Wagner de Melo Ferreira

MICROPROPAGATION AND GENETIC STABILITY OF A DENDROBIUM HYBRID (ORCHIDACEAE)

SummaryDendrobium hybrids have great economic importance in a number of countries. Asymbiotic seed germination and the conventional vegetative method have been commonly used by growers to propagate these plants. To overcome somaclonal variation, which is commonly exhibited by Dendrobium (Nobile group) when micropropagated from protocorm-like bodies, a protocol for propagating Dendrobium Second Love in vitro using axillary buds in the presence of thidiazuron was developed. Random amplified polymorphic DNA analysis was also carried out to check for possible genetic alterations in plants originating from six consecutive subcultures. The results revealed that the established protocol was efficient for the in vitro cloning of this orchid hybrid and the plants obtained from the six subcultures did not exhibit any type of polymorphism.

Changes in soluble carbohydrates and starch amounts during somatic and zygotic embryogenesis of Acca sellowiana (Myrtaceae)

Comparative analysis of zygotic and somatic embryogenesis of Acca sellowiana showed higher amounts of sucrose, fructose, raffinose, and myo-inositol in zygotic embryos at different developmental stages than in corresponding somatic ones. These differences were mostly constant. In general, glucose levels were significantly lower than the other soluble carbohydrates analyzed, showing minor variation in each embryo stage. Despite the presence of sucrose in the culture medium, its levels conspicuously diminished in somatic embryos compared with the zygotic ones. Raffinose enhanced parallel to embryo development, regardless of its zygotic or somatic origin. Analysis of the soluble carbohydrate composition of mature zygotic cotyledon used as explant pointed out fructose, glucose, myo-inositol, sucrose, and raffinose as the most important. Similar composition was also found in the corresponding somatic cotyledon. Total soluble carbohydrates varied inversely, decreasing in zygotic embryos and increasing in somatic embryos until the 24th d, at which time they increased rapidly about sixfold in zygotic embryos until the 27th d, a period coinciding with the zygotic proembryos formation. Such condition seems to reflect directly the variation of endogenous sucrose level, mainly because glucose and fructose diminished continuously during this time period. This means that, in terms of soluble sugars, zygotic embryo formation occurred under a situation represented by high sucrose amounts, simultaneously with low fructose and glucose levels, while in contrast, somatic embryo formation took place under an endogenous sugar status characterized by a substantial fructose enhancement. Starch levels increased continuously in zygotic embryos and decreased in somatic ones, the reverse to what was found in fructose variation. Starch accumulation was significantly higher in somatic torpedo and cotyledonary embryos than in the corresponding zygotic ones.

Propagation, growth, and carbohydrates of Dendrobium Second Love (Orchidaceae) in vitro as affected by sucrose, light, and dark

In general, plant material grown in vitro has low photosynthetic ability to achieve positive carbon balances. Therefore, a continuous supply of carbohydrates from the culture medium is required, and sucrose has been the most commonly used carbon source. In this paper, we investigate the effects of different sucrose concentrations and the presence and absence of light on the endogenous levels of soluble carbohydrates and starch as well as on the proliferation and growth of Dendrobium Second Love (Orchidaceae) in vitro. The possibility of using etiolated stem segments as a means for micropropagating this hybrid was also verified. The results obtained indicated that the presence and absence of light and the sucrose concentrations used influenced the amounts of soluble carbohydrates and starch and the proliferation of D. Second Love shoots and roots. An increase in sucrose concentration caused a progressive increase in the amounts of total carbohydrates and starch. Under both light conditions, sucrose was the main sugar found in the shoots followed by glucose and fructose. The addition of sucrose to the culture medium up to 2% and 4% was advantageous to the number of shoots produced per explant and the root longitudinal growth in the presence and absence of light, respectively. Shoot and root dry matter and the number of roots formed per explant increased as sucrose concentration was raised up to 6% in both light treatments. The use of dark-grown shoot segments proved to be a useful and reliable alternative for the micropropagation of this hybrid.

Estudo da germinação e crescimento in vitro de Hadrolaelia tenebrosa (Rolfe) Chiron & V.P. Castro (Orchidaceae), uma espécie da flora brasileira ameaçada de extinção

Orchids are seriously endangered species. For that reason, studies regarding their propagation and development are extremely important. Thus, the present study analyzed the influence of the culture medium on the in vitro germination of Hadrolaelia tenebrosa seeds, on the initial development of protocorms until they form seedlings and on seedling growth during the first twelve months in vitro. The results revealed that the ideal methodology for the in vitro culture of Hadrolaelia tenebrosa involves the use the Knudsons C medium for seed germination and seedling initial growth, and the subsequent transfer of six-month-old plants to VW medium where they should remain until acclimatization is carried out. The obtained data showed that the most efficient culture medium for seed germination of that species was not the most adequate for the development of their seedlings. Therefore, the outcomes of such studies are very important for the optimization of propagation techniques for orchid species.

