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 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.  

scholarly journals Ethylene enhances root water transport and aquaporin expression in trembling aspen (Populus tremuloides) exposed to root hypoxia

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xiangfeng Tan ◽  
Mengmeng Liu ◽  
Ning Du ◽  
Janusz J. Zwiazek
Keyword(s):  
Gas Exchange ◽  
Water Transport ◽  
Populus Tremuloides ◽  
Leaf Gas Exchange ◽  
Hydraulic Conductance ◽  
Root Hydraulic Conductance ◽  
Trembling Aspen ◽  
Expression Levels ◽  
Root Hypoxia ◽  
Exogenous Ethylene

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.

scholarly journals Responses of Tomato to Potassium Rates in a Calcareous Soil

HortScience ◽  
2017 ◽  
Vol 52 (5) ◽  
pp. 764-769 ◽  
Author(s):  
Qiang Zhu ◽  
Monica Ozores-Hampton ◽  
Yuncong Li ◽  
Kelly Morgan ◽  
Guodong Liu ◽  
...  
Keyword(s):  
Calcareous Soil ◽  
Plant Biomass ◽  
Winter Season ◽  
Calcareous Soils ◽  
Leaf Tissue ◽  
Dry Weight ◽  
The United States ◽  
Ammonium Bicarbonate ◽  
Soluble Solids ◽  
Postharvest Quality

Florida produces the most vegetables in the United States during the winter season with favorable weather conditions. However, vegetables grown on calcareous soils in Florida have no potassium (K) fertilizer recommendation. The objective of this study was to evaluate the effects of K rates on leaf tissue K concentration (LTKC), plant biomass, fruit yield, and postharvest quality of tomatoes (Solanum lycopersicum L.) grown on a calcareous soil. The experiment was conducted during the winter seasons of 2014 and 2015 in Homestead, FL. Potassium fertilizers were applied at rates of 0, 56, 93, 149, 186, and 223 kg·ha−1 of K and divided into preplant dry fertilizer and fertigation during the season. No deficiency of LTKC was found at 30 days after transplanting (DAT) in both years. Potassium rates lower than 149 kg·ha−1 resulted in deficient LTKC at 95 DAT in 2014. No significant responses to K rates were observed in plant (leaf, stem, and root combined) dry weight biomass at all the sampling dates in both years. However, at 95 DAT, fruit dry weight biomass increased with increasing K rates to 130 and 147 kg·ha−1, reaching a plateau thereafter indicated by the linear-plateau models in 2014 and 2015, respectively. Predicted from quadratic and linear-plateau models, K rates of 173 and 178 kg·ha−1 were considered as the optimum rates for total season marketable yields in 2014 and 2015, respectively. Postharvest qualities, including fruit firmness, pH, and total soluble solids (TSS) content, were not significantly affected by K rates in both years. Overall, K rate of 178 kg·ha−1 was sufficient to grow tomato during the winter season in calcareous soils with 78 to 82 mg·kg−1 of ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extracted K in Florida.

Adaptation to Water Stress of the Leaf Water Relations of Four Tropical Forage Species

1980 ◽  
Vol 7 (2) ◽  
pp. 207 ◽  
Author(s):  
JR Wilson ◽  
MM Ludlow ◽  
MJ Fisher ◽  
E Schulze
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Water Relations ◽  
Bound Water ◽  
Leaf Tissue ◽  
Dry Weight ◽  
Panicum Maximum ◽  
Soil Drying ◽  
Buffel Grass ◽  
Heteropogon Contortus

Three tropical grasses, green panic (Panicum maximum var, trichoglume), spear grass (Heteropogon contortus) and buffel grass (Cenchrus ciliaris) and the tropical legume siratro (Macroptilium atropurpureum), were grown in plots in a semi-arid field environment. The water relations characteristics of leaves from plants subjected to a soil drying cycle were compared with those of unstressed leaves from plants in irrigated plots. Minimum water potentials attained in the stressed leaves were c. -44, - 38, - 33 and - 13 bar for the four species, respectively. The grass leaves adjusted osmotically to water stress, apparently through accumulation of solutes, so that there was a decrease in osmotic potential at full turgor (Ψπ100) of 5.5, 3.9 and 7.1 bar, and in water potential at zero turgor (Ψ0) of 8.6, 6.5 and 8.6 bar for green panic, spear grass and buffel respectively. Water stress appeared to increase slightly the proportion of bound water (B) and the bulk modulus of elasticity (ε) of the grass leaves, but it did not alter the relative water content at zero turgor (RWC0) or the ratio of turgid water content to dry weight of the tissue. The Ψπ100 and Ψ0 of stressed siratro leaves decreased by 2.5-4 bar and 3-5 bar respectively when subjected to soil drying cycles. These changes could be explained by the marked decrease in the ratio of turgid water content to dry weight of the leaf tissue rather than by accumulation of solutes. The values of RWC0 and ε for siratro leaves were not altered by stress but, in contrast to the grasses, B was apparently decreased although the data exhibited high variability. Adjustments in Ψπ100 and Ψ0 of stressed leaves of buffel grass and siratro were largely lost within 10 days of rewatering.

