Disoriented growth of pollen tubes of Lilium longiflorum Thunb. induced by prolonged treatment with the calcium-chelating antibiotic, chlorotetracycline.

Pollen of Lilium longiflorum Thunb. was germinated for 12 h in growth medium containing 1·10(-4) M chlorotetracycline (CTC), or growing tubes were treated with 1·10(-4) M CTC for up to 2 h. These treatments have drastic effects: In the CTC-containing medium, out-growing tubes form only short tubes. Irregular wall thickenings are visible. Thirty minutes CTC-treatment cause growing tubes to bend and grow back toward the grain. Electron micrographs of CTC-treated tubes show that CTC affects the organelle distribution: The polar zonation of organelles is disturbed. Vesicle-and endoplasmic reticulum-accumulations are found in the wrong places, together with extensive wall thickenings and a very irregular plasma membrane. The structural details of most cell organelles look normal after CTC treatment, but the mitochondria possess unusual cristae, and microtubules are absent. The disoriented growth is interpreted as an effect of the ability of CTC to chelate intracellular calcium ions, to bind them to membranes, and thus to disturb the dynamics of the delicate Ca(2+)-equilibria thought to regulate oriented exocytosis.