scholarly journals Concentrated Exogenous Abscisic Acid Drenches Reduce Root Hydraulic Conductance and Cause Wilting in Tomato

HortScience ◽  
2011 ◽  
Vol 46 (12) ◽  
pp. 1640-1645 ◽  
Author(s):  
Manuel G. Astacio ◽  
Marc W. van Iersel
Keyword(s):  
Abscisic Acid ◽  
Water Transport ◽  
Water Flux ◽  
Hydraulic Conductance ◽  
Root Hydraulic Conductance ◽  
Fresh Weight ◽  
Cumulative Volume ◽  
Effective Transport ◽  
Relative Water ◽  
Root Conductance

Previous work has shown that exogenous abscisic acid (ABA) applications can reduce transpiration, delay wilting, and thereby extend the shelf life of unwatered plants. Paradoxically, we have seen that drenches with concentrated ABA solutions may actually induce wilting. These wilting symptoms occur despite the presence of ample water in the substrate, suggesting that ABA may interfere with the ability of roots to take up water. Our objective was to develop a better understanding of this wilting effect using tomato (Solanum lycopersicum) as a model. In the first study, ABA drenches (125–2000 mg·L−1) reduced transpiration and water use compared with the control plants, yet the relative water content (RWC) of the leaves of ABA-treated plants was lower than that of control plants at 24 h after the ABA drench. Control plants had a leaf RWC of 97%, whereas plants treated ABA had a RWC of 57% to 62%. ABA concentrations of 500 mg·L−1 or higher caused the plants to wilt within 24 h despite the presence of ample water in the substrate. Leaf ABA concentrations 24 h after the ABA application ranged from 2.6 (control) to 62.6 nmol·g−1 fresh weight (FW) in the 2000-mg·L−1 ABA treatment, indicating effective transport of ABA from the roots to the leaves. The reduced leaf RWC suggests that ABA drenches are limiting water transport through the roots to the leaves. The effects of ABA on the hydraulic conductance of the roots and stems of tomatoes were quantified to determine if ABA drenches limit water transport through the roots. The cumulative volume of water conducted by the root systems during a 4-day period ranged from 36.7 mL in the control treatments to 8.1 mL in roots systems drenched with 1000 mg·L−1 ABA, a reduction of 78%. When the conductance study was repeated using decapitated roots and excised stems, root water flux was again reduced by ABA, but water flux through internodal stem sections did not show an ABA effect. Results suggest that ABA-induced wilting is caused by a reduction in root conductance and we hypothesize that ABA affects aquaporins in the roots, limiting water uptake.

Changes in Water Relations, Water Flux, and Root Exudate Abscisic Acid Content With Cold Acclimation of Pinus sylvestris L

1984 ◽  
Vol 11 (5) ◽  
pp. 431 ◽  
Author(s):  
B Smit-Spinks ◽  
BT Swanson ◽  
AH Iii Markhart
Keyword(s):  
Abscisic Acid ◽  
Water Content ◽  
Cold Acclimation ◽  
Transpiration Rate ◽  
Relative Water Content ◽  
Root Exudate ◽  
Hydraulic Conductance ◽  
Root Hydraulic Conductance ◽  
Xylem Pressure ◽  
Relative Water

Scotch pine seedlings (Pinus sylvestris L.) were subjected to 6 week photoperiod and thermoperiod treatments to induce different levels of cold acclimation. The water content, relative water content, xylem pressure potential, transpiration rate, root hydraulic conductance, and abscisic acid (ABA) content of root exudate were then measured. Water content decreased in woody stems and needles with cold acclimation but not in the roots and green stems. There was a close correlation between relative water content and water content of woody stems and needles as well as a decrease in xylem pressure potentials of hardy needles, indicating that the reduction in water content was at least partially due to increased water deficit. The increased water deficit was not caused by increased water loss since transpiration rates decreased in hardy shoots. Water uptake was reduced by decreased root hydraulic conductance which could account for the shoot water deficits. Root hydraulic conductance and transpiration rate returned to non-acclimated levels after warm temperature exposure. ABA levels were highest in the root exudate collected in the morning from non-acclimated plants.

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 Measuring Root Hydraulic Parameters of Container-grown Herbaceous and Woody Plants Using the Hydraulic Conductance Flow Meter

HortScience ◽  
2016 ◽  
Vol 51 (2) ◽  
pp. 192-196 ◽  
Author(s):  
Lesley A. Judd ◽  
Brian E. Jackson ◽  
William C. Fonteno ◽  
Jean-Christophe Domec
Keyword(s):  
Woody Plants ◽  
Vascular System ◽  
Hydraulic Conductance ◽  
Plant Performance ◽  
Hydraulic Parameters ◽  
Root Mass ◽  
Root Hydraulic Conductance ◽  
Flow Meter ◽  
Root Conductance ◽  
Intact Roots

