Relationships among xylem transport, biomechanics and storage in stems and roots of nine Rhamnaceae species of the California chaparral

Pratt, R. Brandon; Jacobsen, Anna L.; Ewers, Frank W.; Davis, Stephen D.

doi:10.1111/j.1469-8137.2007.02061.x

Cited by 316 publications

(375 citation statements)

References 45 publications

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“…However, thick roots have low surface:volume ratio (SVR) and offer higher resistance to the radial flow of water, both causing lower root absorption potential (Larcher 1995;Huang and Eissenstat 2000). Furthermore, the abundance of xylem parenchyma is negatively correlated with the resistance to cavitation (Pratt et al 2007b). The existence of a trade-off between carbohydrate storage and drought tolerance in roots may contribute to explain the differences in below-ground structure between R+ and R-species.…”

Section: Discussionmentioning

confidence: 98%

Root traits explain different foraging strategies between resprouting life histories

Paula

Pausas

2010

Oecologia

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Drought and fire are prevalent disturbances in Mediterranean ecosystems. Plant species able to regrow after severe disturbances (i.e. resprouter life history) have higher allocation to roots and higher water potential during the dry season than coexisting non-resprouting species. However, seedlings of non-resprouters have higher survival rate after summer drought. We predict that, to counteract their shallow-rooting systems and to maximize seedling survival, non-resprouters have root traits that confer higher efficiency in soil resource acquisition than resprouters. We tested this prediction in seedlings of less than 1.5 months old. We select 13 coexisting woody species (including both resprouters and non-resprouters), grew them in common garden and measured the following root traits: length, surface, average diameter, root tissue density (RTD), specific root length (SRL), surface:volume ratio (SVR), specific tip density (STD), tip distribution in depth, internal links ratio (ILR) and degree of branching. These root traits were compared between the two resprouting life histories using both standard cross-species and phylogenetic-informed analysis. Non-resprouters showed higher SRL and longer, thinner and more branched laterals, especially in the upper soil layers. The abundance, total length, diameter and SVR of external links (i.e. the most absorptive root region) were also higher for non-resprouters. The results were supported by the phylogenetic-informed analysis for the root traits most strongly related to soil resource acquisition (SRL, SVR and branching pattern). The seedling root structure of non-resprouters species allows them to explore more efficiently the upper soil layer, whereas seedling roots of resprouters will permit both carbon storage and deep soil penetration.

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Section: Discussionmentioning

confidence: 98%

Root traits explain different foraging strategies between resprouting life histories

Paula

Pausas

2010

Oecologia

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“…Low wood density species show, therefore, a faster height growth (Muller-Landau 2004;Poorter 2008;King et al 2005) and a low wood density is therefore especially advantageous for light-demanding species that need to monopolize gaps by growing rapidly in height and complete their life cycle before they are being overtopped by competing neighbouring plants. Wood density is emerging as a core functional trait (Chave et al 2009), not only because of its importance for tree stability and architecture (King et al 2006) but also because of its importance for defence against pathogens (Loehle 1988), stem hydraulics and cavitation resistance (Pratt et al 2007;Markesteijn et al 2011), and hence, photosynthetic carbon gain (Santiago et al 2004). The effect of wood density was largely maintained in the ANCOVA analysis, suggesting that wood density may contribute to architectural variation not only between families but also within families.…”

Section: Wood Densitymentioning

confidence: 99%

Architecture of Iberian canopy tree species in relation to wood density, shade tolerance and climate

et al. 2012

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Tree architecture has important consequences for tree performance as it determines resource capture, mechanical stability and dominance over competitors. We analyzed architectural relationships between stem and crown dimensions for 13 dominant Iberian canopy tree species belonging to the Pinaceae (six Pinus species) and Fagaceae (six Quercus species and Fagus sylvatica) and related these architectural traits to wood density, shade tolerance and climatic factors. Fagaceae had, compared with Pinaceae, denser wood, saplings with wider crowns and adults with larger maximal crown size but smaller maximal height. In combination, these traits enhance light acquisition and persistence in shaded environments; thus, contributing to their shade tolerance. Pinaceae species, in contrast, had low-density wood, allocate more resources to the formation of the central trunk rather than to branches and attained taller maximal heights, allowing them to grow rapidly in height and compete for light following disturbances; thus, contributing to their high light requirements. Wood density had a strong relationship with tree architecture, with dense-wooded species having smaller maximum height and wider crowns, probably because of cheaper expansion costs for producing biomechanically stable branches. Species from arid environments had shorter stems and shallower crowns for a given stem diameter, probably to reduce hydraulic path length and assure water transport. Wood density is an important correlate of variation in tree architecture between species and the two dominant families, with potentially large implications for their resource foraging strategies and successional dynamics.