scholarly journals Growth and grain yield of eight maize hybrids is aligned with water transport, stomatal conductance, and photosynthesis in a semi-arid irrigated system

2021 ◽  
Author(s):  
Sean M Gleason ◽  
Lauren Nalezny ◽  
Cameron Hunter ◽  
Robert Bensen ◽  
Satya Chintamanani ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Grain Yield ◽  
Water Transport ◽  
Co2 Assimilation ◽  
Specific Conductance ◽  
Soil Conditions ◽  
Transport Pathway ◽  
Crop Species ◽  
Leaf Level ◽  
Improved Performance

There is increasing interest in understanding how trait networks can be manipulated to improve the performance of crop species. Working towards this goal, we have identified key traits linking the acquisition of water, the transport of water to the sites of evaporation and photosynthesis, stomatal conductance, and growth across eight maize hybrid lines grown under well-watered and water-limiting conditions in Northern Colorado. Under well-watered conditions, well-performing hybrids exhibited high leaf-specific conductance, low operating water potentials, high rates of midday stomatal conductance, high rates of net CO2 assimilation, greater leaf osmotic adjustment, and higher end-of-season growth and grain yield. This trait network was similar under water-limited conditions with the notable exception that linkages between water transport, midday stomatal conductance, and growth were even stronger than under fully-watered conditions. The results of this experiment suggest that similar trait networks might confer improved performance under contrasting climate and soil conditions, and that efforts to improve the performance of crop species could possibly benefit by considering the water transport pathway within leaves, as well as within the whole-xylem, in addition to root-level and leaf-level traits.

scholarly journals Turnover of Minerals and Organics in the Postharvest Herbage of Annuals and Perennials: Winter Wheat and Goldenrod

Agriculture ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 170 ◽  
Author(s):  
Gerhard Gramss ◽  
Klaus-Dieter Voigt
Keyword(s):  
Winter Wheat ◽  
Lignin Content ◽  
Root Exudation ◽  
Soil Formation ◽  
Dry Weight ◽  
Water Soluble ◽  
Co2 Efflux ◽  
Transient Rise ◽  
Biomass N ◽  
Microbial Carbon

Crossing annual cereals, legumes, and oilseeds with wild rhizomatous relatives is used to create perennial lines that fruit over 2–3 seasons. Contrary to annual crops, the year-round vegetation cover should contribute to carbon sequestration, soil formation, and root mineral preservation. Soil erosion, nutrient leaching, and labor expenses may be reduced. While deep-rooted grasses actually inhibit nitrate leaching, advantages in nutrient storage and soil formation are not yet shown. Therefore, the turnover of organics and minerals in the perennial goldenrod was compared with that of winter wheat between blooming and resprouting (28 February) by gravimetry and ICP-MS. From blooming (23 August) to harvest (13 November), goldenrod stalks of 10,070 (given in kg ha−1) lost 23% by dry weight (DW) and released 14.9/9.6/65.7 in NPK and 2193 in water-soluble organics via leaching and root exudation. Apart from a transient rise of 28.8 in N around 13 November, the stubble/rhizome system held CaKMg(N)P stable at a level avoiding metal stress from 23 August to 28 February. Filling seeds in wheat excluded net losses of minerals and organics from anthesis to harvest (23 July). Stubbles (16 cm) and spilt grains of 2890 represented 41.8/2.91/62.5 in NPK and lost 905 in biomass with 25.4/1.8/59.8 in NPK to the soil by 28 February. In wheat-maize rotations, ploughing was avoided until early March. Weeds and seedlings emerged from spilt grains replaced losses in stubble biomass, N, and P but left 40.5 in K unused to the soil. In wheat-wheat rotations, organics and minerals lost by the down-ploughed biomass were replenished by the next-rotation seedlings that left only 18.3 in K to the soil. In summary, off-season goldenrod rhizomes did not store excess minerals. The rate of mineral preservation corresponded with the quantity of the biomass irrespective of its perennial habit. Released water-soluble organics should foster microbial carbon formation and CO2 efflux while soil improving gains in humate C should depend on the lignin content of the decaying annual or perennial biomass. Clues for NPK savings by perennials were not found.

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