In vitro germination and growth of lily pollen tubes is affected by calcium inhibitor with reference to calcium distribution

The calcium inhibitors A23187, EGTA and La3+ inhibit pollen grain germination and growth of pollen tubes of Lilium davidii var. unicolor at different concentrations. Treatment with 10−4 or 10−5 M ionophores A23187 reduced germination rate and resulted in distortion of pollen tube. Addition of 2 or 10 mM of the chelator EGTA disturbed the direction of pollen tube growth and extended the diameter of pollen tube as observed by light and confocal microscopy. The Ca2+-channel blocker lanthanum chloride (La3+) restrained germination or markedly caused transformation of pollen tube. Furthermore, all treatments led to disappearance of any calcium gradient. Calcium distribution in pollen grain and pollen tube was altered as shown by confocal microscopy for each treatment. This indicates that the inhibitors influence pollen development by affecting the calcium gradient which may play a critical role in germination and tube growth. Fourier transform infrared (FTIR) spectra indicated slight increases in contents of amide I and a substantial decrease in the content of aliphatic esters and saturated esters in treated pollen tubes compared with normal pollen tubes. The FTIR analysis confirmed that EGTA and La3+ weakened the accumulation of ester in pollen tubes, which may be associated with an increased content of amide I.