Shortened anther–stigma distance reduces compatible pollination in two distylous<i>Primula</i>species

Liu, Shujuan; Wu, Ling‐Yun; Huang, Shuang‐Quan

doi:10.1093/jpe/rtv049

Cited by 20 publications

(19 citation statements)

References 43 publications

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“…According to the disassortative hypothesis, pollen grains from the anthers in different positions in a flower are likely to be attached to different parts of a pollinator’s body and thus transferred to the stigmas of opposite morphs ( Olesen 1979 ; Wolfe and Barrett 1987 ; Brys et al 2008 ). Many approaches, such as using man-made flowers as the pollen receptor ( Stone and Thomson 1994 ), manually changing the herkogamy of the flower ( Liu et al 2015 ), or controlling the pollinator when it visits the flowers of cultivated plants ( Keller et al 2014 ) have generally supported the hypothesis, but these approaches might affect the pollinator’s behaviour, such as the duration per visit and the foraging preference. Meanwhile, notably more pollen grains were deposited on the stigma when a controlled pollinator visited the flower.…”

Section: Discussionmentioning

confidence: 99%

“…Some studies examined the disassortative pollination hypothesis using manipulating experiment ( Keller et al 2014 ) or molecular methods ( Zhou et al 2015 ). Most studies quantified disassortative pollen movement by analysing pollen deposition on stigmas under natural conditions ( Ganders 1976 ; Ornduff 1979 ; Nishihiro et al 2000 ; Valois-Cuesta et al 2011 ; Liu et al 2015 ).…”

Section: Introductionmentioning

confidence: 99%

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Variation in the degree of reciprocal herkogamy affects the degree of legitimate pollination in a distylous species

2018

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Distyly is a widespread floral polymorphism characterized by the flowers within a population showing reciprocal placement of the anthers and stigma. Darwin hypothesizes that distyly evolves to promote precise pollen transfer between morphs. Primula chungensis exhibits two types of anther heights, and these two types of anthers show pollen of two different size classes. To understand whether the stigma could capture more pollen grains from the anthers of the pollen donor as the separation between the stigma of pollen receiver and the anther of pollen donor decreased, the present research assessed the source of the pollen load in a series of open-pollinated flowers with continuous variation of style lengths. Individuals with continuous variation of style length were tagged, and the selected flowers in the tagged plants were emasculated the day before dehiscence. The stigma of the emasculated flowers was fixed in fuchsin gel at the end of blooming. We assessed the pollen sources on each stigma by taking photos under a microscope and measured the diameter of each conspecific pollen grain with ImageJ. We found that a shorter distance from the stigmas to the anthers of a pollen donor gave the flower a higher capacity to receive pollen from those anthers. Our result provides a new evidence that distyly could promote the pollen transfer between morphs, which is consistent with Darwin’s hypothesis of disassortative pollination. An alternative hypothesis for the evolution of distyly (e.g. selfing avoidance) might also be true, but less likely, because self-incompatibility would greatly avoid self-fertilization for many distylous species.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variation in the degree of reciprocal herkogamy affects the degree of legitimate pollination in a distylous species

2018

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“…In recent years, most studies of the Primula SI system have focused on differences in pollination behaviors between morphs, such as the roles of bumblebee nectar robbers and syrphid flies in P. secundiflora pollination, the strength of SI and distylous syndrome in P. veris , the effect of anther–stigma distance on stigma pollen grains in two Primula species, and the relationship between flower display and SI in P. tibetica [ 27 , 28 , 29 , 30 ]. However, little is known about the biological events that occur during the process of Primula SI.…”

Section: Introductionmentioning

confidence: 99%

Transcriptomics Investigation into the Mechanisms of Self-Incompatibility between Pin and Thrum Morphs of Primula maximowiczii