Root hydraulic conductance and conductivity are physiological traits describing the ease with which water can move through the belowground vascular system of a plant, and are used as indicators of plant performance and adaptability to a given environment. The ability to measure hydraulic conductance of container-grown herbaceous and semiwoody plants with soft conductive tissue was tested using a hydraulic conductance flow meter (HCFM). Although the HCFM is a hydraulic apparatus that has been used on woody plants to measure hydraulic conductance of intact roots, it has never been reportedly used on container-grown horticultural plants. Two herbaceous species, Chrysanthemum L. and Solenstemon scutellarioides Thonn., were grown in containers and hydraulic parameters were measured, including root conductance and root conductivity, as well as physical traits such as stem diameter and dry root mass. The HCFM was easily connected to intact roots even on herbaceous stems and was used to determine hydraulic conductance and conductivity directly on container-grown plants with minimal disturbance on the root system. Chrysanthemums, Buddleja davidii Franch., and Hibiscus moscheutos L. were grown in three different substrates, and both root mass and root hydraulic parameters were determined. Chrysanthemums showed a positive response with increasing root hydraulic conductance with increasing root mass. The substrates used in these studies only had an effect on root biomass of chrysanthemums, but substrates had no differential effect on root hydraulic conductivity.

scholarly journals ROOT CONDUCTANCE AND MORPHOLOGY OF SOLUTION- AND SAND-CULTURED HONEY LOCUST SEEDLINGS OF DIFFERENT AGES

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1069c-1069
Author(s):  
William R. Graves
Keyword(s):  
Surface Area ◽  
Sharp Decrease ◽  
Dry Weight ◽  
Hydraulic Conductance ◽  
Root Hydraulic Conductance ◽  
Root Dry Weight ◽  
State Water ◽  
Honey Locust ◽  
Using Data ◽  
Root Conductance

Root hydraulic conductance is often expressed on the basis of dry weight or surface area of leaves or roots of plants produced in solution or aggregate culture. In this study, biomass partitioning and its influence on the interpretation of root hydraulic conductance data were compared in 21- to 63-day-old Gleditsia triacanthos inermis Willd. (honey locust) seedlings grown in solution and sand cultures. The ratio of lamina to root dry weight decreased as seedlings aged but was always greater for solution-grown plants than for sand-grown plants. Expressed on the basis of root dry weight, steady-state water fluxes at applied pressures ≥ 0.28 MPa and hydraulic conductivity coefficients declined with root system age, with a sharp decrease among solution-grown plants between ages 21 and 35 days. Such a difference was not detected using data expressed on lamina surface area or dry weight, illustrating that caution must be exercised when reporting and comparing the conductance of roots cultured in different media.

Abscisic acid-mediated modifications in water transport continuum are involved in cadmium hyperaccumulation in Sedum alfredii

Chemosphere ◽  
2021 ◽  
Vol 268 ◽  
pp. 129339
Author(s):  
Qi Tao ◽  
Radek Jupa ◽  
Qin Dong ◽  
Xin Yang ◽  
Yuankun Liu ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Water Transport ◽  
Sedum Alfredii ◽  
Cadmium Hyperaccumulation

scholarly journals Influence of Abscisic Acid and Sucrose on Somatic Embryogenesis in CactusCopiapoa tenuissimaRitt. formamostruosa

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
J. Lema-Rumińska ◽  
K. Goncerzewicz ◽  
M. Gabriel
Keyword(s):  
Somatic Embryogenesis ◽  
Abscisic Acid ◽  
Somatic Embryos ◽  
Sucrose Concentration ◽  
Turgor Pressure ◽  
Direct Somatic Embryogenesis ◽  
Fresh Weight ◽  
High Concentration ◽  
Globular Stage ◽  
Indirect Somatic Embryogenesis

Having produced the embryos of cactusCopiapoa tenuissimaRitt. formamonstruosaat the globular stage and callus, we investigated the effect of abscisic acid (ABA) in the following concentrations: 0, 0.1, 1, 10, and 100 μM on successive stages of direct (DSE) and indirect somatic embryogenesis (ISE). In the indirect somatic embryogenesis process we also investigated a combined effect of ABA (0, 0.1, 1 μM) and sucrose (1, 3, 5%). The results showed that a low concentration of ABA (0-1 μM) stimulates the elongation of embryos at the globular stage and the number of correct embryos in direct somatic embryogenesis, while a high ABA concentration (10–100 μM) results in growth inhibition and turgor pressure loss of somatic embryos. The indirect somatic embryogenesis study in this cactus suggests that lower ABA concentrations enhance the increase in calli fresh weight, while a high concentration of 10 μM ABA or more changes calli color and decreases its proliferation rate. However, in the case of indirect somatic embryogenesis, ABA had no effect on the number of somatic embryos and their maturation. Nevertheless, we found a positive effect of sucrose concentration for both the number of somatic embryos and the increase in calli fresh weight.

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