Germinação e crescimento in vitro de Cattleya bicolor Lindley (Orchidaceae)

A germinacao de sementes de orquideas in vitro vem sendo utilizada desde o inicio do seculo passado. Apesar disso, o conhecimento disponivel a respeito da composicao nutricional dos meios de cultura que favorecem a germinacao e o crescimento in vitro de orquideas ainda e bastante escasso. Diante da ameaca de extincao da Cattleya bicolor e devido a escassez de conhecimento a respeito da germinacao e do crescimento in vitro dessa especie, este trabalho teve como objetivo avaliar a influencia do meio de cultura na germinacao in vitro de suas sementes, no desenvolvimento inicial dos protocormos ate a formacao das plântulas, bem como avaliar o crescimento das plântulas ate os primeiros doze meses de cultivo in vitro. Os resultados mostraram que o meio de cultura ideal para a germinacao in vitro das sementes e para o desenvolvimento inicial das plântulas de Cattleya bicolor e o de Vacin & Went. Recomenda-se que apos seis meses de cultivo as plântulas sejam transferidas para o meio MS ou VW, que promovem o desenvolvimento das plântulas, e mante-las em um destes meios de cultura ate o inicio da aclimatizacao. Tais informacoes sao de grande importância para a otimizacao do processo de propagacao das especies de orquideas nativas do Brasil.

Dark-induced hormone changes coincide with the resumption of light-inhibited shoot growth in Catasetum fimbriatum (Orchidaceae)

Catasetum fimbriatum plants cultivated in the absence of light exhibit continuous shoot growth leading to the formation of nodes and internodes. On the other hand, when these plants are incubated in the presence of light, shoot longitudinal growth is inhibited and pseudobulbs develop just below the shoot apical meristem. These facts provide evidence of a possible influence of light on mitotic cell division in the shoot apex as well as on pseudobulb initiation. The effects of light and dark on the interruption and/or maintenance of shoot apex mitotic activity and the subsequent formation of pseudobulbs in the sub-meristematic regions were investigated by means of histological and hormonal studies. The interruption of shoot apex development occurred around the 150th d of light incubation and seems to have resulted from the establishment of a strong storage sink in the region of the future pseudobulb, in detriment to the continuous activity of the shoot apical meristem. The reduced total cytokinins/IAA ratio in the apex, mainly due to high levels of IAA, could be a key factor in the interruption of cell divisions. Transfer to the dark brings about the resumption of shoot apex development of plants through the re-entrance of cells in the cell cycle which coincides with a significant increase in the total cytokinins/IAA ratio.

Asymbiotic germination, multiplication and development of Alatiglossum fuscopetalum (Orchidaceae) as affected by culture medium, sucrose and growth regulators

Germinacao assimbiotica multiplicacao e desenvolvimento de Alatiglossum fuscopetalum (Orchidaceae) influenciados pelo meio de cultura, sacarose e reguladores de crescimento. Este trabalho teve como objetivo estudar a germinacao e o desenvolvimento in vitro de Alatiglossum fuscopetalum (Hoehne) Baptista. Foram avaliados os efeitos dos meios Murashige/Skoog (MS e ½MS), Knudson (KN), e Vacin/ Went (VW) na germinacao. Analisou-se tambem a infl uencia desses meios na multiplicacao e crescimento de plântulas com 90 dias de idade, e de diferentes concentracoes de sacarose, benziladenina [BA] e acido indolilbutirico [AIB] na multiplicacao e crescimento de plantas com 120 dias de idade. O meio ½MS proporcionou a maior germinabilidade. O meio MS foi superior aos demais em relacao ao crescimento de plântulas de 90 dias, enquanto que o ½MS foi o mais efi caz para a multiplicacao e crescimento de plantas de 120 dias. Concentracoes de 1% a 3% de sacarose favoreceram o crescimento. Para a proliferacao de brotos e crescimento radicial os melhores tratamentos foram 1 mg L-1 de BA e 2 mg L-1 de AIB, respectivamente.

