RESUMO
Chenopodium hircinum, the putative wild ancestor of quinoa, is a source of traits that could improve the tolerance of crop quinoa to high temperatures. However, seeds of C. hircinum have physiological dormancy (PD), which is an obstacle for plant propagation and use in breeding programs. We studied the intraspecific variability in morpho-anatomical traits of embryo covering structures and their association with PD. We also evaluated the effects of different dormancy-breaking treatments on PD alleviation and germination. Seeds were dispersed with a remnant perianth and a persistent pericarp that could be removed by scraping. The seed coat was formed by palisade cells impregnated with tannins, and the seed contained a thin layer of peripheral endosperm surrounding the embryo. In our investigation, the thickness of the pericarp (P) and/or seed coat (SC) varied among populations. Populations with higher P and/or SC thickness showed lower percentages of germination and water absorption. The combined dormancy-breaking treatment (bleach + perforated coverings + gibberellic acid) promoted dormancy release and increased germination. C. hircinum seeds showed non-deep physiological dormancy. Based on previous knowledge about quinoa, and our results, we conclude that embryo coverings, especially the seed coat, have an important role in dormancy control, imposing a mechanical restraint on radicle emergence.
RESUMO
Seed germination in Melocactus and other cactus species is hampered by dormancy. However, most studies failed to achieve high seed-germination rates, suggesting a complex mechanism of dormancy in Cactaceae. Thus, the objective of this study was to evaluate whether factors such as light and phytoregulators overcome the dormancy in the seeds of the friar's crown cactus (Melocactus zehntneri). Two consecutive experimental sets were designed: one with seed germination under filter paper conditions and different wavelengths and Photosynthetically Photon Flux Densities (PPFDs); and one in vitro experiment using a culture medium to evaluate the influence of different phytoregulators, such as gibberellic acid (GA3), benzylaminopurine (BAP) and ethephon (ET), both in the germination of seeds of M. zehntneri. Seeds of M. zehntneri are positive photoblastic. Red light and gradual increases in PPFD resulted in the highest germination rates (60.8-61.7%) and germination speed index (4.4-4.5). In vitro seeding in culture media increased the germination percentage to 76% in control without phytoregulators. Ethephon showed a major effect in releasing the germination of dormant seeds of M. zehntneri, totaling 98% of seeds germinated under in vitro conditions, while GA3 and BAP showed minor or no effect on germination. The present study resulted in an efficient in vitro technique for germination and a better understanding of cacti seed dormancy.
RESUMO
Nas sementes de anonáceas, há substâncias inibidoras de germinação que provocam dormência e que, juntamente com um tegumento resistente e impermeável, proporcionam fatores antagônicos à germinação rápida e uniforme. Objetivou-se neste trabalho estudar o efeito da escarificação mecânica e embebição de sementes em ácido giberélico sobre emergência e crescimento inicial de plântulas de biribá. O experimento foi conduzido no Setor de Horticultura da Escola de Agronomia, Universidade Federal de Goiás (EA/UFG), Goiânia, GO. Os tratamentos consistiram da combinação dos fatores escarificação (sementes escarificadas mecanicamente ou não) e embebição de sementes por 20 horas, em concentrações crescentes de ácido giberélico (0, 125, 250, 500 e 1000mg L-1), em delineamento experimental de blocos ao acaso. As caraterísticas avaliadas foram a porcentagem e índice de velocidade de emergência de plântulas aos 24, 34 e 43 dias após a semeadura, o comprimento da raiz principal e da parte aérea, a massa seca das raízes, da parte aérea e total de plântulas. A escarificação mecânica em sementes de biribá promove maior porcentagem e índice de velocidade de emergência de plântulas. O aumento das concentrações de ácido giberélico incrementa linearmente a percentagem e o índice de velocidade de emergência, além do comprimento da raiz principal e da parte aérea de plântulas. Por permitir emergência mais rápida e consequente ganho de tempo na produção de mudas, recomenda-se que sementes de biribá sejam escarificadas.
