Albinism in plants - far beyond the loss of chlorophyll: Structural and physiological aspects of wild-type and albino royal poinciana (Delonix regia) seedlings.

The partial or complete loss of chlorophylls, or albinism, is a rare phenomenon in plants. In the present study, we provide the first report of the occurrence in albino Delonix regia seedlings and describe the morpho-physiological changes associated with albinism. Wild-type (WT) and albino seedlings were characterized. Leaflets samples were processed following common procedures for analysis with light, scanning and transmission electron microscopy. The chlorophyll a fluorescence parameters and the carbohydrate, lipid and soluble protein content were also determined in leaf and cotyledon samples of both albino and WT seedlings. Albino seedlings showed reduced growth. They also had lower chlorophyll and protein content in foliar tissues than WT seedlings, in addition to lower concentrations of lipids and carbohydrates stored in cotyledons. The chloroplasts of albino seedlings were poorly developed, with an undefined internal membrane system and the presence of plastoglobules. Wild-type seedlings had a uniseriate and hypoestomatic epidermis. The mesophyll was dorsiventral, consisting of a layer of palisade parenchyma and two to four layers of spongy parenchyma. In albino seedlings, the spongy parenchyma was compact, with few intercellular spaces, and the thickness of the mesophyll was larger, resulting in increased thickness of the leaf blade. Albino seedlings had higher stomatal density and number of pavement cells, although the stomata had smaller dimensions. In addition to the partial loss of chlorophylls, albino D. regia showed changes at physiological and structural levels, demonstrating the crucial nature of photosynthetic pigments during the development and differentiation of plant leaf tissues/cells.

Pollination ecology of two species of Elleanthus (Orchidaceae): novel mechanisms and underlying adaptations to hummingbird pollination.

Relationships among floral biology, floral micromorphology and pollinator behaviour in bird-pollinated orchids are important issues to understand the evolution of the huge flower diversity within Orchidaceae. We aimed to investigate floral mechanisms underlying the interaction with pollinators in two hummingbird-pollinated orchids occurring in the Atlantic forest. We assessed floral biology, nectar traits, nectary and column micromorphologies, breeding systems and pollinators. In both species, nectar is secreted by lip calli through spaces between the medial lamellar surfaces of epidermal cells. Such a form of floral nectar secretion has not been previously described. Both species present functional protandry and are self-compatible yet pollinator-dependent. Fruit set in hand-pollination experiments was more than twice that under natural conditions, evidencing pollen limitation. The absence of fruit set in interspecific crosses suggests the existence of post-pollination barriers between these sympatric co-flowering species. In Elleanthus brasiliensis, fruits resulting from cross-pollination and natural conditions were heavier than those resulting from self-pollination, suggesting advantages to cross-pollination. Hummingbirds pollinated both species, which share at least one pollinator species. Species differences in floral morphologies led to distinct pollination mechanisms. In E. brasiliensis, attachment of pollinarium to the hummingbird bill occurs through a lever apparatus formed by an appendage in the column, another novelty to our knowledge of orchid pollination. In E. crinipes, pollinarium attachment occurs by simple contact with the bill during insertion into the flower tube, which fits tightly around it. The novelties described here illustrate the overlooked richness in ecology and morphophysiology in Orchidaceae.

Capacidade de enraizamento de estacas de Maytenus muelleri Schwacke com a aplicação de ácido indol butírico relacionada aos aspectos anatômicos / Rooting capacity of Maytenus muelleri Schwacke cuttings with indolebutyric acid application related to anatomical aspects

