Water Transport in Isolated Maize Roots

House, C. R.; Findlay, Nele

doi:10.1093/jxb/17.2.344

Cited by 79 publications

(18 citation statements)

References 10 publications

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“…These values are slightly lower than those obtained by House and Findlay (1966) Ginzburg (1964a, 1964b) have shown that there is a decrease in the hydraulic conductivity of algal cells with increases in solute concentration. They suggested that the decrease in permeability resulted from a shrinking of the membrane caused by a decrease in chemical potential of the surrounding water.…”

Section: (B) Effects Of Osmotic Pressure On Permeabilitycontrasting

confidence: 64%

“…If in the experiments of van Overbeek (1942) the osmotic pressure measured at the cut stump was lower than that in the root tips, then it need not mean that there had been a non-osmotic uptake of water, only that some of the salt which caused the entry of water in the lower part of the root was removed before the fluid left the root. The data of House and Findlay (1966) show a linear relation of flow to concentration differential and a positive intercept on the ordinate which implies that there may have been non-osmotic uptake of water. If there had been any re-absorption of salt from the xylem between the location of the entry of water and the cut stump, the measured concentration differential would be lower than the actual differential and would have caused the curve to show a non-osmotic uptake of water that did not really exist.…”

Section: (D) "Active" Water Uptakementioning

confidence: 94%

“…When House and Findlay (1966) plotted J w against the concentration difference from the external medium to the xylem sap of maize root tips, they got a straight line with a positive intercept on the ordinate. The positive intercept indicated that there might be a non-osmotic component to the water uptake.…”

Section: Introductionmentioning

confidence: 99%

“…The positive intercept indicated that there might be a non-osmotic component to the water uptake. House and Findlay (1966) devised the formula J w = LpRT(O~-Og) + </>' :v, (2) where 0; and O~ are the osmolarities of salt in the exudate and in the external medium respectively and </>' ;; is a net fiux of water independent of any osmotic gradient. Van Overbeek(1942) had previously found that the osmotic pressure of the xylem exudate from tomato roots was about 1 atm less than the osmotic pressure of the mannitol solution required to stop exudation.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Osmotic Pressure on Exudation from Corn Roots

Klepper¹

1967

Aust. Jnl. Of Bio. Sci.

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SummaryFor single, unbranched roots of corn (Zea mays L., Pioneer Hybrid 309-B), the rate of exudation per square centimetre of root surface (Jw ) decreased logarithmically with increases in the external osmotic pressure (IIo). The formulawhere Lp is the conductivity of the root to osmotic water movement and II, is the osmotic pressure of the xylem sap, is useful but has limitations. Lp may vary with II., and II, is difficult to measure because the exudate is not always a reliable sample of the xylem sap.The rate of exudation was predicted by the relationThe constants c and k were determined (c = 181'1/cm 2 /18 hr; k = O· 94/bar) for roots grown in Hoagland's solution to which various amounts of sodium chloride had been added to increase II •.Roots preconditioned to a high salinity were compared to roots which were grown in Hoagland's solution and then tested at higher osmotic pressures. The similarities of J w and the differences in the osmotic pressures of the xylem exudates for these two sets of roots indicated that salt was being removed from the xylem sap in the upper part of the root.

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Section: (B) Effects Of Osmotic Pressure On Permeabilitycontrasting

confidence: 64%

Section: (D) "Active" Water Uptakementioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Osmotic Pressure on Exudation from Corn Roots

Klepper¹

1967

Aust. Jnl. Of Bio. Sci.

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“…Nitrate also enhanced the exudation volumes relative to other forms of nitrogen (27,28). Xylem exudation is a function of the osmotic pressure difference between the xylem sap and the root-bathing solution and it also depends on the hydraulic conductivity of the root tissue (15,22). For the observed difference in exudation (Fig.…”

Section: Discussionmentioning

confidence: 85%

Nitrate Translocation by Detopped Corn Seedlings

Ezeta¹,

Jackson²

1975

Plant Physiol.

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Five-day-old seedlings of corn (Zea mays L.) grown without nitrate were decapitated and exposed to 0.5 mM KNOs or 0.5 mM KCI in aerated solutions at 30 C. Uptake of nitrate, chloride, and potassium was determined by replacing solutions hourly and measuring their depletion. Translocation of these ions and of organic nitrogen was determined by hourly analysis of the vascular exudate. Nitrate reduetion was estimated by the difference between nitrate uptake and nitrate recovered in the tissue and exudate. Nitrate uptake exhibited its usual pattern of apparent induction resulting in the development of an accelerated uptake phase. Chloride uptake remained fairly constant throughout the experimental period. Translocation of nitrate increased progressively for at least 7 hours whereas chloride translocation reached a maximum about the 3d hour and then declined to a lower rate than nitrate translocation. Nitrate uptake and translocation were restricted by anaerobiosis, by 20 and 40 C relative to 30 C, and by 0.05 mM 6-methylpurine, an RNA-synthesis inhibitor. Accumulation, reduction and translocation of nitrate had different sensitivities to all these factors. (17,18). Data are presented to support the concept that continuous nitrate uptake is required to maintain significant translocation of nitrate. In addition, the translocation of organic nitrogen was strongly dependent upon continuous nitrate uptake. MATERIALS AND METHODSThe procedures were, in general, similar to those described by Jackson et al. (17). All experiments were conducted with corn (Zea mays L.) hybrid DeKalb XL45. Four days after germination in darkness with 0.1 mm CaSO, the secondary roots were excised and five seedlings were assembled in a Plexiglas holder especially designed to fit the top of a 75-ml Taylor tube. Seedlings were then placed in a pretreatment solution for 24 to 36 hr in darkness prior to initiating the experiment. The pretreatment solutions contained per liter 0.25 mM (NH)2SO,, 0.6 mmY K2SO4, 0.4 mM KH2PO4, 1.6 mM MgSO4, 0.8 mm CaSO4, and 250 mg CaCO,. Iron was supplied as Fe-EDTA at 1.8 mg per liter; the remaining five micronutrients were present at one-fifth the concentration of Hoagland's solution (13).The standard uptake solution contained 0.5 mM KNO or 0.5 mM KCl plus 0.25 mm CaSO4, pH 6. For the experiments involving temperature, 6-methylpurine, or anaerobiosis variables, the uptake solutions also contained 1 mm Na 2-[Nmorpholino]ethanesulfonate as a buffer and the bactericide chloramphenicol at 20 jtg mP. Except where indicated, solutions were continuously aerated and the temperature was maintained at 30 C. Solutions were changed hourly and nitrate, chloride, and potassium uptake determined from depletion of the solutions. Five plants per 70 ml were employed for each replication. Four of these five-seedling units were used as replicates for each treatment and the data presented are the averages of the four replicates.Immediately after placing the plants in the uptake solutions, the mesocotyls were excised below the firs...

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Transport of Water in Plant-Atmosphere System

Plaut¹,

Moreshet²

1973

Arid Zone Irrigation

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Water Transport in Isolated Maize Roots

Cited by 79 publications

References 10 publications

Effects of Osmotic Pressure on Exudation from Corn Roots

Effects of Osmotic Pressure on Exudation from Corn Roots

Nitrate Translocation by Detopped Corn Seedlings

Transport of Water in Plant-Atmosphere System

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