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Pollen Viability (pollen + viability)
Selected AbstractsDelayed Selfing in an Alpine Biennial Gentianopsis paludosa (Gentianaceae) in the Qinghai-Tibetan PlateauJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2010Yuan-Wen Duan Delayed selfing could provide ovules with an opportunity to be fertilized as a means of "pollination assurance" before the flowers wilt. It could, thus, be regarded as an adaptation to unpredictable pollinator environments. Within the alpine biennial Gentianopsis paludosa, the showy flowers and herkogamy at the early stage of a flower's life cycle may favor outcrossing. As the flower ages, anthers contact the central stigma due to the elongation of all filaments, resulting in autonomous selfing. Flower visitors are extremely rare in a high altitude population; and examination of the mating system indicates that G. paludosa is self-pollinated under natural conditions in this population. While at the lower altitude, the bumblebee visitation rate is relatively high but possibly unreliable. Stigma receptivity is the highest on the third day of anthesis, and decreases thereafter. Pollen viability is the highest when flowers open, and gradually decreases later. Self-pollination of G. paludosa occurs at the late stage of a flower's lifecycle when stigma receptivity and pollen viability have both decreased, suggesting delayed selfing and assurance of seed production. This delayed selfing could assure seed production under the constraints of pollinator scarcity, but ensure outcrossing when pollinators were available. Such a flexible pollination mechanism is highly adaptive in the alpine environment of the Qinghai-Tibetan Plateau. [source] CROSSING RELATIONSHIPS AMONG ANCIENT AND EXPERIMENTAL SUNFLOWER HYBRID LINEAGESEVOLUTION, Issue 3 2000Loren H. Rieseberg Abstract., Reproductive barrier formation between newly derived hybrid taxa and their parental species represents a major evolutionary hurdle. Here, I examine the development of a sterility barrier during hybrid speciation by examining the fertility of progeny from all combinations of crosses involving three experimentally synthesized sunflower hybrid lineages, their natural hybrid counterpart, Helianthus anomalus, and their parents, H. annuus and H. petiolaris. Crosses between the parental species and H. anomalus generated almost completely sterile offspring (pollen viability < 5%; seed set < 1%). A fairly strong sterility barrier also has developed between three hybrid lineages and both parental species (pollen viability 11.1,41.6%; seed set 0.84,20.1%). In contrast, the three hybrid lineages are almost fully interfertile (pollen viabilities 83.1,88.6%; seed set 72.1,75.3%), as predicted by molecular mapping studies that indicate they have converged on a similar set of gene combinations and chromosomal rearrangements. A modest decline in compability is observed in crosses between the three hybrid lineages and H. anomalus (pollen viabilities 64.1,70.7%; seed set 37,43%), a result that agrees well with prior data demonstrating significant congruence between the genomes of the natural and experimental hybrid lineages. These observations not only indicate that reproductive isolation can arise as a by-product of fertility selection in hybrid populations, but also testify to the repeatability of this mode of speciation. [source] Intrafloral differentiation of stamens in heterantherous flowersJOURNAL OF SYSTEMATICS EVOLUTION, Issue 1 2009Zhong-Lai LUO Abstract Flowers that have heteromorphic stamens (heterantherous flowers) have intrigued many researchers ever since the phenomenon was discovered in the 19th century. The morphological differentiation in androecia has been suggested as a reflection of "labor division" in pollination in which one type of stamens attracts pollinators and satisfies their demand for pollen as food and the other satisfies the plant's need for safe gamete dispersal. The extent and patterns of stamen differentiation differ notably among taxa with heterantherous flowers. Seven species with heteromorphic stamens in three genera were sampled from Leguminosae and Melastomataceae, and the morphological difference of androecia, pollen content, pollen histochemistry and viability, pollen micro-morphology, as well as the main pollinators were examined and compared. Pollen number differs significantly between stamen sets of the same flower in most species investigated, and a correlation of pollen number and anther size was substantiated. Higher pollen viabilities were found in the long (pollinating) stamens of Senna alata (L.) Roxb. and S. bicapsularis (L.) Roxb. Dimorphic pollen exine ornamentation is reported here for the first time in Fordiophyton faberi Stapf. The height of stigma and anther tips of the long stamens in natural conditions was proved to be highly correlated, supporting the hypothesis that they contact similar areas of the pollinator's body. [source] CROSSING RELATIONSHIPS AMONG ANCIENT AND EXPERIMENTAL SUNFLOWER HYBRID LINEAGESEVOLUTION, Issue 3 2000Loren H. Rieseberg Abstract., Reproductive barrier formation between newly derived hybrid taxa and their parental species represents a major evolutionary hurdle. Here, I examine the development of a sterility barrier during hybrid speciation by examining the