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The accumulation of plutonium (238Pu) and americium (241Am) in seeds and roots of Phaseolus vulgarisL. was investigated following foliar interception. Under controlled conditions plants were exposed to well‐characterized aerosols of fresh and aged Pu‐dioxide, fresh Am‐oxides, and Pu‐nitrate and Pu‐citrate complexes to assess the influence of chemical form and long‐term weathering on foliar absorption and subsequent translocation to other plant parts. Mean values for Pu and Am accumulated in seeds and roots 28 days after foliar exposure ranged from 9 to 427 × 10−4% of that deposited on foliage. These results and previous plant uptake studies indicate that the foliar route is potentially of equal importance to the soil‐root pathway as a route of transport. The levels of Pu and Am in seeds and roots resulting from foliar absorption and translocation from foliage were significantly affected by simulated rainfall and by the size of particles to which foliage was exposed. The influence of relative humidity and solution aging of oxides was less definitive; however, results suggest that either or both may influence foliar absorption and subsequent translocation of Pu and Am to seeds and roots.

Submicron particles of Pu and Am were aerosolized, deposited onto foliage of bush bean (Phaseolus vulgarisL.), and their subsequent retention and behavior determined. Particles having mass median diameters of < 1 µm are not readily dislodged from leaf surfaces at wind speeds of −400 m min−1. Under conditions of simulated rainfall, weathering half‐times range from 164 to 1,000 days, and are dependent on both particle size and initial solubility. The residence time of contaminants on foliar surfaces prior to leaching influences subsequent foliar retention and leachate characteristics. Foliar retention of particles ranges from 20 to 92% and is dependent on particle size of Pu‐ and Am‐oxides, chemical form of Pu, and environmental conditions such as humidity, simulated rainfall, and acidity of the simulated rain.

Recombinant glycoprotein B (gB) of herpes simplex virus (HSV) was processed and presented by class I major histocompatibility complex (MHC) molecules after delivery into cells by using N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl sulfate (DOTAP), a commercially available cationic lipid used for DNA transfection. Cells treated with DOTAP-associated gB were susceptible to lysis by class I MHC-restricted, HSV-specific cytotoxic T lymphocytes (CTL), and the treated cells restimulated memory gB-specific CTL activity in spleen cells from HSV-infected mice. gB-specific CTL responses were detected in mice immunized with recombinant gB and DOTAP but not in those receiving gB emulsified in complete Freund's adjuvant. Thus, cationic lipids may facilitate induction of CD8+ T-cell responses in vaccinations with recombinant antigens, and they may serve as readily available reagents for dissecting class I MHC immunity to viruses and other intracellular pathogens.

An enzymatic digestion procedure is presented which allows for the isolation of large quantities of mesophyll cells and minor veins of Nicotiana tabacumL. cv. ‘Wisconsin 38’. Isolated mesophyll cells exhibited CO2fixation rates in excess of 150 μmoles CO2mg chl‐1hr‐1, while bundles consistently fixed CO2at much lower rates, viz. 10–20 μmoles CO2mg chl‐1hr‐1. Various physical and biochemical parameters of the isolates have been compared with intact leaf disks.

The movement of both essential and pollutant trace elements through agricultural food chains is a complex problem, influenced in part by plant‐mediated changes in trace element speciation that may alter the rate and extent of gastrointestinal absorption after ingestion of plant tissues by animals. An overview is provided of a series of investigations undertaken to describe the processes governing the chemical behavior of several cations (Pu, Ni, Cd, and Fe) and anions (Tc, Se, and S) during transport in the plant xylem and after deposition in plant tissues. Cations were generally present in xylem exudale as organic acid, amino acid, and peptide complexes specific to the element, whereas anions tended to remain in the inorganic forms initially absorbed by the root. Once deposited in tissues, both cations and anions were associated with more complex, but soluble, plant metabolites. The cations (Pu, Ni, Cd) were directly associated with >10 000 molecular weight proteins, whereas the anions (Se and Tc) appeared to undergo chemical reduction and incorporation into proteins using enzymatic processes functioning for S metabolism. The importance of these plant processes on gastrointestinal absorption was demonstrated for Pu and Tc, which differed markedly in their behavior in plants and animals.

Cultivars of Avena sativaL. that have high (cv. ‘Dal’) or low (cv. ‘Orbit’) groat protein concentration were evaluated for their ability to enzymatically reduce nitrate and to store and remobilize nitrogenous compounds and nonstructural carbohydrates. Nitrate reductase (E.C. 1.6.6.1) activity/plant (i.e., potential for reducing nitrate) was similar for the two cultivars grown in the field or environmental chambers, and exceeded the level needed to account for the actual accumulation of reduced N in the whole plant. The contribution of various plant parts to total reduced N varied ontogenetically. Leaf sheaths, roots, and bracts, as well as leaf blades, had significant levels of nitrate reductase at specific times in development. Accumulation of total reduced N by the groats was comparable in the two cultivars, but the contribution from remobilized N differed. On a whole‐plant basis, Dal continued to accumulate N until maturity, whereas Orbit ceased accumulation just after anthesis. Although the yield of groats per primary shoot was 14% lower in Dal as compared to Orbit, the accumulation of total nonstructural carbohydrates in groats of Dal was 25% lower than in Orbit. Total deposition of nonstructural carbohydrates in vegetative tissues was 75% higher in Orbit than in Dal. Losses of total nonstructural carbohydrates (respiration and remobilization to groats) from vegetative tissues of Orbit during groat development exceeded losses from Dal by 124%. Since respiration rates were comparable, Orbit apparently remobilized much more stored carbohydrates to developing groats than did Dal. Differences in C metabolism of these cultivars may be more important than differences in N metabolism in influencing groat protein concentration.

The ultrastructure of minor veins of Beta vulgariswas examined with reference to possible models for vein loading of translocate. Structural evidence was reviewed in the light of recent physiological observations as a basis for proposed mechanisms. Features which appeared to be of significance in formulating a model included the open, differentiated sieve plates, the predominance of organelle‐rich parenchyma cells, and the branched plasmodesmata connecting sieve tubes and parenchyma cells. The resulting model views cell to cell movement of photosynthate via the symplast to the specialized parenchyma cells. The actively accumulated sucrose appears to move from the specialized parenchyma cells into the sieve tubes via plasmodesmata in the lateral and end walls.

A method is proposed for analysis of total nitrogen in plant tissues enabling predigestion (to reduce nitrate to ammonium) and digestion to be performed in a Folin‐Wu tube. Following digestion, a sensitive colorimetric assay for ammonium is used to quantitate N‐content in an aliquot of the digest. The proposed method has several advantages: 1) up to 110 tissue samples can be predigested and digested in one batch; 2) small tissue samples (5 to 100 mg) can be accommodated; 3) the colorimetric assay for ammonia is very sensitive; 4) tissues can be predigested to recover all nitrate in the samples; and 5) aliquot size from the diluted digest can be varied to effectively detect as little as 1 µg of N.

Metastasis is the predominant cause of death in patients with cancer and reach relatively frequently specific secondary target organs such as the lungs. According to the “seed and soil” paradigm, these blood-borne metastases can be favored by a permissive microenvironment in these organs promoting tumor cells arrival and metastases growth.