A espinheira-santa (Maytenus muelleri - Celastraceae) é a planta medicinal nativa do Sul do Brasil, cujas folhas são tradicionalmente utilizadas pela medicina popular para o tratamento de úlceras e outros problemas gástricos. Existem poucos trabalhos publicados sobre a produção de mudas e técnicas de propagação vegetativa da espécie. A propagação de espinheira-santa por estaquia poderia ser um método eficiente para obtenção de material homogêneo, com características genéticas desejáveis, produzido a partir de plantas matrizes selecionadas. O presente trabalho teve por objetivo estudar os efeitos da aplicação de ácido indol butírico (AIB), em solução e em pó, no enraizamento de estacas de espinheira-santa coletadas nas quatro estações do ano (abril/2005 a janeiro/2006), bem como averiguar, por meio de análises anatômicas e histoquímicas das estacas, a presença de possíveis impedimentos à iniciação do enraizamento adventício. Estacas provenientes de ramos de plantas matrizes de seis anos cultivadas da Estação Experimental do Canguiri, Pinhais, PR, foram coletadas e tratadas com AIB (0, 1500, 3000 mg L-1 ou mg kg-1), em solução alcoólica (50 por cento v/v) e em talco. Aos 365 dias foram avaliadas as porcentagens de estacas enraizadas e mortas, número e comprimento médio de raízes formadas por estaca. Análises anatômicas e histoquímicas com lugol e cloreto férrico foram realizadas. A estação mais promissora para o enraizamento foi o verão/2006 com 62,50 por cento para o tratamento controle, devido à menor lignficação dos ramos no período de intenso crescimento vegetativo. O número médio de raízes formadas por estaca foi de 6,94 (solução) e o comprimento médio de raízes formadas/estaca chegou a 4,82 cm nesta mesma estação. As concentrações de AIB aplicadas não foram eficientes na indução radicial, independentemente do modo de aplicação. Foi detectada a presença de uma camada quase contínua de fibras e braquiesclereídes, a qual constitui barreira anatômica à indução radicial. Os testes histoquímicos revelaram a presença de amido e de compostos fenólicos nas estacas, em todas as estações do ano. A dificuldade ou demora no enraizamento não pode ser justificada pela falta de reservas de amido nos tecidos das estacas, mas pode ser justificada pela presença de compostos fenólicos, possivelmente do grupo dos monofenóis, que causam a degradação do AIA, interferindo negativamente na indução do enraizamento.

"Espinheira-santa" (Maytenus muelleri - Celastraceae) is a medicinal plant native to Southern Brazil, the leaves of which are traditionally used in popular medicine for the treatment of stomach ulcers and other gastric problems. There are few published studies about seedling production and vegetative propagation techniques for this species. The propagation of "espinheira-santa" by cuttings could be an efficient method to obtain homogeneous material, with desirable genetic characteristics, produced from selected mother plants. This paper aimed to study the effects of indolebutyric acid (IBA) application, in solution and in powder, on the rooting of "espinheira-santa" cuttings, collected in four seasons (April/2005 to January/2006), as well as to investigate, by means of cutting anatomical and histochemical analyses, the presence of possible impediments to adventitious rooting initiation. Cuttings from branches of six-year mother plants grown at "Estação Experimental do Canguiri", Pinhais, Paraná State, Brazil, were collected and treated with IBA (0, 1500, 3000 mg L-1 or mg kg-1) in alcoholic solution (50 percent v/v) and in powder. After 365 days, the percentages of rooted and dead cuttings, the number and mean length of roots/cutting were evaluated. Anatomical and histochemical analyses were performed with lugol and ferric chloride. The most promising season for rooting was Summer/2006, with 62.50 percent of rooting for the control treatment, due to the lesser lignification degree of branches in intense vegetative growth period. The mean number of roots/cutting was 6.94 (solution) and the mean length of roots/cutting was 4.82 cm in that same season. The applied IBA concentrations were not efficient in inducing root growth, regardless of the application method. An almost continuous layer of fibers and stone cells was detected, constituting an anatomical barrier for rooting induction. The histochemical tests revealed the presence of starch and phenolic compounds in cuttings, in all seasons. The difficulty or delay in rooting cannot be justified by the absence of starch reserve in the cutting tissues but by the presence of phenolic compounds, possibly of the group of monophenols, which cause IAA degradation, negatively affecting rooting induction.