▎ 摘　　要

The production of graphene based materials (GBMs) is steadily increasing but the effects of the possible release of GBMs in the environment are far from being understood. Graphene oxide (GO) is among the most active GBMs and it causes widely varying effects on the vegetative body of seed plants. However, nothing is known yet about its potential effects on the reproductive process. This study addresses the effects of GO on pollen germination and pollen tube elongation in the model species Nicotiana tabacum and in the non-model species Corylus avellana. In vitro germination experiments were conducted without or with GO (control and treated samples, respectively) at concentrations of 25, 50 and 100 g mL(-1). Pollen germination and tube elongation were affected at GO concentrations 50 g mL(-1), decreasing by 20% and 19% in N. tabacum and by 68% and 58% in C. avellana, respectively. GO did not affect the viability of N. tabacum pollen, but doubled the frequency of bent tubes. Microscopy observations of pollen tubes exposed to a cell-permeant, dual-excitation ratiometric pH indicator revealed that GO affected the intracellular pH homeostasis. Further germination experiments on C. avellana conducted by inverting the pH conditions of the control and treated (100 g GO mL(-1)) samples demonstrated that the main factor influencing the pollen performance is the acidic properties of GO. This might affect the reproductive process of numerous seed plants thus being relevant from an environmental point of view. Environmental significance The introduction of graphene nanomaterials into the environment is raising concerns on environmental safety. Despite the increasing understanding of the toxic effects of graphene oxide (GO) on photoautotrophic organisms, nothing is known yet concerning the effects on the sexual reproduction of seed plants. We found that in vitro exposure to high concentrations of GO impairs the pollen performances of two species, the tobacco plant (Nicotiana tabacum L.) and the common hazel (Corylus avellana L.), due to the acidic properties of GO. For this reason, the pollen of numerous other plants might exhibit a similar sensitivity to GO. These results raise some concerns for the possible implications in different fields, from crop production to ecosystem functionality.