%0 Journal Article %1 livingston_henson_98 %A Livingston, D. P. %A Henson, C. A. %D 1998 %J Plant Physiology %K bibtex-import, citeulikeExport freezing, ice, solutes, spread %P 403--408 %T Apoplastic Sugars, Fructans, Fructan Exohydrolase, and Invertase in Winter Oat: Responses to Second-Phase Cold Hardening %V 116 %X Changes in apoplastic carbohydrate concentrations and activities of carbohydrate-degrading enzymes were determined in crown tissues of oat ( Avena sativa L., cv Wintok) during cold hardening. During second-phase hardening (23C for 3 d) levels of fructan, sucrose, glucose, and fructose in the apoplast increased significantly above that in nonhardened and first-phase-hardened plants. The extent of the increase in apoplastic fructan during second-phase hardening varied with the degree of fructan polymerization (DP) (e.g. DP3 and DP4 increased to a greater extent than DP7 and DP > 7). Activities of invertase and fructan exohydrolase in the crown apoplast increased approximately 4-fold over nonhardened and first-phase-hardened plants. Apoplastic fluid extracted from nonhardened, first-phase-hardened, and second-phase-hardened crown tissues had low levels, of symplastic contamination, as determined by malate dehydrogenase activity. The significance of these results in relation to increases in freezing tolerance from second-phase hardening is discussed.

@article{livingston_henson_98, abstract = {{Changes in apoplastic carbohydrate concentrations and activities of carbohydrate-degrading enzymes were determined in crown tissues of oat ( Avena sativa L., cv Wintok) during cold hardening. During second-phase hardening (23C for 3 d) levels of fructan, sucrose, glucose, and fructose in the apoplast increased significantly above that in nonhardened and first-phase-hardened plants. The extent of the increase in apoplastic fructan during second-phase hardening varied with the degree of fructan polymerization (DP) (e.g. DP3 and DP4 increased to a greater extent than DP7 and DP > 7). Activities of invertase and fructan exohydrolase in the crown apoplast increased approximately 4-fold over nonhardened and first-phase-hardened plants. Apoplastic fluid extracted from nonhardened, first-phase-hardened, and second-phase-hardened crown tissues had low levels, of symplastic contamination, as determined by malate dehydrogenase activity. The significance of these results in relation to increases in freezing tolerance from second-phase hardening is discussed.}}, added-at = {2019-03-31T01:14:40.000+0100}, author = {Livingston, D. P. and Henson, C. A.}, biburl = {https://www.bibsonomy.org/bibtex/2d55a0f8f9158b7eec4d56d4b4b0d484c/dianella}, citeulike-article-id = {1523814}, comment = {(private-note)2PH: Tumenov describe this as a second phase of hardening that occurs at sub-freezing temperatures (1PH is the first phase, hardening at above-freezing temperatures) Induces yet greater freezing tolerance Involves increased levels of glucose fructose and sucrose. Suggested that this was osmotic protection. (Trunova 1965) Olien (1984), using a perfusion technique, reported an increase in apoplastic sugars during 2PH and suggested that these sugars helped prevent adhesion of ice to critical cellular tissue during freezing. Methods: 3 days in a freezer in a bag inoculated with ice. -3oC Surveyed for enzymes MDH and glucose, sucrose, fructose, fructans More glu, suc, fru and MDH in apoplast on 2PH than could be attributed to cellular leakage. However, Canny (1995) showed that the solute concentration in the apoplast is not uniform, but that solutes tend to accumulate in discrete regions termed sumps. In addition to sugars being distributed unevenly in the apoplast, the layer of liquid water into which sugars have apparently been released would be very small due to the presence of apoplastic ice at 23C (Gusta and Fowler, 1977; Single and Marcellos, 1981; Pearce and Ashworth, 1992). This could lead to regions of very high sugar concentrations in the apoplast of crown tissue, which could prevent ice adhesions and possibly provide other forms of protection to cell walls and membranes. 2PH certainly provides substrates for both enzymes, the products of which are known cryoprotectants. However, the changes we measured in this study may also be coincidental to the increase in freezing tolerance during 2PH. There are undoubtedly other alterations we did not measure that will help provide answers to the exact nature of the increased freezing survival during 2PH.}, interhash = {3e3c86164c353b95b49c8dbe9d85f7a8}, intrahash = {d55a0f8f9158b7eec4d56d4b4b0d484c}, journal = {Plant Physiology}, keywords = {bibtex-import, citeulikeExport freezing, ice, solutes, spread}, pages = {403--408}, posted-at = {2007-07-31 06:37:44}, priority = {2}, timestamp = {2019-03-31T01:16:26.000+0100}, title = {{Apoplastic Sugars, Fructans, Fructan Exohydrolase, and Invertase in Winter Oat: Responses to Second-Phase Cold Hardening}}, volume = 116, year = 1998 }