Orientador: Edvaldo Aparecido Amaral da Silva / Banca: Ceci Castilho Custodio / Banca: Camila de Aquino Tomaz / Resumo: A Brachiaria humidicola cv. BRS Tupi é a primeira cultivar de B. humidicola indicada para uso no Brasil e surge como mais uma opção para áreas úmidas de baixa e média fertilidades. C omo a maioria das gramíneas forrageiras tropicais, sementes recém - colhidas dessa cultivar são afetadas pelo fenômeno da dormência . Apesar da evidente importância da dormência em sementes recém - colhidas de Brachiaria , os mecanismos que estão envolvidos na superação da dormência que ocorre durante o armazenamento ainda são pouco elucidados. Assim, este estudo foi conduzido com o objetivo de avaliar a superação da dormência em sementes de B. humidicola cv. BRS Tupi durante diferentes períodos de armazenament o (0, 3, 6, 9, e 12 meses). Sementes de B. humidicola cv. BRS Tupi foram multiplicadas em campo e, após o processo de secagem em ambiente natural e beneficiamento , foram armazenadas. Após os períodos de armazenamento , as sementes foram avaliadas quanto as suas alterações fisiológicas através de curvas de embebição, do teor de água das partes da semente (embrião e endosperma) durante a embebição, germinação de sementes inteiras , germinação de sementes inteiras e cariops es nuas em diferentes concentrações de ácido giberélico, potencial de crescimento do embrião de cariopses nuas em restrição hídric a e germinação de sementes escarificadas. O armazenamento favorece o aumento do teor de água das partes da semente durante a e mbebição. A superação da dormência ocorre com a retirada das coberturas da semente indicando possíveis impedimentos mecânicos que são superados durante o armazenamento devido ao aumento no potencial de crescimento do embrião, provavelmente relacionado à aç ão de GA nas sementes . A escarificação química não foi eficiente na superação da dormência durante o armazenamento / Abstract: The Brachiaria humidicola cv. BRS Tupi is the first cultivar of B. humidicola indicated for use in Brazil and comes up as one more option for the humid areas of low and average fertility. As the majority of the tropical forage grass, freshly harvested se eds of this cultivar are affected by the phenomenon of dormancy. Despite the obvious importance of dormancy in freshly harvested seeds of Brachiaria , the mechanisms that are involved in overcoming dormancy that occurs during storage are still poorly unders tood. Thus, the present study was carried out with the aim to evaluate the overcoming dormancy in seeds of B. humidicola cv. BRS Tupi during different storage periods (0, 3, 6, 9, and 12 months). Seeds of B. humidicola cv. BRS Tupi were multiplied in the f ield, and after the drying process in the natural environment and processing, were stored. After the storage periods the seeds were evaluated according to its physiological changes through imbibition curves, evaluation of the water content of the seed part s (embryo and endosperm) during imbibition, germination of whole seeds , germination in different concentrations of gibberellic acid of whole seeds and naked caryopses, potential of growth of the embryo of naked caryopses in water restriction and germination of scarified seeds. The storage favors the increase of the water conten t of the parts of the seed during the imbibitions. The overcoming of dormancy happens with the removal of the seed coat showing possible mechanical barrier which is overcome during the storage due to the raise in the potential of growth of the embryo, possibly related to the action of GA on the seeds. The chemical scarific ation was not efficient in overcoming the dormancy during the storage / Mestre

No description available.

Revision of AZ1267 / 2 pp. / Alfalfa varieties differ in fall dormancy, defined as growth during the fall. Nondormant alfalfa varieties are usually planted in mild winter areas for their ability to grow in the late fall, winter, and early spring. Select alfalfa varieties that have resistance to potential pest problems. Alfalfa varieties are available that have salt tolerance or are Roundup Ready. Ratings are provided in this publication. Many of the varieties listed in this publication have been tested for yield and final stand by the University of Arizona in small plot trials.

No description available.

