In order to determine the response of pollen to UV-B irradiation and cumulative effects of UV-B exposure time on pollen germination and tube growth, 19 taxa of higher plants were investigated in vitro concerning the exposure of pollen grains to two levels of enhanced ultraviolet-B (UV-BBE) (280-320nm, 350 and 500mW:m2 biologically effective UV-B radiation) simulating 8 and 21% stratospheric ozone depletion in Lanzhou, China (36.04°N, 1550 m) and to no UV-B (control group). Compared with the control, enhanced UV-B radiation significantly inhibited pollen germination and tube growth in most species. Higher UV-B flux rate caused a greater inhibitory effect than lower UV-B radiation level. Several taxa exhibited insensitivity of pollen germination and tube growth to UV-B and were even stimulated by UV-B. Reduction in pollen germination rates and tube growth increased with longer exposure time and this indicated a cumulative effect of UV-B radiation. It is concluded that changes in pollen susceptibility to UV-B would lead to severe ecological consequences under natural conditions.