-(Phenology of leguminous trees in an area of cerrado in the northeast of Maranhão). The phenological patterns of trees from cerrado, savannah and others seasonally dry forest are not well known and causes for observed periodicity are still obscure; it is said to be caused either by abiotic factors like precipitation or to biotic ones or even both, or also enforced by phylogenetic restriction. In an area of cerrado in the far northeast of Maranhão, the ten most frequent leguminous trees were monitored during twenty-two months. The phenological records were made montly in a sample of ten individuals of each species. Either vegetative or reproductive growth are periodical and seasonal events and in the most species flowering occur during the dry season simultaneous to leaves renewal. Most species produce fruits during the wet period and the propagules are dispersed almost exclusively during the dry one. Tree phenological patterns are discernible: species that renew their leaves and bloom early during the dry season, fruiting and dispersing their propagules at the same season (1), species that renew their leaves late in the dry season, flowering at this time (2) or flowering during the wet season (3), fruiting in the wet period and dispersing their propagules during the following dry one. Periods of vegetative growth and dormancy seem to occur alternately more synchronised with variation of the photoperiod, thermoperiod, and irradiance, than seasonal variations of water availability. Phenological patterns, flowering and fruting periods vary inter and intra families considered as monophyletic, being the only convergence, at this taxonomic level, the synchronisation of the propagules dispersal in the dry season. The vegetative reproduction does not seem to be a common event in the leguminous species studied.RESUMO -(Fenologia de leguminosas arbóreas em uma área de cerrado marginal no nordeste do Maranhão). Os padrões fenológicos da vegetação arbórea do cerrado, savanas e demais formações florestais periodicamente secas ainda são pouco conhecidos, assim como são ainda obscuras as causas da periodicidade observada, ora atribuída a fatores abióticos, ora a fatores bióticos, ou a ambos, ou ainda determinada por restrição filogenética. Em uma área de cerrado marginal no extremo nordeste do Maranhão foram estudadas, durante vinte e dois meses, as dez espécies de leguminosas arbóreas mais freqüentes. As observações foram mensais em uma amostra de dez indivíduos por espécie. Nestas leguminosas, tanto o crescimento vegetativo quanto o reprodutivo são eventos periódicos e sazonais e, na maioria das espécies, a floração ocorre durante a estação seca sendo simultânea à renovação das folhas. Três padrões fenológicos podem ser distinguidos: espécies que renovam suas folhas e florescem precocemente na seca, frutificam e dispersam seus propágulos ainda nesta estação (1), espécies que renovam suas folhas tardiamente na seca e florescem nesta ocasião (2) ou florescem na estação chuvosa (3), frutificando na estação chuvosa e d...
A Importância das matas ciliares na manutenção dos recursos bióticos e abióticos e o estado avançado de degradação destes ecossistemas ripários justificam o desenvolvimento de técnicas de reflorestamento em larga escala. Neste trabalho foram selecionadas seis espécies arbóreas nativas e comparada a sobrevivência em função da distância do leito do rio utilizando-se duas metodologias de reflorestamento: plantio de mudas e semeadura direta a lanço. Estimativas das taxas de germinação potencial, germinação no campo, e as taxas de crescimento relativo das plântulas (TCR), em viveiro, foram utilizadas como critério eletivo e correlacionadas com os dados de sobrevivência no campo. A sobrevivência foi estimada após seis meses do plantio de 108 mudas por espécies e após semeadura de 10800 sementes/espécie numa área desmatada de 5400 m 2 da mata ciliar às margem do rio Mearim. No método do plantio de mudas, destacam-se, Triplaris surinamensis Cham., Anadenanthera Macrocarpa (Benth.) Brenam. e Tabebuia sp., a primeira com altas taxas de germinação potencial, de crescimento em viveiro e sobrevivência no campo e as demais satisfazendo um ou outro destes critérios. Neste método, sobrevivência não se correlaciona com TCR e não é afetada pela distância do leito do rio. No método de semeadura direta, destacam-se T. surinamensis, e Enterolobium contortisiliquum (Vell.) Morong com maior sobrevivência a qual é maior em áreas mais distantes do rio e se correlaciona positivamente com a germinação no campo e com a