In a solution culture experiment with 4-week-old barley plants (variety Villa) the influence of NaCl salinization and of KCl additions on the uptake and turnover of labelled NC-^NHi'^NOj) was studied. Labelled N was applied for 24 h at the end of the growth period, Salinization impaired growth and uptake of labelled N, The incorporation of labelled N into the protein fraction, however, was improved by NaCl salinization. Additions of KCl to the nutrient solution diminished the negative effect of NaCl salinization on growth. At both NaCl salinization levels (60 and 120 mM) K additions favoured the uptake of labelled N and particularly its incorporation into the protein fraction.It is suggested that the negative influence of the NaCI stress is not primarily due to an impaired protein synthesis, but is possibly caused by a detrimental effect of Na on other metabolic processes.

Several researchers reported that high nitrogen rates for cereals require also an ample potassium supply in order to produce maximum grain yields. The physiological relationships between N and K in grain production are not yet completely understood. For this reason experiments have been carried out to study the effect of K on the translocation of N in wheat plants and its incorporation into the grains during the grain filling period. Spring wheat (Triticum aestivum L. cv. ‘Kolibri’) was gown in solution culture at two K levels throughout the growing period and at three N levels during the reproductive stage. Nitrogen was labeled 15N with the beginning of anthesis. Plants at the higher K rate produced more vegetative dry matter, higher grain yields, fewer unproductive tillers and improved translocation of N from the vegetative plant parts into the grain. Between 87.4 and 89.0% of the N absorbed during the reproductive stage was present in the grain of plants which had received the higher K supply. In plants grown with the lower K level the percentage ranged from 78.9 to 81.0%. This improved translocation of nitrogenous compounds from the various plant parts to the grain caused by K resulted mainly in higher contents of prolamin, glutelin, and soluble amino acids in the grain. For the content of albumin and globulin the reverse was true. All four grain protein fractions showed the same degree of N labeling indicating that none of the four protein fractions was preferably supplied by the N absorbed during the reproductive stage. The label of the soluble amino acids in the grain was lower than that of the grain proteins. It is assumed that at the last stage of grain filling a relatively high amount of N from senescing plant parts is exploited for grain filling, thus diluting the N taken up from the nutrient solution. The higher N levels applied during the reproductive stage had a negative rather than a positive effect on grain yield. The additional N increased mainly the content of soluble amino acids, prolamin, and glutelin in the grain.

Earlier investigations have shown that the potassium ion (K+) promotes grain protein synthesis. It is not yet known whether this K+ effect is directly related to the requirement of K+ for formation of peptide bonds or is more indirectly related to the translocation of amino acids into developing grain. Wheat (Triticum aestivum L. “Kolibri”) was grown in solution culture to study the N transformations in developing grain of wheat. At two K levels (K1:0.3 and K2:2.0 me/liter) plants were treated with 15N labeled ammonium nitrate for 2 days (2 weeks after anthesis) and then grain samples were obtained from both K treatments periodically until full maturation. Initially, grain from the K2 treatment contained almost twice as much free amino acids as grain from the K1 treatment. This treatment difference gradually disappeared with grain development. The 15N label in the free amino acids declined faster in grain from the K2 treatment. Concomitant with this decline the 15N content of the grain proteins increased with the K2 treatment exceeding the K1 treatment. Potassium increased the rate of amino acid translocation into the grain as well as the conversion of amino acids into grain proteins (albumin, globulin, prolamin, and glutelin). The accumulation of free amino acids hi the K2 treated grain suggests the influence of K was stronger on the translocation of amino acids into the grain than the conversion into proteins. The K concentration of the grain was not influenced greatly by K treatment, whereas, stalk and leaf levels showed remarkable differences. It is concluded that an indirect effect of K+ on grain protein formation results from amino acid translocation into the grain and not from the influence of K+ on peptide bond formation. The heaviest 15N label was found in glutamine, whereas glutamate showed the highest rate of N turnover.

In a pot experiment sugar beet Beta vulgaris L. ssp. vulgaris, cv. Kawetina, was grown on alluvial soil (21 mg exchangeable K 100 g−1) containing 0 (K1), 20 (K2), 40 (K3) and 60mg fertiliser K 100 g−1 soil (K4). The plants were sown on 15 March 1983 and harvested on 23 June, 14 July and 30 August 1983. At final harvest root dry weight/plant had reached 269 g in K1 and between 304 and 310 g in K2‐K4. Sucrose values were 15% (K1) and 17.3–17.7% of root fresh weight (K2‐K4) respectively. The osmotic potential of the storage root decreased with increasing K nutrition and time. At final harvest ψ, was between −1.83 (K1) and −2.26 MPa (K4), 75–79% thereof being contributed by sucrose. Sucrose concentrations in press sap increased from 340–400 mM on 23 June to 475 (K1) and 540–570 mM (K2‐K4) at the end of August. In the same period K concentrations declined from 40–100 to 10–35 mM K+. The sucrose, K and Mg concentrations measured in the press sap were lower than those calculated from sucrose, K, Mg and moisture content of the storage root. This indicates that press sap from thawed storage root tissue is not fully representative. Betaine, analysed only at final harvest, significantly increased with increasing K concentrations in the storage root (r=0.83) and a significant linear regression was found between betaine and sucrose accumulation (r=0.57). This is consistent with the role of betaine as a cytosolic osmoticum for sugar beet storage tissue. Other solutes in the cytosol may also contribute to osmoregulation as sucrose accumulates in the vacuoles.