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• Background and Aims Soybean (Glycine max) is among the many legumes that are well known for ‘hardseededness’. This feature can be beneficial for long-term seed survival, but is undesirable for the food processing industry. There is substantial disagreement concerning the mechanisms and related structures that control the permeability properties of soybean seed coats. In this work, the structural component that controls water entry into the seed is identified.• Methods Six soybean cultivars were tested for their seed coat permeabilities to water. To identify the structural feature(s) that may contribute to the determination of these permeabilities, fluorescent tracer dyes, and light and electron microscopic techniques were used.• Key Results The cultivar ‘Tachanagaha’ has the most permeable seed coat, ‘OX 951’ the least permeable seed coat, and the permeabilities of the rest (‘Harovinton’, ‘Williams’, ‘Clark L 67-3469’, and ‘Harosoy 63’) are intermediate. All seeds have surface deposits, depressions, a light line, and a cuticle about 0·2 µm thick overlaying the palisade layer. In permeable cultivars the cuticle tends to break, whereas in impermeable seeds of ‘OX 951’ it remains intact. In the case of permeable seed coats, the majority of the cracks are from 1 to 5 µm wide and from 20 to 200 µm long, and occur more frequently on the dorsal side than in other regions of the seed coat, a position that correlates with the site of initial water uptake.• Conclusions The cuticle of the palisade layer is the key factor that determines the permeability property of a soybean seed coat. The cuticle of a permeable seed coat is mechanically weak and develops small cracks through which water can pass. The cuticle of an impermeable seed coat is mechanically strong and does not crack under normal circumstances. [ABSTRACT FROM AUTHOR]

Maturation of the exodermis involves development of a Casparian band, a structure that blocks the apoplastic movement of ions. The position at which this band is formed is not readily predictable, since it depends on species and growing conditions. Until now, Casparian band detection necessitated destructive methods which involved sectioning or clearing the roots. In the present study, a method for detecting exodermal Casparian bands in vivo is presented. Undisturbed onion roots were incubated for 2 h in 0.1% 8-hydroxy-1,3,6-pyrenetrisulphonate (PTS) and then thoroughly rinsed in running water. Under UV light, the tracer was evident in the cortex of the root regions with an immature exodermis but not in older regions of the root where the Casparian band had developed. PTS had entered the protoplasts of the cortical cells in the younger part of the root and had not been removed by rinsing. The first order kinetics of uptake, and insensitivity to external pH and probenecid indicated that PTS entered the cell by fluid-phase endocytosis. PTS-loaded vesicles that released their contents into the vacuole were seen using confocal laser scanning microscopy. When applied to undisturbed, whole root systems, PTS was not detected in aqueous extracts of the leaves. Thus, there is no major apoplastic bypass in healthy onion roots.Key words: exodermis, Casparian bands, apoplastic bypass, PTS, fluid-phase endocytosis.La maturation de l'exoderme implique le développement de la bande de Caspari, une structure qui bloque les mouvement apoplastiques des ions. La position à laquelle se forme cette bande n'est pas directement prévisible, puisqu'elle dépend de l'espèce et des conditions de croissance. Jusqu'à maintenant, la détection des bandes de Caspari nécessitait des méthodes destructives faisant appel à la découpe et l'éclaircissement des racines. Les auteurs présentent ici une méthode pour la détection in vivo des bandes de Caspari. On incube des racines d'oignon intactes pendant 2 h dans du 8-hydroxy-1,3,6-pyrénétrisulphonate (PTS) à 0,1 %, avant de les rincer dans l'eau courante. Sous éclairage UV, le traceur est évident dans le cortex des régions racinaires où se trouve l'exoderme immature, mais non dans les régions plus âgées de la racine où la bande de Caspari s'est développée. Le PTS est ainsi entré dans les protoplastes des cellules corticales des parties les plus jeunes des racines, mais n'a pas été éliminé par le rinçage. La cinétique de premier ordre de l'absorption et l'insensibilité au pH externe et au probénécide indiquent que le PTS entre dans la cellule par endocytose en phase liquide. Avec la microscopie confocale par balayage au laser, on peut apercevoir des vésicules chargées de PTS qui relâchent leurs contenus dans la vacuole. Lorsqu'on applique ce colorant à des systèmes racinaires entiers non-perturbés, on ne détecte pas le PTS dans les extraits aqueux de feuilles. Ainsi, il n'y a pas de contournement apoplastique chez les racines d'oignon en santé.Mots clés : exoderme, bandes de Caspari, contournement apoplastique, PTS, endocytose en phase liquide.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

