Tree Physiology

Elliott, Katherine, J.;Vose, James, M.

doi: 10.1093/treephys/14.5.439pmid: 14967681

Abstract We measured net photosynthesis, leaf conductance, xylem water potential, and growth of Pinus strobus L. seedlings two years after planting on two clear-cut and burned sites in the southern Appalachians. Multiple regression analysis was used to relate seedling net photosynthesis to vapor pressure deficit, seedling crown temperature, photosynthetically active radiation (PAR), needle N, xylem water potential, and soil water, and to relate seedling size and growth to physiological measurements (average net photosynthesis, leaf conductance, and cumulative xylem water potential), soil water, needle N, seedling temperature, and PAR. Seedling net photosynthesis was significantly related to vapor pressure deficit, midday water potential, crown temperature, and PAR (r2 = 0.70) early in the growing season (May 1992) with vapor pressure deficit alone explaining 42% of the variation. As neighboring vegetation developed, light became more limiting and significantly reduced seedling net photosynthesis later in the growing season (July, August, and September). Final seedling diameter was significantly related to competitor biomass, average photosynthetic rate, and needle N (r2 = 0.68). This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Tyree, Melvin, T.;Kolb, Kimberley, J.;Rood, Stewart, B.;Patiño,, Sandra

doi: 10.1093/treephys/14.5.455pmid: 14967682

Abstract Vulnerability of xylem to loss of hydraulic conductivity caused by drought-induced cavitation was determined for three riparian cottonwood species in Lethbridge, Alberta: Populus deltoides Bartr., P. balsamifera L., and P. angustifolia James. These species suffered 50% loss of hydraulic conductivity in one-year-old stem segments when xylem pressure potential fell to –0.7 MPa for P. deltoides and –1.7 MPa for P. balsamifera and P. angustifolia, making them the three most vulnerable tree species reported so far in North America. The possible contribution of drought-induced xylem dysfunction to the decline of riparian ecosystems in dammed rivers is discussed. This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Yokota,, Taketo;Ogawa,, Kazuharu;Hagihara,, Akio

doi: 10.1093/treephys/14.5.467pmid: 14967683

Abstract Nighttime respiration was measured at monthly intervals over one year on the aboveground parts of five sample trees in an 8-year-old hinoki cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) stand, by an enclosed standing-tree method. The respiration rate rose rapidly from early spring to a maximum in June, and decreased abruptly in July and then gradually toward autumn and winter. The seasonal change in the respiration rate was synchronized with stem volume increment rather than with monthly mean air temperature. The respiration rate, r, of individual trees increased with increasing tree dimensions, such as stem volume, vS, and stem girth at the base of the live crown, GB. The dependence of respiration rate on tree size was successfully represented by a power function. The r – vS dependence was rather stronger than the r – GB2 dependence, especially toward the end of the growing season (from July to September). The observed respiration rate was almost the same as the respiration rate corrected for the monthly mean air temperature. The annual respiration of individual trees was directly proportional to their phytomass or to its increment. Although the annual respiration of individual trees decreased proportionally to the square root of the leaf mass, it decreased abruptly in the range close to the smallest sample tree. Combining the monthly relationship between respiration rate and stem volume with the tree size distribution in the stand, the stand aboveground annual respiration was estimated to be 20.4 Mg CO2 ha−1 year−1 (= 12.5 Mg dry mass ha−1 year−1) for an aboveground biomass of 17.4 Mg ha−1 with an annual increment of 6.51 Mg ha−1 year−1, i.e., the stand aboveground annual respiration amounted to the equivalent of 72% of the biomass or to almost twice the biomass increment. This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Martin, Timothy, A.;Teskey, Robert, O.;Dougherty, Phillip, M.

