The embryo and endosperm development in Ranalisma rostratum was studied in this paper.The zygote divides by a transverse wall to form basal and apical cells.The larger basal cell undergoes no further division and beco...The embryo and endosperm development in Ranalisma rostratum was studied in this paper.The zygote divides by a transverse wall to form basal and apical cells.The larger basal cell undergoes no further division and becomes the basal suspensor cell.The embryo development conforms to the Caryophyllad type.In the mature seed,the embryo is U shaped and forms the embryonic shoot apex accompanied by one intraseminal leaf.The endosperm development belongs to the Hebolial type.The primary endosperm nucleus (invariably lying in the chalazal part of the embryo sac) divides and forms a large micropylar chamber and a small chalazal chamber.The chalazal endosperm chamber remains uninucleate,and free nuclear divisions occur in the micropylar chamber.Cellularization of the endosperm begins simultaneously from the micropylar and the chalazal ends.The cellularization is related to phragmoplast and cell plate, and does not arise from the free growth wall.Accompanying the embryo development,the endosperm degrades and does not exist in the mature seed.In the proembryo developing stages, the basal suspensor cell and chalazal endosperm cell grow to a considerable size.The nucleus and cytoplasm stain densely.Sometimes, binucleate or trinucleate was observed in both of the two cells.In the laterally concave embryo stage,they begin to degenerate which coincides with the cellularization of the endosperm.They are presumed to participate in the nourishment of the embryo proper in the early stages of embryo development.展开更多
Ranalisma rostratum (Alismataceae) is an endangered aquatic plant, and now there is only one population existing in China. In its natural habitat, Huli marsh in Chaling, Hunan province, the best growing plants have be...Ranalisma rostratum (Alismataceae) is an endangered aquatic plant, and now there is only one population existing in China. In its natural habitat, Huli marsh in Chaling, Hunan province, the best growing plants have been observed at microsites where the water depth is 5～10cm, and the plants grow in emergent form.R. rostratum reproduces asexually or sexually. The recruitment of asexual propagules into population is a very important way to maintain the natural population size. Although seed production does not appear to limitR. rostratum, restricted dispersal of propagules and seeds, low seed viability, low germinability, slow growth of seedlings under all conditions, and habitat loss due to agriculture appear to be more important reasons for the endangerment of this plant.展开更多
Aims small plant populations may be more likely to suffer more severe pollen limitation due to the lower number of potential mates or suitable pollinators.For invasive species,this phenomenon may be more common when a...Aims small plant populations may be more likely to suffer more severe pollen limitation due to the lower number of potential mates or suitable pollinators.For invasive species,this phenomenon may be more common when an invading population colonizes a new habitat.Here,we investigated whether pollen limitation occurs in invasive populations of Solanum rostratum during its invasion from North america to China and evaluated the patterns between pollen limitation and population size.Methods Pollen addition experiments were performed on six invasive populations of S.rostratum.by comparing fruit set and seed production with open pollination treatment,we calculated the index of pollen limitation and regressed it to population size and density.Important Findingsamong the six sampled invasive populations of S.rostratum,the fruit set and seed production per fruit were 0.346±0.014 and 52.38±9.29,respectively,with open pollination treatment and 0.572±0.022 and 56.28±10.79,respectively,with pollen addition treatment.Compared with open pollination,pollen addition significantly increased fruit set and seed production by 65.3 and 7.4%,respectively.The standardized index of pollen limitation ranged from 0.022 to 0.125,with an average of 0.065,suggesting that invasive populations of S.rostratum do suffer from pollen limitation.The index of pollen limitation was negatively correlated with population size,which is consistent with the pattern that smaller populations suffer from more severe pollen limitation.展开更多
文摘The embryo and endosperm development in Ranalisma rostratum was studied in this paper.The zygote divides by a transverse wall to form basal and apical cells.The larger basal cell undergoes no further division and becomes the basal suspensor cell.The embryo development conforms to the Caryophyllad type.In the mature seed,the embryo is U shaped and forms the embryonic shoot apex accompanied by one intraseminal leaf.The endosperm development belongs to the Hebolial type.The primary endosperm nucleus (invariably lying in the chalazal part of the embryo sac) divides and forms a large micropylar chamber and a small chalazal chamber.The chalazal endosperm chamber remains uninucleate,and free nuclear divisions occur in the micropylar chamber.Cellularization of the endosperm begins simultaneously from the micropylar and the chalazal ends.The cellularization is related to phragmoplast and cell plate, and does not arise from the free growth wall.Accompanying the embryo development,the endosperm degrades and does not exist in the mature seed.In the proembryo developing stages, the basal suspensor cell and chalazal endosperm cell grow to a considerable size.The nucleus and cytoplasm stain densely.Sometimes, binucleate or trinucleate was observed in both of the two cells.In the laterally concave embryo stage,they begin to degenerate which coincides with the cellularization of the endosperm.They are presumed to participate in the nourishment of the embryo proper in the early stages of embryo development.
文摘Ranalisma rostratum (Alismataceae) is an endangered aquatic plant, and now there is only one population existing in China. In its natural habitat, Huli marsh in Chaling, Hunan province, the best growing plants have been observed at microsites where the water depth is 5～10cm, and the plants grow in emergent form.R. rostratum reproduces asexually or sexually. The recruitment of asexual propagules into population is a very important way to maintain the natural population size. Although seed production does not appear to limitR. rostratum, restricted dispersal of propagules and seeds, low seed viability, low germinability, slow growth of seedlings under all conditions, and habitat loss due to agriculture appear to be more important reasons for the endangerment of this plant.
基金This work was supported by the National Natural Science Foundation of China(31270462).
文摘Aims small plant populations may be more likely to suffer more severe pollen limitation due to the lower number of potential mates or suitable pollinators.For invasive species,this phenomenon may be more common when an invading population colonizes a new habitat.Here,we investigated whether pollen limitation occurs in invasive populations of Solanum rostratum during its invasion from North america to China and evaluated the patterns between pollen limitation and population size.Methods Pollen addition experiments were performed on six invasive populations of S.rostratum.by comparing fruit set and seed production with open pollination treatment,we calculated the index of pollen limitation and regressed it to population size and density.Important Findingsamong the six sampled invasive populations of S.rostratum,the fruit set and seed production per fruit were 0.346±0.014 and 52.38±9.29,respectively,with open pollination treatment and 0.572±0.022 and 56.28±10.79,respectively,with pollen addition treatment.Compared with open pollination,pollen addition significantly increased fruit set and seed production by 65.3 and 7.4%,respectively.The standardized index of pollen limitation ranged from 0.022 to 0.125,with an average of 0.065,suggesting that invasive populations of S.rostratum do suffer from pollen limitation.The index of pollen limitation was negatively correlated with population size,which is consistent with the pattern that smaller populations suffer from more severe pollen limitation.
