In this study, the effects of heat stress (30 degrees C, 35 degrees C, 40 degrees C) on pollen performance of Echinopsis chamaecereus Friedrich & Glaetzle were analyzed. Heat-treated pollen grains showed a insignificant reduction in germination rate. Pollen tubes treated by temperatures above 30 degrees C exhibited a decrease in tube length and a negative effect on pollen performance according to cumulative stress response index data. Pollen tube abnormality was enhanced by increased temperature, and bifurcated pollen tubes were very dominant than the other abnormalities. Callose accumulation on tube tips was enhanced by increased temperature. In bifurcated pollen tubes, one of the tubes blocked by callose plugs or dense callose accumulation was observed on tips. Actin organization showed disruption, and anisotropy of actin filaments increased at temperatures above 30 degrees C. The findings show that high temperatures cause destructive effects on male reproductive biology even in species such as cacti known to be temperature tolerant.