TCR. Comparativamente, T. surinamensis e E. contortisiliquum são mais indicadas para reflorestamento a partir de semeadura direta enquanto A. macrocarpa, Tabebuia sp. e Senna spectabilis (DC.) Irwin et Barn para reflorestamento a partir do plantio de mudas. PALAVRAS -CHAVE:Recuperação de mata ciliar, Seleção de espécies, Plantio de mudas, Semeadura direta, Sobrevivência. Riparian forest restoration along the Mearim river in the municipality of Barra do Corda -MA: species selection and comparison of forest recovery methodologies ABSTRACTThe importance of riparian forests in the maintenence of biotic and abiotic resources and the advanced state of degradation of these ecosystems justify the development of restoration techniques on a large scale. In this study six native arboreal species were selected, and the survival of each was compared in relation to their distance from the river, through two restoration techniques: the seedlings plantation method and direct sowing. The germination potential estimates in laboratory (potential germination) and field, and the relative growth rates (RGR) of seedlings, in nursery, were used as elective criteria, and were correlated to survival data in the field. The survival was estimated after six months of plantation of 108 seedlings per species, and from direct sowing of 10800 seeds/species in a 5400 m 2 lodged area of the Mearin River riparian forest. By the method of seedling plantation, Triplaris surinamensis Cham., Anadenanthera Macrocarpa (Benth.) Brenam. and Tabebuia sp. stood out, the...
-(Predation and parasitism on seeds of two populations of Parkia platycephala Benth., from "cerrado" areas in Northeast Brazil). Two morphologically distinct populations of Parkia platycephala with different densities in the Cerrado, have their seeds preyed by larvae of the coleoptera Acanthoscelides imitator Kingsolver 1985, which are parasitized by the hymenoptera Stenocorse bruchivora Crawford 1900. In this study the effects of nesting, predation, and parasitism on seed germination were evaluated, and the rates of these events were compared between the two populations. Germination tests were conducted in laboratory, using four replicates of 50 seeds. Nesting, predation and parasitism rates for each population were estimated by sampling seeds from 20 fruits per individual, and from 15 individuals per population. The seeds of P. platycephala exhibit dormancy enforced by the seed coat. The nesting breaks the dormancy, and the pre-dispersal predation of seeds by the coleoptera larvae make them inviables. The larvae predation is biologically controlled by the hymenoptera parasitism. The seed predation rates for each population were 28% and 12%, respectively, being significantly higher in the white population, which produces more and smaller seeds per fruit than the other population. The highest predation occurs because of the highest nesting rate by the coleopterans, which is positively correlated with the number of seeds per fruit. The parasitism rate was 8%, approximately, and was not significantly different between the populations. The results indicate that the differences between the densities of these populations were not related to the biological interactions, as seed predation and parasitism.Key words -"cerrado", germination, parasitism, Parkia platycephala, seed predation RESUMO -(Predação e parasitismo em sementes de duas populações de Parkia platycephala Benth., em áreas de cerrado no nordeste do Brasil). Duas populações morfologicamente distintas de Parkia platycephala, que diferem quanto à densidade no cerrado, têm suas sementes predadas por larvas de coleópteros Acanthoscelides imitator Kingsolver 1985 as quais são parasitadas por himenópteros Stenocorse bruchivora Crawford 1900. Neste trabalho determinou-se o efeito da nidificação, predação e parasitismo na germinação das sementes, comparando-se as taxas destes eventos entre as duas populações. Os testes de germinação foram conduzidos em laboratório, utilizando-se quatro repetições de 50 sementes. As taxas de nidificação, predação e parasitismo nas populações no cerrado foram estimadas em amostras de sementes colhidas de 20 frutos por indivíduo, em 15 indivíduos por população. As sementes de P. platycephala exibem dormência imposta pelo tegumento. A nidificação quebra a dormência e a predação pré-dispersão das sementes por larvas dos coleópteros as inviabiliza, sendo biologicamente controlada pelo parasitismo das larvas pelos himenópteros. A taxa de predação das sementes foi de 28% e 12% respectivamente, sendo significativamente maior na pop...
