Two New Species of Nematodes (Rhabditida: Diplogasteridae and Rhabditidae) Parasites of Gryllodes laplatae (Orthoptera: Gryllidae) in Argentina

Cephalobium magdalensis n. sp. (Rhabditida: Diplogasteridae) found in Magdalena, Buenos Aires, and Cruznema lincolnensis n. sp. (Rhabditida: Rhabditidae) found in Lincoln, Buenos Aires, parasitizing the cricket Gryllodes laplatae (Orthoptera: Gryllidae) are described and illustrated. C. magdalensis n. sp. is characterized by having the excretory pore between the pseudobulb and the basal bulb and seven pairs of postanal papillae in the male. C. lincolnensis n. sp. can be distiguished by having meanly two pairs of preanal papillae, one pair of adanal papillae and six pairs of postanal papillae in the male.

Effects of light stress on the growth of the epiphytic orchid Cattleya forbesii Lindl. X Laelia tenebrosa Rolfe

Considering the performance of CAM epiphytes under high levels of radiation or in shaded environments, with growth rate proportional to light intensity, the objective of this work was to evaluate the effects of long-term light stress on the growth of a Brazilian epiphytic orchid, Cattleya forbesii Lindl. X Laelia tenebrosa Rolfe. Two groups of plants were used in the first experiment, one under 90% (@ 1,650 µmol.m-2.s-1) of Photosynthetically Active Radiation (PAR) and the other maintained under 22.5% (@ 400 µmol.m-2.s-1). In the second experiment the diffusive resistance, transpiration rate and fluorescence levels were monitored for plants that were under 22.5% of PAR, under 90% and plants transferred from 22.5 to 90%. Our results show that light intensity interfered with growth and development of this orchid. Data on the changes in pseudobulb volume throughout the time course of growth suggest that water and reserves stored in the back shoots are translocated to the current shoot. Regarding stomatal resistance, plants under 22.5% of PAR reached a largest stomatal aperture during the night, whereas those under 90% only after dawn. After transfer from 22.5% PAR to 90% PAR the ratio of Fv/Fm decreased from approximately 0.8 to 0.7. This suggests the limitation of photoprotection mechanisms in the leaf and the results observed after the transfer of plants from 22.5% to 90% reinforce the possibility that a photoinhibition is reflected in a decrease in growth rate.

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. (C) 2009 Elsevier GmbH. All rights reserved.

Morfo-anatomia caulinear de nove espécies de Orchidaceae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Growth and flowering of miltonia flavescens lindl. var. stellata regel orchid under different doses of a slow release fertilizer

The Orchidaceae is one of the most numerous and diversified families in the Plant Kingdom. Miltonia flavescens Lindl. is a native orchid to the southern region of Brazil. Studies related to the nutrition and fertilization of orchids are scarce, specific and existent only for few species. The objective of this work was to evaluate the effect of different doses of a slow release fertilizer (Osmocote (R) 9/15/12 + micro) on the development of M. flavescens var. stellata Regel cultivated in pots with pine bark and coconut fiber (1:1, v:v) as the substrate. The treatments consisted of: no fertilizer application (control), application of 2.5 g, 5 g and 10 g of fertilizer per liter of substrate. The experimental design was set in randomized blocks, with five replications and three plants per plot. The experiment was carried out along 25 months and the fertilizer was applied every five months. The evaluated plant parameters were: length of the longest pseudobulb, number of pseudobulbs, diameter of pseudobulbs, number of shoots, number of leaves and flowering. There was a significant increment on all evaluated characteristics with the increase of the fertilizer dose. The highest dose provided a more profuse flowering, with a larger number of flower stems and flowers, in addition to bigger flower stems and flowers. These results show that the supply of nutrients in an appropriate amount is of a great importance for the development and flowering of M. flavescens.

New Thelastomatoidea (Nematoda : Oxyurida) from Australian burrowing cockroaches (Blaberidae : Geoscapheinae, Panesthiinae)

Four new species and two new genera of thelastomatoid are described from several species of Australian burrowing cockroaches (Blattodea: Panesthiinae; Geoscapheinae). Corpicracens munozae n. g., n. sp., Pseudodesmicola botti n. g., n. sp. and Cephalobellus nolani n. sp. are described from Geoscapheus dilatatus (Blattodea: Geoscapheinae) from Mendooran, New South Wales; one new thelastomatid, Blattophila praelongicauda n. sp., is described from Panesthia cribrata from Lamington National Park, Queensland. Corpicracens munozae n. g., n. sp. is long and slender, with a monodelphic female reproductive system, a clavate corpus with a slight posterior pseudobulb, oval eggs flattened at the poles, and a relatively robust, subulate tail. Pseudodesmicola botti n. g., n. sp. is slightly more robust in body, also has a monodelphic reproductive system, a cylindrical corpus with a posterior pseudobulb, ovoid eggs and a very long, subulate tail. Cephalobellus nolani n. sp. is distinguished from other members of the genus by its relatively short and broad body and egg shape. Lastly, Blattophila praelongicauda n. sp. is distinguished from other members of the genus by having eggs with a single, polar operculum, tail length, and position of the vulva, nerve ring and excretory pore. An additional species, known by a single specimen from Panesthia tryoni tryoni from the same locality is characterised but not named. The species found are all relatively rare parasites of Australian burrowing cockroaches, each having a prevalence of less than 10%.