Inositol and Sugars in Adaptation of Tomato to Salt

Abstract

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 ...

Identification of Soluble Carbohydrates and Their Subcellular Concentrations in Petals during Flower Opening in <i>Eustoma grandiflorum</i>

“…The D-bornesitol content in the leaf, stem, and other floral organs was relatively high, suggesting that D-bornesitol plays some important role as a reserve carbohydrate. Cyclitols including pinitol have been found to act as osmoregulators or compatible solutes (Ford, 1984;Keller and Ludlow, 1993;Paul and Cockburn, 1989;Sacher and Staples, 1985). Pinitol, an isomer of bornesitol, has been found mainly in the cytoplasm of Mesembryanthemum crystallinum leaves (Paul and Cockburn, 1989).…”

Variations in Leaf Soluble Amino Acids and Ammonium Content in Subtropical Seagrasses Related to Salinity Stress

“…proline, betaine), while salt-sensitive vascular glycophytes generally produce carbohydrates (e.g. polyols, sucrose), to counteract the osmotic stress of salt (4,15,18). Kylin and Quatrano (10) considered accumulation of toxic levels of certain amino acids and NH4, resulting from derangement of protein synthesis, as a potential mechanism of salt damage.…”

A Simple and Rapid Extraction Method of Carbohydrates from Petals or Sepals of Four Floricultural Plants for Determination of Their Content

“…For many fruits, sugars are the most important determinant of their quality. Soluble carbohydrate also plays a role in stress tolerance, including tolerance to cold (Sasaki et al, 1996), drought (Keller and Ludlow, 1993), and salt (Sacher and Staples, 1985). The new method may be available to investigate the role of carbohydrates from these aspects.…”