The effects of drought and shade on the performance, morphology and physiology of Ghanaian tree species
Amissah, L. ; Mohren, G.M.J. ; Kyereh, B. ; Poorter, L. - \ 2015
PLoS ONE 10 (2015)4. - ISSN 1932-6203
tropical forest - water relations - rain-forest - seedling establishment - desiccation-tolerance - carbon gain - trade-offs - photosynthetic acclimation - niche differentiation - relative importance
In tropical forests light and water availability are the most important factors for seedling growth and survival but an increasing frequency of drought may affect tree regeneration. One central question is whether drought and shade have interactive effects on seedling growth and survival. Here, we present results of a greenhouse experiment, in which seedlings of 10 Ghanaian tree species were exposed to combinations of strong seasonal drought (continuous watering versus withholding water for nine weeks) and shade (5% irradiance versus 20% irradiance). We evaluated the effects of drought and shade on seedling survival and growth and plasticity of 11 underlying traits related to biomass allocation, morphology and physiology. Seedling survival under dry conditions was higher in shade than in high light, thus providing support for the “facilitation hypothesis” that shade enhances plant performance through improved microclimatic conditions, and rejecting the trade-off hypothesis that drought should have stronger impact in shade because of reduced root investment. Shaded plants had low biomass fraction in roots, in line with the trade-off hypothesis, but they compensated for this with a higher specific root length (i.e., root length per unit root mass), resulting in a similar root length per plant mass and, hence, similar water uptake capacity as high-light plants. The majority (60%) of traits studied responded independently to drought and shade, indicating that within species shade- and drought tolerances are not in trade-off, but largely uncoupled. When individual species responses were analysed, then for most of the traits only one to three species showed significant interactive effects between drought and shade. The uncoupled response of most species to drought and shade should provide ample opportunity for niche differentiation and species coexistence under a range of water and light conditions. Overall our greenhouse results suggest that, in the absence of root competition shaded tropical forest tree seedlings may be able to survive prolonged drought.
Predicting leaf traits of herbaceous species from their spectral characteristics
Roelofsen, H.D. ; Bodegom, P.M. van; Kooistra, L. ; Witte, J.P.M. - \ 2014
Ecology and Evolution 4 (2014)6. - ISSN 2045-7758 - p. 706 - 719.
optical-properties - conifer needles - plant traits - squares regression - tropical forests - canopy structure - carbon gain - wide-range - nitrogen - reflectance
Trait predictions from leaf spectral properties are mainly applied to tree species, while herbaceous systems received little attention in this topic. Whether similar trait–spectrum relations can be derived for herbaceous plants that differ strongly in growing strategy and environmental constraints is therefore unknown. We used partial least squares regression to relate key traits to leaf spectra (reflectance, transmittance, and absorbance) for 35 herbaceous species, sampled from a wide range of environmental conditions. Specific Leaf Area and nutrient-related traits (N and P content) were poorly predicted from any spectrum, although N prediction improved when expressed on a per area basis (mg/m2 leaf surface) instead of mass basis (mg/g dry matter). Leaf dry matter content was moderately to good correlated with spectra. We explain our results by the range of environmental constraints encountered by herbaceous species; both N and P limitations as well as a range of light and water availabilities occurred. This weakened the relation between the measured response traits and the leaf constituents that are truly responsible for leaf spectral behavior. Indeed, N predictions improve considering solely upper or under canopy species. Therefore, trait predictions in herbaceous systems should focus on traits relating to dry matter content and the true, underlying drivers of spectral properties.
Stimulating seedling growth in early stages of secondary forest succession: a modeling approach to guide tree liberation
Kuijk, M. ; Anten, N.P.R. ; Oomen, R.J. ; Schieving, F. - \ 2014
Frontiers in Plant Science 5 (2014). - ISSN 1664-462X - 13 p.