The article describes the somatic polymorphism in Crotalaria retusa L. seeds.Each individual may produce yellow dormant seeds, brown quiescent seeds and unviable dark brown ones. Therefore, regarding physiology it is a dimorphism. We show that autogamy reduces dimorphism, favoring the formation of dormant seeds. However, the significant variation in dimorphism is seasonal as consequence of increased viability of dormant seeds under drier weather conditions. The variation is a phenotypic response to changes of humidity in the environment during plant reproduction, a mechanism inducing the prevalence of dormant seeds in the dry season and quiescent seeds during the rainy season. The seasonal alternation between dormancy and quiescence in seasonally dry environments has an apparent adaptive value. The chromatic polymorphism increases on the more humid coast and during the rainy season, due to increased mortality of dormant seeds under wetter weather conditions. Unviable seeds accumulate oxidized phenols in their seed coat that possibly act as induced chemical defenses. Its proportion increases with humidity, accentuating polymorphism, also in response to the increase in the predation rate by larvae of U. ornatrix during the rainy season.
-(Reproductive strategy of Cochlospermum orinocense (Kunth) Steud.: phenology, fl oral biology and breeding system of an Amazonian forest pioneer species). Cochlospermum orinocense (Kunth) Steud. is an arboreal species found in forest edges, canopy gaps and secondary forests. Phenology, fl oral biology and breeding system data was gathered at the edge of an 80 ha primary terra-fi rme Amazonian forest fragment in the São Luís Island, Maranhão state. Cochlospermum orinocense is a deciduous species which fl ower annually, showing intense and synchronized fl owering early in the dry season. Its hermaphrodite and slightly zygomorphic fl owers are arranged in terminal infl orescences and last only one day. Each ovary has on average 250 ovules and the androecium about 160 poricidal dehiscence anthers presenting 81.6% viable pollen and P/O ratios of 16,019.2. Anthesis is diurnal and the fl owers are pollinated mainly by solitary bees of the species Centris spp. Cochlospermum orinocense is self-compatible (ISI = 0.98) with high reproductive effi cacy (RE = 0.81) and reduced or null apomixis. Clustered distribution in deciduous trees together with intense and synchronized fl owering in the dry season leads to highly effi cient pollination. Fecundity is thus limited to resources constraints and not by pollen availability. Geitonogamy, the commonest form of endogamy, may assure the reproductive success of isolated individuals in the forest but leads to endogamic depression. The high density clustering often found in this species encourages allogamy and may allow high reproductive effi ciency and higher fecundity as endogamic depression is minimized.Key words -Cochlospermum orinocense, geitonogamy, inbreeding depression, mixed mating system RESUMO -(Estratégia reprodutiva de Cochlospermum orinocense (Kunth) Steud.: fenologia, biologia fl oral e sistema de cruzamento em uma espécie pioneira de fl orestas na Amazônia). Cochlospermum orinocense (Kunth) Steud. é uma espécie arbórea freqüente em clareiras, na borda da fl oresta e em fl orestas secundárias na Amazônia. Dados da fenologia, biologia fl oral e sistema de cruzamento foram obtidos em indivíduos na borda de um fragmento de 80 ha de fl oresta Amazônica primária, de terra fi rme, na ilha de São Luís, MA. Cochlospermum orinocense é uma espécie decídua com fl oração anual precoce, intensa e sincronizada na estação seca. Suas fl ores hermafroditas e levemente zigomorfas estão dispostas em infl orescências terminais e têm duração de um dia. Cada ovário possui em média 250 óvulos e o androceu é composto por cerca de 160 anteras, de deiscência poricida, apresentando 81,6% de pólen viável e razão P/O de 16.019,2. A antese é diurna e as fl ores são polinizadas predominantemente por abelhas solitárias Centris spp. A espécie é autocompatível (IAI = 0,98) com alta efi cácia reprodutiva (ER = 0,81), sendo a apomixia reduzida ou nula. Distribuição agrupada e fl oração intensa e sincronizada na seca, em árvores decíduas, induzem alta efi ciência na polinização, sendo a fecundi...
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