Abstract
A vacuum infiltration technique was developed that enabled the extraction of apoplastic solution with very little cytoplasmic contamination as evident from a malate dehydrogenase activity of less than 1% in the apoplastic solution relative to that in bulk leaf extracts. The volume of apoplastic water, a prerequisite for determination of the concentration of apoplastic solutes, was determined by vacuum infiltration of indigo carmine with subsequent analysis of the dilution of the dye in apoplastic extracts. Indigo carmine was neither transported across the cell membrane nor significantly adsorbed to the cell walls, ensuring reproducible (SE < 2%) and precise determination of apoplastic water. Analysis of leaves from four different positions on senescing Brassica napus plants showed a similar apoplastic pH of 5.8, while apoplastic NH4+ increased from 1.1 mM in lower leaves to 1.3 mM in upper leaves. Inhibition of glutamine synthetase in young B. napus plants resulted in increasing apoplastic pH from 6.0 to 6.8 and increasing apoplastic NH4+ concentration from 1.0 to 25.6 mM, followed by a marked increase in NH3 emission. Calculating NH3 compensation points for B. napus plants on the basis of measured apoplastic H+ and NH4+ concentrations gave values ranging from 4.3 to 5.9 nmol NH3 mol-1 air, consistent with an estimate of 5.3 [plus or minus] 3.6 nmol NH3 mol-1 air obtained by NH3 exchange experiments in growth chambers. A strong linear relationship was found between calculated NH3 compensation points and measured NH3 emission rates in glutamine synthetase-inhibited plants.
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- Bobbink R., Heil G. W., Raessen M. B. Atmospheric deposition and canopy exchange processes in heathland ecosystems. Environ Pollut. 1992;75(1):29–37. doi: 10.1016/0269-7491(92)90053-d. [DOI] [PubMed] [Google Scholar]
- Farquhar G. D., Firth P. M., Wetselaar R., Weir B. On the Gaseous Exchange of Ammonia between Leaves and the Environment: Determination of the Ammonia Compensation Point. Plant Physiol. 1980 Oct;66(4):710–714. doi: 10.1104/pp.66.4.710. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Giaquinta R. Phloem Loading of Sucrose: pH Dependence and Selectivity. Plant Physiol. 1977 Apr;59(4):750–755. doi: 10.1104/pp.59.4.750. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hartung W., Radin J. W., Hendrix D. L. Abscisic Acid Movement into the Apoplastic solution of Water-Stressed Cotton Leaves: Role of Apoplastic pH. Plant Physiol. 1988 Mar;86(3):908–913. doi: 10.1104/pp.86.3.908. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jacobs M., Ray P. M. Rapid Auxin-induced Decrease in Free Space pH and Its Relationship to Auxin-induced Growth in Maize and Pea. Plant Physiol. 1976 Aug;58(2):203–209. doi: 10.1104/pp.58.2.203. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kleiner D. The transport of NH3 and NH4+ across biological membranes. Biochim Biophys Acta. 1981 Nov 9;639(1):41–52. doi: 10.1016/0304-4173(81)90004-5. [DOI] [PubMed] [Google Scholar]
- Raven J. A., Farquhar G. D. Methylammonium Transport in Phaseolus vulgaris Leaf Slices. Plant Physiol. 1981 Apr;67(4):859–863. doi: 10.1104/pp.67.4.859. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Roberts J. K., Wemmer D., Ray P. M., Jardetzky O. Regulation of Cytoplasmic and Vacuolar pH in Maize Root Tips under Different Experimental Conditions. Plant Physiol. 1982 Jun;69(6):1344–1347. doi: 10.1104/pp.69.6.1344. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sentenac H., Grignon C. A model for predicting ionic equilibrium concentrations in cell walls. Plant Physiol. 1981 Aug;68(2):415–419. doi: 10.1104/pp.68.2.415. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Speer M., Kaiser W. M. Ion Relations of Symplastic and Apoplastic Space in Leaves from Spinacia oleracea L. and Pisum sativum L. under Salinity. Plant Physiol. 1991 Nov;97(3):990–997. doi: 10.1104/pp.97.3.990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Terry M. E., Bonner B. A. An Examination of Centrifugation as a Method of Extracting an Extracellular Solution from Peas, and Its Use for the Study of Indoleacetic Acid-induced Growth. Plant Physiol. 1980 Aug;66(2):321–325. doi: 10.1104/pp.66.2.321. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wang M. Y., Siddiqi M. Y., Ruth T. J., Glass ADM. Ammonium Uptake by Rice Roots (I. Fluxes and Subcellular Distribution of 13NH4+). Plant Physiol. 1993 Dec;103(4):1249–1258. doi: 10.1104/pp.103.4.1249. [DOI] [PMC free article] [PubMed] [Google Scholar]