FLOWERING-SHOOT DEFOLIATION AFFECTS POLLEN GRAIN-SIZE AND POSTPOLLINATION POLLEN PERFORMANCE IN ALSTROEMERIA-AUREA

We evaluated the effects of flowering-shoot defoliation on pollen prod uction, individual grain size, pollen germination, pollen-tube growth and attrition, and airing ability between paired defoliated and contro l flowering shoots of Alstroemeria aurea, a common understory herb of the south Andean temperate forest. Defoliation was performed similar t o 15 d before anthesis. We estimated pollen production and grain volum e from two anthers per shoot from a total of 84 shoot pairs. We used p ollen from different control and defoliated paired shoots to pollinate ''blocks'' of six cut flowers (three per treatment) in the laboratory . From styles fixed at 3, 6, and 12 h after pollination, we estimated pollen germination and tube-growth rates. We also used pollen from dif ferent pairs of control and defoliated shoots in single-donor pollinat ions in the held. From styles collected from field recipient flowers a t senescence, we estimated the number of pollen tubes reaching the bas e of the style after statistically controlling for the number of germi nated pollen grains. We counted seeds from mature fruits. Pollen produ ction did not differ significantly between control and defoliated shoo ts, but defoliation did affect pollen quality. Pollen from defoliated shoots was smaller, produced tubes that grew at a slower rate and abor ted more frequently, and sired fewer seeds in recipient flowers than d id pollen from control shoots. The degree to which pollen-tube growth and attrition differed between a given defoliated shoot and its paired control shoot was positively related to the relative difference the p aired shoots exhibited in pollen-grain size. We conclude that leaf rem oval negatively affects paternal fitness of this hermaphrodite plant b y hindering the performance of its pollen within recipient pistils.