Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was ...Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was one_celled, irregular in shape, nonsaccate, and the surface was covered with orbicules. When pollen became hydrated, the intine swelled and the exine bursted. The exine usually remained on the surface of water or on the pollination drop all the time, while the rest portion of the pollen sank into the drop of water or the pollination drop. In the late August, the down_curved female buds could be observed in the field trees. The downturning of the female buds was an characteristic feature discriminating from the vegetative buds. At this stage ovular primordium was present in the female bud with a dome_shaped nucellar primordium encircled by a rudimentary integument. The integument grew fast and overgrew the nucellus. In the March of the following year, the ovule formed a micropylar canal about 1?000 μm in length, 200-300 μm in width. Except the micropyle, the other part of the ovule was enclosed by 20-25 scales. During the early stage of the ovule development, the nucellar surface clearly showed cell configuration; but a membrane_like structure covering the nucellar apex appeared in the late stage of the ovule development, and subsequently broke down with nucellar cell disintegration before pollen shedding. The disintegrated cell products might partake in the formation of the pollination drop. Before and during pollination, the nucellar cells contained abundant mitochondria, endospermic reticulum and dictysomes with vesicles; the plasma membrane was undulated and there was no accumulation of electron_dense substances in the pericytoplasm. Pollination drops usually occurred at night, and disappeared by noon in the field tree. 15 days before pollination, the in vitro ovules from the field trees already had the capability of producing pollination drops, which could last for 4-5 days indoors. However, after these drops received pollen, they did not withdraw noticeably compared with the unpollinated ones. The retraction of the pollination drop was presumed not to be a nonmetabolic outcome but rather a result of evaporation.展开更多
Aims Adaptive convergence in floral phenotype among plants sharing a pollinator guild has been acknowledged in the concept of pollination syndrome.However,many plants display traits associated with a given syndrome,bu...Aims Adaptive convergence in floral phenotype among plants sharing a pollinator guild has been acknowledged in the concept of pollination syndrome.However,many plants display traits associated with a given syndrome,but are visited by multiple pollinators.This situation may indicate the beginning of a pollinator shift or may result in a stable situation with adaptations to different pollinators.In Salvia stachydifolia,a previous study suggested that flower shape is optimized to maximize the contribution to pollination of bees and hummingbirds.Here,we studied three additional aspects of its floral biology:sexual phases,nectar dynamics and breeding system,and examined their connection with pollinators’behaviour to explore the presence of adaptations to bee and/or hummingbird pollination.Methods Using a greenhouse population,we applied five pollination treatments to characterize breeding system.To determine sexual phases,we recorded flower opening,anther dehiscence,corolla fall and stigma receptivity.Additionally,we characterized nectar volume and concentration dynamics along the day.Finally,to determine pollinator assemblage and visitation patterns,we performed field observations and recorded pollinators’behaviour.Important Findings Salvia stachydifolia was partially protandrous and self-compatible,but open-pollinated plants attained the highest reproductive success,suggesting that reproduction is mainly dependent on pollinator activity.Bombus opifex bumblebees were the most frequent visitors,but Sappho sparganura hummingbirds dominated visits early in the morning and at dusk.Nectar was typical of bumblebee pollination.We suggest that the bee–hummingbird mixed visitation constitutes an unstable evolutionary situation,making S.stachydifolia an ideal system to understand the ecological circumstances in which pollination shifts occur.展开更多
文摘Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was one_celled, irregular in shape, nonsaccate, and the surface was covered with orbicules. When pollen became hydrated, the intine swelled and the exine bursted. The exine usually remained on the surface of water or on the pollination drop all the time, while the rest portion of the pollen sank into the drop of water or the pollination drop. In the late August, the down_curved female buds could be observed in the field trees. The downturning of the female buds was an characteristic feature discriminating from the vegetative buds. At this stage ovular primordium was present in the female bud with a dome_shaped nucellar primordium encircled by a rudimentary integument. The integument grew fast and overgrew the nucellus. In the March of the following year, the ovule formed a micropylar canal about 1?000 μm in length, 200-300 μm in width. Except the micropyle, the other part of the ovule was enclosed by 20-25 scales. During the early stage of the ovule development, the nucellar surface clearly showed cell configuration; but a membrane_like structure covering the nucellar apex appeared in the late stage of the ovule development, and subsequently broke down with nucellar cell disintegration before pollen shedding. The disintegrated cell products might partake in the formation of the pollination drop. Before and during pollination, the nucellar cells contained abundant mitochondria, endospermic reticulum and dictysomes with vesicles; the plasma membrane was undulated and there was no accumulation of electron_dense substances in the pericytoplasm. Pollination drops usually occurred at night, and disappeared by noon in the field tree. 15 days before pollination, the in vitro ovules from the field trees already had the capability of producing pollination drops, which could last for 4-5 days indoors. However, after these drops received pollen, they did not withdraw noticeably compared with the unpollinated ones. The retraction of the pollination drop was presumed not to be a nonmetabolic outcome but rather a result of evaporation.
基金This study was supported by Fondo para la Investigacion Cientffica y Tecnoldgica(FONCyT)grant PICT 2017-2196 to S.B.V.and by FONCyT grant PICT-2018-03192 to F.S.
文摘Aims Adaptive convergence in floral phenotype among plants sharing a pollinator guild has been acknowledged in the concept of pollination syndrome.However,many plants display traits associated with a given syndrome,but are visited by multiple pollinators.This situation may indicate the beginning of a pollinator shift or may result in a stable situation with adaptations to different pollinators.In Salvia stachydifolia,a previous study suggested that flower shape is optimized to maximize the contribution to pollination of bees and hummingbirds.Here,we studied three additional aspects of its floral biology:sexual phases,nectar dynamics and breeding system,and examined their connection with pollinators’behaviour to explore the presence of adaptations to bee and/or hummingbird pollination.Methods Using a greenhouse population,we applied five pollination treatments to characterize breeding system.To determine sexual phases,we recorded flower opening,anther dehiscence,corolla fall and stigma receptivity.Additionally,we characterized nectar volume and concentration dynamics along the day.Finally,to determine pollinator assemblage and visitation patterns,we performed field observations and recorded pollinators’behaviour.Important Findings Salvia stachydifolia was partially protandrous and self-compatible,but open-pollinated plants attained the highest reproductive success,suggesting that reproduction is mainly dependent on pollinator activity.Bombus opifex bumblebees were the most frequent visitors,but Sappho sparganura hummingbirds dominated visits early in the morning and at dusk.Nectar was typical of bumblebee pollination.We suggest that the bee–hummingbird mixed visitation constitutes an unstable evolutionary situation,making S.stachydifolia an ideal system to understand the ecological circumstances in which pollination shifts occur.