fertility of progeny from all combinations of crosses involving three experimentally synthesized sunflower hybrid lineages, their natural hybrid counterpart, Helianthus anomalus, and their parents, H. annuus and H. petiolaris. Crosses between the parental species and H. anomalus generated almost completely sterile offspring (pollen viability < 5%; seed set < 1%). A fairly strong sterility barrier also has developed between three hybrid lineages and both parental species (pollen viability 11.1,41.6%; seed set 0.84,20.1%). In contrast, the three hybrid lineages are almost fully interfertile (pollen viabilities 83.1,88.6%; seed set 72.1,75.3%), as predicted by molecular mapping studies that indicate they have converged on a similar set of gene combinations and chromosomal rearrangements. A modest decline in compability is observed in crosses between the three hybrid lineages and H. anomalus (pollen viabilities 64.1,70.7%; seed set 37,43%), a result that agrees well with prior data demonstrating significant congruence between the genomes of the natural and experimental hybrid lineages. These observations not only indicate that reproductive isolation can arise as a by-product of fertility selection in hybrid populations, but also testify to the repeatability of this mode of speciation. [source] Effects of elevated temperature and carbon dioxide on seed-set and yield of kidney bean (Phaseolus vulgaris L.)GLOBAL CHANGE BIOLOGY, Issue 8 2002P. V. Vara Prasad Abstract It is important to quantify and understand the consequences of elevated temperature and carbon dioxide (CO2) on reproductive processes and yield to develop suitable agronomic or genetic management for future climates. The objectives of this research work were (a) to quantify the effects of elevated temperature and CO2 on photosynthesis, pollen production, pollen viability, seed-set, seed number, seeds per pod, seed size, seed yield and dry matter production of kidney bean and (b) to determine if deleterious effects of high temperature on reproductive processes and yield could be compensated by enhanced photosynthesis at elevated CO2 levels. Red kidney bean cv. Montcalm was grown in controlled environments at day/night temperatures ranging from 28/18 to 40/30 °C under ambient (350 µmol mol,1) or elevated (700 µmol mol,1) CO2 levels. There were strong negative relations between temperature over a range of 28/18,40/30 °C and seed-set (slope, ,,6.5% °C,1) and seed number per pod (, 0.34 °C,1) under both ambient and elevated CO2 levels. Exposure to temperature >,28/18 °C also reduced photosynthesis (, 0.3 and ,,0.9 µmol m,2 s,1 °C,1), seed number (, 2.3 and ,,3.3 °C,1) and seed yield (, 1.1 and ,,1.5 g plant,1 °C,1), at both the CO2 levels (ambient and elevated, respectively). Reduced seed-set and seed number at high temperatures was primarily owing to decreased pollen production and pollen viability. Elevated CO2 did not affect seed size but temperature >,31/21 °C linearly reduced seed size by 0.07 g °C,1. Elevated CO2 increased photosynthesis and seed yield by approximately 50 and 24%, respectively. There was no beneficial interaction of CO2 and temperature, and CO2 enrichment did not offset the negative effects of high temperatures on reproductive processes and yield. In conclusion, even with beneficial effects of CO2 enrichment, yield losses owing to high temperature (> 34/24 °C) are likely to occur, particularly if high temperatures coincide with sensitive stages of reproductive development. [source] Reproductive isolation and hybrid pollen disadvantage in IpomopsisJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2003D. R. Campbell Abstract One cause of reproductive isolation is gamete competition, in which conspecific pollen has an advantage over heterospecific pollen in siring seeds, thereby decreasing the formation of F1 hybrids. Analogous pollen interactions between hybrid pollen and conspecific pollen can contribute to post-zygotic isolation. The herbaceous plants Ipomopsis aggregata and I. tenuituba frequently hybridize in nature. Hand-pollination of I. aggregata with pollen from F1 or F2 hybrids produced as many seeds as hand-pollination with conspecific pollen, suggesting equal pollen viability. However, when mixed pollen loads with 50% conspecific pollen and 50% hybrid pollen were applied to I. aggregata stigmas, fewer than half of the seeds had hybrid sires. Such pollen mixtures are frequently received if plants of the two species and F1 and F2 hybrids are intermixed, suggesting that this advantage of conspecific over hybrid pollen reduces backcrossing and contributes to reproductive isolation. [source] Delayed Selfing in an Alpine Biennial Gentianopsis paludosa (Gentianaceae) in the Qinghai-Tibetan PlateauJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2010Yuan-Wen Duan Delayed selfing could provide ovules with an opportunity to be fertilized as a means of "pollination assurance" before the flowers wilt. It could, thus, be regarded as an adaptation to unpredictable pollinator environments. Within the alpine biennial Gentianopsis paludosa, the showy flowers and herkogamy at the early stage of a flower's life cycle may favor outcrossing. As the flower ages, anthers contact the central stigma due to the elongation of all filaments, resulting in autonomous selfing. Flower visitors are extremely