ABSTRACT

The common green alga Trentepohlia sp. was found growing as a biofilm on galvanised iron lamp posts where it was exposed to high zinc levels and periodic desiccation. Its sole water sources were rainfall and dewfall. Photosynthesis studies using PAM techniques showed that the alga was a shade-adapted species with a very low optimum irradiance (E_opt) of about 90 μmol photons m⁻² s⁻¹, and ETR_max about 80 μmol e⁻ g⁻¹ chlorophyll-a s⁻¹. But, within minutes, it recovered from desiccation (homiochlorophyllous). The alga has a high chlorophyll-b/a ratio (0.470 ± 0.016) and conspicuous chlorophyll-b absorption in vivo, but no measureable Zn-chlorophyll derivatives were found spectrophotometrically. Mannitol experiments using up to 1.5 Osmol kg⁻¹ showed that photosynthesis in Trentepohlia sp. was highly resistant to water stress. Photosynthesis of Trentepohlia sp. was unaffected by pH even though the abundance of CO₂ in the experimental medium dropped from 477 mmol m⁻³ at pH 5 to less than 1 mmol m⁻³ at pH 9. Thus, Trentepohlia sp. can use both CO₂ and HCO₃ ⁻ as inorganic carbon sources. Acid pH (pH 5) did not increase toxicity of Zn. Trentepohlia sp. was resistant to added Zn with little effect on photosynthetic parameters even at 30 mol m⁻³ Zn.

摘要

常见的绿藻Trentepohlia sp。被发现在镀锌铁灯柱上以生物膜的形式生长，在那里暴露于高锌水平和定期干燥。它唯一的水源是降雨和露水。使用PAM技术进行的光合作用研究表明，藻类是一种适应阴影的物种，其最佳辐照度（E _opt）非常低，约为90μmol光子m ^-2 s ^-1，而ETR _max约为80μmole ^- g ^-1叶绿素- a s ^-1。但是，在几分钟之内，它就从干燥（纯叶绿素）中恢复了。藻类的叶绿素b / a高比值（0.470±0.016）和体内明显的叶绿素b吸收，但用分光光度法未发现可测量的Zn-叶绿素衍生物。使用高达1.5 Osmol kg ^-1的甘露醇实验表明，Trentepohlia sp。的光合作用。高度耐水。Trentepohlia sp。的光合作用 是通过pH的影响，即使CO的丰度₂在实验培养基从477毫摩尔米降至^-3在pH 5至小于1毫摩尔米^-3，在pH 9。因此，Trentepohlia藻。可以同时使用CO ₂和HCO ₃ ^-作为无机碳源。酸性pH（pH 5）不会增加锌的毒性。特兰氏菌属 甚至在30 mol m ^-3 Zn时，对添加的Zn具有抗性，对光合参数的影响很小。