natural regeneration - rain-forest - light interception - south kalimantan - carbon gain - costa-rica - canopy photosynthesis - subtropical forests - dipterocarp forest - tropical pasture
Excessive growth of non-woody plants and shrubs on degraded lands can strongly hamper tree growth and thus secondary forest succession. A common method to accelerate succession, called liberation, involves opening up the vegetation canopy around young target trees. This can increase growth of target trees by reducing competition for light with neighboring plants. However, liberation has not always had the desired effect, likely due to differences in light requirement between tree species. Here we present a 3D-model, which calculates photosynthetic rate of individual trees in a vegetation stand. It enables us to examine how stature, crown structure, and physiological traits of target trees and characteristics of the surrounding vegetation together determine effects of light on tree growth. The model was applied to a liberation experiment conducted with three pioneer species in a young secondary forest in Vietnam. Species responded differently to the treatment depending on their height, crown structure and their shade-tolerance level. Model simulations revealed practical thresholds over which the tree growth response is heavily influenced by the height and density of surrounding vegetation and gap radius. There were strong correlations between calculated photosynthetic rates and observed growth: the model was well able to predict growth of trees in young forests and the effects of liberation there upon. Thus, our model serves as a useful tool to analyze light competition between young trees and surrounding vegetation and may help assess the potential effect of tree liberation.
Trade-off between light interception efficiency and light use efficiency: implications for species coexistence in one-sided light competition
Onoda, Y. ; Saluñga, J.B. ; Akutsu, K. ; Aiba, S.I. ; Yahara, T. ; Anten, N.P.R. - \ 2014
Journal of Ecology 102 (2014)1. - ISSN 0022-0477 - p. 167 - 175.
herbaceous plant community - temperate rain-forest - secondary forest - canopy structure - carbon gain - height - growth - photosynthesis - populations - stratification
1. Taller plant species can pre-empt solar energy and suppress growth of subordinate species in vegetation stands, which is described through one-sided competition. Yet, in much of the world’s vegetation species of different statures coexist. This study aims to clarify the mechanisms underlying this apparent paradox. 2. We quantified how co-occurring species and individuals intercepted and used light for growth in a mature, warm-temperate evergreen forest. This was performed by determining the 3D distribution of foliage and light with a ground-based lidar system in combination with nondestructive measurements of plant growth. 3. Taller trees intercepted light more efficiently per unit of above-ground biomass than shorter trees did (=higher light interception efficiency, LIE). However, taller trees tended to have lower biomass production per unit light interception (=lower light use efficiency, LUE). Reduced LUE in taller trees was associated with their higher biomass allocation to nonphotosynthetic organs and probably with over-saturated light intensity for photosynthesis at high canopy positions. Due to the increased LIE and decreased LUE with tree heights, a trade-off between LIE and LUE was found, and this trade-off resulted in trees of different statures having similar relative growth rates. 4. Synthesis. Light competition drives trees to grow taller, and the light interception efficiency is higher in taller trees; however, this benefit comes at a cost of decreased efficiency of light use for growth. This trade-off allows trees of different statures to grow at proportionally comparable rates and may promote coexistence of tree species in one-sided light competition.
Plasticity influencing the light compensation point offsets the specialization for light niches across shrub species in a tropical forest understorey
Sterck, F.J. ; Duursma, R.A. ; Pearcy, R.W. ; Valladares, F. ; Cieslak, M. ; Weemstra, M. - \ 2013
Journal of Ecology 101 (2013)4. - ISSN 0022-0477 - p. 971 - 980.
rain-forest - shade tolerance - crown architecture - carbon gain - interception efficiency - traits determine - neutral theory - woody-plants - trade-offs - growth
1.Shade tolerance can be defined as the light level at which plants can survive and possibly grow. This light level is referred to as the whole-plant light compensation point (LCP). The LCP depends on multiple leaf and architectural traits. We are still uncertain how often interspecific trait differences allow species to specialize for separate light niches, as observed between shade-tolerant species and light-demanding species. Alternatively, trait plasticity may allow many species to grow in similar light conditions. 2.We measured leaf and architectural traits of up to 1.5-year-old seedlings of 15 sympatric Psychotria shrub species grown at three light levels. We used a 3D plant model to estimate the impacts of leaf traits, architectural traits and plant size on the whole-plant light compensation point (LCPplant). Plant growth rates were estimated from destructive harvests and allometric relationships. 3.At lower light levels, plants of all species achieved a lower leaf light compensation point (LCPleaf). The light interception efficiency (LIE), an index of self-shading, decreased with increasing plant size and was therefore lower in high-light treatments where plants grew more rapidly. When corrected for size, LIE was lower in the low-light treatment, possibly as a result of lower investments in woody support. Species did not show trade-offs in growth under low- and high-light conditions, because species with the greatest plasticity in LCPplant and underlying traits (LCPleaf and LIE) achieved the highest growth rates at lower light levels. 4.Synthesis. The interspecific differences in LCPplant did not result in a growth or survival trade-off between low- and high-light conditions. Instead, these differences were more than offset by the greater plasticity in LCPplant in some species, which was driven by greater plasticity in both leaves and architecture. The most plastic species achieved the fastest growth at different light levels. The results show that plasticity largely neutralizes the separation of light niches amongst species in this forest understorey genus and imply that differential preferences of species for either gaps or forest understorey occur in later life phases or are driven by other stress factors than low light alone.
