大呼吸作用未达到扩散限制点，证实了早期关于耗氧率对环境PO₂依赖性的生理学测量结果。尽管气孔密度低于5%，间隙气体分数低于叶片中常见值的2%，但通过适当的小花大小仍能实现所有细胞的充分通气。
