Stipular extranuptial nectaries new to Polygala: morphology and ontogeny

Although taxonomic studies indicate that approximately one‐third of the genera of Polygalaceae have nodal glands, few anatomical data are available on the structure and ontogeny of these secretory organs. We studied the as yet unknown origin, structure and function of such glands in Polygala laureola. During field observations, we detected glucose in the secretion using Glicofita Plus® and visitors were recorded. Vegetative shoot apices and nodal glands were examined using light microscopy and scanning electron microscopy. The presence of glucose in the secretion allowed us to identify these nodal glands as extranuptial nectaries. Secretory cells occupy a medullary position and are surrounded by phloem. Vascular bundles are concentric, and xylem is only observed at the basal region of the nectary. Nectar is released during the daytime through a pore at the top of the nectary. A stipular origin was confirmed by the fact that the procambial strand is connected to the leaf trace, opposite the leaf gap. The occurrence of stipular extranuptial nectaries in a nodal position is new to Polygala. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 40–50.     

Physical localization of NORs and ITS length variants in old Portuguese durum wheat cultivars

The variation at the internal transcribed spacer (ITS) region of the ribosomal DNA has been correlated with the number of nucleolar organizer regions (NORs) in some plant species. Besides, the number of NORs might influence the rate of homogenization of the rDNA repeats. In recent studies, ITS length variants were detected in bread wheat cultivars but no reports about their presence in durum wheat were found. In the present study, we localized and identified the NORs of 51 old Portuguese durum wheat cultivars by using sequential silver staining and fluorescence in situ hybridization performed with the pTa71 rDNA probe. We also detected ITS length variants by PCR-RFLP. No variation at the number of Ag-NORs per metaphase was found among the 51 durum wheat cultivars, but the PCR-RFLP technique carried out with the restriction enzyme HpaII, allowed the detection of ITS length variants among them. The molecular data was used in order to establish the genetic relationships among cultivars and botanical varieties of durum wheat. The knowledge of this feature could be useful for future design of breeding strategies, involving this collection that constitutes an excellent repository of germplasm in Portugal.     

Kinetics of xylem loading,membrane potential maintenance,and sensitivity of K+‐permeable channels to reactive oxygen species: physiological traits that differentiate salinity tolerance between pea and barley

Salt sensitive (pea) and salt tolerant (barley) species were used to understand the physiological basis of differential salinity tolerance in crops. Pea plants were much more efficient in restoring otherwise depolarized membrane potential thereby effectively decreasing K⁺ efflux through depolarization‐activated outward rectifying potassium channels. At the same time, pea root apex was 10‐fold more sensitive to physiologically relevant H₂O₂ concentration and accumulated larger amounts of H₂O₂ under saline conditions. This resulted in a rapid loss of cell viability in the pea root apex. Barley plants rapidly loaded Na⁺ into the xylem; this increase was only transient, and xylem and leaf Na⁺ concentration remained at a steady level for weeks. On the contrary, pea plants restricted xylem Na⁺ loading during the first few days of treatment but failed to prevent shoot Na⁺ elevation in the long term. It is concluded that superior salinity tolerance of barley plants compared with pea is conferred by at least three different mechanisms: (1) efficient control of xylem Na⁺ loading; (2) efficient control of H₂O₂ accumulation and reduced sensitivity of non‐selective cation channels to H₂O₂ in the root apex; and (3) higher energy saving efficiency, with less ATP spent to maintain membrane potential under saline conditions.     

SENSORY AND INSTRUMENTAL EVALUATION OF STRAWBERRY YOGURT COLOR

Eleven samples of strawberry yogurt prepared with different red color concentrations using Ponceau 4R (E-124) were evaluated by instrumental and sensory methods. Color intensity evaluation was carried out by a panel of eight assessors specifically trained to measure strawberry color in yogurt. Color acceptability was measured with 120 regular and frequent consumers of yogurt. Color was measured with a Minolta Chroma Meter CR-200b, obtaining parameters L*, a* and b*. Principal component analysis was performed on the instrumental variables. Regression models between the instrumental first principal component, red color concentration, sensory intensity, and acceptability allowed determining quality control limits for red color attribute. These limits may be controlled by selecting either instrumental or sensory methods, being the latter easy to implement and providing dependable results.     