Growth and nutrient accumulation in mycorrhized papaya seedlings cultivated in a phosphorus-fertilized substrate

The indiscriminate use of mineral fertilizers in papaya orchards has increased production costs, and the use of arbuscular mycorrhizal fungi is a promising alternative to reduce such expenses. Therefore, the present research aimed at studying the efficiency of arbuscular mycorrhizal fungi (AMF) on dry matter and nutrient accumulation in Sunrise Solo papaya seedlings, by applying doses of P2O5 (triple superphosphate) that are harmful to the symbiosis. The experiment was carried out in a protected environment and was set up in a randomized block design with four replications, and consisted of four P2O5 doses (0, 672, 1386 and 2100 mg dm-3), three mycorrhizal fungi species (Gigaspora margarita, Entrophospora colombiana and Scutellospora heterogama) and the control treatment (mycorrhiza-free). Shoot and root dry matter as well as nitrogen, phosphorus and potassium contents in leaf and root tissues were assessed. Mycorrhizal inoculation promoted a 30% increase in shoot dry matter in relation to the control treatment. Mycorrhizal fungi promoted increases in leaf and root nitrogen content up to 672 mg dm-3 P2O5. Inoculation of E. colombiana favored the highest gains in root and shoot dry matter. P2O5 fertilization increased foliar and root phosphorus content.

Crescimento inicial de Parkia platycephala (Benth.) e Enterolobium timbouva (Mart.) sob condições de campo numa área de Cerrado

Este trabalho teve como objetivo analisar o crescimento inicial de Parkia platycephala e de Enterolobium timbouva (Mimosaceae), especies arboreas nativas de Cerrado, em uma area de Cerrado sentido restrito, no municipio de Porto Nacional, Tocantins. Foram analisados 20 individuos, com leituras realizadas a cada 30 dias, de fevereiro de 2008 a fevereiro de 2010, observando-se as seguintes variaveis: numero de folhas, altura da planta e diâmetro do caule. Entre agosto de 2008 e fevereiro de 2010, estudou-se tambem a dinâmica foliar, para a qual foram selecionados, aleatoriamente, cinco individuos de cada especie, nos quais foram escolhidos tres ramos e todas as suas folhas foram marcadas. Para cada folha marcada, foram anotados os periodos de natalidade e de abscisao. Avaliou-se, ainda, a herbivoria foliar, por meio de uma escala de quatro classes com intervalos de 25% entre elas. De acordo com os dados analisados, pode-se verificar que P. platycephala e E. timbouva apresentaram maior producao de folhas, bem como maior crescimento em altura, no periodo chuvoso. Em relacao ao diâmetro, P. platycephala apresentou resultados superiores aqueles observados em E. timbouva. A taxa de crescimento relativo apresentou aumentos mais pronunciados durante o periodo chuvoso, em ambas as especies. No que se refere a herbivoria, tambem foi verificado um aumento em sua intensidade, no periodo chuvoso, nas duas especies. Como elas foram expostas a condicoes ambientais semelhantes, a maior taxa de crescimento relativo, observada em P. platycephala, pode ser atribuida as suas caracteristicas fisiologicas e anatomicas, que, dentre outros fatores, contribuiram para menor predacao por herbivoros.

Caracterização anatômica e micromorfométrica em folhas de Caryocar brasiliense

The current study aims to study the anatomy and micromorphometry of C. brasiliense leaves in three Cerrado (savanna) vegetation-types: dense, typical and sparse) in the municipality of Porto Nacional-TO. Samples were collected, fixed and stored in alcohol 70%. Transverse, longitudinal and paradermal sections of the median leaflet were prepared for anatomical and micromorphometric studies using standard techniques. C. brasiliense leaflets show uniestratified epidermis covered by thick cuticle on the adaxial surface and by paracytic stomata and multicellular non-glandular trichomes on the abaxial surface. The mesophyll is formed by two or three layers of palisade parenchyma adaxially and spongy parenchyma abaxially. The vascular bundle is of the collateral type and the accessory bundles show a sheath extending into the epidermides. The micromorphometric analyses pointed to significant differences in the thickness of both adaxial epidermis and spongy parenchyma in all specimens from the three vegetation-types. The highest averages were found in the leaflets of sparse cerrado plants, suggesting that environmental factors may have an influence over the plants morphological responses.current study aims to study the anatomy and micromorphometry of C. brasiliense leaves in three Cerrado (savanna) vegetation-types: dense, typical and sparse) - in the municipality of Porto Nacional-TO. Samples were collected, fixed and stored in alcohol 70%. Transverse, longitudinal and paradermal sections of the median leaflet were prepared for anatomical and micromorphometric studies using standard techniques. C. brasiliense leaflets show uniestratified epidermis covered by thick cuticle on the adaxial surface and by paracytic stomata and multicellular non-glandular trichomes on the abaxial surface. The mesophyll is formed by two or three layers of palisade parenchyma adaxially and spongy parenchyma abaxially. The vascular bundle is of the collateral type and the accessory bundles show a sheath extending into the epidermides. The micromorphometric analyses pointed to significant differences in the thickness of both adaxial epidermis and spongy parenchyma in all specimens from the three vegetation-types. The highest averages were found in the leaflets of sparse cerrado plants, suggesting that environmental factors may have an influence over the plants morphological responses.