The effects of aluminum on the accumulation of sugars, amino acids and organic acids in two hybrid cultivars of sorghum were studied.The concentration of these organic compounds increased in the roots of the Al-treated plants, mainly in the tolerant cultivar. The composition of the organic acid fraction showed a significantly higher accumulation of trans-aconitate and malate in the tolerant cultivar as compared with the sensitive one. The higher levels of these acids in the Al-treated plants could be interpreted as being indicative of a chelating detoxifying mechanism of aluminum in these plants. 313Copyright© 1983 by Marcel Dekker, Inc.

Aluminum (Al) effects on fatty acid composition and on the lipid peroxidation of a puri®ed plasma membrane fraction of root apices of two sorghum cultivars were studied. Palmitic and linoleic acids were the major fatty acids in the root apices of sorghum, independent of the Al presence in nutrient solution. After Al treatment, the C18:0aC18:3 and C18:2aC18:3 ratios increased, while the C18:2aC16:0 ratio remained unchanged in the Al-sensitive cultivar but all three ratios decreased in the Al-tolerant cultivar. The double bond index and unsaturated JOURNAL

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Resumo -O objetivo deste trabalho foi estudar a translocação e a redistribuição de S pelo transporte acrópeto e basípeto em plantas de milho e de soja. Plantas das duas espécies foram cultivadas em solução nutritiva contendo 35 S em casa de vegetação. O 35 S aplicado em uma única raiz foi prontamente absorvido e translocado para a parte aérea, assim como para as demais raízes cultivadas na ausência de enxofre. O radioisótopo aplicado em uma única folha foi transportado tanto na direção acrópeta quanto na basípeta. Entretanto, o milho e a soja mostraram comportamentos diferentes na absorção e na redistribuição do enxofre. O milho, apesar de ter apresentado maior absorção radicular, reteve grande parte desse elemento na raiz, enquanto a soja absorveu consideravelmente menos, porém apresentou maior eficiência de translocação. Nas plantas de soja, as folhas superiores, principalmente as mais novas, mostraram ser os principais drenos fisiológicos do enxofre.Termos de indexação: Zea mays, Glycine max, transporte de nutrientes, raiz, absorção. Translocation and redistribution of sulphur in corn and soybean plantsAbstract -The objective of this work was to study the S translocation and redistribution by acropetal and basipetal transport in corn and soybean plants. Plants of both species were cultivated in nutritive solution containing labeled 35 S, in a greenhouse. The 35 S applied to only one root was absorbed quickly and transported to the shoot, as well as to the other roots cultivated in non-labeled solution. The 35 S applied to only one leaf was transported both to acropetal and basipetal direction. However, corn and soybean showed different behaviors in S absorption and redistribution. In spite of having larger root absorption, corn retained great part of that S in the root, while soybean absorbed considerably less, but presented greater translocation efficiency. The upper leaves, mainly the youngest, showed to be the main physiologic sinks for S in soybean plants.

The effects of aluminum on the uptake and translocation of N in two hybrid cultivars of sorghum with differential tolerance to aluminum were studied.Aluminum decreased the amount of N accumulated and the % of N in the aerial parts of the plants. In the roots the amount of N accumulated also decreased but the % of N increased, in both cultivars. Besides an effect on dry matter yield, Al probably reduces the uptake of N and its translocation to the aerial parts of the plant. Apparently, this impairment on N translocation resulted from Al effects on the root pressure. 457 458 GOMES ET AL.Aluminum not only reduced the amount of N translocated but also changed the sap composition. The % of NO 3 -N decreased while the % of amino acid-N increased suggesting an Al effect on N uptake and also on protein degradation. Asparagine and glutamine contributed about 80% of the free amino acid fraction; however, their proportions changed in presence of Al. Therefore, Al also interfered with the synthesis and/or interconversion of these amino acids.

The anticipated commercialization of TIBA as one of the first growth regulators for use on a major field crop in the USA, created a need for information on its absorption and movement in the soybean plant under field conditions. Such information would be of assistance in metabolite and residue studies. TIBA tagged with I‐131 was applied at early bloom in two field experiments and in a third study it was applied at the beginning of the pod filling stage of growth. Whole plants were sampled periodically, divided into their morphological parts and their dry weights and I‐131 activities were determined. Approximately 45 percent of the total activity measured at “zero time” was lost from the plants within 48 hours. Biological half lifes of 40.3 and 42.0 days were found for the I‐131 in the early spray experiments. The rapid absorption and movement into the vascular stream was indicated by the detection of I‐131 activity in the roots of the “zero time” samples. Sites of active TIBA I‐131 activity were regions of high meristematic activity. Such sites of accumulation loss I‐131 activity to other areas when their relative metabolic activity declined. Ultraviolet light was shown to cause small but significant deiodozation of TIBA. Sixty days after TIBA was applied the plant parts were found to contain the following percentages of the applied radioactivity: roots 4%, leaves that were sprayed with TIBA 15%, leaves that emmerged after TIBA application 1.5%, petioles that received application of TIBA 2.5%, stems 3.0%, pods including seeds 7%. When the TIBA was applied at the beginning of the pod filling period, the seeds at physiological maturity contained 0.56 ppp TIBA equivalent or 2.5% of the originally applied activity.