Leaf water stable isotopes and water transport outside the xylem

2016 ◽  
Vol 40 (6) ◽  
pp. 914-920 ◽  
Author(s):  
M. M. Barbour ◽  
G. D. Farquhar ◽  
T. N. Buckley
Keyword(s):  
Stable Isotopes ◽  
Water Transport ◽  
Leaf Water

scholarly journals Hypernodulating soybean mutant line nod4 lacking ‘Autoregulation of Nodulation’ (AON) has limited root-to-shoot water transport capacity

2019 ◽  
Vol 124 (6) ◽  
pp. 979-991 ◽  
Author(s):  
Emile Caroline Silva Lopes ◽  
Weverton Pereira Rodrigues ◽  
Katherine Ruas Fraga ◽  
José Altino Machado Filho ◽  
Jefferson Rangel da Silva ◽  
...  
Keyword(s):  
Plant Growth ◽  
Water Potential ◽  
Water Transport ◽  
Leaf Water Potential ◽  
Root Nodules ◽  
Leaf Water ◽  
Transport Capacity ◽  
N Content ◽  
Photosynthetic Rates ◽  
Root Conductance

AbstractBackground and AimsAlthough hypernodulating phenotype mutants of legumes, such as soybean, possess a high leaf N content, the large number of root nodules decreases carbohydrate availability for plant growth and seed yield. In addition, under conditions of high air vapour pressure deficit (VPD), hypernodulating plants show a limited capacity to replace water losses through transpiration, resulting in stomatal closure, and therefore decreased net photosynthetic rates. Here, we used hypernodulating (nod4) (282.33 ± 28.56 nodules per plant) and non-nodulating (nod139) (0 nodules per plant) soybean mutant lines to determine explicitly whether a large number of nodules reduces root hydraulic capacity, resulting in decreased stomatal conductance and net photosynthetic rates under high air VPD conditions.MethodsPlants were either inoculated or not inoculated with Bradyrhizobium diazoefficiens (strain BR 85, SEMIA 5080) to induce nitrogen-fixing root nodules (where possible). Absolute root conductance and root conductivity, plant growth, leaf water potential, gas exchange, chlorophyll a fluorescence, leaf ‘greenness’ [Soil Plant Analysis Development (SPAD) reading] and nitrogen content were measured 37 days after sowing.Key ResultsBesides the reduced growth of hypernodulating soybean mutant nod4, such plants showed decreased root capacity to supply leaf water demand as a consequence of their reduced root dry mass and root volume, which resulted in limited absolute root conductance and root conductivity normalized by leaf area. Thereby, reduced leaf water potential at 1300 h was observed, which contributed to depression of photosynthesis at midday associated with both stomatal and non-stomatal limitations.ConclusionsHypernodulated plants were more vulnerable to VPD increases due to their limited root-to-shoot water transport capacity. However, greater CO2 uptake caused by the high N content can be partly compensated by the stomatal limitation imposed by increased VPD conditions.

scholarly journals Leaf cell wall properties and stomatal density influence oxygen isotope enrichment of leaf water

2020 ◽  
Author(s):  
Patrick Ellsworth ◽  
Patricia Ellsworth ◽  
Rachel Mertz ◽  
Nuria Koteyeva ◽  
Asaph B. Cousins
Keyword(s):  
Cell Wall ◽  
Water Transport ◽  
Water Movement ◽  
Transport Model ◽  
Stomatal Density ◽  
Oxygen Isotopic Composition ◽  
Cell Wall Composition ◽  
Leaf Water ◽  
Suberin Lamellae ◽  
The Difference

AbstractOxygen isotopic composition (Δ18OLW) of leaf water can help improve our understanding of how anatomy interacts with physiology to influence leaf water transport. Leaf water isotope models of Δ18OLW such as the Péclet effect model have been developed to predict Δ18OLW, and it incorporates transpiration rate (E) and the mixing length between unenriched xylem water and enriched mesophyll water, which can occur in the mesophyll (Lm) or veins (Lv). Here we used two cell wall composition mutants grown under two light intensities and RH to evaluate the effect of cell wall composition on Δ18OLW. In maize (Zea mays), the compromised ultrastructure of the suberin lamellae in the bundle sheath of the ALIPHATIC SUBERIN FERULOYL TRANSFERASE mutant (Zmasft) reduced barriers to apoplastic water movement, resulting in higher E and Lv and, consequently, lower Δ18OLW. In cellulose synthase-like F6 (Cslf6) mutants and wildtype of rice (Oryza sativa), the difference in Δ18OLW in plants grown under high and low growth light intensity co-varied with their differences in stomatal density. These results show that cell wall composition and stomatal density influence Δ18OLW by altering the Péclet effect and that stable isotopes can facilitate the development of a physiologically and anatomically explicit water transport model.

