Reversible Inhibition of the Pollen Germination and the Stigma Penetration in Crocus vernus ssp. vernus (Iridaceae) Following Fumigations with NO2, CO, and O3 Gases

: We assessed the pollen hydration, the pollen germination, and the stigma papilla penetration of Crocus vernus subsp. vernus (Iridaceae) after 2 h fumigations with O3, NO2, and CO gases within humidified (90 - 100 % RH) box experiments. When the pollen and the pistil were separately fumigated, the pollen retained the capacity to emit a tube which penetrated papilla, and the stigma papillae retained the receptivity; when the pistils were first pollinated and then fumigated, the capacity of pollen to hydrate was not affected, but the germination was significantly reduced. The vulnerability to gases became evident at 0.3 ppm O3, 0.2 ppm NO2, and 0.5 ppm CO. The inhibition curves as a function of the gas concentrations were of an exponential type, and they saturated at 2 ppm NO2, 25 ppm CO, and 0.5 ppm O3, with germination percentages of 17 %, 27 %, and 60 %, respectively. Both the pollen germination and the papilla penetration were fully restored by prolonging for 60 - 90 min the incubation at 90 - 100 % RH, after the cessation of fumigations. The vulnerability of the pollen-papilla system is discussed.