In Annonaceae seed germination there inhibitory substances that cause dormancy, which together with a tough seed coat and antagonistic factors provide the rapid and uniform germination. The objective of this research was to study the effect of mechanical scarification and seed soaking in gibberellic acid on emergence and early growth of Biribá plantlets . The experiment was conducted in the Horticulture Sector of the School of Agronomy, Federal University of Goiás (EA/UFG), Goiânia, GO. The seeds used in the test were manually extracted from fruits harvested in the municipality of Itapuranga, GO. Treatments included a combination of factors scarification (seeds scarified mechanically or not) and seed soaking for 20 hours with increasing concentrations of gibberellic acid (0, 125, 250, 500 and 1000mg L-1) in experimental design of randomized blocks. The characteristics evaluated were the percentage and emergency speed index of plantlets at 24, 34 and 43 days after sowing, the length of the main root and aerial part, dry weight of root, shoot and total of plantlets. The mechanical scarification in Biribá seeds promotes higher percentage and of plantlets emergence speed index. Increased concentrations of gibberellic acid linearly increase the percentage and the emergency speed index and the length of the main root and shoots of plantlets. Allowing more rapid emergence and consequently saving time in the production of seedlings, it is recommended scarification of biribá seeds.
RESUMO
Nas sementes de anonáceas, há substâncias inibidoras de germinação que provocam dormência e que, juntamente com um tegumento resistente e impermeável, proporcionam fatores antagônicos à germinação rápida e uniforme. Objetivou-se neste trabalho estudar o efeito da escarificação mecânica e embebição de sementes em ácido giberélico sobre emergência e crescimento inicial de plântulas de biribá. O experimento foi conduzido no Setor de Horticultura da Escola de Agronomia, Universidade Federal de Goiás (EA/UFG), Goiânia, GO. Os tratamentos consistiram da combinação dos fatores escarificação (sementes escarificadas mecanicamente ou não) e embebição de sementes por 20 horas, em concentrações crescentes de ácido giberélico (0, 125, 250, 500 e 1000mg L-1), em delineamento experimental de blocos ao acaso. As caraterísticas avaliadas foram a porcentagem e índice de velocidade de emergência de plântulas aos 24, 34 e 43 dias após a semeadura, o comprimento da raiz principal e da parte aérea, a massa seca das raízes, da parte aérea e total de plântulas. A escarificação mecânica em sementes de biribá promove maior porcentagem e índice de velocidade de emergência de plântulas. O aumento das concentrações de ácido giberélico incrementa linearmente a percentagem e o índice de velocidade de emergência, além do comprimento da raiz principal e da parte aérea de plântulas. Por permitir emergência mais rápida e consequente ganho de tempo na produção de mudas, recomenda-se que sementes de biribá sejam escarificadas.(AU)
In Annonaceae seed germination there inhibitory substances that cause dormancy, which together with a tough seed coat and antagonistic factors provide the rapid and uniform germination. The objective of this research was to study the effect of mechanical scarification and seed soaking in gibberellic acid on emergence and early growth of Biribá plantlets . The experiment was conducted in the Horticulture Sector of the School of Agronomy, Federal University of Goiás (EA/UFG), Goiânia, GO. The seeds used in the test were manually extracted from fruits harvested in the municipality of Itapuranga, GO. Treatments included a combination of factors scarification (seeds scarified mechanically or not) and seed soaking for 20 hours with increasing concentrations of gibberellic acid (0, 125, 250, 500 and 1000mg L-1) in experimental design of randomized blocks. The characteristics evaluated were the percentage and emergency speed index of plantlets at 24, 34 and 43 days after sowing, the length of the main root and aerial part, dry weight of root, shoot and total of plantlets. The mechanical scarification in Biribá seeds promotes higher percentage and of plantlets emergence speed index. Increased concentrations of gibberellic acid linearly increase the percentage and the emergency speed index and the length of the main root and shoots of plantlets. Allowing more rapid emergence and consequently saving time in the production of seedlings, it is recommended scarification of biribá seeds.(AU)