%0 Journal Article %1 MartinezVilalta_Pockman_02 %A Martinez-Vilalta, J. %A Pockman, W. T. %D 2002 %J American Journal of Botany %K bibtex-import, citeulikeExport dependance, distribution, embolism, freezebolism, limits, papercopy, refilling, snowgumpapermaybe, temperature, unread %P 1916--1924 %T The vulnerability to freezing-induced xylem cavitation of Larrea tridentata (Zygophyllaceae) in the Chihuahuan desert %V 89 %X The temperature dependence of freezing-induced xylem cavitation was studied in a Chihuahuan desert population of Larrea tridentata (Zygophyllaceae). Field measurements of wood temperature and xylem embolism were combined with anatomical studies and laboratory measurements of embolism in stem and root samples frozen under controlled conditions. Our laboratory experiments corroborated the previously observed relationship between minimum freezing temperature and embolism. The area of the low-temperature exotherms produced during the freezing treatments was correlated with the resulting embolism, suggesting that the freezing of water inside parenchyma cells is associated with the occurrence of xylem embolism. In the laboratory experiments, embolism in stems increased only at temperatures below 2148C. Although this meant that the studied population was more resistant to freezing-induced xylem embolism than a previously studied population from the Sonoran desert, the impact of freezing was nevertheless greater because of much lower environmental temperatures. This result suggests that dieback associated with periodic extreme freezes may contribute to limiting the present distribution of L. tridentata in central New Mexico. Although laboratory experiments showed that root xylem embolism increased after freezing to less negative minimum temperatures than stems (significant effects at T 5 278C), root embolism in the field was lower than shoot embolism in accordance with measured soil temperatures throughout the study.

@article{MartinezVilalta_Pockman_02, abstract = {{The temperature dependence of freezing-induced xylem cavitation was studied in a Chihuahuan desert population of Larrea tridentata (Zygophyllaceae). Field measurements of wood temperature and xylem embolism were combined with anatomical studies and laboratory measurements of embolism in stem and root samples frozen under controlled conditions. Our laboratory experiments corroborated the previously observed relationship between minimum freezing temperature and embolism. The area of the low-temperature exotherms produced during the freezing treatments was correlated with the resulting embolism, suggesting that the freezing of water inside parenchyma cells is associated with the occurrence of xylem embolism. In the laboratory experiments, embolism in stems increased only at temperatures below 2148C. Although this meant that the studied population was more resistant to freezing-induced xylem embolism than a previously studied population from the Sonoran desert, the impact of freezing was nevertheless greater because of much lower environmental temperatures. This result suggests that dieback associated with periodic extreme freezes may contribute to limiting the present distribution of L. tridentata in central New Mexico. Although laboratory experiments showed that root xylem embolism increased after freezing to less negative minimum temperatures than stems (significant effects at T 5 278C), root embolism in the field was lower than shoot embolism in accordance with measured soil temperatures throughout the study.}}, added-at = {2019-03-31T01:14:40.000+0100}, author = {Martinez-Vilalta, J. and Pockman, W. T.}, biburl = {https://www.bibsonomy.org/bibtex/26bc5327faacf926fd8b33894bcd5d0aa/dianella}, citeulike-article-id = {1523826}, comment = {(private-note)there is a relationship between the area of LTE and embolism. This implies that living cells contribute to the maintenance of xylem function following the apoplastic freezing identified by an HTE (e.g., Fig. 5; 2118C), and that this contribution is diminished as minimum temperature declines. However, the possible role of parenchyma cells in the formation/removal of xylem embolism remains unclear. One possibility is that refilling occurs passively as a result of the positive pressures associated with the expansion of water during ice formation (Hammel, 1967). Second, and more likely, increased intracellular freezing and cell injury with decreasing minimum temperature could nucleate cavitation in surrounding xylem conduits if the rupture of cell membranes causes the entrance of cytoplasmatic materials into vessel lumens. An alternative interpretation of the association between intracellular freezing and xylem embolism is provided by recent work suggesting that parenchyma cells may contribute actively to the integrity of the conducting system following droughtinduced cavitation (Salleo et al., 1996; Holbrook and Zwieniecki,1999; Zwieniecki and Holbrook, 2000). If vessels can be hydraulically isolated, by gas entrapment in pits or another mechanism, as proposed to explain refilling at low water potentials (Holbrook and Zwieniecki, 1999), the local generation of positive or near-positive hydrostatic pressures might be sufficient to force gas bubbles into solution. Living parenchyma cells adjacent to the vessels might cause the required positive pressures, although the mechanism is not well understood (Holbrook and Zwieniecki, 1999).}, interhash = {dce713af164381906679162b7fdb2f1d}, intrahash = {6bc5327faacf926fd8b33894bcd5d0aa}, journal = {American Journal of Botany}, keywords = {bibtex-import, citeulikeExport dependance, distribution, embolism, freezebolism, limits, papercopy, refilling, snowgumpapermaybe, temperature, unread}, pages = {1916--1924}, posted-at = {2007-07-31 06:38:40}, priority = {0}, timestamp = {2019-03-31T01:16:26.000+0100}, title = {{The vulnerability to freezing-induced xylem cavitation of Larrea tridentata (Zygophyllaceae) in the Chihuahuan desert}}, volume = 89, year = 2002 }