Effects of acid mist on invivo pollen tube growth in red maple
The effects of mist acidity on invivo pollen germination and tube elongation of red maple (Acerrubrum L.) were investigated. Branches with female flowers were exposed to simulated mist at pH values of 5.6, 4.6, 3.6, and 2.6. After exposure, stigmas were pollinated with fresh, untreated pollen. Following a growth period of 24 h, styles were excised, stained, and observed with fluorescence microscopy to determine the number of grains that had germinated and the number of tubes that had grown to the base of the style. Both germination and tube growth were sensitive to the pH of mist. During one trial, as mist pH decreased from 5.6 to 2.6, the mean number of grains that germinated decreased from 60 to 19 and the mean number of tubes that grew to the base of the style decreased from 3.8 to 1.0. Only at pH 2.6 was there a significant relationship between number of germinating pollen grains and number of tubes reaching the base of the style. The effects of acidity on pollen germination invivo were similar to, but not as severe as, those obtained previously with pollen germinated invitro.