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Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in BioEssays 32 (2010): 514-523, doi:10.1002/bies.200900173., The medium surrounding cells either in culture or in tissues contains a chemical mix varying with cell state. As solutes move in and out of the cytoplasmic compartment they set up characteristic signatures in the cellular boundary layers. These layers are complex physical and chemical environments whose profiles both reflect cell physiology and provide conduits for intercellular messaging. Here we review some of the most relevant characteristics of the extracellular/intercellular space. Our initial focus is primarily with cultured cells but we extend our consideration to the far more complex environment of tissues and discuss how chemical signatures in the boundary layer can or may affect cell function. Critical to the entire essay are the methods used, or being developed, to monitor chemical profiles in the boundary layers. We review recent developments in ultramicro electrochemical sensors and tailored optical reporters suitable for the task in hand., The development and the application of self-referencing electrodes were funded largely by grant number NIH:NCRR P41 RR001395 to the BioCurrents Research Center (PJSS).

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in BioEssays 32 (2010): 514-523, doi:10.1002/bies.200900173., The medium surrounding cells either in culture or in tissues contains a chemical mix varying with cell state. As solutes move in and out of the cytoplasmic compartment they set up characteristic signatures in the cellular boundary layers. These layers are complex physical and chemical environments whose profiles both reflect cell physiology and provide conduits for intercellular messaging. Here we review some of the most relevant characteristics of the extracellular/intercellular space. Our initial focus is primarily with cultured cells but we extend our consideration to the far more complex environment of tissues and discuss how chemical signatures in the boundary layer can or may affect cell function. Critical to the entire essay are the methods used, or being developed, to monitor chemical profiles in the boundary layers. We review recent developments in ultramicro electrochemical sensors and tailored optical reporters suitable for the task in hand., The development and the application of self-referencing electrodes were funded largely by grant number NIH:NCRR P41 RR001395 to the BioCurrents Research Center (PJSS).

Aluminium (Al) toxicity and drought are the two major abiotic stress factors limiting common bean production in the tropics. Using hydroponics, the short-term effects of combined Al toxicity and drought stress on root growth and Al uptake into the root apex were investigated. In the presence of Al stress, PEG 6000 (polyethylene glycol)-induced osmotic (drought) stress led to the amelioration of Al-induced inhibition of root elongation in the Al-sensitive genotype VAX 1. PEG 6000 (>> PEG 1000) treatment greatly decreased Al accumulation in the 1 cm root apices even when the roots were physically separated from the PEG solution using dialysis membrane tubes. Upon removal of PEG from the treatment solution, the root tips recovered from osmotic stress and the Al accumulation capacity was quickly restored. The PEG-induced reduction of Al accumulation was not due to a lower phytotoxic Al concentration in the treatment solution, reduced negativity of the root apoplast, or to enhanced citrate exudation. Also cell-wall (CW) material isolated from PEG-treated roots showed a low Al-binding capacity which, however, was restored after destroying the physical structure of the CW. The comparison of the Al(3+), La(3+), Sr(2+), and Rb(+) binding capacity of the intact root tips and the isolated CW revealed the specificity of the PEG 6000 effect for Al. This could be due to the higher hydrated ionic radius of Al(3+) compared with other cations (Al(3+) >> La(3+) > Sr(2+) > Rb(+)). In conclusion, the results provide circumstantial evidence that the osmotic stress-inhibited Al accumulation in root apices and thus reduced Al-induced inhibition of root elongation in the Al-sensitive genotype VAX 1 is related to the alteration of CW porosity resulting from PEG 6000-induced dehydration of the root apoplast.

Seed-coat development in Ranunculus sceleratus L. has been studied by electron microscopy. Three layers developed from the single integument. The outer epidermis consisted of elongated and flattened cells that were always well attached to each other. The cells were characterized by thin walls, the presence of chloroplasts and small vacuoles. The cells of the middle layer were originally closely packed. Gradually, extensive intercellular spaces were formed. The cells of the inner epidermis elongated initially, until they became cubic and developed a thick wall with numerous wall ingrowths at the side bordering the nucellus. Thus, they give rise to a mechanical layer protecting the inner part of the seed. The elongation of cells, the thickening of cell walls, the formation of wall ridges, and the formation of intercellular spaces each coincided with characteristic configurations of microtubules. Plasmodesmata were originally found between all cells of the integument but their number decreased drastically during development, especially between the three developing seed-coat layers. Well-differentiated chloro-amyloplasts, present in all cells of the developing seed-coat, pointed to autotrophy during development. Maturation eventually led to the disappearance of cytoplasm in all cells, the compression of the cells of the outer epidermis and middle layers, and the formation of a mechanical layer from the inner epidermis.