Two measures of leaf capacitance: insights into the water transport pathway and hydraulic conductance in leaves

2011 ◽  
Vol 38 (2) ◽  
pp. 118 ◽  
Author(s):  
Chris J. Blackman ◽  
Tim J. Brodribb
Keyword(s):  
Water Transport ◽  
Lignin Content ◽  
Leaf Tissue ◽  
Dry Weight ◽  
Hydraulic Conductance ◽  
Leaf Water ◽  
Transport Pathway ◽  
Transpiration Stream ◽  
Two Measures ◽  
Key Indicators

The efficiency and stress tolerance of leaf water transport are key indicators of plant function, but our ability to assess these processes is constrained by gaps in our understanding of the water transport pathway in leaves. A major challenge is to understand how different pools of water in leaves are connected to the transpiration stream and, hence, determine leaf capacitance (Cleaf) to short- and medium-term fluctuations in transpiration. Here, we examine variation across an anatomically and phylogenetically diverse group of woody angiosperms in two measures of Cleaf assumed to represent bulk-leaf capacitance (Cbulk) and the capacitance of leaf tissues that influence dynamic changes in leaf hydration (Cdyn). Among species, Cbulk was significantly correlated with leaf mass per unit area, whereas Cdyn was independently related to leaf lignin content (%) and the saturated mass of leaf water per unit dry weight. Dynamic and steady-state measurements of leaf hydraulic conductance (Kleaf) agreed if Cdyn was used rather than Cbulk, suggesting that the leaf tissue in some species is hydraulically compartmentalised and that only a proportion of total leaf water is hydraulically well connected to the transpiration stream. These results indicate that leaf rehydration kinetics can accurately measure Kleaf with knowledge of the capacitance of the hydraulic pathway.

scholarly journals Influences of relative humidity and Indian monsoon precipitation on leaf water stable isotopes from the southeastern Tibetan Plateau

2014 ◽  
Vol 41 (21) ◽  
pp. 7746-7753 ◽  
Author(s):  
Wusheng Yu ◽  
Baiqing Xu ◽  
Chun-Ta Lai ◽  
Yaoming Ma ◽  
Lide Tian ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Relative Humidity ◽  
Tibetan Plateau ◽  
Indian Monsoon ◽  
Leaf Water ◽  
Monsoon Precipitation ◽  
Southeastern Tibetan Plateau

scholarly journals Stable isotopes in leaf water of terrestrial plants

2016 ◽  
Vol 39 (5) ◽  
pp. 1087-1102 ◽  
Author(s):  
Lucas A. Cernusak ◽  
Margaret M. Barbour ◽  
Stefan K. Arndt ◽  
Alexander W. Cheesman ◽  
Nathan B. English ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Leaf Water ◽  
Terrestrial Plants

scholarly journals Influence of hydraulic properties of rootstocks and the rootstock-scion graft on water use and productivity of apple trees

2001 ◽  
Author(s):  
Shabtai Cohen ◽  
Melvin Tyree ◽  
Amos Naor ◽  
Alan N. Lakso ◽  
Terence L. Robinson ◽  
...  
Keyword(s):  
High Pressure ◽  
Water Transport ◽  
Hydraulic Conductance ◽  
Leaf Conductance ◽  
Leaf Water ◽  
Graft Union ◽  
Large Trees ◽  
The Us ◽  
Before And After ◽  
Dwarfing Rootstocks

This one year exploratory project investigated hydraulic architecture of apple dwarfing rootstocks. The hypothesis was that hydraulic conductance is correlated with rootstock vigor. A previous study of trees on three rootstocks in Israel showed that dwarfed trees used less water than un-dwarfed trees. Analysis showed that if the tree maintains leaf water potentials above minimum values, then this implies that the dwarfed trees have lower leaf conductance, which may also be the cause of dwarfing. The current project studied small 2-year old unworked rootstock trees, and full sized trees bearing commercial yields. In both cases hydraulic conductance was determined with two methods - the non-destructive evaporative flux (EF)-leaf water potential (L WP) method, and a destructive method in which water was forced through the plant at known pressure using the "high pressure flow meter" (HPFM). Detailed work allowed measurement of conductance of the rootstock-scion union. This was achieved both with the HPFM and with the EF-LWP methods, the former in the US and the latter in Israel. Direct measurements of leaf conductance were made, and carbon isotope ratios ( d ¹³ C) were determined for leaves sampled at the end of the season. The latter can indicate sustained differences in leaf conductance behavior. HPFM and EF-LWP methods did not give the same results. In the small plants results were similar in magnitude, but not significantly correlated. In large trees, EF- L WP measurements were a fraction of those obtained with the HPFM. The latter indicates that some of the xylem is not normally functional but transports water when pressurized. Additional experimental work targeted this result. Xylem was stained before and after perfusion with water at high pressure. This showed that at least for one rootstock a significant amount of xylem was blocked before perfusion. The "air method" for determining xylem vessel properties was improved and employed. Length, radius and density of xylem vessels of different rootstocks were found to be similar, and significant differences found were not clearly related to rootstock vigor. Measurements in the commercial orchard in Israel showed that the graft union in a dwarfing rootstock was a large obstacle for water transport (i.e. had a high resistance). This apparently led to low leaf conductance to water vapor, as indicated by lower d ¹³ C, which implies low internal CO ₂ concentrations. In the US orchard, d ¹³ C in 2001 was correlated with rootstock vigor, and significant differences were found in leaf conductance. However, the d ¹³ C differences were not observed in 2002, were opposite to those found in the Israeli orchard, and measurements of the graft union with the HPFM did not find large resistances. We speculate that the graft union is not necessarily a large impediment to water transport unless the scion starts to separate from the rootstock. It was concluded that significant differences in hydraulic conductance exist between different dwarfing rootstocks. These differences may be caused by differences in xylem properties and in the degree of cavitation, as well as resistance in the graft union. However, no general relationship to rootstock vigor was found. Therefore, hydraulic conductance alone cannot explain dwarfing, but may be one of two or more factors that lead to dwarfing. Future work should integrate more factors with hydraulic relations, e.g. nutrient and solute transport and production of hormones.  

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