Physiological mechanisms in plant growth models: do we need a supra-cellular systems biology approach?
Poorter, H. ; Anten, N.P.R. ; Marcelis, L.F.M. - \ 2013
Plant, Cell & Environment 36 (2013)9. - ISSN 0140-7791 - p. 1673 - 1690.
nitrogen-use efficiency - net assimilation rate - leaf-area - elevated co2 - carbon gain - tomato plants - gas-exchange - chemical-composition - biomass production - critical-appraisal
In the first part of this paper, we review the extent to which various types of plant growth models incorporate ecophysiological mechanisms. Many growth models have a central role for the process of photosynthesis; and often implicitly assume C-gain to be the rate-limiting step for biomass accumulation. We subsequently explore the extent to which this assumption actually holds and under what condition constraints on growth due to a limited sink strength are likely to occur. By using generalized dose–response curves for growth with respect to light and CO2, models can be tested against a benchmark for their overall performance. In the final part, a call for a systems approach at the supra-cellular level is made. This will enable a better understanding of feedbacks and trade-offs acting on plant growth and its component processes. Mechanistic growth models form an indispensable element of such an approach and will, in the end, provide the link with the (sub-)cellular approaches that are yet developing. Improved insight will be gained if model output for the various physiological processes and morphological variables (‘virtual profiling’) is compared with measured correlation networks among these processes and variables. Two examples of these correlation networks are presented
An evolutionary game of leaf dynamics and its consequences for canopy structure
Hikosaka, K. ; Anten, N.P.R. - \ 2012
Functional Ecology 26 (2012)5. - ISSN 0269-8463 - p. 1024 - 1032.
nitrogen-use efficiency - elevated co2 - carbon gain - photosynthetic capacity - xanthium-canadense - plant-populations - individual plants - chenopodium-album - carex-acutiformis - deciduous forest
1. Canopy photosynthesis models combined with optimization theory have been an important tool to understand environmental responses and interspecific variations in vegetation structure and functioning, but their predictions are often quantitatively incorrect. Although evolutionary game theory and the dynamic modelling of leaf turnover have been suggested useful to solve this problem, there is no model that combines these features. 2. Here, we present such a model of leaf area dynamics that incorporates game theory. 3. Leaf area index (LAI; leaf area per unit ground area) was predicted to increase with an increasing degree of interaction between genetically distinct neighbour plants in light interception. This implies that stands of clonal plants that consist of genetically identical daughter ramets have different LAI from other plants. LAI was also sensitive to the assumed vertical pattern of leaf shedding: LAI was predicted to increase with the degree to which leaves were assumed to be shed from higher positions in the canopy. Our model provides more realistic predictions of LAI than previous static optimization, dynamic optimization or static game theoretical models. 4. We suggest that both leaf dynamics and game theoretical considerations of plant competition are indispensable to scale from individual leaf traits to the structure and functioning of vegetation stands, especially in herbaceous species.