X-ray computed tomography (CT), a non-destructive imaging technique, has recently been effectively applied to botanical research. In this study an X-ray microCT technique was developed to allow for anatomical study of the overwintering corms of Eriophorum vaginatum, an ecologically important sedge species in arctic tussock-tundra and boreal peatlands. Using a GE Medical MS8X-130 X-ray microCT scanner, optimal imaging parameters included scanning isolated corms at 80 k Vp and 100 microA with a 3500 ms exposure time and an isotropic voxel size of 10 microm. A Gaussian blur image filter with a blur radius (sigma) of two pixels was applied to the optimal dataset to improve visual detection and contrast of tissues while removing 99.2% of image noise. Using the developed X-ray microCT technique several undocumented anatomical characteristics of the corm were identified including the vascular connection between a parent corm and branching cormel and the 3D shape of sclereid clusters. The 3D structure of sclereid clusters was determined whereby the perimeter of their lance shape is greatly reinforced by sclereids with thicker secondary cell walls as compared to those of the interior of the cluster. The structure of sclereid clusters and their association with leaf traces suggests they may be stabilizing the corm-leaf connection to protect vascular tissues from physical damage. The proposed X-ray microCT technique is an excellent tool for determination of the 3D structure of E. vaginatum corms and may be used to detect alterations in tissue structure and chemistry in response to environmental change in this and other Cyperaceous species., (Copyright 2010 Elsevier Inc. All rights reserved.)

The adsorption behavior of the cationic surfactant N-decyl-N,N,N-trimethylammonium triflate (DeTATf) on the Au(111) electrode surface was characterized using cyclic voltammetry, differential capacity, and chronocoulometry. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DeTATf has a multistate character. At low bulk DeTATf concentrations, the adsorption state is consistent with the formation of an adsorbed film of nearly flat molecules. At higher concentrations this film may represent a three-dimensional aggregated state. At negative potentials and charge densities close to 0 microC cm-2, the data suggest the formation of a film of tilted molecules oriented with the hydrocarbon tail toward the metal surface and the polar head toward the solution. A surprising result of this study is that DeTATf displays adsorption characteristics of a zwitterionic rather than a cationic surfactant. This behavior indicates that the adsorbed species is an ion pair.

Lipid particles have been isolated from seeds of wax bean (Phaseolus vulgaris), a species in which starch and protein rather than lipid are the major seed storage reserves. These lipid particles resemble oil bodies present in oil-rich seeds in that > 90% of their lipid is triacylglycerol. Moreover, this triacylglycerol is rapidly metabolized during seed germination indicating that it is a storage reserve. The phospholipid surfaces of oil bodies are known to be completely coated with oleosin which prevents their coalescence, particularly during desiccation of the developing seed. This would appear to be necessary since lipid is the major storage reserve in oil seeds, and there are very few alternate types of storage particles in the cytoplasm of oil seed endosperm to provide a buffer against coalescence of oil bodies by isolating them from one another. The present study indicates that the surfaces of lipid particles from wax bean are not completely coated with oleosin and feature regions of naked phospholipid. This finding has been interpreted as reflecting the fact that lipid particles in wax been seeds are less prone to coalescence than oil bodies of oil-rich seeds. This arises because the individual lipid particles are interspersed in situ among highly abundant protein bodies and starch grains and hence less likely to come in contact with one another, even during desiccation of the developing seed.