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Cd(NO3)2 crystallizes in the orthorhombic Pbcn space group. The structure is zero-dimensional and consists of four cadmium hydroxide (cd(oh)2) molecules and eight nitrous acid molecules.
Cd(NO3)2 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.35–2.43 Å. In the second Cd2+ site, Cd2+ is bonded in a 7-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.35–2.44 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. All N–O bond lengths are 1.27 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.26 Å) and two longer (1.27 Å) N–O bond length. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.26 Å) and two longer (1.27 Å) N–O bond length. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. All N–O bond lengths are 1.27 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Cd2+ and one N5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the fifth O2- site, O2- is bonded in a distorted water-like geometry to one Cd2+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one Cd2+ and one N5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one N5+ atom. In the twelfth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cd2+ and one N5+ atom.
Cd(NO3)2(O2)2 crystallizes in the orthorhombic Fdd2 space group. The structure is zero-dimensional and consists of sixteen hydrogen peroxide molecules and eight Cd(NO3)2 clusters. In each Cd(NO3)2 cluster, Cd is bonded in a 4-coordinate geometry to four O atoms. There are two shorter (2.26 Å) and two longer (2.30 Å) Cd–O bond lengths. N is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.22 Å) and two longer (1.30 Å) N–O bond length. There are three inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one N atom. In the second O site, O is bonded in an L-shaped geometry to one Cd and one N atom. In the third O site, O is bonded in an L-shaped geometry to one Cd and one N atom.
Soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO3-, 0.67 mM NO3- plus 0.33 mM NH4+, 0.33 mM NO3- plus 0.67 mM NH4+, and 1.0 mM NH4+) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N-source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH4+ at pH 4.5. Shoot-to-root ratios increased in plants which had an increased proportion [correction of proporiton] of NH4(+)-N in their nutrient solutions at all levels of root-zone pH. Uptake of NO3- and NH4+ was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO3- plus NH4+, NH4+ was absorbed at a ratio of 2:1 over NO3- at pH 6.0. As the pH of the root-zone declined, however, NH4+ uptake decreased and NO3- uptake increased. Thus, the NH4+ to NO3- uptake ratio declined with decreases in root-zone pH. The data indicate a negative effect of declining root-zone pH on NH4+ uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH4(+)-N at low pH is due to a decline in NH4+ uptake and a consequential limitation of growth by N stress.
Tobacco plants (Nicotiana tabacum L. cv NC82) were supplied with (NH4)2SO4 or NH4Cl at root-zone pH of 6.0 and 4.5 in hydroponic culture for 28 days. Dry matter accumulation, total N and C content, and leaf area and number were not affected by the NH4+ source or root-zone pH. Plants supplied with NH4Cl accumulated up to 1.2 mM Cl g DW-1, but accumulated 37% less inorganic H2PO4- and 47% less SO4(2-) than plants supplied with (NH4)2SO4. The large Cl- accumulation resulted in NH4Cl- supplied plants having a 31% higher inorganic anion (NO3-, H2, PO4-, SO4(2-), and Cl-) charge. This higher inorganic anion charge in the NH4Cl-supplied plants was balanced by a similar increase in K+ charge. Plants supplied with NH4Cl accumulated greater concentrations of Cl- in leaves (up to 5.1% of DW) than plants supplied with (NH4)2SO4 (less than -% DW). Despite the high Cl- concentration of leaves in NH4Cl supplied plants, these plants showed no symptoms of Cl- toxicity. This demonstrates that toxicity symptoms are not due solely to an interaction between high Cl- concentration in tissue and NH4+ nutrition. The increase in root-zone acidity to pH 4.5 from 6.0 did not induce toxicity symptoms.
The relationship between specific rate of respiration (respiration rate per unit root dry weight) and concentration of reduced nitrogen was examined for maize (Zea mays L.) roots. Plants with 2 primary nodal root axes were grown for 8 days in a split-root hydroponic system in which NO3- was supplied to both axes at 1.0 mol m-3, to one axis at 1.0 mol m-3 and the other axis at 0.0 mol m-3, or to both axes at 0.0 mol m-3. Respiration rates and root characteristics were measured at 2-day intervals. Specific rate of respiration was positively correlated in a nonlinear relationship with concentration of reduced nitrogen. The lowest specific rates of respiration occurred when neither axis received exogenous NO3- and the concentration of reduced nitrogen in the axes was less than 9 mg g-1. The greatest rates occurred in axes that were actively absorbing NO3- and contained more than 35 mg g-1 of reduced nitrogen. At 23 mg g-1 of reduced nitrogen, below which initiation of lateral branches was decreased by 30-50%, specific rate of respiration was 17% greater for roots actively absorbing NO3- than for roots not absorbing NO3-. Increases in specific rate of respiration associated with concentrations of reduced nitrogen greater than 23 mg g-1 were concluded to be attributable primarily to proliferation of lateral branches.
Dry matter accumulation of plants utilizing NH4+ as the sole nitrogen source generally is less than that of plants receiving NO3- unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH4+ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH4+ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 +/- 0.1 by automatic additions of 0.01 N H2SO4 or Ca(OH)2. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH4+ uptake per gram root dry weight were calculated from these data. Net CO2 exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO2 exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH4+ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO2 exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH4+, which were initially about 50% lower at pH 4.1 than at 6.1 continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.