Early harvest increases post-harvest physiological quality of Araucaria angustifolia (Araucariaceae) seeds

ResumenAraucaria angustifolia es una conífera nativa de Brasil y una especie en peligro de extinción. Sus semillas tienen un corto período de viabilidad, factor que contribuye a su vulnerabilidad. Este estudio tuvo como objetivo evaluar la calidad fisiológica durante el período de desarrollo y post-almacenamiento de semillas de A. angustifolia. Conos de A. angustifolia fueron recolectados en poblaciones naturales en Curitibanos, Santa Catarina, Brasil, en marzo, abril, mayo y junio y clasificados en los estadios de desarrollo cotiledonar i, ii y iii de acuerdo con el mes de recolecta. Un total de 10 conos fueron recolectados para cada estadio. Las semillas fueron almacenadas en refrigerador durante 60 y 120 días y posteriormente sometidas a pruebas de germinación (25 °C - fotoperiodo de 12 h) siendo evaluados el contenido de humedad, tetrazolio y el vigor (conductividad eléctrica [75 mL de agua destilada a 25 °C], índice de velocidad de germinación, y la longitud de la parte aérea y de la raíz). Durante el desarrollo de las semillas, el contenido de humedad se redujo desde el estadio cotiledonar (66.54 %) al estadio iii (47.44%), y el vigor aumentaron en el último estadio. Durante el almacenamiento, el contenido de humedad en el estadio cotiledonar y estadio i fue estable. Entretanto, las semillas almacenadas mostraron una reducción en el contenido de humedad después de 120 días en los estadios ii y iii. La calidad fisiológica en el estadio cotiledonar mostró un aumento de 86 % y 93 % de germinación después de 60 y 120 días de almacenamiento, respectivamente, a diferencia de los estadios ii y iii, los cuales mostraron una disminución en la viabilidad de las semillas y en el vigor después del almacenamiento. La conductividad eléctrica fue mayor para las semillas en estadio cotiledonar recién recolectadas que para aquellas almacenadas durante 60 y 120 días. Sin embargo, en otras estadios, el contenido de lixiviados después de 120 días de almacenamiento aumentó con el avance del período de recolecta. El índice de velocidad de germinación y la longitud de la parte aérea y raíz después del almacenamiento eran más altos para las semillas en el estadio cotiledonar y el estadio i, a diferencia del estadio ii y iii, los cuales tenían raíz y parte aérea de menor longitud durante el almacenamiento. Por lo tanto, el mantenimiento del contenido de humedad de la semilla durante el almacenamiento fue variable y depende del período de recolecta. Además, la calidad fisiológica de las semillas difiere entre los estadios más tempranos o tardíos. Una recolección precoz favoreció la calidad fisiológica de las semillas, y puede ser una estrategia para aumentar la conservación de semillas de A. angustifolia.

AbstractAraucaria angustifolia is a conifer native to Brazil and is an endangered species. Since this species seeds have a short period of viability, its vulnerability is higher. Thus the aim of this study was to evaluate the physiological quality of A. angustifolia seeds during the development and post-storage periods. For this, cones of A. angustifolia were collected from a natural population in Curitibanos, Santa Catarina, Brazil, in March, April, May and June 2012. The collected seeds were classified into developmental stages of cotyledonary, i, ii and iii according to the month of collection; a total of 10 cones were collected for each stage. Seeds were stored in a refrigerator for 60 and 120 days, and were submitted to a chamber germination test (25 °C-photoperiod 12 h). Additionally, seeds were tested for moisture content (105 °C for 24 hours), tetrazolium (0.1 % for 1 hour) and vigor (electric conductivity [75 mL distilled water at 25 °C], germination speed index, and shoot and root length). Our results showed that during seed development, moisture content decreased from the cotyledonary stage (66.54 %) to stage iii (49.69 %), and vigor increased in the last stage. During storage, moisture content at cotyledonary stage and stage i was stable. On the other hand, stored seeds exhibited a decrease in moisture content after 120 days at stages ii and iii. Physiological quality at the cotyledonary stage resulted in an increased germination rate of 86 % and 93 % after 60 and 120 days of storage, respectively; unlike stages ii and iii exhibited a decrease in seed viability and vigor after storage. Electrical conductivity was higher for fresh seeds at the cotyledonary stage, than for those stored for 60 and 120 days. However, in other stages, released leachate content after 120 days of storage, increased with the advance of the collection period. Germination speed index and shoot and root lengths after storage were highest for seeds at the cotyledonary stage and stage i; unlike stages ii and iii which had short root and shoot lengths during storage. Thus, the maintenance of seed moisture content during storage was variable and dependent on the period of collection. Furthermore, the physiological quality differed among earlier and later stages. Early collection favored seed physiological quality, and may be a strategy for better conservation of A. angustifolia seeds. Rev. Biol. Trop. 64 (2): 885-896. Epub 2016 June 01.

Cloning and expression of embryogenesis-regulating genes in Araucaria angustifolia (Bert.) O. Kuntze (Brazilian Pine)

Angiosperm and gymnosperm plants evolved from a common ancestor about 300 million years ago. Apart from morphological and structural differences in embryogenesis and seed origin, a set of embryogenesis-regulating genes and the molecular mechanisms involved in embryo development seem to have been conserved alike in both taxa. Few studies have covered molecular aspects of embryogenesis in the Brazilian pine, the only economically important native conifer in Brazil. Thus eight embryogenesis-regulating genes, viz.,ARGONAUTE 1, CUP-SHAPED COTYLEDON 1, WUSCHEL-related WOX, S-LOCUS LECTIN PROTEIN KINASE, SCARECROW-like, VICILIN 7S, LEAFY COTYLEDON 1, and REVERSIBLE GLYCOSYLATED POLYPEPTIDE 1, were analyzed through semiquantitative RT-PCR during embryo development and germination. All the eight were found to be differentially expressed in the various developmental stages of zygotic embryos, seeds and seedling tissues. To our knowledge, this is the first report on embryogenesis-regulating gene expression in members of the Araucariaceae family, as well as in plants with recalcitrant seeds.

Morphology and structure of the pollen cone and pollen grain of the Araucaria species from Argentina

The pollen cone and the pollen grain of the two Argentinean species of Araucaria are described with LM, SEM and TEM. Primordia of pollen cones are formed in April and May and reach maturity by mid-October in A. angustifolia (Bert.) O. Kuntze and by mid-November in A. araucana. (Mol.) K. Koch. Characters of the mature pollen cones and microsporophylls between both taxa are clearly differentiated.Pollen grains are spheroidal-subspheroidal, inaperturate, and asaccate with granulate exine and a subequatorial annular area that corresponds to the sexine thickness. Sculpturing consists of irregularly dispersed granules that are sometimes fused to each other (A. angustifolia) or forming microrugulae (A. araucana). Microgranules and microspinules are also present. The pollen wall ultrastructure is formed by a granular ect exine and lamellated endexine. Granular elements in A. angustifolia are more loosely disposed, form more interstices, and are gradually smaller towards the endexine than in A. araucana. To asses the probable relationships within the family, we compared the pollen grains of the two Araucaria species with those of other extant genera (Agathis, Wollemia) and also with fossil pollen (Araucariacites, Balmeiopsis, Cyclusphaera, Dilwynites) attributed to Araucariaceae.