Light interception efficiency explained by two simple variables: a test using a diversity of small- to medium-sized woody plants
Duursma, R.A. ; Falster, D.S. ; Valladares, F. ; Sterck, F.J. ; Pearcy, R.W. ; Lusk, C. ; Sendall, K.M. ; Nordenstahl, M. ; Houter, N.C. ; Atwell, B.J. ; Kelly, N. ; Kelly, J.W.G. ; Liberloo, M. ; Tissue, D.T. ; Medlyn, B.E. ; Ellsworth, D.S. - \ 2012
New Phytologist 193 (2012)2. - ISSN 0028-646X - p. 397 - 408.
carbon gain - crown architecture - capture efficiency - heteromeles-arbutifolia - radiation interception - understory plants - canopy structure - rain-forest - model - trees
Plant light interception efficiency is a crucial determinant of carbon uptake by individual plants and by vegetation. Our aim was to identify whole-plant variables that summarize complex crown architecture, which can be used to predict light interception efficiency. •We gathered the largest database of digitized plants to date (1831 plants of 124 species), and estimated a measure of light interception efficiency with a detailed three-dimensional model. Light interception efficiency was defined as the ratio of the hemispherically averaged displayed to total leaf area. A simple model was developed that uses only two variables, crown density (the ratio of leaf area to total crown surface area) and leaf dispersion (a measure of the degree of aggregation of leaves). •The model explained 85% of variation in the observed light interception efficiency across the digitized plants. Both whole-plant variables varied across species, with differences in leaf dispersion related to leaf size. Within species, light interception efficiency decreased with total leaf number. This was a result of changes in leaf dispersion, while crown density remained constant. •These results provide the basis for a more general understanding of the role of plant architecture in determining the efficiency of light harvesting.
How plant architecture affects light absorption and photosynthesis in tomato: towards an ideotype for plant architecture using a functional-structural plant model
Sarlikioti, V. ; Visser, P.H.B. de; Buck-Sorlin, G.H. ; Marcelis, L.F.M. - \ 2011
Annals of Botany 108 (2011)6. - ISSN 0305-7364 - p. 1065 - 1073.
carbon gain - leaf - interception - canopy - morphology - yield - assimilation - efficiency - avoidance - capture
Background and Aims - Manipulation of plant structure can strongly affect light distribution in the canopy and photosynthesis. The aim of this paper is to find a plant ideotype for optimization of light absorption and canopy photosynthesis. Using a static functional structural plant model (FSPM), a range of different plant architectural characteristics was tested for two different seasons in order to find the optimal architecture with respect to light absorption and photosynthesis. Methods - Simulations were performed with an FSPM of a greenhouse-grown tomato crop. Sensitivity analyses were carried out for leaf elevation angle, leaf phyllotaxis, leaflet angle, leaf shape, leaflet arrangement and internode length. From the results of this analysis two possible ideotypes were proposed. Four different vertical light distributions were also tested, while light absorption cumulated over the whole canopy was kept the same. Key Results Photosynthesis was augmented by 6 % in winter and reduced by 7 % in summer, when light absorption in the top part of the canopy was increased by 25 %, while not changing light absorption of the canopy as a whole. The measured plant structure was already optimal with respect to leaf elevation angle, leaflet angle and leaflet arrangement for both light absorption and photosynthesis while phyllotaxis had no effect. Increasing the length : width ratio of leaves by 1·5 or increasing internode length from 7 cm to 12 cm led to an increase of 6–10 % for light absorption and photosynthesis. Conclusions - At high light intensities (summer) deeper penetration of light in the canopy improves crop photosynthesis, but not at low light intensities (winter). In particular, internode length and leaf shape affect the vertical distribution of light in the canopy. A new plant ideotype with more spacious canopy architecture due to long internodes and long and narrow leaves led to an increase in crop photosynthesis of up to 10 %.
Influence of foliar phenology and shoot inclination on annual photosynthetic gain in individual beech saplings: A functional-structural modeling approach
Umeki, K. ; Kikuzawa, K. ; Sterck, F.J. - \ 2010
Forest Ecology and Management 259 (2010)11. - ISSN 0378-1127 - p. 2141 - 2150.
