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      Tamaño y viabilidad de semillas: implicancias en la evolución y conservación de Phaius tankervilleae (Orchidaceae) Translated title: Seed size and viability: implications on the evolution and conservation of Phaius tankervilleae (Orchidaceae)

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          Abstract

          RESUMEN Phaius tankervilleae es una orquídea terrestre altamente apreciada como ornamental y medicinal, razón por la cual se encuentra en peligro de extinción en algunos países como Australia y Japón. Generar información sobre las dimensiones y el vigor de la semilla es importante para entender aspectos de la evolución de la especie y encontrar métodos de conservación. Este estudio tuvo como finalidad poner a prueba la hipótesis, de que el tamaño y viabilidad de las semillas de P. tankervilleae están positivamente relacionados con el tamaño del fruto. Para realizar el estudio se cosecharon frutos de diferentes tamaños, de los cuales se tomaron muestras de 2,5 mg de semillas por frutos. Se realizó la caracterización morfológica de las semillas mediante observaciones en microscopio. Las semillas de cada tamaño de fruto fueron sometidas a un test de Tetrazolio para determinar viabilidad y se les tomaron mediciones del largo, ancho y volumen tanto de la testa como del embrión. Las semillas con embrión son fusiformes y las vanas son filiformes, el embrión es relativamente pequeño y las semillas de fruto mediano son las que presentan menor espacio de aire. Los resultados confirman la hipótesis planteada, cuanto más pequeño es el fruto menor es el tamaño y la cantidad de semillas viables. Por consiguiente, si se desea tener mayor cantidad de semillas de buena calidad es recomendable cosechar frutos de mayor tamaño.

          Translated abstract

          ABSTRACT Phaius tankervilleae is a terrestrial orchid highly prized as ornamental and medicinal, which is why it is in danger of extinction in some countries such as Australia and Japan. Generating information on seed size and vigor is important in understanding aspects of the evolution of the species and finding conservation methods. This study aimed to test the hypothesis that the size and viability of P. tankervilleae seeds are positively related to fruit size. In order to carry out the study, fruits of different sizes were harvested, from which samples of 2.5 mg of seeds per fruit were taken. Morphological characterization of the seeds was carried out by means of microscope observations. A Tetrazolium test was carried out to determine the viability of seeds and measurements were taken of the length, width, and volume of both the testa and the embryo. Seeds with embryos are fusiform and the empty one are filiform, the embryo is relatively small and the seeds of medium size fruit are those that have less air space. The results confirm the hypothesis, the smaller the fruit the smaller the size and the number of viable seeds. Therefore, to have more seeds of good quality it is advisable to harvest larger fruits.

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          A brief history of seed size.

          Improved phylogenies and the accumulation of broad comparative data sets have opened the way for phylogenetic analyses to trace trait evolution in major groups of organisms. We arrayed seed mass data for 12,987 species on the seed plant phylogeny and show the history of seed size from the emergence of the angiosperms through to the present day. The largest single contributor to the present-day spread of seed mass was the divergence between angiosperms and gymnosperms, whereas the widest divergence was between Celastraceae and Parnassiaceae. Wide divergences in seed size were more often associated with divergences in growth form than with divergences in dispersal syndrome or latitude. Cross-species studies and evolutionary theory are consistent with this evidence that growth form and seed size evolve in a coordinated manner.
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            Orchid phylogenomics and multiple drivers of their extraordinary diversification

            Orchids are the most diverse family of angiosperms, with over 25 000 species,more than mammals, birds and reptiles combined. Tests of hypotheses to account for such diversity have been stymied by the lack of a fully resolved broad-scale phylogeny. Here,we provide such a phylogeny, based on 75 chloroplast genes for 39 species representing all orchid subfamilies and 16 of 17 tribes, time-calibrated against 17 angiosperm fossils. Asupermatrix analysis places an additional 144 species based on three plastid genes. Orchids appear to have arisen roughly 112 million years ago (Mya); the subfamilies Orchidoideae and Epidendroideae diverged from each other at the end of the Cretaceous; and the eight tribes and three previously unplaced subtribes of the upper epidendroids diverged rapidly from each other between 37.9 and 30.8 Mya. Orchids appear to have undergone one significant acceleration of net species diversification in the orchidoids, and two accelerations and one deceleration in the upper epidendroids. Consistent with theory, such accelerations were correlated with the evolution of pollinia, the epiphytic habit, CAM photosynthesis, tropical distribution (especially in extensive cordilleras),and pollination via Lepidoptera or euglossine bees. Deceit pollination appears to have elevated the number of orchid species by one-half but not via acceleration of the rate of net diversification. The highest rate of net species diversification within the orchids (0.382 sp sp(-1) My(-1)) is 6.8 times that at the Asparagales crown.
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              Variation in sexual reproduction in orchids and its evolutionary consequences: a spasmodic journey to diversification

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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                cal
                Caldasia
                Caldasia
                Instituto de Ciencias Naturales, Facultad de Ciencias-Universidad Nacional de Colombia (Bogotá, Cundinamarca, Colombia )
                0366-5232
                December 2017
                : 39
                : 2
                : 388-399
                Affiliations
                [1] Misiones orgnameUniversidad Nacional de Misiones orgdiv1Facultad de Ciencias Forestales Argentina
                [2] Misiones orgnameUniversidad Nacional de Misiones orgdiv1Facultad de Ciencias Forestales Argentina
                Article
                S0366-52322017000200388
                10.15446/caldasia.v39n2.62184
                01b05415-bc83-4821-80b5-063a05392c68

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : 28 August 2017
                : 16 February 2017
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 59, Pages: 12
                Product

                SciELO Colombia


                Embryo,orchid,testa,orquídea,tetrazolium,tetrazolio,seed Coat,volumen,volume,Embrión

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