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Laurentius A C J Voesenek - One of the best experts on this subject based on the ideXlab platform.

  • is elongation induced leaf emergence beneficial for submerged rumex species
    Annals of Botany, 2009
    Co-Authors: Ronald Pierik, Jan Aken, Laurentius A C J Voesenek
    Abstract:

    †Background and Aims Plant species from various taxa ‘escape’ from low oxygen conditions associated with submergence by a suite of traits collectively called the low oxygen escape syndrome (LOES). The expression of these traits is associated with costs and benefits. Thus far, remarkably few studies have dealt with the expected benefits of the LOES. †Methods Young plants were fully submerged at initial depths of 450 mm (deep) or 150– 240 mm (shallow). Rumex palustris leaf tips emerged from the shallow flooding within a few days, whereas a slight lowering of shallow flooding was required to expose R. acetosa leaf tips to the atmosphere. Shoot biomass and petiole porosity were measured for all species, and treatments and data from the deep and shallow submergence treatments were compared with non-flooded controls. †Key Results R. palustris is characterized by submergence-induced enhanced petiole elongation. R. acetosa lacked this growth response. Upon leaf tip emergence, R. palustris increased its biomass, whereas R. acetosa did not. Furthermore, petiole porosity in R. palustris was twice as high as in R. acetosa. †Conclusions Leaf emergence restores gas exchange between roots and the atmosphere in R. palustris. This occurs to a much lesser extent in R. acetosa and is attributable to its lower petiole porosity and therefore limited internal gas transport. Leaf emergence resulting from fast petiole elongation appears to benefit biomass accumulation if these plants contain sufficient aerenchyma in Petioles and roots to facilitate internal gas exchange.

  • contrasting interactions between ethylene and abscisic acid in rumex species differing in submergence tolerance
    Plant Journal, 2005
    Co-Authors: Joris J Benschop, Robert A M Vreeburg, Anton J M Peeters, Stephen J Croker, Michael B Jackson, Kerstin Guhl, Laurentius A C J Voesenek
    Abstract:

    *† ‡ § Summary Complete submergence of flooding-tolerant Rumex palustris plants strongly stimulates petiole elongation. This escape response is initiated by the accumulation of ethylene inside the submerged tissue. In contrast, Petioles of flooding-intolerant Rumex acetosa do not increase their elongation rate under water even though ethylene also accumulates when they are submerged. Abscisic acid (ABA) was found to be a negative regulator of enhanced petiole growth in both species. In R. palustris, accumulated ethylene stimulated elongation by inhibiting biosynthesis of ABA via a reduction of RpNCED expression and enhancing degradation of ABA to phaseic acid. Externally applied ABA inhibited petiole elongation and prevented the upregulation of gibberellin A 1 normally found in submerged R. palustris .I nR. acetosa submergence did not stimulate petiole elongation nor did it depress levels of ABA. However, if ABA concentrations in R. acetosa were first artificially reduced, submergence (but not ethylene) was then able to enhance petiole elongation strongly. This result suggests that in Rumex a decrease in ABA is a prerequisite for ethylene and other stimuli to promote elongation.

  • the roles of ethylene auxin abscisic acid and gibberellin in the hyponastic growth of submerged rumex palustris Petioles
    Plant Physiology, 2004
    Co-Authors: Marjolein C H Cox, Joris J Benschop, Robert A M Vreeburg, Anton J M Peeters, Thomas Moritz, Cornelis Wagemaker, Laurentius A C J Voesenek
    Abstract:

    Rumex palustris responds to complete submergence with upward movement of the younger Petioles. This so-called hyponastic response, in combination with stimulated petiole elongation, brings the leaf blade above the water surface and restores contact with the atmosphere. We made a detailed study of this differential growth process, encompassing the complete range of the known signal transduction pathway: from the cellular localization of differential growth, to the hormonal regulation, and the possible involvement of a cell wall loosening protein (expansin) as a downstream target. We show that hyponastic growth is caused by differential cell elongation across the petiole base, with cells on the abaxial (lower) surface elongating faster than cells on the adaxial (upper) surface. Pharmacological studies and endogenous hormone measurements revealed that ethylene, auxin, abscisic acid (ABA), and gibberellin regulate different and sometimes overlapping stages of hyponastic growth. Initiation of hyponastic growth and (maintenance of) the maximum petiole angle are regulated by ethylene, ABA, and auxin, whereas the speed of the response is influenced by ethylene, ABA, and gibberellin. We found that a submergence-induced differential redistribution of endogenous indole-3-acetic acid in the petiole base could play a role in maintenance of the response, but not in the onset of hyponastic growth. Since submergence does not induce a differential expression of expansins across the petiole base, it is unlikely that this cell wall loosening protein is the downstream target for the hormones that regulate the differential cell elongation leading to submergence-induced hyponastic growth in R. palustris.