temperate deciduous forests - broad-leaved trees - light conditions - leaf development - fagus-crenata - woody-plants - canopy gaps - carbon gain - growth - architecture
We developed a functional-structural plant model for Fagus crenata saplings and calculated annual photosynthetic gains to determine the influences of foliar phenology and shoot inclination on the carbon economy of saplings. The model regenerated the three-dimensional shoot structure and spatial and temporal display of leaves; we calculated the hourly light interception of each leaf with a detailed light model that allowed us to estimate hourly leaf photosynthetic gain taking leaf age into account. To evaluate the importance of simultaneous foliar phenology and slanting shoots in beech saplings, we calculated the photosynthetic budgets for saplings with contrasting foliar phenologies and shoot inclinations. In our simulations, we distinguished between simultaneous and successive foliar phenologies, upright and slanting shoot inclinations, and environments with and without a vertical gradient in light intensity. Other model parameters (including photosynthesis vs. light curve, leaf size, and leaf shape) were obtained directly from live beech saplings. With no vertical gradient in light intensity, modeled saplings with simultaneous foliar phenology and slanting shoots (as in live beech) had larger annual photosynthetic gains than saplings with other combinations of traits. Hence, simultaneous foliar phenology and slanting shoots are efficient ways to display leaves in the shaded forest understory light regime where beech saplings thrive. In the presence of vertical light gradients, which can occur in canopy gaps, saplings with upright shoots had larger annual photosynthetic gains than counterparts with slanting shoots. Although mean daily photosynthetic gains of saplings with successive foliar phenology were elevated by exposing leaves to strong light when young and productive, the annual photosynthetic budget of these saplings was reduced (compared to saplings with simultaneous foliar phenology) by their relatively short leaf lifespan. Overall, our results suggest that slanting shoots with simultaneous foliar phenology are particularly successful in shaded environments, where beech often dominates, because they appear to maximize the annual carbon budget by avoiding self-shading and extending leaf lifespans.
Modelling the crop: from system dynamics to systems biology
Yin, X. ; Struik, P.C. - \ 2010
Journal of Experimental Botany 61 (2010)8. - ISSN 0022-0957 - p. 2171 - 2183.
recombinant inbred lines - quantitative trait loci - in-silico plant - elevated co2 - water-deficit - leaf nitrogen - qtl analysis - carbon gain - photosynthetic acclimation - ecophysiological model
There is strong interplant competition in a crop stand for various limiting resources, resulting in complex compensation and regulation mechanisms along the developmental cascade of the whole crop. Despite decades-long use of principles in system dynamics (e.g. feedback control), current crop models often contain many empirical elements, and model parameters may have little biological meaning. Building on the experience in designing the relatively new model GECROS, we believe models can be made less empirical by employing existing physiological understanding and mathematical tools. In view of the potential added value of robust crop modelling to classical quantitative genetics, model input parameters are increasingly considered to represent ‘genetic coefficients’. The advent of functional genomics and systems biology enables the elucidation of the molecular genetic basis of these coefficients. A number of case studies, in which the effects of quantitative trait loci or genes have been incorporated into existing ecophysiological models, have shown the promise of using models in analysing genotype–phenotype relationships of some crop traits. For further progress, crop models must be upgraded based on understanding at lower organizational levels for complicated phenomena such as sink formation in response to environmental cues, sink feedback on source activity, and photosynthetic acclimation to the prevailing environment. Within this context, the recently proposed ‘crop systems biology’, which combines modern genomics, traditional physiology and biochemistry, and advanced modelling, is believed ultimately to realize the expected roles of in silico modelling in narrowing genotype–phenotype gaps. This review summarizes recent findings and our opinions on perspectives for modelling genotype×environment interactions at crop level.
Soil and light effects on the sapling performance of a shade-tolerant tree species in a Mexican rain forest
Lopez, L. ; Martinez, M. ; Breugel, M. van; Sterck, F.J. - \ 2008
Journal of Tropical Ecology 24 (2008)6. - ISSN 0266-4674 - p. 629 - 637.
dipterocarp seedling growth - tree-seedlings - leaf traits - resource availability - canopy gaps - carbon gain - responses - herbivory - gradient - defense
Many studies conclude that light is the most important resource that determines plant performance of tree saplings in tropical rain forests, and implicitly suggest that soil resources are less important. To provide a quantitative test for soil versus light effects on sapling performance, we studied how saplings of the shade-tolerant tree species Brosimum alicastrum responded to contrasting levels of light availability and soil fertility in a Mexican tropical rain forest. Therefore saplings were selected from ten low-light exposure (crown position index
Leaf size and leaf display of thirty-eight tropical tree species
Poorter, L. ; Rozendaal, D.M.A. - \ 2008
Oecologia 158 (2008)1. - ISSN 0029-8549 - p. 35 - 46.