Bian

Yang

et al. 2018

IJMS

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Heteromorphic self-incompatibility (SI) is an important system for preventing inbreeding in the genus Primula. However, investigations into the molecular mechanisms of Primula SI are lacking. To explore the mechanisms of SI in Primula maximowiczii, the pollen germination and fruiting rates of self- and cross-pollinations between pin and thrum morphs were investigated, and transcriptomics analyses of the pistils after pollination were performed to assess gene expression patterns in pin and thrum SI. The results indicated that P. maximowiczii exhibits strong SI and that the mechanisms of pollen tube inhibition differ between pin and thrum morphs. While self-pollen tubes of the pin morph were able to occasionally, though rarely, enter the style, those of the thrum morph were never observed to enter the style. The transcriptomics analysis of the pistils revealed 1311 and 1048 differentially expressed genes (DEGs) that were identified by comparing pin self-pollination (PS) vs. pin cross-pollination (PT) and thrum self-pollination (TS) vs. thrum cross-pollination (TP). Notably, about 90% of these DEGs exhibited different expression patterns in the two comparisons. Moreover, pin and thrum DEGs were associated with different Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways following enrichment analyses. Based on our results, the molecular mechanisms underlying the pin and thrum SI in P. maximowiczii appear to be distinct. Furthermore, the genes involved in the SI processes are commonly associated with carbohydrate metabolism and environmental adaptation. These results provide new insight into the molecular mechanisms of Primula SI.

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“…Several authors have proposed that dioecy evolves from heterostyly when pollen transfer between floral morphs is highly asymmetrical (Ornduff 1966, Beach & Bawa 1980. The classical Darwinian explanation for the transition to dioecy from distyly proposes that the pollinator-driven asymmetrical pollen transfer between floral morphs, resulting from low reciprocity among sexual organs (e.g., Feinsinger & Busby 1987, Lau & Bosque 2003, Ornelas et al 2004a, Stone & Thomson 1994, Hernández & Ornelas 2007a, García-Robledo 2008 and lower accessibility of low-level sexual organs and pollinator behavior (Liu et al 2016, Yuan et al 2017, would favor maleness in the morph with higher pollen donation efficiency (usually SS), and femaleness in the morph receiving more legitimate pollen (usually LS) (Darwin 1877, Ornduff 1966, Lloyd 1979, Beach & Bawa 1980. Asymmetries in pollen flow might be an important first step towards gender specialization.…”

Section: Discussionmentioning

confidence: 99%

Pollen and anther development malfunction in distylous flowers of Palicourea padifolia (Rubiaceae)

2020

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Background: Heterostyly is a genetic polymorphism in which flowers differ between individual plants of a species in heights at which stamens and style are reciprocally positioned. In these species, sexual selection theory predicts that different allocation patterns affect the functioning of polymorphism, enabling the evolutionary transition between heterostyly and dioecy. Questions: Because heterostyly can transit into dioecy, does anther/pollen development differ between floral morphs (LS and SS) of P. padifolia? Is pollen/anther development malfunction associated with one morph more than the other? Study species: Palicourea padifolia (Rubiaceae), a distylous plant. Methods: Tiny floral buds to flowers at anthesis were collected, processed for microphotography, and examined to describe pollen developmental pathways in LS and SS flowers. In addition, we used the TUNEL test to detect programmed cell death. Results: Stages of normal pollen development are fully described and illustrated in LS and SS flowers. Abnormalities due to tapetal degeneration were observed at various developmental stages; at later stages, SS flowers showed more abnormalities than LS flowers. The TUNEL test showed that degeneration was by programmed cell death. Conclusions: Along with previous results of asymmetrical fecundity and pollen transfer of morphs in P. padifolia, our study of pollen development indicates that the SS morph was more prone to lose the male function, though male sterility is far from being complete, which it might be an initial step towards functional dioecy.

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Shortened anther–stigma distance reduces compatible pollination in two distylousPrimulaspecies

Cited by 20 publications

References 43 publications

Variation in the degree of reciprocal herkogamy affects the degree of legitimate pollination in a distylous species

Variation in the degree of reciprocal herkogamy affects the degree of legitimate pollination in a distylous species

Transcriptomics Investigation into the Mechanisms of Self-Incompatibility between Pin and Thrum Morphs of Primula maximowiczii

Pollen and anther development malfunction in distylous flowers of Palicourea padifolia (Rubiaceae)

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