Tree Physiology

Sun, Osbert, J.;Sweet, Geoffrey, B.;Whitehead,, David;Buchan, Graeme, D.

doi: 10.1093/treephys/15.10.629pmid: 14965996

Abstract Gas exchange and water relations were investigated in Nothofagus solandri var. cliffortioides (Hook. f.) Poole (mountain beech) and Nothofagus menziesii (Hook. f.) Oerst (silver beech) seedlings in response to water stress and waterlogging. At soil matric potentials (Ψsoil) above –0.005 MPa, N. solandri had significantly higher photosynthetic rates (A), and stomatal and residual conductances (gsw and grc), and lower predawn xylem water potentials (Ψpredawn) than N. menziesii. The relative tolerance of plants to water stress was defined in terms of critical soil matric potential (Ψcri) and lethal xylem water potential (Ψlethal). The estimated values of Ψcri and Ψlethal were –1.2 and –7 MPa, respectively, for N. solandri, and –0.7 and –4 MPa, respectively, for N. menziesii. Photosynthesis was sustained to a xylem water potential (Ψxylem) of –7 MPa in N. solandri compared with –4 MPa in N. menziesii. Following rewatering, both A and Ψxylem recovered quickly in N. solandri, whereas the two variables recovered more slowly in N. menziesii. During the development of water stress, nonstomatal inhibition significantly affected A in both N. solandri and N. menziesii. Nothofagus menziesii was more susceptible to inhibition of A by waterlogging than N. solandri. However, the tolerance of N. solandri to severe waterlogging was also limited as a result of a failure to form adventitious roots, suggesting a lack of adaptation to these conditions. The differences in tolerance to water stress and waterlogging between the two species are consistent with the distribution patterns of N. solandri and N. menziesii in New Zealand. This content is only available as a PDF. Author notes 2 New Zealand Forest Research Institute, Private Bag 4800, Christchurch, New Zealand © 1995 Heron Publishing—Victoria Canada

Vann, David, R.;Strimbeck, G., Richard;Johnson, Arthur, H.

doi: 10.1093/treephys/15.10.639pmid: 14965997

Abstract Recent forest studies have established that high-elevation (> 900 m) populations of red spruce (Picea rubens Sarg.) in the northeastern USA are declining. Because it has been suggested that changes in air quality are responsible for the decline, we examined the effects of acidic mists and ozone on several biochemical and growth parameters in mature montane red spruce. We used branch-sized environmental chambers to introduce mists of controlled composition and exclude ambient clouds and ozone from individual branches within a tree. Mists consisting of distilled water increased the end-of-season pigment concentration and shoot length of enclosed branches relative to ambient or artificial mists. Needle and twig weights and starch concentrations were not significantly altered by the acidic mist treatments. Removal of ambient ozone had no apparent effect on the variables measured. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Joyce, Brian, J.;Steiner, Kim, C.

doi: 10.1093/treephys/15.10.649pmid: 14965998

Abstract A 7-m tall white ash tree (Fraxinus americana Marsh.) was dissected, and hydraulic parameters of the xylem were determined by inducing a steady-state flow of water through the stem segments and monitoring volume and velocity flow rates. Leaf-specific conductivity (LSC) was highest in the main stem and lowest in some of the leaf-bearing lateral shoots. The LSC was higher in the main stem than in branches and higher in primary than in secondary branch axes. Terminal leaf-bearing shoots were larger and had a significantly greater mean LSC than subjacent lateral shoots. A significant reduction in LSC was associated with the transition between 1- and 2-year-old growth. In branches of the same age, there was a close correspondence among LSC, branch position and branch size. The average LSC of leaf-bearing shoots from south-facing branches was 43% greater than that of shoots from north-facing branches. Within-crown variation in LSC was associated with variation in velocity flow rate (V). By contrast, the ratio of potentially functional xylem area to supported leaf area (Apf/Al) was relatively stable throughout the crown. Stratification of stems by Strahler order accounted for approximately 70% of the total variation in LSC. These results suggest that (1) there exists a systematic pattern of variation in LSC distribution within the crown of white ash, (2) within-crown variability in LSC is primarily the result of variation in mean vessel diameter, and (3) there is a physiological linkage between LSC and crown morphology that is maintained through a positive feedback mechanism during branch ontogeny. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Panek, Jeanne, A.;Waring, Richard, H.

doi: 10.1093/treephys/15.10.657pmid: 14965999

Abstract The natural abundance of stable carbon isotopes in the annual rings of forest trees is used as a tracer of environmental changes such as climate and atmospheric pollution. Although tree-ring δ13C varies by about 2‰ from year to year, variability within the foliage can be as high as 6‰. Recent studies have shown that branch length affects stomatal response, which influences the integrated foliar δ13C signal. To improve the ability of δ13C to predict climate differences, we examined the relationship between branch length and foliar δ13C in Pseudotsuga menziesii (Mirb.) Franco from four sites across a steep climate gradient in Oregon. The transect spanned the boundary between the ranges of the coastal variety, P. menziesii var. menziesii (three sites), and the Rocky Mountain variety, P. menziesii var. glauca (one site). At the most maritime site, branch length explained 76% of within-site variation of 5‰, whereas at the harshest site, branch length accounted for only 15% of this variation. We considered the possibility that cavitation in the water-conducting xylem obscures the branch length effect in the harsher climates. Cavitation, as measured by dye perfusion, was most extensive at sites where the branch length effect in the coastal variety was weakest. Trees at the site with the most substantial cavitation displayed seasonal xylem refilling. Branch length standardization significantly improved the relationship between δ13C and climate. With standardization to constant length, δ13C values were significantly related to the degree that climatic variables, as modeled with a forest growth simulation model, constrain transpiration (R2 = 0.69, P < 0.0001). Without standardization, the R2 was 0.27. We conclude that sampling standard length branches or tree rings from trees of similar shape and size is desirable when seeking correlations between isotopic composition and climate. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Wang,, Tongli;Tigerstedt, P., M.A.;Viherä-Aarnio,, Anneli

