Thomas Früh. (1997). Simulation of water flow in the branched tree architecture. Silva Fennica vol. 31 no. 3 article id 5625. https://doi.org/10.14214/sf.a8526

Keywords: drought stress; modelling; branches; tree architecture; water flow; finite difference method; hydraulic network; numerical model; hydraulic system

Abstract | View details | Full text in PDF | Author Info

The model HYDRA, which simulates water flow in the branched tree architecture, is characterized. Empirical studies of the last decades give strong evidence for a close structure-function linkage in the case of tree water flow. Like stomatal regulation, spatial patterns of leaf specific conductivity can be regarded as a strategy counteracting conductivity losses, which may arise under drought. Branching-oriented water flow simulation may help to understand how damaging and compensating mechanisms interact within the hydraulic network of trees. Furthermore, a coupling of hydraulic to morphological modelling is a prerequisite if water flow shall be linked to other processes. Basic assumptions of the tree water flow model HYDRA are mass conservation, Darcy's law and the spatial homogeneity of capacitance and axial conductivity. Soil water potential is given as a one-sided border condition. Water flow is driven by transpiration. For unbranched regions these principles are condensed to a nonlinear diffusion equation, which serves as a continuous reference for the discrete method tailored to the specific features of the hydraulic network. The mathematical derivation and model tests indicate that the realization of the basic assumptions is reproducible and sufficiently exact. Moreover, structure and function are coupled in a flexible and computationally efficient manner. Thus, HYDRA may serve as a tool for the comparative study of different tree architectures in terms of hydraulic function.

Früh, E-mail: tf@mm.unknown

article id 5210, category Article

Heikki Smolander, Juha Lappi. (1984). The interactive effect of water stress and temperature on the CO2 response of photosynthesis in Salix. Silva Fennica vol. 18 no. 2 article id 5210. https://doi.org/10.14214/sf.a15389

Keywords: drought stress; willow; temperature; photosynthetic capacity; Salix sp.; Salix sp. cv. Aquatica; CO2 conductance

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The interactive effects of water stress and temperature on the CO₂ response of photosynthesis was studied in Salix sp. cv. Aquatica using the closed IRGA system. A semi-empirical model was used to describe the CO₂ response of photosynthesis. The interactive effect of water stress and temperature was divided into two components: the change in CO₂ conductance and the change in the photosynthetic capacity. The CO₂ conductance was not dependent on the temperature when the willow plant was well watered, but during water stress it decreased as the temperature increased. The photosynthetic capacity of the willow plant increased along with an increase in temperature when well-watered, but during water stress temperature had quite opposite effect.

The PDF includes a summary in Finnish.

Smolander, E-mail: hs@mm.unknown
Lappi, E-mail: jl@mm.unknown

Category : Research article

article id 1176, category Research article

Batoul Al-Hawija, Viktoria Wagner, Monika Partzsch, Isabell Hensen. (2014). Germination differences between natural and afforested populations of Pinus brutia and Cupressus sempervirens. Silva Fennica vol. 48 no. 4 article id 1176. https://doi.org/10.14214/sf.1176

Keywords: nursery; silviculture; drought stress; cold stratification; local adaptation; salt stress; Syria

Highlights: Silvicultural practices of raising and outplanting seedlings yielded contrasting outcomes in our species; Afforested Pinus brutia populations acquired ability to tolerate drought stress at intermediate and hot temperatures compared to natural populations, which may indicate local adaptation; Natural Cupressus sempervirens populations showed higher salt-tolerance than afforested populations; Seed germination was optimal under intermediate temperatures and deionized water for both species.

