Pollen germination and tube growth: dependent on carbon dioxide and independent of ethylene.

The influence of ethylene and CO(2) on pollen germination and tube growth was investigated employing ventilated culture systems. Ethylene had no effect on pollen germinability or tube growth. Germinating pollen did not produce a detectable amount of ethylene (less than 0.1 nl/g.hr). Supplementing the cultures with CO(2) caused a marked increase in germination and tube growth. The half-maximal response for germination was less than 0.5%. CO(2) levels ranging from 1.08 to 2.22% were found in the internal cavity of lily styles. CO(2) derived from stylar metabolism may, therefore, modulate pollen tube growth thus integrating the events leading to fertilization.