Probing water compartments and membrane permeability in plant cells by 1H NMR relaxation measurements

Abstract

(1)H NMR relaxation times (T(1) and T(2)) in parenchyma tissue of apple can identify three populations of water with different relaxation characteristics. By following the uptake of Mn(2+) ions in the tissue it is shown that the observed relaxation times originate from particular water compartments: the vacuole, the cytoplasm, and the cell wall/extracellular space.Proton exchange between these compartments is controlled by the plasmalemma and tonoplast membranes. During the Mn(2+) penetration experiment, conditions occur that cause the relaxation times of protons of cytoplasmic water to be much shorter than their residence time in the cytoplasm. Then the tonoplast permeability coefficient P(d) for water can be calculated from the vacuolar T(1) and T(2) values to be 2.44 10(-5) m.s(-1).

Leaf Development Monitoring and Early Detection of Water Deficiency by Low Field Nuclear Magnetic Resonance Relaxation in Nicotiana tabacum Plants

“…This accumulation of water thus played a role in the increase in the T 2-3 , which limited the reduction in T 2 assumed to be caused by osmotic adjustment. Accumulation of water in palisade cells has been described during senescence, resulting in an increase in the water associated with that tissue [33]. In the present study, the bigger increase in the LWW3 in old leaves of stressed plants suggests that the stress accelerated senescence.…”

“…Each NMR relaxation peak describes a specific water pool in the tissue. In apple fruit, Snaar and Van As [33] suggested that each peak of the multi-exponential NMR relaxation signal describes the water in the specific cell compartment (vacuole, cytosol and apoplast). Indeed, transverse relaxation time T 2 is sensitive to the chemical composition of water solution in each compartment, to the size of the water compartment, and to the diffusional process between different water pools.…”

In Situ Investigation of Leaf Water Status by Portable Unilateral Nuclear Magnetic Resonance

“…However, water molecules in different compartments may not be tightly bound, and the mixing of water from different sources may make assigning relaxation times to particular compartments less clear. The extent of averaging depends on the exchange rates from different intercellular sources, on the intrinsic relaxation times, and on cell morphology (Snaar and Van As, 1992). The effect of the exchange of water molecules usually affects T 1 more than T 2 .…”

“…Differences in T 2 are more pronounced, as water exchange over membranes only results in a partial averaging, which depends on the size of the compartments and on the membrane water permeability (Van As, 2007). As a consequence, in plant tissue, T 2 measurements usually yield more detailed information on the partitioning of water than T 1 measurements (Snaar and Van As, 1992).…”

“…Water bound in chloroplasts and vacuoles of plant cells shows even longer T 2 values (Snaar and Van As, 1992;Sainis and Srinivasan, 1993). However, the interpretation of relaxation parameters in terms of domain size or of proxy properties of the various water fractions remains difficult.…”