Phloem flow and sugar transport in Ricinus communis L. is inhibited under anoxic conditions of shoot or roots
Peuke, A.D. ; Gessler, A. ; Trumbore, S. ; Windt, C.W. ; Homan, N. ; Gerkema, E. ; As, H. van - \ 2015
Plant, Cell & Environment 38 (2015)3. - ISSN 0140-7791 - p. 433 - 447.
carbon-isotope composition - mushrooms agaricus-bisporus - distance water transport - organic-matter - membrane-permeability - assimilate transport - plants - leaves - starch - stress
Anoxic conditions should hamper the transport of sugar in the phloem, as this is an active process. The canopy is a carbohydrate source and the roots are carbohydrate sinks.By fumigating the shoot with N2 or flooding the rhizosphere, anoxic conditions in the source or sink, respectively, were induced. Volume flow, velocity, conducting area and stationary water of the phloem were assessed by non-invasive magnetic resonance imaging (MRI) flowmetry. Carbohydrates and d13C in leaves, roots and phloem saps were determined. Following flooding, volume flow and conducting area of the phloem declined and sugar concentrations in leaves and in phloem saps slightly increased. Oligosaccharides appeared in phloem saps and after 3 d, carbon transport was reduced to 77%. Additionally, the xylem flow declined and showed finally no daily rhythm. Anoxia of the shoot resulted within minutes in a reduction of volume flow, conductive area and sucrose in the phloem sap decreased. Sugar transport dropped to below 40% by the end of the N2 treatment. However, volume flow and phloem sap sugar tended to recover during the N2 treatment. Both anoxia treatments hampered sugar transport. The flow velocity remained about constant, although phloem sap sugar concentration changed during treatments. Apparently, stored starch was remobilized under anoxia.
1H-NMR study of the impact of high pressure and thermal processing on cell membrane integrity of onions
Gonzalez, M.E. ; Barrett, D.M. ; McCarthy, M.J. ; Vergeldt, F.J. ; Gerkema, E. ; Matser, A.M. ; As, H. van - \ 2010
Journal of Food Science 75 (2010)7. - ISSN 0022-1147 - p. E417 - E425.
spin-spin relaxation - mushrooms agaricus-bisporus - nuclear-magnetic-resonance - water diffusion - lactobacillus-plantarum - vacuolar symplast - osmotic-stress - maize roots - pfg-nmr - tissue
Proton nuclear magnetic resonance (1H-NMR) relaxometry was used to study the effects of high pressure and thermal processing on membrane permeability and cell compartmentalization, important components of plant tissue texture. High pressure treated onions were subjected to pressure levels from 20 to 200 MPa at 5 min hold time at initial temperatures of 5 and 20 °C. Thermally treated onions were exposed for 30 min at temperatures from 40 to 90 °C. Loss of membrane integrity was clearly shown by changes in transverse relaxation time (T2) of water at temperatures of 60 °C and above. Destabilization effects on membranes exposed to high pressure were observed at 200 MPa as indicated by T2 measurements and cryo-scanning electron microscopy (Cryo-SEM). T2 relaxation successfully discriminated different degrees of membrane damage based on the T2 shift of the vacuolar component. Analyses of the average water self-diffusion coefficient indicated less restricted diffusion after membrane rupture occurred in cases of severe thermal treatments. Milder processing treatments yielded lower average diffusion coefficients than the controls. 1H-NMR proved to be an effective method for quantification of cell membrane damage in onions and allowed for the comparison of different food processes based on their impact on tissue integrity
Intact plant MRI for the study of cell water relations, membrane permeability, cell-to-cell and long distance water transport
As, H. van - \ 2007
Journal of Experimental Botany 58 (2007)4. - ISSN 0022-0957 - p. 743 - 756.
nuclear-magnetic-resonance - mushrooms agaricus-bisporus - nmr microscopy - field gradient - porous-media - diffusion-coefficient - biological tissues - relaxation-times - spin relaxation - cucumis plants
Water content and hydraulic conductivity, including transport within cells, over membranes, cell-to-cell, and long-distance xylem and phloem transport, are strongly affected by plant water stress. By being able to measure these transport processes non-invasely in the intact plant situation in relation to the plant (cell) water balance, it will be possible explicitly or implicitly to examine many aspects of plant function, plant performance, and stress responses. Nuclear magnetic resonance imaging (MRI) techniques are now available that allow studying plant hydraulics on different length scales within intact plants. The information within MRI images can be manipulated in such a way that cell compartment size, water membrane permeability, water cell-to-cell transport, and xylem and phloem flow hydraulics are obtained in addition to anatomical information. These techniques are non-destructive and non-invasive and can be used to study the dynamics of plant water relations and water transport, for example, as a function of environmental (stress) conditions. An overview of NMR and MRI methods to measure such information is presented and hardware solutions for minimal invasive intact plant MRI are discussed