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Premise: Seed production is frequently limited by the receipt of insufficient or low-quality pollen, collectively termed "pollen limitation" (PL). In taxa with gametophytic self-incompatibility (GSI), incompatible pollen can germinate on stigmas but pollen tubes are arrested in styles. This allows for estimates of pollen performance before, during, and after self-recognition, as well as insight into the factors underlying pollen quality limitation in GSI taxa., Methods: We scored pollen performance following self and outcross pollinations in Argentina anserina to identify the location of self-recognition and establish the relationship between pollen tubes and seed production. We then estimated quantity and quality components of PL from >3300 field-collected styles. We combined our results with other studies to test the prediction that low pollen quality, but not quantity, drives higher PL in self-incompatible (SI) taxa than in self-compatible taxa (SC)., Results: Self and outcross pollen germinated readily on stigmas, but 96% of germinated self-pollen was arrested during early tube elongation. Reproduction in the field was more limited by pollen quality than by quantity, and pollen failure near the location of self-recognition was a stronger barrier to fertilization than pollen germination. Across 26 taxa, SI species experienced stronger pollen quality, but not quantity, limitation than SC species., Conclusions: Evaluating pollen performance at multiple points within pistils can elucidate potential causes of pollen quality limitation. The receipt of incompatible pollen inhibits fertilization success more than insufficient pollen receipt or poor pollen germination in A. anserina. Likewise, pollen quality limitation drives high overall PL in other SI taxa., (© 2022 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

The timing of flowering and other components of phenology such as duration and synchrony can affect reproductive success and recruitment by influencing the environment a plant will experience throughout its flowering period. Pollination is a common explanation for why flowering phenology may affect reproduction, but it is not well understood how variation in pollination might interact with the abiotic environment to affect plant reproduction. Here we monitored a population of spring ephemerals, Claytonia virginica , for one flowering season and examined the effects of flowering phenology and the environment on plant reproduction in two treatments: plants supplemented with additional outcross pollen and unmanipulated control plants. Different aspects of reproduction were measured at both the population and within-plant levels: number of seeds produced by individual plants (seed production), per-fruit seed viability (the proportion of viable seeds out of the total number of seeds per fruit), percent germination, and number of days to germination. Soil surface temperature, light, and moisture data were also collected. The flowering phenology and environmental predictors most important for each measurement of reproduction differed between control and pollen-supplemented plants. For example, in both pollen treatment groups, more days in flower was consistently a positive predictor of seed production, but the environmental factors affecting seed production varied, with increasing pollinator visitation mostly affecting seed production in the nonsupplemented group and soil moisture positively affecting it in supplemented plants. Phenological and environmental predictors also differed for proportion of viable seeds and timing of germination. Our germination results support the hypothesis that the mechanisms that control early flowering time in the maternal plant may affect the timing of other life history events such as seed germination. Additionally, we show some evidence that changes in the maternal abiotic environment, particularly temperature, may alter progeny phenotype. No clear seasonal resource trade-offs were evident, as has been shown in other studies of spring ephemerals. Our results show that the abiotic environment interacts with the pollination environment to affect plant reproduction, with different environmental factors predicting reproduction in control versus pollen-supplemented plants. [ABSTRACT FROM AUTHOR]

Generalized pollinators visit multiple co‐flowering plant species and may transfer heterospecific pollen grains. Recent studies have indicated that the effect of heterospecific pollen (HP) on reproduction success is variable and depends on the identity of donor and recipient species. However, few studies have documented variation in HP receipt and evaluated the reproductive effects of HP receipt across geographic locations under natural conditions. We investigated the spatial variation of pollen deposition across eight sites and how the pollen receipt related to the seed set of Salvia przewalskii, a subalpine perennial herb in Hengduan Mountain in southwest China. We found that stigmatic pollen loads substantially varied among sites for several metrics, including quantities of conspecific and heterospecific pollen, the proportion of HP, and species composition of HP donors. Five different plant families were the most common HP source at one or two sites, and the proportion of HP ranged from 3.4% to 51.3% across sites. The association of conspecific pollen with seed set was positive and variable among sites, whereas the association of HP receipt and seed set was negative and not significantly different among sites. Our results demonstrate variation in the quantity and fitness effect of pollen receipt across sites, which is a precondition for evolution of local adaptation. Further study of variation in patterns and effects of HP receipt for the same recipient species across natural communities would allow better understanding of the ecological and evolutionary consequences of HP receipt. [ABSTRACT FROM AUTHOR]

Seed production can be affected by water availability and also depend on the amount (pollen intensity) and quality of pollen deposited. The way pollen receipt on the stigma translates into seeds produced follows that of a saturating dose–response. Not only can water availability and pollen intensity each influence seed production, these factors could interact in their effects on seed production. Changes to the relationship between seed production and pollen intensity can in turn influence pollinator effectiveness and pollinator-mediated selection. We asked how water availability affected indices of plant fitness (seed set, fruit set and seed mass) and the relationship between pollen intensity and seed production in Phacelia parryi. We conducted a greenhouse experiment where we manipulated water availability (either high- or low-water) to pollen recipient plants and hand-pollinated each plant with a range of pollen intensities. We conducted 703 hand-pollinations on 30 plants. For each hand-pollinated flower we measured pollen deposited, seed production and seed mass. We then generated a piecewise regression of the relationship between pollen intensity and seed production, and determined average effects of water on plant fitness measures. This experiment was paired with a field observational study aimed to document natural variation in pollen deposition. Average seed production per fruit was 21 % higher in the high-watered plants. The relationship between pollen intensity and seed production differed between the two water treatments. Plants under high-water exhibited a wider range in which pollen deposition increased seed production. Average natural pollen intensities fell within different regions of the piecewise regression for low- and high-water plants. Water availability can alter the efficiency by which pollen received is translated into seeds produced. Our greenhouse data suggest that only under certain pollen intensity environments will water availability affect how pollen received is translated into seeds produced. [ABSTRACT FROM AUTHOR]