The first 25 amino acids of brome mosaic virus (BMV) coat protein include 8 basic and no acidic residues and are implicated in binding the encapsidated RNA. Using infectious transcripts from BMV RNA3 cDNA clones, we modified this region of the coat gene. A coat protein mutant with the first 25 amino acids deleted failed to direct either packaging of viral RNA in protoplasts or systemic infection of whole barley plants. Neither symptoms, virions, nor viral RNA was detectable in plants inoculated with this mutant or a mutant with a frameshift mutation in the coat gene. Mutants with the normal start codon changed to AAG or with the first eight codons deleted allowed translation to start at a downstream AUG, resulting in a deletion of the first 7 amino acids of the mature wild-type coat protein. These mutants not only packaged viral RNA in protoplasts but directed symptomatic, systemic infections that developed with normal speed and degree of spread within the host. The AUG-to-AAG point substitution did not revert to the wild type after long-term culture in planta. Wild-type BMV virions were also found to contain small amounts of a protein that coelectrophoresed with the truncated coat protein produced by the viable AAG and eight-codon-deletion mutants. This minor coat protein species presumably arose by infrequent translation initiation at the second AUG in the wild-type coat protein gene. Absence of encapsidation-competent coat protein appeared to stimulate production of nonstructural proteins in protoplast infections.

Tomato (Lycopersicon esculentum Mill. cv New Yorker) plants subjected to 100 millimolar NaCl plus Hoagland nutrients exhibited a pattern of wilting, recovery of turgor, and finally recovery of growth at a reduced level, which required 3 days. During the nongrowing, adaptation phase there were immediate increases in free hexoses and sucrose which declined to near control levels as growth resumed. There was a steady increase in myo-inositol content which reached its maximal level at the time of growth resumption. The myo-inositol level then remained elevated for the remainder of the experiment. Myo-inositol constituted two-thirds of the soluble carbohydrate in leaves and three-fourths of the soluble carbohydrate in roots of salt-adapted plants. Plants which were alternated daily between salt and control solutions accumulated less myo-inositol and exhibited less growth than the continuously salt-treated plants. In tolerance, including salt (18, 19). Differences between species, with regard to salt accumulation, are pronounced and associated with salt tolerance (20). Genetic improvements in the salt tolerance of many crop plants are feasible approaches to overcoming the productivity limitations imposed by salinity in irrigated and dryland situations (2, 3).The tomato is a crop of worldwide importance with further untapped potential for genetic improvement (17, 18). L. pennellii is a genetically compatible distant relative of tomato and is a potential source of improved salt tolerance (1,16,17,21,22,24,25). Comparing closely related L. esculentum x L. pennellii breeding lines, we have found that regulation of foliar sodium, such that the sodium level in salt-treated plants exceeds that of control plants by no more than a 2-to 3-fold increase, is a necessary but not sufficient factor in determining a genotype's salt tolerance (21,22). Approximately 60% of the differences in salt tolerance within this group ofinterspecific breeding lines was accountable to differences in degrees of sodium regulation.The regulation of foliar sodium is not by complete exclusion, however, and large increases in sodium and chloride must still be dealt with by each cell. How a cell copes with an elevated external ionic content is an important question. It Osmoregulation in plants has been found to follow principles which are general across a very wide spectrum of life forms (6,26,27). The ionic content of the cytosol is regulated relative to the external medium and relative to the vacuole (5) such that an acceptable ionic concentration range is maintained. Organic solutes are synthesized to offset the steep osmotic gradients which arise as ions are segregated. In animals, higher plants, algae, fungi and lichens, the organic osmoregulant solutes have been found to be either nitrogenous species such as amino acids and betaines or various carbohydrates and polyols. Nitrogenous materials predominate in grasses and certain halophytic dicots while carbohydrates are most common in glycophytes (4,8,26).We report here the occurrence of ...

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PRACTICAL APPLICATIONSThe results of this work provide a means to predict the Bostwick length from at-line or in-line viscosity measurements. Specifically, the quantitative relationships presented in the article allow in-line process control schemes to improve final product quality.3 Corresponding

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