Pollen tubes and reproductive success of Physaria globosa

Abstract

Physaria globosa (Desv.) O'Kane & Al-Shehbaz (Short's bladderpod) is a Federally endangered species limited to 31 populations in Tennessee, Kentucky, and Indiana. This species may have anywhere from one to 40 compound racemes that undergo anthesis in April through June. This study aims to examine how timing of anthesis within the compound raceme may affect reproductive success. Flowers produced earlier in the season or at specific positions within the inflorescence may experience different probabilities of successful pollination. Likewise, the plant's total resource availability could limit ovule/seed development. To explore how flower position might relate to reproductive success, samples were collected from five populations: two in Tennessee, two in Kentucky, and one in Indiana. 10 plants with ample flowers and fruits were selected at random from each population. For each plant, one whole flowering stem was preserved in FAA and later examined with aniline blue under fluorescence. Pistils were numbered based on their location on the main raceme and their position along each branch. The presence of pollen tubes in the ovary was scored as an indirect measure of successful pollination and fertilization. Preliminary results show that pistils present along the primary inflorescence axis may have greater reproductive success relative to other positions within the inflorescence. These data will be considered with regard to their possible conservation implications for P. globosa.