  • submergence induced petiole elongation in rumex palustris is controlled by developmental stage and storage compounds
    Plant and Soil, 2003
    Co-Authors: Henri W Groeneveld, Laurentius A C J Voesenek
    Abstract:

    Submergence stimulates elongation of the leaves of Rumex palustris and under laboratory conditions the maximum final leaf length (of plants up to 7 weeks old) was obtained within a 9 day period. This elongation response, mainly determined by petiole elongation, depends on the availability of storage compounds and developmental stage of a leaf. A starch accumulating tap root and mature leaves and Petioles were found to supply elongating leaves with substrates for polysaccharide synthesis in expanding cell walls. Changes in the composition of cell wall polysaccharides of elongated Petioles suggest a substantial cell wall metabolism during cell extension. Reduced starch levels or removal of mature leaves caused a substantial limitation of submerged leaf growth. From the 5th leaf onward enough reserves were available to perform submerged leaf growth from early developmental stages. Very young Petioles had a limited capacity to elongate. In slightly older Petioles submergence resulted in the longest final leaf lengths and these values gradually decreased when submergence was started at more mature developmental stages. Submerged leaf growth is mainly a matter of petiole elongation in which cell elongation has a concurrent synthesis of xylem elements in the vascular tissue. Mature Petioles still elongated (when submerged) by cell and tissue elongation only: the annular tracheary elements stretched enabling up to 70% petiole elongation.

  • interactions between plant hormones regulate submergence induced shoot elongation in the flooding tolerant dicot rumex palustris
    Annals of Botany, 2003
    Co-Authors: Laurentius A C J Voesenek, Joris J Benschop, H W Groeneveld, Frank F Millenaar, Robert A M Vreeburg, Anton J M Peeters
    Abstract:

    : Rumex palustris has the capacity to respond to complete submergence with hyponastic (upward) growth and stimulated elongation of Petioles. These adaptive responses allow survival of this plant in habitats with sustained high water levels by re-establishing contact with the aerial environment. Accumulated ethylene in submerged Petioles interacts with ethylene receptor proteins and operates as a reliable sensor for the under-water environment. Further downstream in the transduction pathway, a fast and substantial decrease of the endogenous abscisic acid concentration and a certain threshold level of endogenous auxin and gibberellin are required for hyponastic growth and petiole elongation. Interactions of these plant hormones results in a significant increase of the in vitro cell wall extensibility in submerged Petioles. Furthermore, the pattern of transcript accumulation of a R. palustris alpha-expansin gene correlated with the pattern of petiole elongation upon submergence.

Shengke Tian - One of the best experts on this subject based on the ideXlab platform.

  • supplemental macronutrients and microbial fermentation products improve the uptake and transport of foliar applied zinc in sunflower helianthus annuus l plants studies utilizing micro x ray florescence
    Frontiers in Plant Science, 2015
    Co-Authors: Shengke Tian, Lingli Lu, Minzhe Zhang, Judith A Jernstedt, Cliff Ramsier, Patrick H Brown
    Abstract:

    Enhancing nutrient uptake and the subsequent elemental transport from the sites of application to sites of utilization is of great importance to the science and practical field application of foliar fertilizers. The aim of this study was to investigate the mobility of various foliar applied Zn formulations in sunflower (Helianthus annuus L.) and to evaluate the effects of the addition of an organic biostimulant on phloem loading and elemental mobility. This was achieved by application of foliar formulations to the blade of sunflower (Helianthus annuus L.) and high-resolution elemental imaging with micro X-ray fluorescence (μ-XRF) to visualize Zn within the vascular system of the leaf petiole. Although no significant increase of total Zn in Petioles was determined by ICP-MS, μ-XRF elemental imaging showed a clear enrichment of Zn in the vascular tissues within the sunflower Petioles treated with foliar fertilizers containing Zn. The concentration of Zn in the vascular of sunflower pertioles was increased when Zn was applied with other microelements with EDTA (commercial product Kick-Off) as compared with an equimolar concentration of ZnSO4 alone. The addition of macronutrients N, P, K (commercial product CleanStart) to the Kick-Off Zn fertilizer, further increased vascular system Zn concentrations while the addition of the microbially derived organic biostimulant “GroZyme” resulted in a remarkable enhancement of Zn concentrations in the petiole vascular system. The study provides direct visualized evidence for phloem transport of foliar applied Zn out of sites of application in plants by using µ-XRF technique, and suggests that the formulation of the foliar applied Zn and the addition of the organic biostimulant GroZyme increases the mobility of Zn following its absorption by the leaf of sunflower.

  • supplemental macronutrients and microbial fermentation products improve the uptake and transport of foliar applied zinc in sunflower helianthus annuus l plants studies utilizing micro x ray florescence
    Frontiers in Plant Science, 2015
    Co-Authors: Shengke Tian, Minzhe Zhang, Judith A Jernstedt, Cliff Ramsier, Ruohan Xie, Dandi Hou, Patrick H Brown
    Abstract:

    Enhancing nutrient uptake and the subsequent elemental transport from the sites of application to sites of utilization is of great importance to the science and practical field application of foliar fertilizers. The aim of this study was to investigate the mobility of various foliar applied Zn formulations in sunflower (Helianthus annuus L.) and to evaluate the effects of the addition of an organic biostimulant on phloem loading and elemental mobility. This was achieved by application of foliar formulations to the blade of sunflower (Helianthus annuus L.) and high-resolution elemental imaging with micro X-ray fluorescence (μ-XRF) to visualize Zn within the vascular system of the leaf petiole. Although no significant increase of total Zn in Petioles was determined by ICP-MS, μ-XRF elemental imaging showed a clear enrichment of Zn in the vascular tissues within the sunflower Petioles treated with foliar fertilizers containing Zn. The concentration of Zn in the vascular of sunflower pertioles was increased when Zn was applied with other microelements with EDTA (commercial product Kick-Off) as compared with an equimolar concentration of ZnSO4 alone. The addition of macronutrients N, P, K (commercial product CleanStart) to the Kick-Off Zn fertilizer, further increased vascular system Zn concentrations while the addition of the microbially derived organic biostimulant “GroZyme” resulted in a remarkable enhancement of Zn concentrations in the petiole vascular system. The study provides direct visualized evidence for phloem transport of foliar applied Zn out of sites of application in plants by using µ-XRF technique, and suggests that the formulation of the foliar applied Zn and the addition of the organic biostimulant GroZyme increases the mobility of Zn following its absorption by the leaf of sunflower.

Patrick H Brown - One of the best experts on this subject based on the ideXlab platform.

  • supplemental macronutrients and microbial fermentation products improve the uptake and transport of foliar applied zinc in sunflower helianthus annuus l plants studies utilizing micro x ray florescence
    Frontiers in Plant Science, 2015
    Co-Authors: Shengke Tian, Lingli Lu, Minzhe Zhang, Judith A Jernstedt, Cliff Ramsier, Patrick H Brown
    Abstract:

    Enhancing nutrient uptake and the subsequent elemental transport from the sites of application to sites of utilization is of great importance to the science and practical field application of foliar fertilizers. The aim of this study was to investigate the mobility of various foliar applied Zn formulations in sunflower (Helianthus annuus L.) and to evaluate the effects of the addition of an organic biostimulant on phloem loading and elemental mobility. This was achieved by application of foliar formulations to the blade of sunflower (Helianthus annuus L.) and high-resolution elemental imaging with micro X-ray fluorescence (μ-XRF) to visualize Zn within the vascular system of the leaf petiole. Although no significant increase of total Zn in Petioles was determined by ICP-MS, μ-XRF elemental imaging showed a clear enrichment of Zn in the vascular tissues within the sunflower Petioles treated with foliar fertilizers containing Zn. The concentration of Zn in the vascular of sunflower pertioles was increased when Zn was applied with other microelements with EDTA (commercial product Kick-Off) as compared with an equimolar concentration of ZnSO4 alone. The addition of macronutrients N, P, K (commercial product CleanStart) to the Kick-Off Zn fertilizer, further increased vascular system Zn concentrations while the addition of the microbially derived organic biostimulant “GroZyme” resulted in a remarkable enhancement of Zn concentrations in the petiole vascular system. The study provides direct visualized evidence for phloem transport of foliar applied Zn out of sites of application in plants by using µ-XRF technique, and suggests that the formulation of the foliar applied Zn and the addition of the organic biostimulant GroZyme increases the mobility of Zn following its absorption by the leaf of sunflower.

