Increasing the level of starch that is not digested by the end of the small intestine and therefore enters the colon ('resistant starch') is a major opportunity for improving the nutritional profile of foods. One mechanism that has been shown to be successful is entrapment of starch within an intact plant tissue structure. However, the level of tissue intactness required for resistance to amylase digestion has not been defined. In this study, intact cells were isolated from a range of legumes after thermal treatment at 60 °C (starch not gelatinised) or 95 °C (starch gelatinised) followed by hydrolysis using pancreatic alpha amylase. It was found that intact cells, isolated at either temperature, were impervious to amylase. However, application of mechanical force damaged the cell wall and made starch accessible to digestive enzymes. This shows that the access of enzymes to the entrapped swollen starch is the rate limiting step controlling hydrolysis of starch in cooked legumes. The results suggest that a single cell wall could be sufficient to provide an effective delivery of starch to the large intestine with consequent nutritional benefits, provided that mechanical damage during digestion is avoided.

The long arm of chromosome 4D of wheat (Triticum aestivum L.) contains a gene (or genes) which influences the ability of wheat plants to discriminate between Na(+) and K(+). This discrimination most obviously affects transport from the roots to the shoots, in which less Na(+) and more K(+) accumulate in those plants which contain the long arm of chromosome 4D. Concentrations of Na(+) and K(+) in the roots, and Cl(-) concentrations in the roots and shoots, are not significantly affected by this trait, but Na(+), K(+) and Cl(-) contents of the grain are reduced. The trait operates over a wide range of salinities and appears to be constitutive. At the moment it is not possible to determine accurately the effect of this trait on growth or grain yield because the aneuploid lines which are available are much less vigorous and less fertile than their euploid parents.

K/Na ratios have been determined in the leaves of salt-treated plants of 14 disomic substitution lines in which each of the D-genome chromosomes replaces the homoeologous A- or B-genome chromosome in the tetraploid wheat variety Langdon (AABB genome). Aneuploid lines of hexaploid bread wheat (cv Chinese Spring) having a reduced or an enhanced complement of chromosome 4D have also been examined. These investigations show that the gene(s) determining K/Na ratios in the leaves of wheat plants grown in the presence of salt is located on the long arm of chromosome 4D.

Durum wheat, Triticum turgidum L. (2n= 4x=28, genome formula AABB) is inferior to bread wheat, T. aestivum L. (2n=6x=42, genome formula AABBDD), in the ability to exclude Na(+) under salt strees, in the ratio of the accumulated K(+) to Na(+) in the leaves under salt stress, and in tolerance of salt stress. Previous work showed that chromosome 4D has a major effect on Na(+) and K(+) accumulation in the leaves of bread wheat. The 4D chromosome was recombined with chromosome 4B in the genetic background of durum wheat. The recombinants showed that Na(+) exclusion and enhanced K(+)/Na(+) ratio in the shoots were controlled by a single locus, Kna1, in the long arm of chromosome 4D. The recombinant families were grown in the field under non-saline conditions and two levels of salinity to determine whether Kna1 confers salt tolerance. Under salt stress, the Kna1 families had higher K(+)/Na(+) ratios in the flag leaves and higher yields of grain and biomass than the Kna1 (-) families and the parental cultivars. Kna1 is, therefore, one of the factors responsible for the higher salt tolerance of bread wheat relative to durum wheat. The present work provides conceptual evidence that tolerance of salt stress can be transferred between species in the tribe Triticeae.

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5981. Low-molecular-weight carbohydrates in some salt-stressed plants. A study was made of the effects of salinity on the concentrations of free sugars, glyeinebetaine, proline and other chemieal components oi Asler tripuHum L., Daucus carota L., Honkenya peploides (L.) Ehr. and Plantago coronopus L. (Dieotyledones); and Carex extensa Good., Eleocharis uniglumis (Link) Schutt., Juncus maritima Lam. a.nd Schoenopleetus tabernaemontani (C. C. Gmel.) Palla (Monocotyledones) grown in the laboratory. In Plantago eoronopus the level of the polyol sorbitol increased when the plants were subjected to NaCl stress, while in Honkenya peploides the cyclitol pinitol accumulated. No consistent pattern emerged with respect to the changes in free sugar contents in either the monocotyledonous or dicotyledonous plants, though the monocotyledonous plants generaliy had higher sugar contents.