Petiole length and biomass investment in support modify light interception efficiency in dense poplar plantations.

Leaf architecture, stand leaf area index and canopy light interception were studied in 13 poplar clones growing in a second rotation of a coppice plantation, to determine the role of leaf architectural attributes on canopy light-harvesting efficiency and to assess biomass investment in leaf support tissue. Stand leaf area index (L) varied from 2.89 to 6.99, but L was only weakly associated with canopy transmittance (TC). The weak relationship between TC and L was a result of a higher degree of foliage aggregation at larger values of L, leading to lower light-interception efficiency in stands with greater total leaf area. We observed a strong increase in leaf aggregation and a decrease in light-harvesting efficiency with decreasing mean leaf petiole length (PL) but not with leaf size, possibly because, in cordate or deltoid poplar leaves, most of the leaf area is located close to the petiole attachment to the lamina. Although PL was the key leaf characteristic of light-harvesting efficiency, clones with longer petioles had larger biomass investments in petioles, and there was a negative relationship between PL and L, demonstrating that enhanced light harvesting may lead to an overall decline in photosynthesizing leaf surface. Upper-canopy leaves were generally larger and had greater dry mass (MA) and nitrogen per unit area (NA) than lower-canopy leaves. Canopy plasticity in MA and NA was higher in clones with higher foliar biomass investment in midrib, and lower in clones with relatively longer petioles. These relationships suggest that there is a trade-off between photosynthetic plasticity and biomass investment in support, and also that high light-harvesting efficiency may be associated with lower photosynthetic plasticity. Our results demonstrate important clonal differences in leaf aggregation that are linked to leaf structure and biomass allocation patterns within the leaf.

[1]  G. Campbell,et al.  An Introduction to Environmental Biophysics , 1977 .

[2]  S. T. Gower,et al.  Leaf area index of boreal forests: theory, techniques, and measurements , 1997 .

[3]  R. Ceulemans,et al.  Population dynamics in a 6-year old coppice culture of poplar. I. Clonal differences in stool mortality, shoot dynamics and shoot diameter distribution in relation to biomass production , 2003 .

[4]  R. Dickson,et al.  Translocation pathways in the petioles and stem between source and sink leaves of Populus deltoides Bartr. ex Marsh. , 1982, Planta.

[5]  W. Ruhland.  Encyclopedia of plant physiology. , 1958 .

[6]  F. W. Wiegel,et al.  Optimizing the Canopy Photosynthetic Rate by Patterns of Investment in Specific Leaf Mass , 1988, The American Naturalist.

[7]  J. Bunce.  The effect of leaf size on mutual shading and cultivar differences in soybean leaf photosynthetic capacity , 2004, Photosynthesis Research.

[8]  F. Miglietta,et al.  Leaf area is stimulated in Populus by free air CO2 enrichment (POPFACE), through increased cell expansion and production , 2001 .

[9]  R. Ceulemans,et al.  Photosynthesis, leaf area and productivity of 5 poplar clones during their establishment year , 1994 .

[10]  R. Ceulemans,et al.  Population dynamics in a 6-year-old coppice culture of poplar: II. Size variability and one-sided competition of shoots and stools , 2005 .

[11]  S. Fleck,et al.  Leaf Biomechanics and Biomass Investment in Support in Relation to Long-Term Irradiance in Fagus , 2002 .

[12]  K. Niklas.  The elastic moduli and mechanics of Populus tremuloides (Salicaceae) petioles in bending and torsion , 1991 .

[13]  Jb Miller,et al.  A formula for average foliage density , 1967 .

[14]  Graham D. Farquhar,et al.  Models of Integrated Photosynthesis of Cells and Leaves , 1989 .

[15]  Thomas J. Givnish,et al.  On the economy of plant form and function. , 1988 .

[16]  P. Reich,et al.  Canopy structure and vertical patterns of photosynthesis and related leaf traits in a deciduous forest , 1993, Oecologia.

[17]  A. Takenaka,et al.  Effects of leaf blade narrowness and petiole length on the light capture efficiency of a shoot , 1994, Ecological Research.

[18]  Gregory P. Asner,et al.  SCALE DEPENDENCE OF ABSORPTION OF PHOTOSYNTHETICALLY ACTIVE RADIATION IN TERRESTRIAL ECOSYSTEMS , 1998 .

[19]  F. Valladares,et al.  The geometry of light interception by shoots of Heteromeles arbutifolia: morphological and physiological consequences for individual leaves , 1999, Oecologia.

[20]  H. S. Horn.  The adaptive geometry of trees , 1971 .

[21]  R. Ceulemans,et al.  Clonal variability in biomass production and conversion efficiency of poplar during the establishment year of a short rotation coppice plantation , 1998 .

[22]  H. Drew.  Economy in Design , 1944 .

[23]  Alessandro Cescatti,et al.  Effects of needle clumping in shoots and crowns on the radiative regime of a Norway spruce canopy , 1998 .

[24]  S. Fleck,et al.  Petiole mechanics, leaf inclination, morphology, and investment in support in relation to light availability in the canopy of Liriodendron tulipifera , 2002, Oecologia.

[25]  K. Niklas.  FLEXURAL STIFFNESS ALLOMETRIES OF ANGIOSPERM AND FERN PETIOLES AND RACHISES: EVIDENCE FOR BIOMECHANICAL CONVERGENCE , 1991, Evolution; international journal of organic evolution.

[26]  P. G. Jarvis,et al.  Productivity of temperate de-ciduous and evergreen forests , 1983 .

[27]  G. Campbell.  Extinction coefficients for radiation in plant canopies calculated using an ellipsoidal inclination angle distribution , 1986 .

