Relation of Molybdenum and Manganese to the Free Amino-Acid Content of the Cauliflower

SummaryThe effects on flax of a given concentration of manganese or molybdenum in the nutrient solution were found to depend on the amount and form of nitrogen supplied. The interactions that occurred between either of these two elements on the one hand, and nitrogen source on the other, were highly significant but opposite in effect.Thus, with a given excess of manganese, symptoms were most severe in plants grown in solution supplied with nitrogen as nitrate or urea, and were absent in nitrogen-deficient solutions or those supplied with nitrogen as ammonium. In solutions supplied with ammonium nitrate, no manganese toxicity symptoms occurred or these were only slight. A concentration of 50 p.p.m. of manganese in the solution caused a very significant decrease in growth in the presence of nitrate, had no harmful effect on growth in the presence of· ammonium nitrate, and caused a significant increase in growth with ammonium. With urea, the reduction in growth was not as great as with nitrate. The presence of ammonium ions in the solution markedly reduced the manganese concentration in the plants when compared with that of plants receiving nitrate only.By contrast, at a given excess of molybdenum in the nutrient solution, toxicity symptoms in the test plants were affected by nitrogen source in the following order of decreasing severity: nitrogen deficiency> ammonium> ammonium nitrate> urea> nitrate. In solutions supplied with nitrate, a given concentration of molybdenum was significantly more toxic to growth when applied as ammonium molybdate than as sodium molybdate. In one experiment the addition to the nitrate solution of 10 p.p.m. of molybdenum as sodium molybdate resulted in a significant increase in the dry weight of the plants compared with the controls, even though such plants contained 400 p.p.m. of molybdenum on a dry basis. In the presence of ammonium or urea, no significant differences occurred between the effects of sodium molybdate or ammonium molybdate on plant growth.In the nitrate nutrient solutions less molybdenum was absorbed by the plants when a given excess of this element was added to the solution as sodium molybdate than when it was added as ammonium molybdate. It is concluded that the toxi~ity to flax of a given concentration of molybdenum in the nutrient solution is increased by the presence of ammonium (NH 4 +) ions.Where excess of manganese and molybdenum were added together to the nutrient solution, an interaction between the two elements occurred. Thus the severity of manganese-induced iron-deficiency chlorosis and lower leaf necrosis was reduced. However, a golden-yellow chlorosis, not typical of iron-deficiency chlorosis but similar to molybdenum toxicity symptoms, was induced in the " Plant Research Laboratory, Department of Agriculture, Burnley, Vic. NITROGEN SOURCE AND EXCESS MN OR Moplants in the presence of nitrate, ammonium nitrate, or urea, but not where ammonium was the sole source of nitrogen. The manganese-molybdenum interaction was facilitated by the presence of some ammon...

Section: C"'--supporting

confidence: 80%

Section: C"'--mentioning

confidence: 99%

Relation Between Nitrogen Source and the Effects on Flax of an Excess of Manganese or Molybdenum in the Nutrient Solution

Cr¹

1950

“…However, since the comparisons were made between healthy and deficient plants, the possibility that the differences observed were due to the different physiological age of the plants could not be excluded. Mulder (1948) avoided this complication by comparing deficient plants with those which had been treated with molybdate only 3 days prior to harvest, and produced evidence which confirmed the conclusions of Hewitt, Jones, and Williams (1949).…”

Section: Introducitonsupporting

confidence: 54%

“…Hewitt, Jones, and Williams (1949) showed that not only protein but also amino acid content in molybdenum-deficient plants was low in comparison with that of normal plants, and concluded that molybdenum was required for some step between the initial reduction of nitrate and the formation of amino acids. However, since the comparisons were made between healthy and deficient plants, the possibility that the differences observed were due to the different physiological age of the plants could not be excluded.…”

Section: Introducitonmentioning

confidence: 99%

The Role of Molybdenum in Nitrate Reduction Inhigher Plants

Spencer¹,

Wood²

1954

SummaryExperiments are described which were designed to locate the molybdenumrequiring step in the chain of reactions involved in nitrate utilization in higher plants.Tomato plants deficient in molybdenum were treated with molybdate, and the changes in content of nitrate, nitrite, ammonia, amides, amino acids, and proteins, expressed on a dry weight basis, were followed over a short period. Two days after treatment with molybdate there was a marked decrease in the level of nitrate. During this period the concentrations of nitrite, ammonia, amides, amino acids, and protein increased. The nitrite and ammonia contents of the tops were doubled 4 hr after supplying molybdate to the molybdenumdeficient plants.It is concluded that in the intact plant molybdenum is essential for a reaction involved in the reduction of nitrate to nitrite. The known metabolic functions of molybdenum are discussed briefly.Analytical methods used in these determinations are described.

“…Molybdenum is known to be concerned in the nitrogen metabolism of legumes and non-legumes (Mulder 1948;Anderson and Spencer 1950), and many workers have attempted to elucidate this effect of molybdenum in plant metabolism (Hewitt, Jones, and Williams 1949;Agarwala 1951;Nicholas, Nason, and McElroy 1953).…”

Section: Introducfionmentioning

confidence: 99%

The Effect of Molybdenum on the Organic and Inorganic Phosphorus of Plants

Possingham¹

1954

SummaryMolybdenum, applied 2 days before harvest, had a marked effect on the phosphorus metabolism of molybdenum-de£cient tomato plants grown in waterculture solutions. The molybdenum increased the concentration of organic phosphorus, with a corresponding decrease in the concentration of inorganic phosphorus. Molybdenum increased the yield of dry matter, the absolute amount of phosphorus, and the absolute amount of organic phosphorus; but did not increase the absolute amount of inorganic phosphorus. The concentration of total phosphorus did not change. INTRODUCfIONMolybdenum is known to be concerned in the nitrogen metabolism of legumes and non-legumes (Mulder 1948;Anderson and Spencer 1950), and many workers have attempted to elucidate this effect of molybdenum in plant metabolism (Hewitt, Jones, and Williams 1949;Agarwala 1951;Nicholas, Nason, and McElroy 1953).It has also been shown that molybdenum inhibits the acid phosphatases of plants (Bossard 1947;Courtois and Anagnostopoulos 1949). Acid phosphatases occur extensively in plant tissues (Ignatieff and Wasteneys 1936; Yin 1945), and have been shown to attack a wide variety of organic phosphorus compounds which are important in intermediary plant metabolism (Spencer 1954).The present experiments were done to examine the effect of molybdenum on the distribution of phosphorus between the organic and inorganic fractions within the plant. II. METHODSTomato (Lycopersicon esculentum Mill. var. Pan America) plants were used. These were grown in culture solutions essentially the same as those recommended by Stout and Arnon (1939), but using KH2P04 instead of K2HP04• The macro-elements were purified with 8-hydroxyquinoline in chloroform at a reaction between pH 1· 6 and 5· 6 (Gentry and Sherrington 1950). The microelements were all purified by repeated recrystallization. Tomato seeds, germinated on paraffined gauze placed over glass-distilled water, were transferred at the two-leaf stage to 3-1. Pyrex glass beakers. There were 20 cultures in the experiment and each culture pot held eight plants.