  • supplemental macronutrients and microbial fermentation products improve the uptake and transport of foliar applied zinc in sunflower helianthus annuus l plants studies utilizing micro x ray florescence
    Frontiers in Plant Science, 2015
    Co-Authors: Shengke Tian, Minzhe Zhang, Judith A Jernstedt, Cliff Ramsier, Ruohan Xie, Dandi Hou, Patrick H Brown
    Abstract:

    Enhancing nutrient uptake and the subsequent elemental transport from the sites of application to sites of utilization is of great importance to the science and practical field application of foliar fertilizers. The aim of this study was to investigate the mobility of various foliar applied Zn formulations in sunflower (Helianthus annuus L.) and to evaluate the effects of the addition of an organic biostimulant on phloem loading and elemental mobility. This was achieved by application of foliar formulations to the blade of sunflower (Helianthus annuus L.) and high-resolution elemental imaging with micro X-ray fluorescence (μ-XRF) to visualize Zn within the vascular system of the leaf petiole. Although no significant increase of total Zn in Petioles was determined by ICP-MS, μ-XRF elemental imaging showed a clear enrichment of Zn in the vascular tissues within the sunflower Petioles treated with foliar fertilizers containing Zn. The concentration of Zn in the vascular of sunflower pertioles was increased when Zn was applied with other microelements with EDTA (commercial product Kick-Off) as compared with an equimolar concentration of ZnSO4 alone. The addition of macronutrients N, P, K (commercial product CleanStart) to the Kick-Off Zn fertilizer, further increased vascular system Zn concentrations while the addition of the microbially derived organic biostimulant “GroZyme” resulted in a remarkable enhancement of Zn concentrations in the petiole vascular system. The study provides direct visualized evidence for phloem transport of foliar applied Zn out of sites of application in plants by using µ-XRF technique, and suggests that the formulation of the foliar applied Zn and the addition of the organic biostimulant GroZyme increases the mobility of Zn following its absorption by the leaf of sunflower.

Philipp W. Simon - One of the best experts on this subject based on the ideXlab platform.

  • a cluster of myb transcription factors regulates anthocyanin biosynthesis in carrot daucus carota l root and petiole
    Frontiers in Plant Science, 2019
    Co-Authors: Massimo Iorizzo, Pablo F. Cavagnaro, Hamed Bostan, Yunyang Zhao, Jianhui Zhang, Philipp W. Simon
    Abstract:

    Purple carrots can accumulate large quantities of anthocyanins in their roots and –in some genetic backgrounds- Petioles, and therefore they represent an excellent dietary source of antioxidant phytonutrients. In a previous study, using linkage analysis in a carrot F2 mapping population segregating for root and petiole anthocyanin pigmentation, we identified a region in chromosome 3 with co-localized QTL for all anthocyanin pigments of the carrot root, whereas petiole pigmentation segregated as a single dominant gene and mapped to one of these “root pigmentation” regions conditioning anthocyanin biosynthesis. In the present study, we performed fine mapping combined with gene expression analyses (RNA-Seq and RT-qPCR) to identify candidate genes controlling anthocyanin pigmentation in the carrot root and petiole. Fine mapping was performed in four carrot populations with different genetic backgrounds and patterns of pigmentation. The regions controlling root and petiole pigmentation in chromosome 3 were delimited to 541 kb and 535 kb, respectively. Genome wide prediction of transcription factor families known to regulate the anthocyanin biosynthetic pathway coupled with orthologous and phylogenetic analyses enabled the identification of a cluster of six MYB transcription factors, denominated DcMYB6 to DcMYB11, associated with the regulation of anthocyanin biosynthesis. No anthocyanin biosynthetic genes were present in this region. Comparative transcriptome analysis indicated that upregulation of DcMYB7 was always associated with anthocyanin pigmentation in both root and petiole tissues, whereas DcMYB11 was only upregulated with pigmentation in Petioles. In the petiole, the level of expression of DcMYB11 was higher than DcMYB7. DcMYB6, a gene previously suggested as a key regulator of carrot anthocyanin biosynthesis, was not consistently associated with pigmentation in either tissue. These results strongly suggest that DcMYB7 is a candidate gene for root anthocyanin pigmentation in all the genetic backgrounds included in this study. DcMYB11 is a candidate gene for petiole pigmentation in all the purple carrot sources in this study. Since DcMYB7 is co-expressed with DcMYB11 in purple Petioles, the latter gene may act also as a co-regulator of anthocyanin pigmentation in the Petioles. This study provides linkage-mapping and functional evidence for the candidacy of these genes for the regulation of carrot anthocyanin biosynthesis.

