Phloem is the woody tissue for the storage and long-distance transport of organic matter in vascular bundles.To reveal the process of secondary phloem development and differentiation in Pinus massoniana,the structure ...Phloem is the woody tissue for the storage and long-distance transport of organic matter in vascular bundles.To reveal the process of secondary phloem development and differentiation in Pinus massoniana,the structure of the secondary phloem and the distribution of cell inclusions were observed by histochemical staining,spontaneous fluorescence of phenolic substances and cell segregation.Based on tissue development and differentiation characteristics of P.massoniana secondary phloem,the secondary phloem development was divided into seven stages:the functional phloem stage;the sieve cell lignification stage;the phloem ray bending stage;the parenchyma cell dedifferentiation and division stage;the dedifferentiated parenchyma cell population formation stage;the periderm alteration stage,and the rhytidome stage.An analysis of cell morphology and inclusion distribution characteristics showed that the sieve cells were deformed during lignification,the quantities of parenchyma and resin ducts increased with development and the crystal content in cells,as well as the levels of sugars and lipids in phloem parenchyma cells,increased with development.The results indicate that the P.massoniana phloem first lost longitudinal transport function and then increased its secretory,storage and mechanical functions.Ultimately,the parenchyma differentiated into the cortex and periderm,and the tissue outside the new periderm lignified to form the rhytidome,which fully developed into the protective tissue of the stem.展开更多
The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can b...The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can be confidently traced from embryos and hatched juveniles, to conical adults. However, its zoological affinity remains highly controversial. Here we describe the internal microanatomic structures of the soft-body inside the peridermal theca of Olivooides multisulcatus Qian, 1977, including interradial pairs of tentacles, adradial and perradial frenula, perradial oral marginal lappets and twins of perradial gastric saccule-like humps as well as a circular velarium with striated coronal muscles. Particularly, one specimen shows bifurcated velarial canals along the bell aperture. Both the components of the soft-body and the external theca （or cyst） are arranged in perfect pentaradial symmetry. These characteristics are more compatible with those of living cubomedusans and co-occurring Cambrian athecate embryonic cubozoans. Concerning the presence of peridermal theca, Olivooides most likely represents an extinct thecate stem-group cubomedusae but devoid of both perradial eyes and specialized pedalia. The well-grown soft body inside the peridermal tube displays a set of mixed features of both polyp and medusa.展开更多
基金supported by the Guizhou provincial scientific and technological program 20185261。
文摘Phloem is the woody tissue for the storage and long-distance transport of organic matter in vascular bundles.To reveal the process of secondary phloem development and differentiation in Pinus massoniana,the structure of the secondary phloem and the distribution of cell inclusions were observed by histochemical staining,spontaneous fluorescence of phenolic substances and cell segregation.Based on tissue development and differentiation characteristics of P.massoniana secondary phloem,the secondary phloem development was divided into seven stages:the functional phloem stage;the sieve cell lignification stage;the phloem ray bending stage;the parenchyma cell dedifferentiation and division stage;the dedifferentiated parenchyma cell population formation stage;the periderm alteration stage,and the rhytidome stage.An analysis of cell morphology and inclusion distribution characteristics showed that the sieve cells were deformed during lignification,the quantities of parenchyma and resin ducts increased with development and the crystal content in cells,as well as the levels of sugars and lipids in phloem parenchyma cells,increased with development.The results indicate that the P.massoniana phloem first lost longitudinal transport function and then increased its secretory,storage and mechanical functions.Ultimately,the parenchyma differentiated into the cortex and periderm,and the tissue outside the new periderm lignified to form the rhytidome,which fully developed into the protective tissue of the stem.
基金supported by the Natural Science Foundation of China(NSFC grant 41272019,41372021)the "973 project" of the Ministry of Science and Technology of China"(2013CB835002, 2013CB837100)+1 种基金the "111 project" of the Programs of Introducing Talents of Discipline to Universities(No: W20136100061)the MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest University,China
文摘The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can be confidently traced from embryos and hatched juveniles, to conical adults. However, its zoological affinity remains highly controversial. Here we describe the internal microanatomic structures of the soft-body inside the peridermal theca of Olivooides multisulcatus Qian, 1977, including interradial pairs of tentacles, adradial and perradial frenula, perradial oral marginal lappets and twins of perradial gastric saccule-like humps as well as a circular velarium with striated coronal muscles. Particularly, one specimen shows bifurcated velarial canals along the bell aperture. Both the components of the soft-body and the external theca （or cyst） are arranged in perfect pentaradial symmetry. These characteristics are more compatible with those of living cubomedusans and co-occurring Cambrian athecate embryonic cubozoans. Concerning the presence of peridermal theca, Olivooides most likely represents an extinct thecate stem-group cubomedusae but devoid of both perradial eyes and specialized pedalia. The well-grown soft body inside the peridermal tube displays a set of mixed features of both polyp and medusa.
