Comparative adventitious root development in pre-etiolated and flooded Arabidopsis hypocotyls exposed to different auxins

Adventitious roots (ARs) emerge from stems, leaves or hypocotyls, being strategic for clonal propagation. ARs may develop spontaneously, upon environmental stress or hormonal treatment. Auxins strongly influence AR development (ARD), depending on concentration and kind. However, the role of different types of auxin is rarely compared at the molecular level. Rooting triggered by light exposure and flooding was examined in intact etiolated Arabidopsis thaliana hypocotyls treated with distinct auxin types. Morphological aspects, rooting-related gene expression profiles, and IAA immunolocalization were recorded. NAA and 2,4-D effects were highly dose-dependent; at higher concentrations NAA inhibited root growth and 2,4-D promoted callus formation. NAA yielded the highest number of roots, but inhibited elongation. IAA increased the number of roots with less interference in elongation, yielding the best overall rooting response. IAA was localized close to the tissues of root origin. Auxin stimulated ARD was marked by increased expression of PIN1 and GH3.3. NAA treatment induced expression of CYCB1, GH3.6 and ARF8. These NAA-specific responses may be associated with the development of numerous shorter roots. In contrast, expression of the auxin action inhibitor IAA28 was induced by IAA. Increased PIN1 expression indicated the relevance of auxin efflux transport for focusing in target cells, whereas GH3.3 suggested tight control of auxin homeostasis. IAA28 increased expression during IAA-induced ARD differs from what was previously reported for lateral root development, pointing to yet another possible difference in the molecular programs of these two developmental processes.Plant science

Amido no megagametófito de Araucaria angustifolia (Bert.) O. Ktze: degradação durante a germinação e desenvolvimento do esporófito Starchy reserve of the megagametophyte of Araucaria angustifolia (Bert.) O. Ktze: mobilization during germination and on the developing sporophyte

O pinheiro brasileiro possui um diásporo de grandes dimensões, o pinhão, rico em reservas amiláceas. A mobilização dessas reservas pelo embrião foi quantificada em secções transversais do megagametófito, em cinco estágios de desenvolvimento da plântula, sob dois tratamentos, na luz e no escuro. Na luz, o consumo das reservas do megagametófito pela plântula é mais rápido do que no escuro e, existe uma tendência ao consumo do amido realizar-se primeiro na região do megagametófito próxima ao embrião.<br>The parana pine has a very large dispore, the "pinhão", rich in starchy reserves. The mobilization of these reserves by the embryo was quantified in transversal sections of the megagametophyte, in five stages of seedling development, sampled in the light and in the darkness. The consuption of starch grains was in plantlets grown in light than those grown in darkness. There was a tendency to quicker use up of the the megagametophyte starch near to embryo