%0 Journal Article %1 Gorsuch_Oberbauer_02 %A Gorsuch, D. M. %A Oberbauer, S. F. %D 2002 %J Tree Physiology %K bibtex-import, cellular, cited\_ch2, cited\_cryo, citeulikeExport damage, diameter, freezebolism, freezing, gas\_exchange, hydraulics, snowgumpapermaybe, techniques, temperature %P 1027--1034 %T Effects of mid-season frost and elevated growing season temperature on stomatal conductance and specific xylem conductivity of the arctic shrub, @Salix pulchra %U http://heronpublishing.com.virtual.anu.edu.au/tree/pdf/volume22/22-1027.pdf %V 22 %X An increased risk of frost is expected during the growing season, as climate warming increases spring temperatures in the Arctic. Because deciduous species have a growth season limited in length and also have generally larger conduit volumes, they are more likely than evergreens to be injured by freezethaw-induced cavitation during the growing season. To test whether growth at elevated temperature increases susceptibility to freezethaw damage, we grew a deciduous arctic shrub species (Salix pulchra Cham.) in simulated Alaskan summer temperatures and at 5 Cabove the ambient simulation (+5 C plants) in controlled environments. Stem specific hydraulic conductivity (ks) and leaf stomatal conductance (gs) were measured in plants grown at both temperatures before and after a freeze treatment simulating a mid-season frost. Before the freeze treatment, specific xylem conductivitywas 2.5 times higher and stomatal conductances were 1.3 times higher in +5 C plants than in ambient-grown plants. Reductions in hydraulic conductivity and stomatal conductance as a result of the freeze were 3.5 and 1.8 times greater respectively in +5 C plants than in ambient- grown plants. Many of the +5 C plants showed extensive leaf damage. Plants grown in the two treatments also differed in comparative xylem anatomy; +5 C plants had larger vessel diameters (25.4 versus 22.6 ?m) and higher vessel densities (71 versus 67.4 vesselsmm2) than ambient- grown plants. Our results suggest that higher growing season temperatures will increase the susceptibility of arctic deciduous shrubs to frost damage, which may offset their competitive growth advantage.

@article{Gorsuch_Oberbauer_02, abstract = {{An increased risk of frost is expected during the growing season, as climate warming increases spring temperatures in the Arctic. Because deciduous species have a growth season limited in length and also have generally larger conduit volumes, they are more likely than evergreens to be injured by freezethaw-induced cavitation during the growing season. To test whether growth at elevated temperature increases susceptibility to freezethaw damage, we grew a deciduous arctic shrub species (Salix pulchra Cham.) in simulated Alaskan summer temperatures and at 5 Cabove the ambient simulation (+5 C plants) in controlled environments. Stem specific hydraulic conductivity (ks) and leaf stomatal conductance (gs) were measured in plants grown at both temperatures before and after a freeze treatment simulating a mid-season frost. Before the freeze treatment, specific xylem conductivitywas 2.5 times higher and stomatal conductances were 1.3 times higher in +5 C plants than in ambient-grown plants. Reductions in hydraulic conductivity and stomatal conductance as a result of the freeze were 3.5 and 1.8 times greater respectively in +5 C plants than in ambient- grown plants. Many of the +5 C plants showed extensive leaf damage. Plants grown in the two treatments also differed in comparative xylem anatomy; +5 C plants had larger vessel diameters (25.4 versus 22.6 ?m) and higher vessel densities (71 versus 67.4 vesselsmm2) than ambient- grown plants. Our results suggest that higher growing season temperatures will increase the susceptibility of arctic deciduous shrubs to frost damage, which may offset their competitive growth advantage.}}, added-at = {2019-03-31T01:14:40.000+0100}, author = {Gorsuch, D. M. and Oberbauer, S. F.