[28]  Jing M. Chen,et al.  Quantifying the effect of canopy architecture on optical measurements of leaf area index using two gap size analysis methods , 1995, IEEE Trans. Geosci. Remote. Sens..

[29]  D. Dickmann,et al.  Poplar culture in North America , 2001 .

[30]  P. Heilman,et al.  Genetic variation and productivity of Populustrichocarpa and its hybrids. I. Morphology and phenology of 50 native clones , 1985 .

[31]  N. Holbrook,et al.  Dynamic changes in petiole specific conductivity in red maple (Acer rubrum L.), tulip tree (Liriodendron tulipifera L.) and northern fox grape (Vitis labrusca L.) , 2000 .

[32]  Karl J Niklas,et al.  THE ROLE OF PHYLLOTACTIC PATTERN AS A “DEVELOPMENTAL CONSTRAINT” ON THE INTERCEPTION OF LIGHT BY LEAF SURFACES , 1988, Evolution; international journal of organic evolution.

[33]  H Sinoquet,et al.  Canopy structure and light interception in Quercus petraea seedlings in relation to light regime and plant density. , 2001, Tree physiology.

[34]  T. Hinckley,et al.  Biology of populus and its implications for management and conservation , 1996 .

[35]  R. Ceulemans,et al.  Carbon acquisition and allocation , 1996 .

[36]  Fernando Valladares,et al.  Convergence in light capture efficiencies among tropical forest understory plants with contrasting crown architectures: a case of morphological compensation. , 2002, American journal of botany.

[37]  F. Bazzaz,et al.  Plasticity and acclimation to light in tropical Moraceae of different sucessional positions , 1991, Oecologia.

[38]  J. M. Norman,et al.  Plant Canopies: Their Growth, Form and Function: The description and measurement of plant canopy structure , 1989 .

[39]  K. Niklas.  Petiole mechanics, light interception by Lamina, and “Economy in Design” , 1992, Oecologia.

[40]  T. Hinckley,et al.  Leaf growth characteristics of fast-growing poplar hybrids Populus trichocarpa x P. deltoides. , 1986, Tree physiology.

[41]  John M. Norman,et al.  Characterization of radiation regimes in nonrandom forest canopies: theory, measurements, and a simplified modeling approach. , 1999, Tree physiology.

[42]  Professor Dr. Ulrich Lüttge.  Physiological Ecology of Tropical Plants , 1997, Springer Berlin Heidelberg.

[43]  R. Ceulemans,et al.  Crown architecture of Populus spp. is differentially modified by free-air CO2 enrichment (POPFACE) , 2002 .

[44]  R. Ceulemans,et al.  Leaf allometry in young poplar stands: reliability of leaf area index estimation, site and clone effects , 1993 .

[45]  Roselyne Lacaze,et al.  Retrieval of vegetation clumping index using hot spot signatures measured by POLDER instrument , 2002 .

[46]  Antonio Donato Nobre,et al.  Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit area , 2002 .

[47]  J. Ross.  The radiation regime and architecture of plant stands , 1981, Tasks for vegetation sciences 3.

[48]  R. Ceulemans,et al.  A fractal-based Populus canopy structure model for the calculation of light interception , 1994 .

[49]  B. Gielen,et al.  Leaf area dynamics in a closed poplar plantation under free-air carbon dioxide enrichment. , 2001, Tree physiology.

[50]  N. Nelson,et al.  Crown architecture of short-rotation, intensively cultured Populus II. Branch morphology and distribution of leaves within the crown of Populus 'Tristis' as related to biomass production , 1982 .

[51]  R. Ceulemans,et al.  Biomass production of 17 poplar clones in a short-rotation coppice culture on a waste disposal site and its relation to soil characteristics , 2004 .

[52]  J. Zavitkovski.  Small plots with unplanted plot border can distort data in biomass production studies , 1981 .

[53]  Robert W. Pearcy,et al.  The functional morphology of light capture and carbon gain in the Redwood forest understorey plant Adenocaulon bicolor Hook , 1998 .

[54]  J. Cihlar,et al.  Plant canopy gap-size analysis theory for improving optical measurements of leaf-area index. , 1995, Applied optics.

[55]  Olevi Kull,et al.  An analysis of light effects on foliar morphology, physiology, and light interception in temperate deciduous woody species of contrasting shade tolerance. , 1998, Tree physiology.

[56]  Fernando Valladares,et al.  The greater seedling high-light tolerance of Quercus robur over Fagus sylvatica is linked to a greater physiological plasticity , 2002, Trees.

[57]  J. Zavitkovski.  Characterization of light climate under canopies of intensively-cultured hybrid poplar plantations , 1981 .

[58]  R. Ceulemans,et al.  Spatial distribution of leaf morphological and physiological characteristics in relation to local radiation regime within the canopies of 3-year-old Populus clones in coppice culture. , 2002, Tree physiology.

[59]  D. Baldocchi,et al.  On estimating canopy photosynthesis and stomatal conductance in a deciduous forest with clumped foliage. , 1986, Tree physiology.

[60]  Stefan Fleck,et al.  Three-dimensional lamina architecture alters light-harvesting efficiency in Fagus: a leaf-scale analysis. , 2003, Tree physiology.

[61]  A. Armstrong.  The United Kingdom network of experiments on site/yield relationships for short rotation coppice. , 1997 .

[62]  T. Nilson.  A theoretical analysis of the frequency of gaps in plant stands , 1971 .

[63]  R. Ceulemans,et al.  Crown architecture of Populus clones as determined by branch orientation and branch characteristics. , 1990, Tree physiology.