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

Abstract

We evaluated the effects of flowering-shoot defoliation on pollen production, individual grain size, pollen germination, pollen-tube growth and attrition, and siring ability between paired defoliated and control flowering shoots of Alstroemeria aurea, a common understory herb of the south Andean temperate forest. Defoliation was performed ∼15 d before anthesis. We estimated pollen production and grain volume from two anthers per shoot from a total of 84 shoot pairs. We used pollen 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 different pairs of control and defoliated shoots in single-donor pollinations in the field. From styles collected from field recipient flowers at senescence, we estimated the number of pollen tubes reaching the base of the style after statistically controlling for the number of germinated pollen grains. We counted seeds from mature fruits. Pollen production did not differ significantly between control and defoliated shoots, but defoliation did affect pollen quality. Pollen from defoliated shoots was smaller, produced tubes that grew at a slower rate and aborted more frequently, and sired fewer seeds in recipient flowers than did 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 paired shoots exhibited in pollen-grain size. We conclude that leaf removal negatively affects paternal fitness of this hermaphrodite plant by hindering the performance of its pollen within recipient pistils.