Effects of xylem sap flow on carbon dioxide efflux from stems of birch (Betula pendula Roth)

In this study, we focused on direct and quantitative monitoring of sap dynamics in plant stems, and proposed the microscale xylem sap flow sensor. This sensor facilitates the simultaneous measurement of flow velocity and direction by combining the principles of a Granier sensor and a thermal flow sensor. We fabricated micro-sensor chips for functional verification by using MEMS technology, and assembled them on a resin film to facilitate mounting on the epidermis of plants. Furthermore, we measured the sap dynamics by using an experimental setup, and succeeded in measuring the flow velocity and direction at the same time.

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Vertical Strata and Stem Carbon Dioxide Efflux in Cycas Trees

Plants ◽

10.3390/plants9020230 ◽

2020 ◽

Vol 9 (2) ◽

pp. 230 ◽

Cited By ~ 2

Author(s):

Thomas E. Marler ◽

Murukesan V. Krishnapillai

Keyword(s):

Carbon Dioxide ◽

Carbon Cycling ◽

Sap Flow ◽

Quadratic Model ◽

Maintenance Respiration ◽

Stem Respiration ◽

Ecosystem Carbon ◽

Vertical Location ◽

Carbon Dioxide Efflux ◽

Cycas Revoluta

Stem respiration is influenced by the vertical location of tree stems, but the influence of vertical location on stem respiration in a representative cycad species has not been determined. We quantified the influence of vertical strata on stem carbon dioxide efflux (Es) for six arborescent Cycas L. species to characterize this component of stem respiration and ecosystem carbon cycling. The influence of strata on Es was remarkably consistent among the species, with a stable baseline flux characterizing the full mid-strata of the pachycaulous stems and an increase in Es at the lowest and highest strata. The mid-strata flux ranged from 1.8 μmol·m−2·s−1 for Cycas micronesica K.D. Hill to 3.5 μmol·m−2·s−1 for Cycas revoluta Thunb. For all species, Es increased about 30% at the lowest stratum and about 80% at the highest stratum. A significant quadratic model adequately described the Es patterns for all six species. The increase of Es at the lowest stratum was consistent with the influence of root-respired carbon dioxide entering the stem via sap flow, then contributing to Es via radial conductance to the stem surface. The substantial increase in Es at the highest stratum is likely a result of the growth and maintenance respiration of the massive cycad primary thickening meristem that constructs the unique pachycaulous cycad stem.

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In vivo pressure gradient heterogeneity increases flow contribution of small diameter vessels in grapevine

Nature Communications ◽

10.1038/s41467-019-13673-6 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 8

Author(s):

Martin Bouda ◽

Carel W. Windt ◽

Andrew J. McElrone ◽

Craig R. Brodersen

Keyword(s):

Sap Flow ◽

Xylem Sap ◽

Small Diameter ◽

Fourth Power ◽

First Year ◽

Long Distance ◽

Xylem Sap Flow ◽

Flow Mri ◽

Vessel Network

AbstractLeaves lose approximately 400 H2O molecules for every 1 CO2 gained during photosynthesis. Most long-distance water transport in plants, or xylem sap flow, serves to replace this water to prevent desiccation. Theory predicts that the largest vessels contribute disproportionately to overall sap flow because flow in pipe-like systems scales with the fourth power of radius. Here, we confront these theoretical flow predictions for a vessel network reconstructed from X-ray μCT imagery with in vivo flow MRI observations from the same sample of a first-year grapevine stem. Theoretical flow rate predictions based on vessel diameters are not supported. The heterogeneity of the vessel network gives rise to transverse pressure gradients that redirect flow from wide to narrow vessels, reducing the contribution of wide vessels to sap flow by 15% of the total. Our results call for an update of the current working model of the xylem to account for its heterogeneity.

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