light capture efficiency - rain-forest - shade-tolerance - corners rules - crown architecture - biomass investment - dependent changes - deciduous trees - woody-plants - carbon gain
Trees forage for light through optimal leaf display. Effective leaf display is determined by metamer traits (i.e., the internode, petiole, and corresponding leaf), and thus these traits strongly co-determine carbon gain and as a result competitive advantage in a light-limited environment. We examined 11 metamer traits of sun and shade trees of 38 coexisting moist forest tree species and determined the relative strengths of intra- and interspecific variation. Species-specific metamer traits were related to two variables that represent important life history variation; the regeneration light requirements and average leaf size of the species. Metamer traits varied strongly across species and, in contrast to our expectation, showed only modest changes in response to light. Intra- and interspecific responses to light were only congruent for a third of the traits evaluated. Four traits, amongst which leaf size, specific leaf area (SLA), and leaf area ratio at the metamer level (LAR) showed even opposite intra- and interspecific responses to light. Strikingly, these are classic traits that are thought to be of paramount importance for plant performance but that have completely different consequences within and across species. Sun trees of a given species had small leaves to reduce the heat load, but light-demanding species had large leaves compared to shade-tolerants, probably to outcompete their neighbors. Shade trees of a given species had a high SLA and LAR to capture more light in a light-limited environment, whereas shade-tolerant species have well-protected leaves with a low SLA compared to light-demanding species, probably to deter herbivores and enhance leaf lifespan. There was a leaf-size-mediated trade-off between biomechanical and hydraulic safety, and the efficiency with which species can space their leaves and forage for light. Unexpectedly, metamer traits were more closely linked to leaf size than to regeneration light requirements, probably because leaf-size-related biomechanical and vascular constraints limit the trait combinations that are physically possible. This suggests that the leaf size spectrum overrules more subtle variation caused by the leaf economics spectrum, and that leaf size represents a more important strategy axis than previously thought
Construction costs, chemical composition and payback time of high- and low-irradiance leaves
Poorter, H. ; Pepin, S. ; Rijkers, A.J.M. ; Jong, Y. de; Evans, J.R. ; Körner, C. - \ 2006
Journal of Experimental Botany 57 (2006)2. - ISSN 0022-0957 - p. 355 - 371.
leaf life-spans - nitrogen-use efficiency - rain-forest trees - photosynthetic capacity - carbon gain - elevated co2 - alocasia-macrorrhiza - relative importance - deciduous forest - light conditions
The effect of irradiance on leaf construction costs, chemical composition, and on the payback time of leaves was investigated. To enable more generalized conclusions, three different systems were studied: top and the most-shaded leaves of 10 adult tree species in a European mixed forest, top leaves of sub-dominant trees of two evergreen species growing in small gaps or below the canopy in an Amazonian rainforest, and plants of six herbaceous and four woody species grown hydroponically at low or high irradiance in growth cabinets. Daily photon irradiance varied 3-6-fold between low- and high-light leaves. Specific leaf area (SLA) was 30-130% higher at low light. Construction costs, on the other hand, were 1-5% lower for low-irradiance leaves, mainly because low-irradiance leaves had lower concentrations of soluble phenolics. Photosynthetic capacity and respiration, expressed per unit leaf mass, were hardly different for the low- and high-light leaves. Estimates of payback times of the high-irradiance leaves ranged from 2-4 d in the growth cabinets, to 15-20 d for the adult tree species in the European forest. Low-irradiance leaves had payback times that were 2-3 times larger, ranging from 4 d in the growth cabinets to 20-80 d at the most shaded part of the canopy of the mixed forest. In all cases, estimated payback times were less than half the life span of the leaves, suggesting that even at time-integrated irradiances lower than 5% of the total seasonal value, investment in leaves is still fruitful from a carbon-economy point of view. A sensitivity analysis showed that increased SLA of low-irradiance leaves was the main factor constraining payback times. Acclimation in the other five factors determining payback time, namely construction costs, photosynthetic capacity per unit leaf mass, respiration per unit leaf mass, apparent quantum yield, and curvature of the photosynthetic light-response-curve, were unimportant when the observed variation in each factor was examined
Functional significance of shade-induced leaf senescence in dense canopies: an experimental test using transgenic tobacco
Boonman, A. ; Anten, N.P.R. ; Dueck, T.A. ; Jordi, W.J.R.M. ; Werf, A.K. van der; Voesenek, L.A.C.J. ; Pons, T.L. - \ 2006
American Naturalist 168 (2006)5. - ISSN 0003-0147 - p. 597 - 607.
