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Stem Growth (stem + growth)
Selected AbstractsAllocation of above-ground growth is related to light in temperate deciduous saplingsFUNCTIONAL ECOLOGY, Issue 4 2003D. A. King Summary 1Allocational shifts in response to light may be an important factor in allowing plants to survive in shade, while increasing their extension rates and competitive ability in sun. To investigate this response, the allocation of above-ground growth between leaves, branches and stems was studied in saplings of Acer pensylvanicum L. and Castenea dentata (Marsh.) Borkh. in the Appalachian mountains of western Virginia, USA. Measurements of current leaf biomass, current and past year leaf numbers and the growth ring widths of branches and stem were used to estimate biomass partitioning for saplings growing in locations ranging from forest understorey to large openings. 2Both species showed higher leaf area per unit leaf biomass (SLA) and higher allocation of above-ground growth to leaves in shade than in sun. 3There were no differences between species in the slopes of the relationships of allocation and SLA vs estimated irradiance, but SLA was significantly greater in A. pensylvanicum than in C. dentata at a given light level. Hence, somewhat lower production per unit leaf area is required to maintain the canopy in A. pensylvanicum, consistent with foresters' ratings of greater shade tolerance for this species. 4Greater foliar allocation in shade than sun has also been observed in broad-leaved evergreen saplings, but generally not in seedlings. This difference is probably related to differences in size and age between seedlings and saplings. Young seedlings typically show exponential growth with no immediate foliar losses, while shaded saplings lie closer to the steady state where new leaves replace old ones with little additional stem growth. 5Thus trees shift their allocation patterns in an acclimatory fashion, depending on their size and light environment, with the costs of replacing senesced leaves becoming of consequence as juveniles age. [source] The growth respiration component in eddy CO2 flux from a Quercus ilex mediterranean forestGLOBAL CHANGE BIOLOGY, Issue 9 2004S. Rambal Abstract Ecosystem respiration, arising from soil decomposition as well as from plant maintenance and growth, has been shown to be the most important component of carbon exchange in most terrestrial ecosystems. The goal of this study was to estimate the growth component of whole-ecosystem respiration in a Mediterranean evergreen oak (Quercus ilex) forest over the course of 3 years. Ecosystem respiration (Reco) was determined from night-time carbon dioxide flux (Fc) using eddy correlation when friction velocity (u*) was greater than 0.35 m s,1 We postulated that growth respiration could be evaluated as a residual after removing modeled base Reco from whole-ecosystem Reco during periods when growth was most likely occurring. We observed that the model deviated from the night-time Fc -based Reco during the period from early February to early July with the largest discrepancies occurring at the end of May, coinciding with budburst when active aboveground growth and radial growth increment are greatest. The highest growth respiration rates were observed in 2001 with daily fluxes reaching up to 4 g C m,2. The cumulative growth respiration for the entire growth period gave total carbon losses of 170, 208, and 142 g C m,2 for 1999, 2001, and 2002, respectively. Biochemical analysis of soluble carbohydrates, starch, cellulose, hemicellulose, proteins, lignin, and lipids for leaves and stems allowed calculation of the total construction costs of the different growth components, which yielded values of 154, 200, and 150 g C for 3 years, respectively, corresponding well to estimated growth respiration. Estimates of both leaf and stem growth showed very large interannual variation, although average growth respiration coefficients and average yield of growth processes were fairly constant over the 3 years and close to literature values. The time course of the growth respiration may be explained by the growth pattern of leaves and stems and by cambial activity. This approach has potential applications for interpreting the effects of climate variation, disturbances, and management practices on growth and ecosystem respiration. [source] Interactions between Drought and O3 Stress in Forest TreesPLANT BIOLOGY, Issue 1 2006R. Matyssek Abstract: Temperature increase and altered precipitation are facets of "Global Change", along with enhanced tropospheric ozone (O3) and CO2 levels. Both O3 and drought may curtail the probably limited capacity of "extra" carbon fixation in forest trees under a CO2 -enriched atmosphere. In view of the exceptionally dry year of 2003 in Central Europe, this mini-review highlights O3/drought interactions in biochemical and ecophysiological responses of trees. Such interactions appear to vary, depending on the genotype and factorial scenarios. If O3 perturbs stomatal regulation, tolerance to both drought and persisting O3 exposure may be weakened, although drought preceding O3 stress may "harden" against O3 impact. Stomatal closure under drought may shield trees against O3 uptake and injury, which indeed was the case in 2003. However, the trees "tuning" between O3 uptake and defence capacity is crucial in stress tolerance. Defence may be constrained due to limited carbon fixation, which results from the trade-off with O3 exclusion upon stomatal closure. Drought may cause a stronger reduction in stem growth than does ozone on an annual basis. [source] Ion channels and the transduction of light signalsPLANT CELL & ENVIRONMENT, Issue 7 2000E. P. Spalding ABSTRACT Studies of biological light-sensing mechanisms are revealing important roles for ion channels. Photosensory transduction in plants is no exception. In this article, the evidence that ion channels perform such signal-transducing functions in the complex array of mechanisms that bring about plant photomorphogenesis will be reviewed and discussed. The examples selected for discussion range from light-gradient detection in unicellular algae to the photocontrol of stem growth in Arabidopsis. Also included is some discussion of the technical aspects of studies that combine electrophysiology and photobiology. [source] Species-Specific Growth Responses to Climate Variations in Understory Trees of a Central African Rain ForestBIOTROPICA, Issue 4 2010Camille Couralet ABSTRACT Basic knowledge of the relationships between tree growth and environmental variables is crucial for understanding forest dynamics and predicting vegetation responses to climate variations. Trees growing in tropical areas with a clear seasonality in rainfall often form annual growth rings. In the understory, however, tree growth is supposed to be mainly affected by interference for access to light and other resources. In the semi-deciduous Mayombe forest of the Democratic Republic of Congo, the evergreen species Aidia ochroleuca, Corynanthe paniculata and Xylopia wilwerthii dominate the understory. We studied their wood to determine whether they form annual growth rings in response to changing climate conditions. Distinct growth rings were proved to be annual and triggered by a common external factor for the three species. Species-specific site chronologies were thus constructed from the cross-dated individual growth-ring series. Correlation analysis with climatic variables revealed that annual radial stem growth is positively related to precipitation during the rainy season but at different months. The growth was found to associate with precipitation during the early rainy season for Aidia but at the end of the rainy season for Corynanthe and Xylopia. Our results suggest that a dendrochronological approach allows the understanding of climate,growth relationships in tropical forests, not only for canopy trees but also for evergreen understory species and thus arguably for the whole tree community. Global climate change influences climatic seasonality in tropical forest areas, which is likely to result in differential responses across species with a possible effect on forest composition over time. Abstract in French is available at http://www.blackwell-synergy.com/loi/btp [source] | ||||||||||