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We have used a combination of techniques to study the structure and properties of C-type starch from pea seeds. It was found that all C-type starch granules contain both types of polymorph; the B polymorphs are in the center of the granule and are surrounded by the A polymorphs. During heating in excess salt solution the A and B polymorphs within C-type granules melt independently, giving a double transition in heat capacity and a two-step swelling, compared with single transitions for A- and B-type starches. It was shown that B polymorphs gave a transition with a lower peak temperature than A. The disruption of crystallinity during gelatinization began from the hilum area and was propagated along the granule, accompanied by swelling of disrupted areas. It is proposed that the swelling of disrupted parts of the granule decreases the melting temperature of the neighboring crystallites resulting in the progressive disruption of crystalline areas. The gelatinization process is dependent on the arrangement of A and B polymorphs within the granule. © 1998 John Wiley & Sons, Inc. Biopoly 45: 323–332, 1998

Lathyrus sativus, also known as Khesari dhal in India, is a good source of protein and also desirable from the agricultural point of view as it is drought-resistant and can be grown with low agriculture inputs of fertiliser, irrigation and pesticide. In common with other legume seeds, Lathyrus contains the flatulence causing alpha-galactosides. This is a study of the physico-chemical properties of four selected Lathyrus sativus lines (Red flower, a high beta-ODAP line; EC-242692, a medium beta-ODAP line; L-1276, a low beta-ODAP line; and Pusa-24, a very low beta-ODAP line) to determine the most effective way of removing the flatulence factors by using simple processes such as soaking, dehusking and germination. Physico-chemical properties like swelling and hydration capacity of Lathyrus seeds were higher than other legumes, which suggests higher consumer preference in terms of cooking time and fuel consumption over other beans. Germination was the most effective procedure for removing alpha-galatosides (85-92%). Dehusking of pre-soaked seeds also achieved a high alpha-galactoside reduction (61-80%). Soaking in alkaline medium and thereafter boiling for 9 min brought about a lower reduction (33-74%), but these losses were still higher than those obtained by soaking in drinking water or soaking in boiled water for 2 h (11-49% and 7-44%, respectively).

The levels of the raffinose family of α-galactosides (raffinose, stachyose, verbascose and ciceritol) and of the nutritional carbohydrates (fructose, sucrose and starch) were determined in the seed of a range of lentil lines from germplasm collections and commercial Spanish cultivars. Significant levels of variation were found for all the measured characters, and particularly for the α-galactosides. The greatest variation was found in verbascose content, which ranged from about 1 % of the seed dry weight to undetectable amounts. The relationship between these chemical components and morphological seed characteristics was assessed. The only significant relationship between the different groups of characteristics was a positive correlation between the level of verbascose and the average seed weight for each genotype.

Analyses of seeds from a wide range of pea lines have revealed extensive variation for all of the major fatty acids normally found in pisum. Unlike total lipid content, this variation was not affected by the presence of mutant alleles at the r and rb loci. To allow chemically analysed seed to be used in crosses, which is of particular importance for F 2 seed, a method has been developed by which individual seeds can be analysed non-destructively. This system entails drilling a small hole in the seed, away from the embryonic axis. The small quantity of powder produced by this process can be used for the chemical analysis but does not prevent the seed from being grown to produce progeny. Reducing the sample size had no significant effect upon the compositional analysis of the fatty acids.

SUMMARY Photosynthetic activity in the yellow pods of gp.gp lines has been compared with that in normal Gp.Gp pods. As expected from a previous structural study, the occurrence of aberrant plastids in the mesocarp resulted in reduced activity in the gp.gp lines. Illuminated green fruits, 5–16 d post-anthesis showed net uptake of CO2, from the atmosphere. Positive carbon gain was extended until d 28 in deseeded pods. Conversely, in yellow (gp.gp) fruits no net uptake of CO2, from the atmosphere was observed at any stage, even in deseeded pods, but carbon losses in the light were restricted compared with those in the dark, indicating some photosynthetic activity. Analysis of the photosynthetic machinery within the yellow pods showed considerable differences in the effect of the gp gene on the mesocarp and endocarp layers. Compared with those of green pods, concentrations of RuBP carboxylase in the mesocarp were depressed, and the Hill reaction activity of isolated chloroplasts was virtually undetectable. However, in the parenchyma layer of the endocarp, RuBP carboxylase reached higher concentrations than in Gp.Gp pods, and Hill reaction rates were comparable. There was little difference between the lines in their PEP carboxylase concentrations in either tissue.

The effect of the yellow-podded (gp) gene on pea fruits was studied with reference to changes in their plastids. The main effect of the gene was on the mesocarp. The chlorophyll concentration of this layer was depressed to less than 5 % of that in normal green pods, allowing considerably higher light transmission through the pod wall. Ultrastructural studies showed that the mesocarp of yellow pods contained plastids with an internal membrane system restricted to single and paired membranes and vesicles. Unlike the chloroplasts of green mesocarps they lacked grana. Large starch grains were found in the plastids of mesocarps from both yellow and green pods. WeIl-developed chloroplasts, lacking starch grains, were found in the thin parenchymatous lining of the endocarp in yellow and green pods. Here chlorophyll concentrations were comparable in the two pod types and considerably higher than those found in the normal green mesocarp. However, the higher light levels transmitted to this layer in yellow pods correlated with a higher chlorophyll a: b ratio compared with that in the green pod.