Pollen quality limits seed set in Burchardia umbellata (Colchicaceae)

Abstract

In self-incompatible plants, interference by self pollen or genetically related pollen can potentially exacerbate pollen limitation, although this has rarely been demonstrated. We examined the breeding system, pollen limitation, and pollen interference using self- and cross- pollinations and pollen supplementations in Burchardia umbellata, an insect-pollinated lilioid monocot. Ovule fertilization and seed set were less following selfing than crossing (22 vs. 78% and 4 vs. 73%, respectively), indicating partial self-incompatibility. Flowers were partially protandrous, and flowers opened concurrently on plants potentially allowing self pollen interference. Natural seed set was pollen limited and varied within and among years, probably due to variation in flowering plant density. Interference by self or genetically related pollen caused pollen limitation as evidenced by increased seed set of bagged cross-pollinated plants compared to unbagged pollen-supplemented plants in two years. In 1996, both fertilization and seed set increased in response to cross-pollination, indicating that interference occurred in the style and ovary. In 1997, only seed set increased after cross-pollination indicating that interference occurred in the ovary. Inappropriate pollen deposition may contribute to pollen limitation more often than previously recognized and should select for floral traits that decrease deposition of self or related pollen.

Density-dependent seed set in the Haleakala silversword: evidence for an Allee effect

“…In cases where pollinator visitation is not affected by population size or density, plants in small populations may still suffer reduced seed set if the effectiveness of pollination, due to pollen quality, declines (Kunin 1993;Lamont et al 1993;Wolf and Harrison 2001). This may occur through the deposition of foreign rather than conspecific pollen, or through the transfer of incompatible pollen, if a selfincompatibility mechanism is present (Feinsinger et al 1991;Kunin 1993;Aizen and Feinsinger 1994;Groom 1998;Ramsey and Vaughton 2000). Essentially, the efficiency of pollination, in terms of both the quantity and quality of pollen received, declines as patches become too small or the distance between plants becomes too great (Courchamp et al 1999).…”

Pollen viability, germination, and seed setting of Nelumbo nucifera

“…A low pollen viability reduces the germination rate and lowers the seed setting rate 8,9 . Apart from pollen viability, stigma receptivity, and self-incompatibility are also factors that could affect the seed-setting rate 10,11 . Self-incompatibility is caused by the interaction between pollen and stigma containing a similar genetic pattern; this is a mechanism that prevents inbreeding in plants 10,11 .…”

“…Apart from pollen viability, stigma receptivity, and self-incompatibility are also factors that could affect the seed-setting rate 10,11 . Self-incompatibility is caused by the interaction between pollen and stigma containing a similar genetic pattern; this is a mechanism that prevents inbreeding in plants 10,11 . The mechanism often coexists with protogyny, where the stigma develops faster than the anther, or with protandry, where the anther develops faster than the stigma [12][13][14][15][16] .…”

“…Protogyny and protandry often co-exist with self-incompatibility to prevent self-gamete fertilization 10,12 . Self-incompatibility occurs commonly in many flowering plant species 36 .…”

Pollinator Response to Patch Distribution and Reproductive Consequences in Lasthenia californica

“…Pollinator behavior and genetic incompatibility due to relatedness among individuals within patches may reduce pollen germination and fecundity among genetically similar patch populations as an Allee effect. The observed Allee effect in pollen germination success due to the reduction of compatible pollen persists despite substantial patch population size (Ramsey and Vaughton, 2000;Leducq et al, 2010).…”