doi: 10.1093/treephys/14.5.481pmid: 14967684

Abstract Temperature-independent fluctuations in stem CO2 efflux were measured in Pinus taeda L. seedlings. Stem CO2 efflux was measured during high and low transpiration rates, high and low net photosynthesis rates, and normal and interrupted substrate supply conditions. Stem CO2 efflux rates were an average of 6.7% lower during periods of high transpiration compared to periods of low transpiration. This difference in stem CO2 efflux rates was not due to water stress. The most likely cause was movement of respiratory CO2 in the transpiration stream. Interruption of substrate supply to the stem by phloem girdling reduced stem CO2 efflux rates. Increasing net photosynthesis rates from low to high had no effect on stem CO2 efflux, but decreasing net photosynthesis from high to low caused relatively small reductions in stem CO2 efflux. These results indicate that diurnal changes in net photosynthesis rate may play a small role in temperature-independent afternoon depressions of stem CO2 efflux. The transport of respiratory CO2 by the transpiration stream compromises measurements of woody tissue respiration obtained by commonly accepted gas exchange techniques. This phenomenon could also affect measurement of leaf net photosynthesis and branch woody tissue respiration. This content is only available as a PDF. Author notes 2 Current address: College of Forest Resources, AR-10, University of Washington, Seattle, WA 98195, USA 3 Current address: Southeastern Forest Experiment Station, United States Forest Service, PO Box 12254, Research Triangle Park, NC 27709, USA © 1994 Heron Publishing—Victoria Canada

Syvertsen, J., P.

doi: 10.1093/treephys/14.5.497pmid: 14967685

Abstract Effects of defoliation on partial shoot removal by decapitation on seedling growth, water use and net gas exchange of remaining basal leaves, were examined in Citrus spp. Shoot and root growth rates were manipulated to test for effects of growth demands on net gas exchange. Partially defoliated plants had higher leaf pressure potentials, root conductivities and rates of water use than intact control plants. Shoot regrowth occurred at the expense of root loss. Basal leaves on defoliated plants consistently had higher rates of CO2 assimilation (A) than leaves on intact plants. Stomatal conductance (gs) changed little after defoliation so the higher A of leaves on defoliated plants lowered the ratio of intercellular to ambient CO2 concentration (Ci/Ca) in the mesophyll. In some cases, gs increased with A in defoliated plants but Ci/Ca was not affected. Stomatal conductance only limited A when intact seedlings were stressed by root confinement in small pots or when leaves were exposed to high vapor pressure deficits during gas exchange measurements. Increased carbon demand for shoot regrowth increased photosynthetic capacity and was more important than stomatal responses in determining A after partial shoot loss. This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Mayne, Michael, B.;Subramanian,, Mohan;Blake, Terence, J.;Coleman, John, R.;Blumwald,, Eduardo

doi: 10.1093/treephys/14.5.509pmid: 14967686

Abstract The impact of drought conditioning on the ability of eight-week-old jack pine (Pinus banksiana Lamb.) seedlings to withstand drought was assessed. Two progressive cycles of drought conditioning significantly increased the survival of seedlings subjected to a subsequent prolonged drought. The in vivo accumulation of several root membrane proteins during drought conditioning was correlated with an increase in seedling survival. A group of root proteins, ranging in molecular mass from 43 to 47 kDa, increased accumulation during one cycle of drought conditioning and to a lesser extent during two cycles of drought conditioning. The accumulation of several low molecular mass membrane and soluble proteins also increased during drought conditioning, suggesting that these proteins may play an important role in the enhancement of drought tolerance. In vitro translation studies showed a general increase in the abundance of protein products encoded by mRNAs from drought-conditioned seedlings. Although the majority of the in vitro translation products appeared in both control and drought-conditioned seedlings, one mRNA encoding a 15 kDA translated protein was more prominent during the second cycle of drought conditioning. This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Label,, Philippe;Imbault,, Nadine;Villar,, Marc