Ultrastructural modifications in the apertural intine of Parietaria judaica L. (Urticaceae) pollen during the early stages of hydration

Hydration and activation of the Parietaria judaica L. (Urticaceae) pollen result in ultrastructural modifications in the apertural region. The particularly distinct intine under the apertures forms convex onci that undergo short but significant and reversible changes during the 10 first minutes of pollen grain hydration and activation. Such changes seem to involve the rough endoplasmic reticulum and show that the oncus is a dynamic structure. This confirms the elasticity of the intine and shows a new pattern of activity in this structure during hydration and activation of pollen germination in vitro.     

Reproductive cycle of the rissoid Alvania mediolittoralis Gofas, 1989 (Mollusca,Gastropoda) at São Miguel Island (Azores,Portugal)

Summary

The reproductive cycle of an Alvania species is studied for first time. Alvania mediolittoralis Gofas, 1989 is an endemic Azorean rissoid very common in sheltered places and particularly abundant among the algal turf covering the lower half of the intertidal and upper subtidal rocky shores. This species reproduces throughout the year, with two spawning peaks, one during early spring and the other in late autumn. In an attempt to relate to current paleobiogeographical studies, inferences are made regarding the ecological advantages of species with a continuous type of reproduction, on Azorean shores, during glacial episodes.     

Recombinant expression and characterization of a lysozyme from the midgut of Triatoma brasiliensis (Hemiptera,Reduviidae) in comparison with intestinal muramidase activity

Insect c‐type lysozymes are antibacterial proteins that are synthesized in different organs with high activity against Gram‐positive bacteria. Because lysozymes possess muramidase activity, they also play an important role in the digestion of bacteria in Diptera. Triatomines express lysozyme‐encoding genes constitutively in the anterior region (cardia and stomach) of the midgut and the fat body after injection of bacteria into the haemocoel. The present study describes the overexpression of the Triatoma brasiliensis lysozyme 1 (lys1) in Escherichia coli. Recombinant T. brasiliensis Lys1 (TbLys1) is purified after solubilization of the inclusion bodies. The protein refolds successfully, showing muramidase activity against Micrococcus lysodeikticus lyophilized cells, after enterokinase cleavage of its thioredoxin fusion protein. In in‐gel zymograms and turbidimetric liquid assays TbLys1 is broadly active under alkaline and acid conditions, indicating a possible digestive function in the two physiologically different midgut regions of the bug: the stomach and small intestine. Muramidase activity is shown in the stomach and small intestine content of unfed bugs and bugs at different days after feeding, respectively. Western blot analysis identifies TbLys1 as lysozyme.     

Variation in elasmoid fish scale patterns is informative with regard to taxon and swimming mode

Variations in scales from nine regions on the flank of teleost fish were examined from the point of view of functional adaptation and with regard to which scales best differentiate species. Three teleost species were selected; two are from the genus Mugil, M. cephalus and M. curema, which are phylogenetically distant from the third, Dicentrarchus labrax. Scale form was described using seven landmarks, the coordinates of which were subjected to generalized Procrustes analysis followed by principal components analysis. Principal component scores were submitted to cross‐validated discriminant analysis to assess the utility of each scale in identifying species. The best discrimination (98%) was obtained with the scale from the central‐dorsal area. Scales from the anterior and central zones are relatively wide dorsoventrally and narrow anteroposteriorly. This appears to be related to the profile of the lateral body wall and with subcarangiform swimming. Scales from the posterior region are anteroposteriorly long and dorsoventrally narrow, this shape possibly being related to thrust. Despite the wide phylogenetic separation between mullets and D. labrax, the pattern of scale variation is similar. This may imply strong functional convergence, although studies of sister taxa with different swimming modes are required to confirm this. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 834–844.