doi: 10.1093/treephys/15.10.665pmid: 14966000

Abstract Net photosynthetic rates (A) of leaves in upper and lower crown layers (Aupper and Alower), leaf area index (LAI), mean tilt angle (MTA), several leaf characteristics, and volume growth were observed in fast- and slow-growing families of a 14-year-old full-sib and half-sib family progeny test of Betula pendula Roth. Each measure of net photosynthetic rate was calculated after correcting measured net photosynthesis for the effects of environmental variables. The differences in Aupper and LAI among families were significant. The proportions of the total variance assigned to family for Aupper, Alower and LAI were 33.64, 28.93 and 54.99%, respectively. The mean Aupper and LAI of the fast-growing families were significantly higher than those of the slow-growing families, whereas the mean Alower of the fast-growing families was significantly lower than that of the slow-growing families. There were also significant differences among families in leaf size, leaf shape, and the ratios leaf fresh weight/area and leaf dry weight/area. Between 27.55 and 54.55% of the total variance in these characteristics could be assigned to the family effect. Volume growth was positively correlated with Aupper and LAI, but it was most strongly correlated with Aupper × LAI. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Pelah,, Dan;Shoseyov,, Oded;Altman,, Arie

doi: 10.1093/treephys/15.10.673pmid: 14966001

Abstract We identified a novel 66 kDa boiling-stable protein (BspA) in cultured shoots of aspen (Populus tremula L.) which was highly expressed in response to gradual water stress. The BspA protein, which was highly expressed as early as 1 h after initiation of a drought treatment, accumulated during progressive water stress, decreased on rehydration, and was expressed in response to abscisic acid (ABA) application, as detected by SDS-PAGE protein analysis and Western blotting. Anti-BspA antibodies also cross-reacted with a 119 kDa protein. The 119 kDa protein was also induced by water stress, but it was detected only in the total protein fraction and not in the heat-stable fraction. The BspA protein cross-reacted with antibodies raised against a water-stress-responsive protein isolated from the African resurrection plant Craterostigma plantagineum Hochst. The N-terminal amino acid sequence of BspA was determined and exhibited high homology with the wheat germins GF-2.8 and GF-3.8. The BspA protein was the only major, water-stress-responsive boiling-stable protein detected in aspen. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Wendler,, R.;Carvalho, P., O.;Pereira, J., S.;Millard,, P.

doi: 10.1093/treephys/15.10.679pmid: 14966002

Abstract Six-month-old Eucalyptus globulus Labill. seedlings were grown in sand culture irrigated with a nutrient solution containing 6.0 mol N m−3 for 3 months (November–January). Before rapid growth began in February, seedlings were repotted and irrigated with either 6.0 mol N m−3 (High-N treatment) or 1.0 mol N m−3 (Low-N treatment). Seedlings were analyzed during the subsequent flush of growth to determine the role of old leaves, and in particular the leaf protein Rubsico, as a source of N for new leaf growth. During spring growth, the N content of old leaves of High-N seedlings decreased with decreasing leaf dry weight, although there was no change in leaf number. In High-N seedlings, the net loss of N from old leaves provided less than 10% of the N used for new leaf growth, and the new leaves quickly became the dominant sink for N. In contrast, in Low-N seedlings, the net loss of N from old leaves provided 44% of the N used for new leaf growth. During the period of spring growth, the amount of soluble proteins recovered from old leaves of Low-N seedlings dropped, but there was no change in the content of either Rubisco or chlorophyll. The photosynthetic capacity of old leaves remained constant throughout the study period, and there was no evidence that N was remobilized from Rubisco. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Westin,, Johan;Sundblad,, Lars-Göran;Hällgren,, Jan-Erik

doi: 10.1093/treephys/15.10.685pmid: 14966003

Abstract We investigated changes in photochemical activity and cold hardiness of detached needles of three clones of Picea abies (L.) Karst. by measuring variable chlorophyll fluorescence (Fv/Fm), before and after artificial freezing, from September to June. Photochemical activity varied considerably during the study, but only minor differences in photochemical activity among the clones were observed before freezing. Photochemical activity was high during early fall and then declined from November until April. Photochemical activity was at a minimum in April and then increased quickly to high values in May. During the period from late September to October, and also during the winter, differences in Fv/Fm ratios after artificial freezing to below –10 °C were observed among clones, indicating clonal differences in cold hardiness and hardiness development. The clone having an average height of 2.3 m after 11 years showed consistently lower cold hardiness than clones that had reached average heights of 4.0 and 5.0 m. There were also differences in the temperature requirement for bud flushing among clones. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada

Iriondo, J., M.;, de la Iglesia, M.;Pérez,, C.

doi: 10.1093/treephys/15.10.691pmid: 14966004

Abstract Multiple shoots were obtained from nodal segments of mature trees of Elaeagnus angustifolia L. cultured on MS medium (Murashige and Skoog 1962) supplemented with 0, 0.88 or 2.22 μM N6-benzyladenine. When nodal segments taken from the in vitro proliferated shoots were cultured under the same conditions, additional multiple shoots were obtained. Rooting of the in vitro propagated shoots was achieved on full strength MS medium or on MS supplemented with 2.46 μM indole-3-butyric acid. Regenerated plantlets were acclimatized and successfully transplanted to soil. This content is only available as a PDF. © 1995 Heron Publishing—Victoria Canada