Abstract | Full text in HTML | Full text in PDF | Author Info

In afforestation, silvicultural processes of raising and planting seedlings under certain conditions can yield contrasting outcomes in tree stock performance. Moderate nursery conditions may select against stress tolerance whereas planting seedlings in stressful environments at afforestation sites may select for higher stress tolerance compared to natural populations. We compared germination performance between natural and afforested populations of Pinus brutia Ten. subsp. brutia and Cupressus sempervirens L. var. horizontalis (Mill.) under differing stress treatments. Seeds were collected from both natural stands and from afforested populations outside the natural distribution range, in Syria. Cold, intermediate and hot temperature regimes were simulated (8/4 °C, 20/10 °C and 32/20 °C) along with cold stratification, drought stress (–0.2 and –0.4 MPa), salt stress (50 and 100 mMol l^–1), and deionized water (control) conditions. In addition, we tested the effects of seed weight and climatic conditions on seed germination. In general, intermediate temperatures were optimal for both population types. Afforested P. brutia populations outperformed natural ones under drought stress levels at hot and/or intermediate temperatures. Conversely, in C. sempervirens, cold stratification at all temperatures and higher salt stress at intermediate temperatures significantly decreased germination in afforested populations. Seed weight did not significantly affect germination percentages, which were however significantly negatively related to annual precipitation in P. brutia, and to annual temperature in C. sempervirens. We infer that silvicultural processes led to divergent outcomes in our species: local adaptation to drought stress and hot temperatures in afforested P. brutia populations and lower salt-stress tolerance in C. sempervirens.

Al-Hawija, Martin-Luther-University Halle-Wittenberg, Institute of Biology/Geobotany and Botanical Garden, Am Kirchtor 1, D-06108 Halle/Saale, Germany E-mail: batoulh@gmail.com
Wagner, Department of Botany and Zoology, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic E-mail: wagner@sci.muni.cz
Partzsch, Martin-Luther-University Halle-Wittenberg, Institute of Biology/Geobotany and Botanical Garden, Am Kirchtor 1, D-06108 Halle/Saale, Germany E-mail: monika.partzsch@botanik.uni-halle.de
Hensen, Martin-Luther-University Halle-Wittenberg, Institute of Biology/Geobotany and Botanical Garden, Am Kirchtor 1, D-06108 Halle/Saale, Germany & German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany E-mail: isabell.hensen@botanik.uni-halle.de

article id 160, category Research article

Fan Yang, Ling-Feng Miao. (2010). Adaptive responses to progressive drought stress in two poplar species originating from different altitudes. Silva Fennica vol. 44 no. 1 article id 160. https://doi.org/10.14214/sf.160

Keywords: antioxidant enzymes; drought stress; free proline; hydrogen peroxide; malondialdehyde; Populus

Abstract | View details | Full text in PDF | Author Info

Cuttings of Populus kangdingensis C. Wang et Tung and Populus cathayana Rehder, originating from high and low altitudes in the eastern Himalaya, respectively, were examined during one growing season in a greenhouse to determine the effects of progressive drought stress. The results manifested that the adaptive responses to progressive drought stress were different in these two species from different altitudes. Significant changes in stem height, leaf development, relative water content (RWC), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) appeared earlier in P. cathayana than in P. kangdingensis, whereas changes in soluble protein, soluble sugar, free proline and antioxidant enzymes appeared earlier in P. kangdingensis. In addition, changes in these parameters became more and more significant when the drought stress progressed, especially under severe drought stress in P. cathayana. Plant growth showed significant positive correlations with soluble proteins and sugars, free proline and antioxidants and a significant negative correlation with RWC under water stressed treatment in two poplar species. Compared with P. cathayana, P. kangdingensis was able to maintain a superior height growth and leaf development under drought stress. Also, P. kangdingensis possessed greater increments in soluble protein, soluble sugar, free proline and antioxidant enzymes, but lower increments in MDA and H₂O₂ than did P. cathayana when the cuttings were exposed to progressive drought stress. Our results suggest that P. kangdingensis originating from the high altitude has a better drought tolerance than does P. cathayana originating from the low altitude. Furthermore, this study manifested that acclimation to drought stress are related the rapidity, severity, duration of the drought event and the altitude of two poplar species.

Yang, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, Hubei 430074, P. R. China (yangfan@wbgcas.cn) & Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu, Sichuan 610041, P. R. China E-mail: fanyangmlf6303@163.com
Miao, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei 430071, P. R. China E-mail: lfm@nn.cn

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