nitrogen-use efficiency - multispecies canopy - carbon gain - photosynthesis - plants - leaves - light - area - cytokinin - respiration
Canopy photosynthesis models have predicted an optimal leaf area index (LAI; leaf area per unit surface area) and leaf nitrogen distribution at which whole-plant carbon gain per unit N is maximized. In this study we experimentally tested these models, using transgenic PSAG12-IPT tobacco (SAG; Nicotiana tabacum L.) plants with delayed leaf senescence and therefore a greater LAI and more uniform N distribution than the wild type (WT). In a competition experiment, the increased density of surrounding WT plants caused a greater reduction in dry mass of mature SAG target plants than in that of WT target plants, indicating negative effects of delayed leaf senescence on performance at high canopy density. Vegetative SAG plants achieved a lower calculated daily carbon gain than competing WT plants because the former retained leaves with a negative carbon gain in the shaded, lower part of the canopy. Sensitivity analyses showed that the carbon gain of SAG plants would increase if these lower leaves were shed and the N reallocated from these leaves were used to form additional leaf area at the canopy top. This strategy, which is adopted by the WT, is most advantageous because it results in the shading of competing neighbors. Keywords: carbon gain, senescence, transgenic plants, competition, canopy light gradient.
Leaf traits determine the growth-survival trade-off across rain forest tree species
Sterck, F.J. ; Poorter, L. ; Schieving, F. - \ 2006
American Naturalist 167 (2006)5. - ISSN 0003-0147 - p. 758 - 765.
shade tolerance - relative importance - tropical trees - carbon gain - plant - model - disturbance - canopies - spectrum - size
A dominant hypothesis explaining tree species coexistence in tropical forest is that trade-offs in characters allow species to adapt to different light environments, but tests for this hypothesis are scarce. This study is the first that uses a theoretical plant growth model to link leaf trade-offs to whole-plant performances and to differential performances across species in different light environments. Using data of 50 sympatric tree species from a Bolivian rain forest, we observed that specific leaf area and photosynthetic capacity codetermined interspecific height growth variation in a forest gap; that leaf survival rate determined the variation in plant survival rate under a closed canopy; that predicted height growth and plant survival rate matched field observations; and that fast-growing species had low survival rates for both field and predicted values. These results show how leaf trade-offs influence differential tree performance and tree species' coexistence in a heterogeneous light environment
Optimal Photosynthetic Characteristics of Individual Plants in Vegetation Stands and Implications for Species Coexistence
Anten, N.P.R. - \ 2005
Annals of Botany 95 (2005)3. - ISSN 0305-7364 - p. 495 - 506.
nitrogen-use efficiency - daily canopy photosynthesis - leaf-area indexes - carbon gain - multispecies canopy - biomass allocation - xanthium-canadense - growth-rate - c-3 plants - light
Aims This paper reviews the way optimization theory has been used in canopy models to analyse the adaptive significance of photosynthesis-related plant characteristics and their consequences for the structure and species composition of vegetation stands. Scope In most studies simple optimization has been used with trait values optimal when they lead to maximum whole-stand photosynthesis. This approach is subject to the condition that the optimum for one individual is independent of the characteristics of its neighbours. This seems unlikely in vegetation stands where neighbour plants strongly influence each other's light climate. Not surprisingly, there are consistent deviations between predicted plant traits and real values: plants tend to be taller, distribute nitrogen more evenly among their leaves and produce more leaf area which is projected more horizontally than predicted by models. Conclusions By applying game theory to individual plant-based canopy models, other studies have shown that optimal vegetation stands with maximum whole-stand photosynthesis are not evolutionarily stable. They can be successfully invaded by mutants that are taller, project their leaves more horizontally or that produce greater than optimal leaf areas. While these individual-based models can successfully predict the canopy structure of vegetation stands. they are invariably determined at unique optimal trait values. They do not allow for the co-existence of more than one species with different characteristics. Canopy models can contribute to our understanding of species coexistence through (a) simultaneous analysis of the various traits that determine light capture and photosynthesis and the trade-offs between them, and (b) consideration of trade-offs associated with specialization to different positions in the niche space defined by temporal and spatial heterogeneity of resources. (C) 2004 Annals of Botany Company.
