Phloem networks in leaves

Carvalho, Mónica R.; Losada, Juan M.; Niklas, Karl J.

doi:10.1016/j.pbi.2017.12.007

Cited by 34 publications

(28 citation statements)

References 49 publications

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“…The directional flow in the sieve tubes of the major veins in Illicium leaves contrasts with the anatomy of the sieve tubes in the minor veins, which have numerous sieve areas pervading their lateral walls. The massive presence of sieve areas in the lateral walls of sieve tube elements from minor veins is in line with the idea of a division of function between the minor veins, which mainly work as sugar loaders, and major veins, where directional transport occurs within leaves (Russin and Evert, ; Turgeon, ; Carvalho et al., , ). A high number of symplasmic connections typically associate with passive sugar loading in the minor veins (van Bel et al., ; Turgeon, ; Gamalei et al., ; Rennie and Turgeon, ; Turgeon, ; Davidson et al., ; Zhang et al., ), but the heterogeneity of the species evaluated leave this question still unresolved (Slewinski et al., ).…”

Section: Discussionsupporting

confidence: 66%

“…Shorter sieve tubes in the phloem of the petiole may have implications for the regulation of pressure within the sieve tubes in leaves, especially at the times of maximum turgidity (i.e., maximum sugar export rates). We observed a higher number of sieve areas in the plates connecting the sieve tubes in the petiole; thus, this feature may attenuate at least in part a putative pressure increase (Carvalho et al., ). It would be desirable to obtain pore size in the sieve tubes of different vein orders and therefore check whether it concords with the hydraulic models for energy conservation, such as da Vinci's rule or Murray's law (Murray, ; Richter, ; McCulloh et al., ).…”

Section: Discussionmentioning

confidence: 67%

“…While the hydraulics of the xylem are coupled with the sugar loading of the phloem in the mesophyll (Hölttä et al., ; Liesche et al., ; Nikinmaa et al., ; Rockwell et al., ), the performance of the phloem in leaves is still poorly understood. With a recent exception (Carvalho et al., , ), detailed evaluations of phloem architecture in leaves with reticulate venation are lacking. The paucity is in part due to the challenging manipulations required to quantify the geometry of the sieve tubes in the tapering veins, as well as difficulties in evaluating the velocity of the sap inside the sieve tubes, typically measured using a fluorescent dye tracer (Jensen et al., ; Etxeberria et al., ) or radiolabeled compounds (Knoblauch et al., ).…”

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confidence: 99%

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Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum

Losada

Holbrook

2019

American J of Botany

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Citation: Losada, J. M. and N. M. Holbrook. 2019. Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum. American Journal of Botany 106(2): 244-259. PREMISE OF THE STUDY:Recent studies in canopy-dominant trees revealed axial scaling of phloem structure. However, whether this pattern is found in woody plants of the understory, the environment of most angiosperms from the ANA grade (Amborellales-Nymphaeales-Austrobaileyales), is unknown. METHODS:We used seedlings and adult plants of the understory tropical shrub Illicium parviflorum, a member of the lineage Austrobaileyales, to explore the anatomy and physiology of the phloem in their aerial parts, including changes through ontogeny.KEY RESULTS: Adult plants maintain a similar proportion of phloem tissue across stem diameters, but larger conduit dimensions and number cause the hydraulic resistance of the phloem to decrease toward the base of the plant. Small sieve plate pores resulted in an overall higher sieve tube hydraulic resistance than has been reported in other woody angiosperms. Sieve elements increase in size from minor to major leaf veins, but were shorter and narrower in petioles. The low carbon assimilation rates of seedlings and mature plants contrasted with a 3-fold higher phloem sap velocity in seedlings, suggesting that phloem transport velocity is modulated through ontogeny. CONCLUSIONS:The overall architecture of the phloem tissue in this understory angiosperm shrub scales in a manner consistent with taller trees that make up the forest canopy. Thus, the evolution of larger sieve plate pores in canopy-dominant trees may have played a key role in allowing woody angiosperms to extend beyond their understory origins.