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“…Drought adapted plants have a greater resistance to cavitation, 19,20 which appears related to an increased relative thickness of the conduit or the fibre cell walls, 5,21 and so an increased wood density. 5,22 However, since the mechanical properties are determined by the micro fibril angle (MFA) of the S2 cell wall layer as well as density, 23 the data from the few studies measuring the mechanical effects of hydraulic adaptation have not found consistent effects.…”

mentioning

confidence: 99%

“…5,22 However, since the mechanical properties are determined by the micro fibril angle (MFA) of the S2 cell wall layer as well as density, 23 the data from the few studies measuring the mechanical effects of hydraulic adaptation have not found consistent effects. 24,25 In these studies, complex natural systems were investigated making it difficult to distinguish between various climatic effects. We therefore grew seedlings from the three tree species Ochroma lagopus, Acacia karroo and Betula pendula under well-watered and droughted conditions, respectively, and measured the effect on the modulus of elasticity, the yield stress and the density (unpublished results).…”

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confidence: 99%

Interrelations between hydraulic and mechanical stress adaptations in woody plants

Christensen-Dalsgaard

Ennos

Fournier

2008

Plant Signaling & Behavior

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in the form of positive interactions and trade-offs. In the former case, adaptations with respect to one of the two stresses positively affect the plants ability to withstand the other. Drought adaptation, for instance, is associated with an increase in the density of the tissue, which may result in stiffer and stronger wood. 5,6 Further, increasing the transectional area of the sapwood increases the conductivity as well as the rigidity of the plant and may occur as an adaptation to either drought-or mechanical stress. 7,8 In such cases, because of the importance of hydraulic sufficiency as well as adequate mechanical support, biomass must be partitioned to allow for both functions simultaneously even if this results in a surplus allocation with respect to one. In the case of trade-offs, the hydraulic or mechanical adaptations are detrimental to the plants' capabilities with respect to the other. Within the woody tissue, for instance, larger and more numerous vessels increase the conductivity but may weaken the wood. 1-3,9-11 Analogously, hydraulic optimisation dictates an increase in the transectional sapwood area up though the plant, so that the summed area of all branches at a given height would be greater than that of the trunk 12 but mechanical optimisation a decrease. 13 In the case of physiological parameters within which there are trade-offs, achieving adequate design whilst minimising biomass allocation becomes complex, 4 and a number of possible but less optimal solutions exist.In our study, 14 we looked at how mechanical as well as hydraulic parameters changed along the lateral roots of two tropical tree species, Tachigali melinonii and Xylopia nitida, both of which produce buttress roots. Along the roots of these species there is a strong distal decrease in the magnitude of the locally supported mechanical loads, 15 making them ideal model organisms for investigating mechanical adaptation of the tissue and the impact this has on hydraulic parameters. We measured the density, conductivity, strength, stiffness, sapwood area and second moment of area at various points distally along the roots as well as in the lower trunk, and compared the values to those for strain. In both species, the strength and stiffness of the tissue decreased distally along the roots as the strain dropped, and the conductivity concurrently increased exponentially (Fig. 1). This appeared related to changes in the density of the wood; in both species, the density increased towards the bole and was positively correlated with mechanical properties but negatively with conductivity. As in previous studies, the distal most The fields of plant water relations and plant biomechanics have traditionally been studied separately even though often the same tissues are responsible for water transport and mechanical support. There is now increasing evidence that hydraulic and mechanical adaptations may influence one another. We studied the changes in the hydraulic and mechanical properties of the wood along lateral roots of two species of buttr...

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Relationships among xylem transport, biomechanics and storage in stems and roots of nine Rhamnaceae species of the California chaparral

Cited by 316 publications

References 45 publications

Root traits explain different foraging strategies between resprouting life histories

Root traits explain different foraging strategies between resprouting life histories

Architecture of Iberian canopy tree species in relation to wood density, shade tolerance and climate

Interrelations between hydraulic and mechanical stress adaptations in woody plants

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