  • Table_1_A Cluster of MYB Transcription Factors Regulates Anthocyanin Biosynthesis in Carrot (Daucus carota L.) Root and Petiole.XLSX
    2019
    Co-Authors: Massimo Iorizzo, Pablo F. Cavagnaro, Hamed Bostan, Yunyang Zhao, Jianhui Zhang, Philipp W. Simon
    Abstract:

    Purple carrots can accumulate large quantities of anthocyanins in their roots and –in some genetic backgrounds- Petioles, and therefore they represent an excellent dietary source of antioxidant phytonutrients. In a previous study, using linkage analysis in a carrot F2 mapping population segregating for root and petiole anthocyanin pigmentation, we identified a region in chromosome 3 with co-localized QTL for all anthocyanin pigments of the carrot root, whereas petiole pigmentation segregated as a single dominant gene and mapped to one of these “root pigmentation” regions conditioning anthocyanin biosynthesis. In the present study, we performed fine mapping combined with gene expression analyses (RNA-Seq and RT-qPCR) to identify candidate genes controlling anthocyanin pigmentation in the carrot root and petiole. Fine mapping was performed in four carrot populations with different genetic backgrounds and patterns of pigmentation. The regions controlling root and petiole pigmentation in chromosome 3 were delimited to 541 and 535 kb, respectively. Genome wide prediction of transcription factor families known to regulate the anthocyanin biosynthetic pathway coupled with orthologous and phylogenetic analyses enabled the identification of a cluster of six MYB transcription factors, denominated DcMYB6 to DcMYB11, associated with the regulation of anthocyanin biosynthesis. No anthocyanin biosynthetic genes were present in this region. Comparative transcriptome analysis indicated that upregulation of DcMYB7 was always associated with anthocyanin pigmentation in both root and petiole tissues, whereas DcMYB11 was only upregulated with pigmentation in Petioles. In the petiole, the level of expression of DcMYB11 was higher than DcMYB7. DcMYB6, a gene previously suggested as a key regulator of carrot anthocyanin biosynthesis, was not consistently associated with pigmentation in either tissue. These results strongly suggest that DcMYB7 is a candidate gene for root anthocyanin pigmentation in all the genetic backgrounds included in this study. DcMYB11 is a candidate gene for petiole pigmentation in all the purple carrot sources in this study. Since DcMYB7 is co-expressed with DcMYB11 in purple Petioles, the latter gene may act also as a co-regulator of anthocyanin pigmentation in the Petioles. This study provides linkage-mapping and functional evidence for the candidacy of these genes for the regulation of carrot anthocyanin biosynthesis.

  • Data_Sheet_1_A Cluster of MYB Transcription Factors Regulates Anthocyanin Biosynthesis in Carrot (Daucus carota L.) Root and Petiole.PDF
    2019
    Co-Authors: Massimo Iorizzo, Pablo F. Cavagnaro, Hamed Bostan, Yunyang Zhao, Jianhui Zhang, Philipp W. Simon
    Abstract:

    Purple carrots can accumulate large quantities of anthocyanins in their roots and –in some genetic backgrounds- Petioles, and therefore they represent an excellent dietary source of antioxidant phytonutrients. In a previous study, using linkage analysis in a carrot F2 mapping population segregating for root and petiole anthocyanin pigmentation, we identified a region in chromosome 3 with co-localized QTL for all anthocyanin pigments of the carrot root, whereas petiole pigmentation segregated as a single dominant gene and mapped to one of these “root pigmentation” regions conditioning anthocyanin biosynthesis. In the present study, we performed fine mapping combined with gene expression analyses (RNA-Seq and RT-qPCR) to identify candidate genes controlling anthocyanin pigmentation in the carrot root and petiole. Fine mapping was performed in four carrot populations with different genetic backgrounds and patterns of pigmentation. The regions controlling root and petiole pigmentation in chromosome 3 were delimited to 541 and 535 kb, respectively. Genome wide prediction of transcription factor families known to regulate the anthocyanin biosynthetic pathway coupled with orthologous and phylogenetic analyses enabled the identification of a cluster of six MYB transcription factors, denominated DcMYB6 to DcMYB11, associated with the regulation of anthocyanin biosynthesis. No anthocyanin biosynthetic genes were present in this region. Comparative transcriptome analysis indicated that upregulation of DcMYB7 was always associated with anthocyanin pigmentation in both root and petiole tissues, whereas DcMYB11 was only upregulated with pigmentation in Petioles. In the petiole, the level of expression of DcMYB11 was higher than DcMYB7. DcMYB6, a gene previously suggested as a key regulator of carrot anthocyanin biosynthesis, was not consistently associated with pigmentation in either tissue. These results strongly suggest that DcMYB7 is a candidate gene for root anthocyanin pigmentation in all the genetic backgrounds included in this study. DcMYB11 is a candidate gene for petiole pigmentation in all the purple carrot sources in this study. Since DcMYB7 is co-expressed with DcMYB11 in purple Petioles, the latter gene may act also as a co-regulator of anthocyanin pigmentation in the Petioles. This study provides linkage-mapping and functional evidence for the candidacy of these genes for the regulation of carrot anthocyanin biosynthesis.

Ulo Niinemets - One of the best experts on this subject based on the ideXlab platform.

  • do we underestimate the importance of leaf size in plant economics disproportional scaling of support costs within the spectrum of leaf physiognomy
    Annals of Botany, 2007
    Co-Authors: Ulo Niinemets, Angelika Portsmuth, David Tena, Mari Tobias, Silvia Matesanz, Fernando Valladares
    Abstract:

    †Background Broad scaling relationships between leaf size and function do not take into account that leaves of different size may contain different fractions of support in petiole and mid-rib. †Methods The fractions of leaf biomass in petiole, mid-rib and lamina, and the differences in chemistry and structure among mid-ribs, Petioles and laminas were investigated in 122 species of contrasting leaf size, life form and climatic distribution to determine the extent to which differences in support modify whole-lamina and whole-leaf structural and chemical characteristics, and the extent to which size-dependent support investments are affected by plant life form and site climate. †Key Results For the entire data set, leaf fresh mass varied over five orders of magnitude. The percentage of dry mass in mid-rib increased strongly with lamina size, reaching more than 40 % in the largest laminas. The wholeleaf percentage of mid-rib and petiole increased with leaf size, and the overall support investment was more than 60 % in the largest leaves. Fractional support investments were generally larger in herbaceous than in woody species and tended to be lower in Mediterranean than in cool temperate and tropical plants. Mid-ribs and Petioles had lower N and C percentages, and lower dry to fresh mass ratio, but greater density (mass per unit volume) than laminas. N percentage of lamina without mid-rib was up to 40 % higher in the largest leaves than the total-lamina (lamina and mid-rib) N percentage, and up to 60 % higher than whole-leaf N percentage, while lamina density calculated without mid-rib was up to 80 % less than that with the mid-rib. For all leaf compartments, N percentage was negatively associated with density and dry to fresh mass ratio, while C percentage was positively linked to these characteristics, reflecting the overall inverse scaling between structural and physiological characteristics. However, the correlations between N and C percentages and structural characteristics differed among mid-ribs, Petioles and laminas, implying that the mass-weighted average leaf N and C percentage, density, and dry to fresh mass ratio can have different functional values depending on the importance of within-leaf support investments. †Conclusions These data demonstrate that variation in leaf size is associated with major changes in within-leaf support investments and in large modifications in integrated leaf chemical and structural characteristics. These size-dependent alterations can importantly affect general leaf structure vs. function scaling relationships. These data further demonstrate important life-form effects on and climatic differentiation in foliage support costs.