rare in a high altitude population; and examination of the mating system indicates that G. paludosa is self-pollinated under natural conditions in this population. While at the lower altitude, the bumblebee visitation rate is relatively high but possibly unreliable. Stigma receptivity is the highest on the third day of anthesis, and decreases thereafter. Pollen viability is the highest when flowers open, and gradually decreases later. Self-pollination of G. paludosa occurs at the late stage of a flower's lifecycle when stigma receptivity and pollen viability have both decreased, suggesting delayed selfing and assurance of seed production. This delayed selfing could assure seed production under the constraints of pollinator scarcity, but ensure outcrossing when pollinators were available. Such a flexible pollination mechanism is highly adaptive in the alpine environment of the Qinghai-Tibetan Plateau. [source] Identification of hyperpolarization-activated calcium channels in apical pollen tubes of Pyrus pyrifoliaNEW PHYTOLOGIST, Issue 3 2007Hai-Yong Qu Summary ,,The pollen tube has been widely used to study the mechanisms underlying polarized tip growth in plants. A steep tip-to-base gradient of free cytosolic calcium ([Ca2+]cyt) is essential for pollen-tube growth. Local Ca2+ influx mediated by Ca2+ -permeable channels plays a key role in maintaining this [Ca2+]cyt gradient. ,,Here, we developed a protocol for successful isolation of spheroplasts from pollen tubes of Pyrus pyrifolia and identified a hyperpolarization-activated cation channel using the patch-clamp technique. ,,We showed that the cation channel conductance displayed a strong selectivity for divalent cations, with a relative permeability sequence of barium (Ba2+) , Ca2+ > magnesium (Mg2+) > strontium (Sr2+) > manganese (Mn2+). This channel conductance was selective for Ca2+ over chlorine (Cl,) (relative permeability PCa/PCl = 14 in 10 mm extracellular Ca2+). We also showed that the channel was inhibited by the Ca2+ channel blockers lanthanum (La3+) and gadolinium (Gd3+). Furthermore, channel activity depended on extracellular pH and pollen viability. ,,We propose that the Ca2+ -permeable channel is likely to play a role in mediating Ca2+ influx into the growing pollen tubes to maintain the [Ca2+]cyt gradient. [source] Analysis of sub-populations of rapid-cycling Brassica rapa following recurrent bi-directional selection for cotyledon sizePLANT BREEDING, Issue 1 2007N. Tel-Zur Abstract Recurrent selection programmes use one or just a few selection criteria, however other indirect traits may be unpredictably changed in a population. This study was conducted to determine the indirect effects of 10 cycles of bi-directional recurrent selection for cotyledon size in the model system of rapid-cycling Brassica rapa. Eight sub-populations (four large- and four small-cotyledon sizes) were phenotypically and cytologically evaluated. Each sub-population was measured by five phenotypic traits. Ploidy and pollen viability were studied and compared with the initial population. Total weight was significantly different in broad and bottleneck-1 sub-populations. Total cell number exhibited statistically significant differences in broad and bottleneck-1 sub-populations, while cell number per unit area exhibited statistically significant differences in broad, bottleneck-2 and bottleneck-3 sub-populations. Decreases in pollen viability in comparison with the base population were observed in three sub-populations. Among the eight sub-populations studied, the most significant phenotypic differences were observed within broad sub-populations. Based on the above, it is possible that bi-directional recurrent selection for cotyledon size may have been a result of indirect selection for two processes, endoreduplication and cell division. [source] Natural hybridization in Cardamine (Brassicaceae) in the Pyrenees: evidence from morphological and molecular dataBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2002KAROL MARHOLD FLS While researching Cardamine (Brassicaceae) in the Pyrenees, putative hybrid plants were found at two natural sites. Pollen grain viability, AFLP, and multivariate morphometric analyses were performed in order to assess the plants' presumed hybrid origin, establishing that natural hybridization between the diploids C. crassifolia and C. amara ssp. pyrenaea had occurred. A new diploid nothospecies, C.×enriquei (2n = 2x = 16), is described. Examination of 18 morphological characters showed the intermediacy of the hybrid between the parental taxa in most characters. AFLP analyses of C. amara ssp. amara, ssp. austriaca, ssp. olotensis and C. raphanifolia, demonstrated the close position of the hybrid to C. crassifolia, and revealed that the highest number of markers were shared with the parents. Polymorphism found in the AFLP pattern of the hybrid suggested recurrent origin, segregation and/or backcrosses, although assessment of pollen viability indicated high male sterility. The hybridization event reported here represents the second documented case between the C. pratensis group and C. amara. An account of the nomenclature of C. crassifolia is also presented, including lectotypification of relevant names. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 275,294. [source] | ||||||||||||||||||||||