Sawidis T
Department of Botany, University of Thessaloniki, Thessaloniki, Greece.
Protoplasma. 2008;233(1-2):95-106. doi: 10.1007/s00709-008-0306-y. Epub 2008 Aug 18.
Cadmium had a highly toxic effect on pollen germination and tube growth, which were greatly inhibited as metal concentrations increased. Cadmium concentrations up to 10(-2) M completely stopped pollen germination and pollen showed an increasing tendency to burst within 1 h. At low concentrations, the metal caused a slight stimulation of pollen germination, growth rate and tube elongation at the initial stages of tube development. Comparing the two plants studied, cadmium was more toxic for Nicotiana tabacum than for Lilium longiflorum pollen. Pollen tubes showed a range of strong morphological abnormalities, characterized by uneven or aberrant growth, including apical branching or swelling at the tip of the pollen tube. Cell wall intrusions at or near the tip were evident on the inner side, whereas a loose network formed from fibrillar material was observed on the outer layers. After prolonged cadmium exposure, round (ball-like) aggregates were embedded in a fine fibrillar network. Increased cadmium concentrations (10(-3)-10(-2) M) decreased or completely paralyzed cytoplasmic streaming. No typical cytoplasmic zonation existed, while cell organelles (plastids, lipid droplets) were relocated toward the tip. The vesicular apical zone was drastically reduced, with vesicles dispersed into the subapical region. Mitochondria were distributed throughout the subapical region and among the vesicles of the tube apex. Visible ultrastructural changes in cell organelles were not observed.
镉对花粉萌发和花粉管生长具有高度毒性作用，随着金属浓度的增加，这些过程受到极大抑制。高达10⁻² M的镉浓度完全阻止了花粉萌发，并且花粉在1小时内破裂的趋势增加。在低浓度下，该金属在花粉管发育的初始阶段对花粉萌发、生长速率和花粉管伸长有轻微的刺激作用。比较所研究的两种植物，镉对烟草花粉的毒性比对麝香百合花粉的毒性更大。花粉管表现出一系列强烈的形态异常，其特征为生长不均匀或异常，包括花粉管顶端分支或肿胀。在顶端或其附近的细胞壁内陷在内侧很明显，而在外层观察到由纤维状物质形成的松散网络。长时间暴露于镉后，圆形（球状）聚集体嵌入精细的纤维状网络中。镉浓度增加（10⁻³ - 10⁻² M）会降低或完全使细胞质流动麻痹。不存在典型的细胞质分区，而细胞器（质体、脂滴）向顶端重新定位。泡状顶端区域急剧减少，泡分散到顶端下区域。线粒体分布在整个顶端下区域和花粉管顶端的泡之间。未观察到细胞器明显的超微结构变化。
