To provide evidence insight into the phylogenetic position of Itea L., we observed floral ontogeny of Itea yunnanensis Franch. under the scanning electron microscope (SEM) for the first time. The floral phyllo...To provide evidence insight into the phylogenetic position of Itea L., we observed floral ontogeny of Itea yunnanensis Franch. under the scanning electron microscope (SEM) for the first time. The floral phyllotaxis is whorled and floral organogenesis follows centripetal pattern. Sepal initiation is in a two_fifths helical order. Petal initiation appears simultaneous, and petals grow at an ordinary rate. The haplostemony of this species arises slightly later than petals but earlier than gynoecium in initiation. Two carpels are free at the early stage of floral ontogeny, but incurve, get closer and become appressed to each other later. Paraffin transverse sections series of gynoecium at anthesis show that two carpels are connate on the ventral side through their entire length. At last, two carpels within the ovary fuse completely, forming two locules separated by a septum, the ventral vascular bundles in two stylar lobes are connected through the parenchyma, and the stigma lobes become fused. These observations are different from those by Bensel and Palser (1975). The gynoecia they described might be not mature, but rather at early developmental stage. We compared floral developmental pattern and floral structure of Itea with its related taxa. In I. yunnanensis petals grow in the way that is different from that of some related taxa such as Saxifragaceae sensu stricto, Hydrangeaceae, Ribes, Brexia . The developing pattern of gynoecium in I. yunnanensis is similar to that of some members in the Saxifragaceae sensu stricto and Hydrangeaceae. The treatment to raise taxonomic rank of Itea from genus to family, Iteaceae, is supported by our results.展开更多
Floral ontogeny is described in two species of genus Magnolia （Magnollaceae）, Magnolia alboserlcea Chun et C. Tsoong, and M. amoena Cheng, representing subgenus Magnolia and subgenus Yulani In Magnolia, by using sca...Floral ontogeny is described in two species of genus Magnolia （Magnollaceae）, Magnolia alboserlcea Chun et C. Tsoong, and M. amoena Cheng, representing subgenus Magnolia and subgenus Yulani In Magnolia, by using scanning electron microscope （SEM）. The sequence of Initiation of floral organs Is from proximal to distal. The three distinct outermost and middle organs are Initiated in sequence, but ultimately form a single whorl, thus their ontogeny Is consistent with a sepal Interpretation. The last three tepals （petals） alternate with the preceding tepal whorl. The members of androeclum and gynoeclum arise spirally, although the androecium shows some Intermedlacy between a spiral and whorled arrangement. The carpel prlmordia initiate in group of four to five. The order of stamen Initiation within each tier Is not determined. The floral ontogeny Is remarkably homogeneous between the subgenus Magnolia and subgenus Yulani that does not support the resuming of genus Yulani.展开更多
文摘To provide evidence insight into the phylogenetic position of Itea L., we observed floral ontogeny of Itea yunnanensis Franch. under the scanning electron microscope (SEM) for the first time. The floral phyllotaxis is whorled and floral organogenesis follows centripetal pattern. Sepal initiation is in a two_fifths helical order. Petal initiation appears simultaneous, and petals grow at an ordinary rate. The haplostemony of this species arises slightly later than petals but earlier than gynoecium in initiation. Two carpels are free at the early stage of floral ontogeny, but incurve, get closer and become appressed to each other later. Paraffin transverse sections series of gynoecium at anthesis show that two carpels are connate on the ventral side through their entire length. At last, two carpels within the ovary fuse completely, forming two locules separated by a septum, the ventral vascular bundles in two stylar lobes are connected through the parenchyma, and the stigma lobes become fused. These observations are different from those by Bensel and Palser (1975). The gynoecia they described might be not mature, but rather at early developmental stage. We compared floral developmental pattern and floral structure of Itea with its related taxa. In I. yunnanensis petals grow in the way that is different from that of some related taxa such as Saxifragaceae sensu stricto, Hydrangeaceae, Ribes, Brexia . The developing pattern of gynoecium in I. yunnanensis is similar to that of some members in the Saxifragaceae sensu stricto and Hydrangeaceae. The treatment to raise taxonomic rank of Itea from genus to family, Iteaceae, is supported by our results.
基金Supported by the National Natural Science Foundation of China （30370108 and 30000011） and the Guangdong Provincial Natural Science Foundation of China （5006764）. Acknowledgements The author appreciated Dr Paula Rudall and Mrs Chrissie Prychid in Royal Botanic Gardens, Kew for their supervision and kind help in the laboratory.
文摘Floral ontogeny is described in two species of genus Magnolia （Magnollaceae）, Magnolia alboserlcea Chun et C. Tsoong, and M. amoena Cheng, representing subgenus Magnolia and subgenus Yulani In Magnolia, by using scanning electron microscope （SEM）. The sequence of Initiation of floral organs Is from proximal to distal. The three distinct outermost and middle organs are Initiated in sequence, but ultimately form a single whorl, thus their ontogeny Is consistent with a sepal Interpretation. The last three tepals （petals） alternate with the preceding tepal whorl. The members of androeclum and gynoeclum arise spirally, although the androecium shows some Intermedlacy between a spiral and whorled arrangement. The carpel prlmordia initiate in group of four to five. The order of stamen Initiation within each tier Is not determined. The floral ontogeny Is remarkably homogeneous between the subgenus Magnolia and subgenus Yulani that does not support the resuming of genus Yulani.
