Forced depression of leaf hydraulic conductance in situ: effects on the leaf gas exchange of forest trees

Abstract Background Root hypoxia has detrimental effects on physiological processes and growth in most plants. The effects of hypoxia can be partly alleviated by ethylene. However, the tolerance mechanisms contributing to the ethylene-mediated hypoxia tolerance in plants remain poorly understood. Results In this study, we examined the effects of root hypoxia and exogenous ethylene treatments on leaf gas exchange, root hydraulic conductance, and the expression levels of several aquaporins of the plasma membrane intrinsic protein group (PIP) in trembling aspen (Populus tremuloides) seedlings. Ethylene enhanced net photosynthetic rates, transpiration rates, and root hydraulic conductance in hypoxic plants. Of the two subgroups of PIPs (PIP1 and PIP2), the protein abundance of PIP2s and the transcript abundance of PIP2;4 and PIP2;5 were higher in ethylene-treated trembling aspen roots compared with non-treated roots under hypoxia. The increases in the expression levels of these aquaporins could potentially facilitate root water transport. The enhanced root water transport by ethylene was likely responsible for the increase in leaf gas exchange of the hypoxic plants. Conclusions Exogenous ethylene enhanced root water transport and the expression levels of PIP2;4 and PIP2;5 in hypoxic roots of trembling aspen. The results suggest that ethylene facilitates the aquaporin-mediated water transport in plants exposed to root hypoxia.

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Measurement of Gas Exchange on Excised Grapevine Leaves Does Not Differ from In Situ Leaves, and Potentially Shortens Sampling Time

Applied Sciences ◽

10.3390/app11083644 ◽

2021 ◽

Vol 11 (8) ◽

pp. 3644

Author(s):

Suraj Kar ◽

Thayne Montague ◽

Antonio Villanueva-Morales ◽

Edward Hellman

Keyword(s):

Gas Exchange ◽

Time Window ◽

Leaf Gas Exchange ◽

Growth Yield ◽

Abiotic Stress Response ◽

Gas Exchange Parameters ◽

Minute Post ◽

Exchange Measurement ◽

Similar Accuracy

Use of leaf gas exchange measurement enhances the characterization of growth, yield, physiology, and abiotic stress response in grapevines. Accuracy of a crop response model depends upon sample size, which is often limited due to the prolonged time needed to complete gas exchange measurement using currently available infra-red gas analyzer systems. In this experiment, we measured mid-day gas exchange of excised and in situ leaves from field grown wine grape (Vitis vinifera) cultivars. Depending upon cultivar, we found measuring gas exchange on excised leaves under a limited time window post excision gives similar accuracy in measurement of gas exchange parameters as in situ leaves. A measurement within a minute post leaf excision can give between 96.4 and 99.5% accuracy compared to pre-excision values. When compared to previous field data, we found the leaf excision technique reduced time between consecutive gas exchange measurements by about a third compared to in situ leaves (57.52 ± 0.39 s and 86.96 ± 0.41 s, for excised and in situ, respectively). Therefore, leaf excision may allow a 50% increase in experimental sampling size. This technique could solve the challenge of insufficient sample numbers, often reported by researchers worldwide while studying grapevine leaf gas exchange using portable gas exchange systems under field conditions.

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Gas exchange recovery following natural drought is rapid unless limited by loss of leaf hydraulic conductance: evidence from an evergreen woodland

New Phytologist ◽

10.1111/nph.14652 ◽

2017 ◽

Vol 215 (4) ◽

pp. 1399-1412 ◽

Cited By ~ 43

Author(s):

Robert P. Skelton ◽

Timothy J. Brodribb ◽

Scott A. M. McAdam ◽

Patrick J. Mitchell

Keyword(s):

Gas Exchange ◽

Hydraulic Conductance ◽

Leaf Hydraulic Conductance

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A method for the in situ measurement of fine root gas exchange of forest trees

Environmental and Experimental Botany ◽

10.1016/s0098-8472(96)01048-9 ◽

1997 ◽

Vol 37 (2-3) ◽

pp. 107-113 ◽

Cited By ~ 13

Author(s):

Zoltán Rakonczay ◽

John R. Seiler ◽

Lisa J. Samuelson

Keyword(s):

Gas Exchange ◽

Fine Root ◽

In Situ Measurement ◽

Forest Trees

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Effects of branch height on leaf gas exchange, branch hydraulic conductance and branch sap flux in open-grown ponderosa pine

Tree Physiology ◽

10.1093/treephys/22.8.575 ◽

2002 ◽

Vol 22 (8) ◽

pp. 575-581 ◽

Cited By ~ 24

Author(s):

R. M. Hubbard ◽

B. J. Bond ◽

R. S. Senock ◽

M. G. Ryan

Keyword(s):

Gas Exchange ◽

Ponderosa Pine ◽

Leaf Gas Exchange ◽

Hydraulic Conductance ◽

Sap Flux

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Water transport from stem to stomata: the coordination of hydraulic and gas exchange traits across 33 subtropical woody species

Tree Physiology ◽

10.1093/treephys/tpz076 ◽

2019 ◽

Vol 39 (10) ◽

pp. 1665-1674 ◽

Cited By ~ 3

Author(s):

Xiaorong Liu ◽

Hui Liu ◽

Sean M Gleason ◽

Guillermo Goldstein ◽

Shidan Zhu ◽

...

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Water Transport ◽

Explanatory Power ◽

Woody Species ◽

Hydraulic Conductance ◽

Co2 Assimilation ◽

Leaf Hydraulic Conductance ◽

Net Co2 Assimilation ◽

Leaf Tissues

Abstract Coordination between sapwood-specific hydraulic conductivity (Ks) and stomatal conductance (gs) has been identified in previous studies; however, coordination between leaf hydraulic conductance (Kleaf) and gs, as well as between Kleaf and Ks is not always consistent. This suggests that there is a need to improve our understanding of the coordination among hydraulic and gas exchange traits. In this study, hydraulic traits (e.g., Ks and Kleaf) and gas exchange traits, including gs, transpiration (E) and net CO2 assimilation (Aarea), were measured across 33 co-occurring subtropical woody species. Kleaf was divided into two components: leaf hydraulic conductance inside the xylem (Kleaf-x) and outside the xylem (Kleaf-ox). We found that both Kleaf-x and Kleaf-ox were coordinated with gs and E, but the correlations between Kleaf-ox and gs (or E) were substantially weaker, and that Ks was coordinated with Kleaf-x, but not with Kleaf-ox. In addition, we found that Ks, Kleaf-x and Kleaf-ox together explained 63% of the variation in gs and 42% of the variation in Aarea across species, with Ks contributing the largest proportion of explanatory power, whereas Kleaf-ox contributed the least explanatory power. Our results demonstrate that the coordination between leaf water transport and gas exchange, as well as the hydraulic linkage between leaf and stem, were weakened by Kleaf-ox. This highlights the possibility that water transport efficiencies of stem and leaf xylem, rather than that of leaf tissues outside the xylem, are important determinants of stomatal conductance and photosynthetic capacity across species.

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