Changes in Membrane Permeability of Winter Wheat Cells following Freeze-Thaw Injury as Determined by Nuclear Magnetic Resonance

Abstract

Nuclear etic resoaace (NMR) relaxation times were studied in acclhnated and nonacclmated Kharkov It has been inferred by many investigators that membranes, primarily plasma membranes, are the site of freezing injury. This evidence is based upon loss of semipermeability properties of the membrane following freezing injury (7,19).Pulse NMR3 measurements of the longitudinal relaxation time (T1) and the transverse relaxation time (T2) have been used to study water and water interactions in biological systems (5,14,22 The objective of this study was to evaluate the effect of different freezing stresses (fast freezing versus slow freezing) on the plasma membrane of tender and hardy winter wheat (Triticum aestivum L.). Alterations to plasma water membrane permeability as a result of freezing stresses were studied by observing the effects of freezing on NMR relaxation times. Alterations to Mn2+ permeability were studied by observing the loss in the long T2 water signal as Mn2" diffused into the protoplast. MATERIALS AND METHODS PLANT MATERIALSCrown Tissue. Crowns of a hardy winter wheat cultivar, Kharkov MC22, were cold-acclimated under controlled environment conditions for 7 weeks (11). Fully acclimated plants were also collected from the field in late November and stored in a soilsand-peat mixture (1:1:1) at -3 C. The crowns were maintained under a photoperiod of 24 hr with a light intensity of 2,400 lux supplied from "Gw-Lux WS" fluorescent lamps. The cold hardiness level of these plants, as determined by artificial freeze tests, was -23 ± 1 C (12).Ced Tissue Cultures. Kharkov seeds were sterilized by shaking for 15 min in 10% NaOCl with 0.01% Tween -20. The seeds were washed five times with sterile distilled H20 and germinated in Petri dishes. Following 3 days germination, the mesocotyl of each seedling was dissected and transferred immediately to a flask containing 1-B5 agar medium (9). After 4 to 6 weeks the callus which formed was transferred to a 1-B5 liquid medium and shaken constantly. Cell suspension cultures were propagated by the subculturing method of Gamborg (9)

Influence of Low/High Temperature on Water Status in Developing and Maturing Rice Grains

“…3). T 2 values of long fraction in the grains at milky and dough stages were around 100ms showing the existence of free water (Chen and Gusta, 1978). T 2 values of the short fraction in the grains grown at 20ºC were between 10 and 90 ms, and did not change until 29 DAF but dropped sharply to 20 µs at 36 DAF (Fig.…”

Cold- or Heat-Tolerance of Leaves and Roots in Perennial Ryegrass Determined by1H-NMR

“…T 2 in the long fraction indicating over 200 ms is thought to be mainly associated with vacuole and the fraction with the short T 2 less than 60ms is thought to be associated with the cytosol and apoplastic region in the leaves (Chen and Gusta, 1978). The prolongation of T 2 in the long fraction was accompanied by a gradual increase in signal intensity in the temperature range from 0 to -20ºC.…”

“…Furthermore, the leakage of electrolytes indicated that both leaves and roots exposed to subzero temperatures were severely damaged ( Table 2). The shortening of T 2 has been attributed to a decline in membrane permeability under freezing injury in wheat crowns (Chen and Gusta, 1978). Therefore, the abrupt shortening of T 2 suggested that two water components in leaves froze at -20 to -25 ºC and those in roots froze at -10ºC.…”

Quantificação de sorgoleone em extratos e raízes de sorgo sob diferentes períodos de armazenamento

“…Além do dano físico, podem ocorrer modificações na composição química da parede celular e na permeabilidade da membrana plasmática, que podem também influenciar na quantidade e qualidade do extrato final obtido (Palta et al, 1977;Olien & Smith, 1977;Chen & Gusta, 1978;Weiser et al, 1990;Murai & Yoshida, 1998).…”

“…Em muitos estudos, a extração de sorgoleone tem sido feita a partir de raízes recém-coletadas, e o extrato é usualmente armazenado em baixas temperaturas antes da sua utilização em testes de atividade e do seu fracionamento (Einhelling & Souza, 1992;Rasmussen et al, 1992;Nimbal et al, 1996;Souza et al, 1999;Kagan et al, 2003;Czarnota et al, 2003b;Hejl & Koster, 2004). Alguns estudos mostram que o armazenamento de órgãos vegetais antes da extração pode acarretar alterações no extrato final obtido (Palta et al, 1977;Olien & Smith, 1977;Chen & Gusta, 1978;Weiser et al, 1990;Murai & Yoshida, 1998). Além disso, as condições de armazenamento de extratos vegetais podem influenciar na estabilidade e degradação dos compostos químicos presentes (Srivastava et al, 2007;Tabart et al, 2007).…”