Cow cockle (Vaccaria hispanica [P. Mill.] Rauschert) is a summer annual species introduced to North America from Europe. It has been investigated as a potential crop for the Canadian prairies because of its ultra–fine starch, cyclo–peptides, and saponins. However, cow cockle has a long history of being a weed in Canada and may need additional scrutiny of its weediness potential before initiating commercial production. In addition, cultivating poorly domesticated species may lead to further environmental and weed management risks; hence, an understanding of the domestication status is required. The objectives of this research were to evaluate available cow cockle germplasm i) to identify populations that are best adapted to cultivation as well as the traits responsible for such adaptation, ii) to determine seed dormancy levels in cow cockle populations and to determine how temperature and light affect seed dormancy and germination, and iii) to determine whether cow cockle populations are persistent and form a seed bank. A total of 15 cultivated, weedy, and wild cow cockle populations from different parts of the world were compared for agro–morphological, seed dormancy and seed persistence characters from 2009 to 2011. In the field persistence study, two populations including weedy (Scott weedy) and cultivated (Scott) lines were included. Cluster analysis revealed three main groups among the populations based on the traits studied. Physiological maturity, seed size, plant height and seed yield differed most among populations. The cultivated populations, Pink Beauty, Turkey, PB–87, Scott and a weedy population, UMan–89 had higher seed yield, larger seeds, and greater biomass compared to the other populations. Although weedy populations showed some adaptation to cultivation, characters relating to plant architecture, seed size and yield suggested a weedy habit. Freshly matured seeds of all the populations showed high levels of primary conditional dormancy except “Mongolia”. At optimum temperature conditions for germination (10 C), the effect of temperature regime (alternating and constant) and light on seed dormancy were insignificant. The variation in optimum temperature, light, and their interactions among the cow cockle populations may be due to the plants evolving to adapt to their local environments. In the field persistence study, the weedy population had higher seedling emergence at two out of three locations and a larger residual seed bank at all the locations. Despite the differences in seed persistence between the populations, considerable numbers of seed of both weedy and cultivated lines were recovered from the soil seed bank at the end of the study. This concurs with the results of the laboratory persistence study, as both the populations had greater seed longevity (p50 values > 50 days) which suggests a field persistence of over three years. In conclusion, higher seed yield, larger seeds, and greater biomass in cultivated populations may result from certain pre–adaptation towards domestication, which may have been acquired during the process of pre–domestication cultivation. From a domestication perspective, if cow cockle were grown as a crop, the conditional dormancy may not be considered a barrier to domestication and can be viewed as a physiological mechanism to avoid germination at harvest. The major concern in cow cockle domestication would be seed persistence, as it can form a reasonably long–term seed bank. This may pose some concerns for the production of cow cockle as a crop in the Canadian Prairies. The current research suggests that cow cockle populations from Canada, although they showed some adaptation to cultivation; are largely weedy and can be considered as variants of an early introduced species which might have evolved to adapt to non–native conditions.

Seeds of many grasses and legumes from the Canadian Prairies have dormancy which prevents the germination of viable seeds in otherwise favorable conditions. Plant-derived smoke can improve germination in dormant seeds. Seeds of eight grasses, two legumes, and Lactuca sativa were investigated for the effects of seed priming in aqueous smoke solutions on germination, seedling emergence, seedling growth, and standing crop. Aqueous smoke solutions were produced by bubbling smoke generated from the incomplete combustion of wheat straw (Triticum aestivum cv. Unity) or prairie hay (Festuca hallii) through distilled water. Seeds were primed for 24 h in darkness using serial dilutions (1/1000v/v, 1/100v/v, 1/10v/v and 1/1v/v) of the aqueous smoke solutions. After priming, seeds were dried at 20°C in darkness for 7d and placed in petri dishes containing filter paper, after which 5 mL of distilled water were applied. Seeds were incubated at 10/0°C or 25/15°C in 12h light/12h darkness or 24 h darkness for 49 d. Seeds were also primed using 1/100v/v aqueous smoke solutions of wheat straw or prairie hay and seeded in the field. Non-primed seeds and those primed in distilled water (0/1v/v) were used as controls. Within species, germination varied significantly (P≤0.05) among concentrations of aqueous solutions of smoke, smoke type, light, temperature, and their interactions. Total germination of Astragalus cicer, Trifolium ambiguum, Hesperostipa comata, Stipa viridula, and Pascopyrum smithii was not changed by priming seeds. Depending on light or temperature treatments, priming seeds of Agropyron dasystachyum, Elymus junceus, Dactylis glomerata, Elymus angustus, and Festuca hallii in aqueous smoke solutions improved germination by 16%, 20%, 32%, 49%, and 50%, respectively. Priming seeds in aqueous smoke solutions reduced the number of days to 50% germination for Trifolium ambiguum, Lactuca sativa, Festuca hallii, and Stipa viridula (2 d), Elymus junceus (3 d), Dactylis glomerata (4 d), Hesperostipa comata (10 d), and Pascopyrum smithii (15 d). Priming seeds in aqueous smoke solutions increased seedling lengths (combined hypocotyl and radicle lengths) for Elymus angustus and Hesperostipa comata by 28% and 100%, respectively, but it reduced seedling lengths of Lactuca sativa, Festuca hallii, and Trifolium ambiguum. Seedlings from seeds primed in aqueous smoke solutions generated from wheat straw were longer for Lactuca sativa (83%), Elymus angustus (52%), and Hesperostipa comata (36%) as compared with prairie hay, respectively. Priming seeds interacted with smoke type to increase seedling lengths for Pascopyrum smithii (92%), Elymus junceus (100%), and Agropyron dasystachyum (100%), but it reduced seedling lengths for Astralagus cicer (26%), Trifolium ambiguum (55%), and Dactylis glomerata (90%). Exposing seeds to aqueous smoke solutions partially substituted a light requirement for germination in Pascopyrum smithii, Festuca hallii, Hesperostipa comata, Dactylis glomerata, Agropyron dasystachyum, Stipa viridula, and Elymus junceus. Priming seeds in aqueous smoke solutions increased standing crop of Dactylis glomerata by 57%, but total seedling emergence and rate of emergence of seedlings in the field were not different (P>0.05) among priming treatments. Priming seeds in aqueous smoke solutions generated from wheat straw or prairie hay can stimulate germination in Agropyron dasystachyum, Dactylis glomerata, Elymus junceus, Elymus angustus, and, Festuca hallii.

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis (Ph. D.)--Miami University, Dept. of Zoology, 2009. / Title from second page of PDF document. Includes bibliographical references (p. 41-45).

Thesis (M. Sc.)--Carleton University, 1988. / Also available in electronic format on the Internet.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 62-63.