Half-strength Hoagland Nutrient Solution Research Articles

Gas Exchange in Populus maximowiczii in Relation to Potassium and Phosphorus Nutrition

Summary Cuttings of Populus maximowiczii Henry were grown in half-strength Hoagland nutrient solution with varying levels of K (0, 0.3 and 3 mM) and P (0, 0.05 and 0.5 mM). The effects of K and P deficiency on gas exchange and biomass of the plants was investigated. The absence of K markedly suppressed plant growth and reduced biomass of the roots more than that of the shoots. The 0.3 mM K and zero K (0 mM) treatments produced a significant increase in stomatal resistance and a decrease in net photosynthesis rate and RuBP carboxylase activity. The transpiration rate in all treatments was closely correlated with stomatal resistance (r = 0.94). The CO 2 compensation point increased with K supply. Biomass accumulation at 0.05 mM P was equal to that of the control, but was greatly reduced in the zero P treatment where the growth of shoots was much more affected than that of the roots. In the 0.05 mM P treatment stomatal resistance also increased. There was, however, a lower correlation between stomatal resistance and transpiration rate. Net photosynthesis and RuBP carboxylase activity markedly declined with the zero P treatment but not in the treatment with 0.05 mM P. The data show that K and P deficiency affect gas exchange and growth of poplar in different ways. Their influence on gas exchange and growth of the plants is discussed.

Effects of NaCl and KCl on Growth and Ionic Composition of the Halophytic C4 Succulent Chenopods Salsola kali, Suaeda monoica and Suaeda aegyptiaca

Salsola kali, Suaeda monoica and Suaeda aegyptiaca plants were grown in sand culture under controlled conditions and treated with half-strength Hoagland's nutrient solution (control), and control plus 150 mol m-3 KCl or NaCl. Fresh weight of Salsola kali was doubled in the NaCl and KCl treatments, but the increase in dry matter as compared with the control was not significant. Ionic content in this species revealed high selectivity for K v. Na. Fresh weight of Suaeda monoica and S. aegyptiaca was raised by NaCl 5 and 10 times respectively. Control and KCl-treated plants were poorly developed and plants of S. aegyptiaca exhibited sodium deficiency symptoms under these treatments. The two Suaeda species had lower selectivity of K v. Na than Salsola kali. Of the two annual species, Suaeda kali and S. aegyptiaca, S. kali flowered under all three treatments, whereas S. aegyptiaca flowered only under the Na treatment. In spite of the fact that all three species are inorganic ion accumulators and C4-succulent chenopods, they exhibit wide differences in their response to the two chloride salts.

A comparative study of the effects of natural and synthetic ligands on iron uptake by plants

The uptake of iron by wheat seedlings was investigated using half-strength Hoagland's nutrient solution containing 2.0 μM ferric chloride labelled with59Fe. The iron content of root tissue, which includes adsorbed iron, was depressed by the presence in the solution of the synthetic ligands EDTA and polymaleic acid (PMA) and by the natural ligands, humate, fulvate and a water-extractable soil polycarboxylate. The patterns of change in iron content of the shoots were in all cases different from those of the roots and were of two types. EDTA and humate increased the iron content of the shoots to maximum values, at ligand concentrations of 5.0 μM and 2.5 mg l−1 respectively, and decreased it at higher concentrations. Fulvate, water-extractable soil polycarboxylate and PMA increased the iron content of the shoots up to the maximum ligand concentrations tested (25 mg l−1). These results are discussed in the light of the likely solution chemistry of iron and the various ligands.

Endogenous rhythmic activity of nitrate reductase in a selection of Chenopodium rubrum

Oscillations of nitrate reductase (NR) activity occurred after transfer of seedlings of Chenopodium rubrum L., ecotype 60°47′ N 137°32′ W, from an alternating temperature and light intensity germination program to constant temperature and light conditions; there were peaks of activity at 18, 30, and 45 h. The presence of half-strength Hoagland's nutrient solution during the germination period increased the range of the oscillations but did not affect the period. Changes in levels of nitrate and nitrite within the seedlings were consistent with the periodicity of NR activity during the light period after germination. Enzyme activity decreased if seedlings were placed in darkness, but the phasing of the oscillations was not altered by the transition from light to darkness. In addition, oscillations of NR activity with a period length of about 18 h occurred during continuous light after dark periods. This secondary rhythmicity is apparently superimposed upon the pattern of fluctuations previously established.On the basis of the rhythmicity that is characterized by these findings, and also in the light of other previously observed effects of altered environmental conditions on the activity of NR, hypotheses are presented to account for the endogenous oscillations of NR activity in Chenopodium rubrum. It is suggested that such rhythmic behavior of NR may occur in higher plants in general.

Effect of Nitrogen on Growth and Composition of Fruits from ‘Thompson Seedless’ Grapevines1

Abstract Growth, yield, and composition of ‘Thompson Seedless’ fruits from 4-year-old vines growing in a perlite-vermiculite mixture and irrigated with half-strength Hoagland nutrient solution modified to contain 0, 1/2, 1, 2, 4, or 8 mM NO3 were studied. Vines grown without N added to tap water produced no fruits. Number of clusters per vine and number of berries per cluster were significantly less for vines grown with 1/2 or 8 mM NO3 than for vines which received 1, 2, or 4 mM NO3. Weight, pH, and malate level of berries increased with increasing levels of NO3 in the nutrient solution. The concn of arginine in berry juice increased linearly with increasing levels of NO3 from 1/2 through 4 mM, and then remained relatively constant, with about a 12-fold increase between the lowest and highest NO3 treatments. A second-degree quadratic equation best described this relationship with a correlation coefficient of 0.95. The level of proline, however, continued to increase between 1/2 and 8 mM NO3 with about a 4-fold overall increase. The concn of proline in the juice of grapes at harvest was much more sensitive to level of ripeness (°Brix) than to N treatment, whereas the opposite relationship was true for arginine. The arginine levels in fruits grown with 1/2 to 8 mM NO3 increased 9 to 20-fold when compared at the same stage of ripeness (°Brix). Total soluble solids, total acidity, and tartrate in berries were not significantly affected by N treatment.