}, biburl = {https://www.bibsonomy.org/bibtex/22c2f56fb876d0429ebad203cb0f3210d/dianella}, citeulike-article-id = {1523707}, citeulike-linkout-0 = {http://heronpublishing.com.virtual.anu.edu.au/tree/pdf/volume22/22-1027.pdf}, comment = {(private-note)global climate change = more frosts (Cannell and Smith 1986, Maxwell 1997). Maxwell, B. 1997. Recent climate patterns in the Arctic. In Global Change and Arctic Terrestrial Ecosystems. Eds. W.C. Oechel, T. Callaghan, T. Gilmanov, J.I. Holten, B. Maxwell, U. Molau and B. Sveinbjornsson. Springer-Verlag, New York, pp 2146. temperature dependence of: conduit diameter pre and post-freeze .... hydraulic conductivity stomatal conductance because tundra plants grown at elevated temperatures have higher maximum photosynthetic rates than plants grown at ambient temperatures (Chapin and Shaver 1996), we predicted that they would also have higher stomatal conductances and specific hydraulic conductivities, as found for other species grown at elevated temperatures (Comstock 2000, Maherali and DeLucia 2000). Plants grown at elevated temperatures should be more susceptible to freezethaw-induced cavitation than plants grown at ambient temperatures, as a result of changes in xylem anatomy coinciding with higher conductivity. In this paper, we report the effects of elevated growing season temperatures on the sensitivity of the deciduous arctic shrub species, Salix pulchra Cham., to mid-season frost. The objective of the study was to test two hypotheses: (1) Salix plants grown at elevated temperatures have larger vessel diameters, longer vessels and a higher proportion of larger-diameter vessels contributing to overall flow than plants grown at ambient temperatures; and (2) Salix plants grown at elevated temperatures are more susceptible to a freezethawthan plants grown at current ambient growing season temperatures. Temperature treatments and freezing technique is perfect. g and K seems to be good too. Gravity-fed, watch bubbles staining afterward (and controls) paint infusion for vessel length diameter: The contribution of each conduit to hydraulic conductivity was calculated from mean vessel diameter in accordance with the Hagen-Poiseuille law by dividing the diameter of each vessel raised to the fourth power by the sum of all vessels raised to the fourth power. Vessels diameters were categorized as small (< 20 um), medium (2030 um) and large (> 30 um) based on their percentage contribution to total flow. These data were used to determine the relative susceptibility of plants from each treatment to embolism caused by freezethaw events. Elevated temperature: Higher K pre-freeze Higher g pre-freeze more of vessels were functional pre-freeze bigger PLC bigger change in stomatal conductance same change in proportion of vessels functional bigger conduits, more conduits longer conduits Plants grown in the elevated-temperature regime also had greater stem and leaf biomass, and we speculate that they have higher water and nutrient demands associated with higher rates of photosynthesis compared with plants grown under ambient conditions. This suggestion is supported by the increased percentage of functional vessels in +5 C plants. The elevated temperature treatment had significant effects on vessel diameter and vessel density (Table 1, Figure 3). Mean vessel diameters of +5 C plants and ambient-grown plants were 25.4 and 22.6 um, respectively. Vessel density in +5 C plants was 71 vessels mm2 compared with 67.4 vessels mm2 in ambient-grown plants. A comparison of the contribution of small, medium, and large vessels to overall flow based on conduit diameter showed significant differences in both the large and small size classes (Figure 4, P < 0.05). Each vessel in the large size class contributed more than 2\% to total flow. Each vessel in the medium and small size classes contributed between 0.4 and 2.0\% and less than 0.4\% to total flow, respectively. Because our data show significant differences between treatments in the proportions of vessels in four of the six length classes, volume determination of susceptibility to cavitation would indicate a greater difference in susceptibility than predicted by diameter alone. However, we did not measure vessel diameters of the various vessel length classes so we have no specific information about the relationship between vessel length and vessel volume, though in other studies they are positively correlated (Villar-Salvador et al. 1997).}, interhash = {1538454e1aa33ae016f274de5f151cca}, intrahash = {2c2f56fb876d0429ebad203cb0f3210d}, journal = {Tree Physiology}, keywords = {bibtex-import, cellular, cited\_ch2, cited\_cryo, citeulikeExport damage, diameter, freezebolism, freezing, gas\_exchange, hydraulics, snowgumpapermaybe, techniques, temperature}, pages = {1027--1034}, posted-at = {2007-07-31 06:17:29}, priority = {2}, timestamp = {2019-03-31T01:16:26.000+0100}, title = {{Effects of mid-season frost and elevated growing season temperature on stomatal conductance and specific xylem conductivity of the arctic shrub, @Salix pulchra}}, url = {http://heronpublishing.com.virtual.anu.edu.au/tree/pdf/volume22/22-1027.pdf}, volume = 22, year = 2002 }