Expression of Characteristics of Ammonium Nutrition as Affected by pH of the Root Medium

To study the effect of root-zone pH on characteristic responsesof -fed plants, soybeans (Glycine max {L.}Merr. cv. Ransom) were grown in flowing solution culture for21 d on four sources of N (1.0 mol m^–3 , 0.67 mol m^–3 plus 0.33 mol m^–3, 0.33 mol m^–3 plus 0.67 mol m^–3 , and 1.0 mol m^–3) with nutrient solutions maintained at pH 6.0, 5.5, 5.0, and 4.5. Amino acid concentration increased inplants grown with as the sole source of N at all pH levels. Total amino acid concentration in the rootsof -fed plants was 8 to 10 times higher than in -fed plants, with asparagine accounting for more than 70% of the total in the roots of these plants.The concentration of soluble carbohydrates in the leaves of-fed plants was greater than that of -fed plants, but was lower in roots of -fed plants, regardless of pH. Starch concentration was only slightlyaffected by N source or root-zone pH. At all levels of pH tested,organic acid concentration in leaves was much lower when was the sole N source than when all or part of theN was supplied as . Plants grown with mixed plus N sources were generally intermediate between - and -fed plants. Thus, changes in tissue compositioncharacteristic of nutrition when root-zone pH was maintained at 4.5 and growth was reduced, still occurredwhen pH was maintained at 5.0 or above, where growth was notaffected. The changes were slightly greater at pH 4.5 than athigher pH levels. Key words: Ammonium, nitrogen nutrition, root-zone pH, soybean, tissue composition     

Hydrolysis Rate of Resistant Pentosan of White Birch Wood in Sulfuric Acid of Medium Strength

The purpose of this study is to find optimal conditions for pre-hydrolysis in the new wood saccharification process with strong sulfuric acid. In the experiment, the hydrolysis rate of resistant fraction of pentosan of white birch (Shirakamba, Betula platyphylla Sukatchev var. japonica Hara) wood and the decomposition rate of xylose are measured in acid concentrations ranging from 30 to 60% at temperatures ranging from 30 to 90°C. The hydrolysis of resistant pentosan of white birch and the decomposition of xylose are the first-order reactions. The first-order reaction constant of hydrolysis of resistant pentosan, k_B min^-1, is expressed by the following empirical equations as the function of percentage concentration of sulfuric acid, C, and reaction temperature described by absolute temperature, T°K, ranging from 40 to 80°C:

where sulfuric acid concentrations range from 30 to 50%;

where sulfuric acid concentration is 60%.

The first-order reaction constant of decomposition of xylose, k₂ min^-1, is expressed by the following empirical equation as the function of sulfuric acid strength described by acidity function, H₀, and reaction temperature described by absolute temperature, T°K, in sulfuric acid concentrations ranging from 30 to 60% at temperatures within the range of 40 to 100°C.

where C is sulfuric acid strength described by acidity function, H₀.     

Determination of production of nitric oxide by lower airways of humans---theory

Hyde, Richard W., Edgar J. Geigel, Albert J. Olszowka, JohnA. Krasney, Robert E. Forster II, Mark J. Utell, and Mark W. Frampton.Determination of production of nitric oxide by the lower airwaysof humanstheory. J. Appl. Physiol.82(4): 1290-1296, 1997.Exercise and inflammatory lung disorderssuch as asthma and acute lung injury increase exhaled nitric oxide(NO). This finding is interpreted as a rise in production of NO by thelungs (NO)but fails to take into account the diffusing capacity for NO(DNO) that carries NO into thepulmonary capillary blood. We have derived equations to measureNO from thefollowing rates, which determine NO tension in the lungs(PL) at any moment from 1) production(NO);2) diffusion, whereDNO(PL) = rate of removal by lung capillary blood; and3) ventilation, whereA(PL)/(PB  47) = the rate of NO removal by alveolar ventilation(A) and PB is barometric pressure. During open-circuit breathingwhen PL is not in equilibrium,d/dtPL[V_L/(PB  47)] (where V_L is volumeof NO in the lower airways) = NO  DNO(PL)  A(PL)/(PB  47). When PL reaches asteady state so that d/dt = 0 andA iseliminated by rebreathing or breath holding, then PL = NO/DNO.PL can be interpreted as NOproduction per unit of DNO. Thisequation predicts that diseases that diminishDNO but do not alterNO willincrease expired NO levels. These equations permit precise measurementsof NO thatcan be applied to determining factors controlling NO production by thelungs.

     

Importance of the lactate anion in control of breathing

Hardarson, Thorir, Jon O. Skarphedinsson, and TorarinnSveinsson. Importance of the lactate anion in control ofbreathing. J. Appl. Physiol. 84(2):411-416, 1998.The purpose of this study was to examine theeffects of raising the arterialLa andK⁺ levels on minute ventilation(E) in rats. EitherLa or KCl solutions wereinfused in anesthetized spontaneously breathing Wistar rats to raisethe respective ion arterial concentration ([La] and[K⁺]) gradually tolevels similar to those observed during strenuous exercise.E, blood pressure, and heart rate wererecorded continuously, and arterial[La],[K⁺], pH, and bloodgases were repeatedly measured from blood samples. To prevent changesin pH during the Lainfusions, a solution of sodium lactate and lactic acid was used. Raising [La] to13.2 ± 0.6 (SE) mM induced a 47.0 ± 4.0% increase inE without any concomitant changes ineither pH or PCO₂. Raising[K⁺] to 7.8 ± 0.11 mM resulted in a 20.3 ± 5.28% increase inE without changes in pH. Thus ourresults show that Laitself, apart from lactic acidosis, may be important in increasing E during strenuous exercise, and weconfirm earlier results regarding the role of arterial[K⁺] in the control ofE during exercise.