  • petiole length and biomass investment in support modify light interception efficiency in dense poplar plantations
    Tree Physiology, 2004
    Co-Authors: Ulo Niinemets, Najwa Al Afas, Alessandro Cescatti, A Pellis, R Ceulemans
    Abstract:

    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 (T C ). The weak relationship between T C 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 (P L ) 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 P L 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 P L 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 (M A ) and nitrogen per unit area (N A ) than lower-canopy leaves. Canopy plasticity in M A and N A 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.

  • Petiole mechanics, leaf inclination, morphology, and investment in support in relation to light availability in the canopy of Liriodendron tulipifera
    Oecologia, 2002
    Co-Authors: Ulo Niinemets, Stefan Fleck
    Abstract:

    To determine the role of leaf mechanical properties in altering foliar inclination angles, and the nutrient and carbon costs of specific foliar angle variation patterns along the canopy, leaf structural and biomechanical characteristics, biomass partitioning into support, and foliar nitrogen and carbon concentrations were studied in the temperate deciduous species Liriodendron tulipifera L., which possesses large leaves on long Petioles. We used beam theory to model leaf lamina as a uniform load, and estimated both the lamina and petiole flexural stiffness, which characterizes the resistance to bending of foliar elements at a common load and length. Petiole and lamina vertical inclination angles with respect to horizontal increased with increasing average daily integrated photon flux density (Q int). Yet, the light effects on lamina inclination angle were primary determined by the petiole inclination angle. Although the Petioles and laminas became longer, and the lamina loads increased with increasing Q int, the flexural stiffness of both lamina and petiole increased to compensate for this, such that the lamina vertical displacement was only weakly related to Q int. In addition, increases and decreases in the petiole inclination angle with respect to the horizontal effectively reduced the distance of lamina load from the axis of rotation, thereby reducing the bending moments and lamina inclination due to gravity. We demonstrate that large investments, up to 30% of total leaf biomass, in petiole and large veins are necessary to maintain the lamina at a specific position, but also that light has no direct effect on the fractional biomass investment in support. However, we provide evidence that apart from light availability, structural and chemical characteristics of the foliage may also be affected by water stress, magnitude of which scales positively with Q int.

  • biomass investment in leaf lamina versus lamina support in relation to growth irradiance and leaf size in temperate deciduous trees
    Tree Physiology, 1999
    Co-Authors: Ulo Niinemets, Olevi Kull
    Abstract:

    Foliar biomass investment in support and assimilative compartments was studied in four temperate deciduous tree species along a natural light gradient across the canopy. The species ranked according to shade tolerance as Betula pendula Roth. < Populus tremula L. < Fraxinus excelsior L. < Tilia cordata Mill. Long-term light conditions at sampling locations were characterized as seasonal mean integrated quantum flux density (Q(int), mol m(-2) day(-1)) estimated by a method combining hemispherical photography and light measurements with quantum sensors. Leaf morphology was altered by Q(int) in all species. Both lamina and petiole dry mass per lamina area (LMA and PMA, respectively) increased with increasing Q(int). Shade-tolerant species had lower LMA at low Q(int) than shade-intolerant species; however, PMA was not related to shade tolerance. Across species, the ratio of petiole dry mass to lamina dry mass (PMR) varied from 0.07 to 0.21. It was independent of Q(int) in the simple-leaved species, but decreased with increasing Q(int) in the compound-leaved F. excelsior, which also had the largest foliar biomass investment in Petioles. Differences in leaf mass and area, ranging over four orders of magnitude, provided an explanation for the interspecific variability in PMR. Species with large leaves also had greater biomass investments in foliar support than species with smaller leaves. This relationship was similar for both simple- and compound-leaved species. There was a negative relationship between PMR and petiole N concentration, suggesting that Petioles had greater carbon assimilation rates and paid back a larger fraction of their construction cost in species with low PMR than in species with high PMR. This was probably the result of a negative relationship between PMR and petiole surface to volume ratio. Nevertheless, Petioles had lower concentrations of mineral nutrients than laminas. Across species, the ratio of petiole N to lamina N varied from only 3 to 6%, demonstrating that petiole costs are less in terms of nutrients than in terms of total biomass, and that the petiole contribution to carbon assimilation is disproportionately lower than that of the lamina contribution.