doi: 10.1093/treephys/14.5.521pmid: 14967687

Abstract A method of fractionation, quantitation and identification of abscisic acid (ABA) in poplar flowers is presented in the context of intra- and interspecific pollination studies in Populus nigra × P. nigra and P. nigra × P. deltoides, respectively. Poplar flowers were dissected into stigma, ovary and pedicel. Abscisic acid concentrations were measured at receptivity and 5 days after pollination in each part of the flower. Abscisic acid was fractionated by reverse-phase HPLC followed by an enzyme-linked immunosorbent assay (ELISA) with anti-ABA polyclonal antibody and GC–MS identification of the immunoreactive ABA fractions. Samples were fractionated and ABA was identified by the presence of a cross-reactive metabolite of ABA in the extracts. The interspecific cross (P. nigra × P. deltoides) had a high concentration of ABA in the pedicel, where abscission occurred, whereas in the intraspecific cross, ABA concentration in the pedicel was low. The results are discussed with reference to the control ABA exerts on the abscission of poplar flowers after interspecific incompatible pollinations. This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Zhang,, Jianwei;Fins,, Lauren;Marshall, John, D.

doi: 10.1093/treephys/14.5.531pmid: 14967688

Abstract Photosynthetic gas exchange, stable carbon isotope discrimination (Δ), height and diameter were compared among five open-pollinated families of 12-year-old western larch trees growing in a common garden in Moscow, Idaho, USA. Statistically significant variation was detected among the families in the two growth traits, Δ and stomatal conductance to water vapor (g) (P ≤ 0.013), but differences among families in photosynthetic rate (A) and water-use efficiency (W) were not significant (P ≥ 0.203). Water-use efficiency was strongly correlated with Δ (r = –0.95, P < 0.01). Neither growth trait was correlated with A (r ≤ 0.05, P > 0.93) and height was not significantly correlated with Δ (r = –0.75, P = 0.15). Tree diameter and Δ were significantly correlated (r = –0.92, P = 0.03). These results were strongly influenced by a single family. Both the variation in Δ and correlation trends between Δ and the growth traits height and diameter suggest the possibility of selecting for high water-use efficiency with the potential for simultaneous gains in height and diameter growth. This content is only available as a PDF. © 1994 Heron Publishing—Victoria Canada

Rennenberg,, Heinz;Schupp,, Robert;Glavac,, Vjekoslav;Jochheim,, Hubert

doi: 10.1093/treephys/14.5.541pmid: 14967689

Abstract During different phases of the annual growth cycle, xylem sap was collected from trunk segments of adult beech (Fagus sylvatica L.) trees by the water displacement technique. Irrespective of the height of the trunk, both sulfate and reduced sulfur compounds were detected in the xylem sap throughout the year. Sulfate was the predominant sulfur compound in all samples analyzed. Its concentration in the xylem sap varied between 10 and 350 μmol l−1, with highest concentrations in April, shortly before bud break. In contrast to other tree species, cysteine and not glutathione was the predominant thiol transported in the xylem sap of beech trees. The cysteine concentration ranged between 0.1 and 1 μmol l−1. As observed for sulfate, maximum cysteine concentrations were found in April. Apparently, both sulfate and cysteine transport contribute to the sulfur supply of the developing leaves. Seasonal changes in the axial distribution of cysteine and sulfate differed, indicating differences in the source–sink relations of these sulfur compounds. High, but uniform, xylem sap sulfate concentrations in April may originate from balanced sulfate uptake by the roots, whereas high cysteine concentrations in April, increasing with increasing height of the trunk, may originate in part from protein breakdown in the trunk. Reversal of the axial distribution of xylem sap cysteine in late summer–early fall to higher concentrations in the lower part of the trunk than in the upper part of the trunk suggests that the upper part of the trunk becomes a sink for cysteine as a result of the synthesis of storage proteins at this time of the year. This content is only available as a PDF. Author notes 3 Present-address: Fachbereich Biologie/Chemie der Gesamthochschule Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany © 1994 Heron Publishing—Victoria Canada