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Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 67%

mentioning

confidence: 99%

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Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum

Losada

Holbrook

2019

American J of Botany

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“…maximum sugar export rates). We observed a higher number of sieve areas in the plates connecting the sieve tubes in the petiole, thus this feature may attenuate at least in part a putative pressure increase (Carvalho et al ., 2018). It would be desirable to obtain pore size in the sieve tubes of different vein orders and therefore check whether it concords with the hydraulic models for energy conservation, such as the da Vinci’s or Murray’s rules (Murray, 1926; Richter, 1980; McCulloh et al ., 2003).…”

Section: Discussionmentioning

confidence: 73%

Phloem structure and development in Illicium parviflorum, a basal angiosperm shrub

Losada

Holbrook

2018

Preprint

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SUMMARYRecent studies in canopy-dominant trees revealed a structure-function scaling of the phloem. However, whether axial scaling is conserved in woody plants of the understory, the environments of most basal-grade angiosperms, remains mysterious. We used seedlings and adult plants of the shrub Illicium parviflorum to explore the anatomy and physiology of the phloem in their aerial parts, and possible changes through ontogeny. Adult plants maintain a similar proportion of phloem tissue across stem diameters, but scaling of conduit dimensions and number decreases the hydraulic resistance towards the base of the plant. Yet, the small sieve plate pores resulted in an overall higher sieve tube hydraulic resistance than has been reported in other woody angiosperms. Sieve elements scaled from minor to major leaf veins, but were shorter and narrower in petioles. The low carbon assimilation rates of seedlings and mature plants contrasted with a three-fold higher phloem sap velocity in seedlings, suggesting that phloem transport velocity is modulated through ontogeny. While the overall architecture of the phloem tissue in basal-angiosperm understory shrubs scales in a manner consistent with trees, modification of conduit connections may have allowed woody angiosperms to extend beyond their understory origins.

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“…In addition, endodermis has been proposed to prevent ice formation (Kuang et al 2007;Roden et al 2009) and to biophysical properties related to needle flexibility (Meicenheimer et al 2008). In conjunction with transfusion tissue, endodermis also contributes to phloem loading (Liesche et al 2011;Carvalho et al 2018;Liesche and Schulz 2018). Transfusion tissue comprises specialised cells of transfusion tracheids and transfusion parenchyma cells.…”

Section: Introductionmentioning

confidence: 99%

Tissue-specific element profiles in Scots pine (Pinus sylvestris L.) needles

Pongrac

Baltrėnaitė

Vavpetič

et al. 2018

Trees

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Key message Element profile signatures of needle tissues differentiated four tissues: epidermis (main contributor: calcium), endodermis (main contributors: magnesium, sulphur and manganese), mesophyll (main contributor: potassium), and transfusion parenchyma (main contributor: zinc). Abstract Distribution of elements in cross-sections of Scots pine (Pinus sylvestris L.) needles was investigated using microproton-induced X-ray emission. Tissue-specific distributions of magnesium (Mg), sulphur (S), calcium (Ca), phosphorus (P), potassium (K), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), aluminium (Al) and silicon (Si) were resolved in a quantitative manner. Distribution maps and tissue-specific concentrations revealed the largest concentration of Ca in epidermis, of Mg, S and Mn in endodermis, of K in mesophyll and phloem and of Zn in transfusion parenchyma. Phosphorus, Cl, Fe, Al and Si did not exhibit apparent tissue-specific distribution. Inverse allocation of P and Ca was observed, a likely mechanism to prevent their precipitation. Taking the area of tissues into account, relative element distribution calculations indicated that mesophyll contained the majority of the elements studied, except Ca, which predominated in the epidermis (79% of total Ca concentration) and Mn, which predominated in the endodermis (40% of total Mn concentration). When considering a complete element profile of a particular tissue, four clusters were differentiated, which generally supported single-element observations. The first cluster differentiated mesophyll, xylem, phloem, transfusion tracheids and Strasburger cells with predominance of K, the second cluster differentiated epidermis on the basis of Ca, the third cluster differentiated endodermis with contributions from Mg, S and Mn, and the fourth cluster differentiated transfusion parenchyma with contribution from Zn. Information on tissue-specific-element allocations will complement structural and functional knowledge of needle tissues and advance our understanding of element/nutrient transfers in Scots pine.

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Phloem networks in leaves

Cited by 34 publications

References 49 publications

Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum

Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum

Phloem structure and development in Illicium parviflorum, a basal angiosperm shrub

Tissue-specific element profiles in Scots pine (Pinus sylvestris L.) needles

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