The consequences of crown traits for the growth and survival of tree saplings in a Mexican lowland rain forest
Sterck, F.J. ; Martinez-Ramos, M. ; Dryer-Leal, G. ; Rodriguez-Velazquez, J. ; Poorter, L. - \ 2003
Functional Ecology 17 (2003)2. - ISSN 0269-8463 - p. 194 - 200.
rain-forest trees - understory plants - leaf dynamics - light capture - carbon gain - canopy gaps - architecture - compensation - morphology - seedlings
1. Many studies discuss the adaptive value of plant architecture, but few have actually measured architectural effects on plant growth and survival. In this study, sapling growth and survival are related to crown traits for two tree species, Trophis mexicana (Liebm.) Bur. and Pseudolmedia oxyphyllaria Donn. Sm., in the Los Tuxtlas lowland rainforest of Mexico. The traits investigated were crown width, crown depth, number of leaves, number of leaves per unit crown area (horizontal self-shading), and number of leaves per unit silhouette area (vertical self-shading). 2. Self-shading indices decreased with crown size, but were unaffected by the number of leaves per tree. Larger crowns thus had more diffuse foliage, with less self-shading. 3. The number of leaves had positive effects on growth and survival, while self-shading indices had no effect. This indicates that shaded leaves do not necessarily have negative carbon balances. 4. Negative effects of crown width on horizontal crown growth, and positive effects on vertical crown growth, suggest that saplings tend to grow towards a shape intermediate between the narrow and wide crown extremes. 5. Survival was positively correlated with crown width in Pseudolmedia, and with the number of leaves in Trophis. Apparently, dependence of survival on crown traits differed among species. 6. Crown traits affected plant growth and survival, but the hypothesis emerging from light-limited carbon acquisition was confounded by other factors, such as tree size and the inherent branching patterns. 7. Crown traits are good and rather simple predictors of future sapling growth and survival, and may help foresters to select potential crop trees
Some quantitative relationships between leaf area index and canopy nitrogen content and distribution
Yin, X. ; Lantinga, E.A. ; Schapendonk, A.H.C.M. ; Zhong, X. - \ 2003
Annals of Botany 91 (2003). - ISSN 0305-7364 - p. 893 - 903.
carbon gain - dry-matter - photosynthesis - wheat - crop - light - plant - allocation - impact - growth
In a previous study (Yin et al. 2000. Annals of Botany 85: 579-585), a generic logarithmic equation for leaf area index (L) in relation to canopy nitrogen content (N) was developed: L = (1/k(tn))1n(1 +k(tn)N/n(b)). The equation has two parameters: the minimum leaf nitrogen required to support photosynthesis (n(b)), and the leaf nitrogen extinction coefficient (k(tn)). Relative to n(b), there is less information in the literature regarding the variation of k(tn). We therefore derived an equation to theoretically estimate the value of k(tn). The predicted profile of leaf nitrogen in a canopy using this theoretically estimated value of k(tn) is slightly more uniform than the profile predicted by the optimum nitrogen distribution that maximizes canopy photosynthesis. Relative to the optimum profile, the predicted profile is somewhat closer to the observed one. Based on the L-N logarithmic equation and the theoretical k(tn) value, we further quantified early leaf area development of a canopy in relation to nitrogen using simulation analysis. In general, there are two types of relations between L and N, which hold for canopies at different developmental phases. For a fully developed canopy where the lowest leaves are senescing due to nitrogen shortage, the relationship between L and N is described well by the logarithmic model above. For a young, unclosed canopy (i.e. L <1.0), the relation between L and N is nearly linear. This linearity is virtually the special case of the logarithmic model when applied to a young canopy where its total nitrogen content approaches zero and the amount of nitrogen in its lowest leaves is well above nb. The expected patterns of the L-N relationship are discussed for the phase of transition from young to fully developed canopies. (C) 2003 Annals of Botany Company.