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The general properties, classification and distribution of plant proteins are discussed within an agricultural context and the protein content and composition of several grain crops are tabulated. The major proteins of legume seeds are salt soluble proteins (i.e. globulins) and the methodology for their extraction, separation and characterisation is reviewed. The structure, location and distribution of legume globulins are described and the properties of various purified legume globulins are compared. The major seed proteins of Pisum sativum are legumin and vicilin and seed globulins with properties similar to those of legumin and vicilin have been extracted from other legumes. The isolation and partial characterisation of vicilin-like proteins from seeds of Phaseolus vulgaris and Vigna vinguiaulata and of legumin-like proteins from these two species and Phaseolus aureus is described. The potential usefulness of the examination of seed proteins by polyacrylamide gel electrophoresis to taxonomic problems in Phaseolus and Vigna is investigated and the data obtained are discussed in relation to recent re-classifications of the species. Procedures for the extraction and partial characterisation of proteins from an archaeological sample of maize grains are described and the proteins from this sample are compared with the proteins from a modern variety of maize. It is suggested that protein data from archaeological samples could be useful in studies of crop plant origins and in cultural studies, and that the procedures employed may be applicable to archaeological samples of other grains. Nutritional aspects of plant proteins are discussed briefly. A possible strategy for the improvement of the sulphur amino acid content of legumes with a relatively low legumin content is suggested and it is demonstrated that polyacrylamide gel electrophoresis may provide a basis for a screening procedure for protein quality in legume breeding programmes.

The present investigations were primarily aimed at confirming the presence and defining the properties and function of cytochrome P-450 in higher plants. This involved a survey of the metabolism of various compounds including, fatty acid oxidation, the biosynthesis of phenolic compounds, as well as 'foreign compounds'. Comparative studies were undertaken with hepatic and extra-hepatic mammalian tissues. Cytochrome P-450 was demonstrated in both microsomal and mitochondrial fractions from various mammalian tissues; but is associated only with the 105,000g x 60 min pellet fractions of the higher plants investigated, including avocado pear, pea seedlings, bean cotyledons and sweet com seedlings. With the exception of the avocado mesocarp, the cytochrome P-450 detected in higher plants was found to be transient in the absence of added thiol reagents and glycerol. The avocado pear type of 'P-450' was more akin to rat liver cytochrome P-450 especially in response to storage, deoxycholate and phospholipase C treatment. Binding spectra studies with various endogenous and 'foreign' substrates metabolized by the liver microsomal mixed function oxidase system showed that the capacity of plant tissue is much more limited. A variety of compounds elevated hepatic microsomal cytochrome P-450, but only safrole significantly altered levels in mesocarp tissues, while in other plant tissues,levels remained unaltered. The ability of some plant tissues (especially avocado mesocarp) to metabolize a variety of anutrients including the hydroxylation of aniline, benzo[a]pyrene and biphenyl, N-demethylation of p-chloro-N-methyl-aniline and the 0-demethylation of p-nitroanisole were compared with rat liver. These activities were either not detectable in plant material or were present at one or more orders of magnitude lower than those found in hepatic tissues. Levels found in extra-hepatic mammalian tissues seemed more akin both in terms of quality and quantity with those found in avocardo mesocarp. Both NADP[2]-cytochrome c and NADPH[2]-cytochrome P-450 reductases were detected in hepatic and mesocarp 105,000g fractions. Inhibitors effective in mammalian cytochrome P-450 mediated reactions caused little or no effect when tested with corresponding reactions in higher plants, this may be a problem of penetration rather than binding. NADH[2] was capable of replacing NADPH[2] in plant reductase systems. Mesocarp and hepatic fractions were found to metabolize lauric acid, and although identifications of metabolites has not been completed, inhibition studies and cofactor requirements indicate possible cytochrome P-450 mediation. Similar studies on cinnamic acid hydroxylation indicate a role for the cytochrome in the biosynthesis of phenolics in various higher plants.

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Concentrations of major biochemical constituents of developing barley endosperm were measured and correlated with morphological changes during maturation. The activities of enzymes concerned with starch meta- bolism in barley endosperm were investigated. It was established that mechanisms by which sucrose can be converted to nucleotide sugars and thus incorporated into starch exist in the endosperm by 5 days after anthesis. Possible variations in these pathways during grain development are discussed. The partition of starch synthetase between soluble and amyloplast fractions of the endosperm was established at various stages of development, and changes in affinity to- wards UDPG and ADPG were demonstrated. The relevance of these results to branching enzyme activity and amylopect in content is considered. A detailed investigation of the activity and control of starch phosphorylase in barley endosperm was carried out. The existence of at least two isoenzymes was indicated by studies of pH dependence and phosphate inhibition, and was further supported by acrylamide gel electrophoresis and column chromatography using DEAE -cellulose. A change in the isoenzyme pattern during grain development was observed. Synthesis of starch by phosphorylase in an apparently primer - free system was demonstrated, and this activity integrated with starch synthetase. A pathway for the conversion of sucrose to glucan polymers via GIP in very young endosperm is proposed. It is suggested that at least one, and possibly both, isoenzymes of phosphorylase are glycoproteins. Spatial arrangements of phosphorylase, starch synthetase, and branching enzyme in relation to the amyloplast are discussed.

The presence of phosphate and dicarboxylate translocators in the outer membranes of the chloroplast is based largely on work with spinach chloroplast suspensions. This project is a comparative study of the relationship between the chloroplast and the photo synthetic cell using isolated chloroplast suspensions from Spinacia (spinach), Pisum, (pea), Helianthus (sunflower), and Kalanchoe. The transport of photosynthetic intermediates across the outer chloroplast membranes was monitored using the technique of silicone-oil centrifugation. Uptake of radioactive metabolites was measured in assays similar to those employed by Heldt et al. The products of 14CO2 fixation were identified for each of the species, and their fate monitored in terms of export from or retention by the plastids. Assay conditions were altered to attempt to affect the distribution of photosynthetic products. Phosphate concentration was altered and photo synthetic metabolites added to the assay medium. For Spinacia investigation was made of the effect on distribution of photosynthate of alteration of bicarbonate concentration, temperature and osmolarity of bathing medium, and additions of MgCl2, MnCl2, CaCl2, NaCl, Na2SO4 and indoleacetic acid. The results of the investigations suggested the presence of a phosphate-translocator in chloroplasts of Spinacia, Pisum, and Helianthus, but there was no compelling evidence for the existence of such a translocator in the Kalanchoe chloroplast. The presence of a dicarboxylate translocator was demonstrated in Spinacia chloroplasts, but definite conclusions as to the presence of such a translocator in the other species were thwarted by probable enzymic contamination in the chloroplast suspensions.

A new technique has been developed for the isolation of nuclei from suspension culture cells of Acer pseudoplatanus L. This technique involves the use of a glycerol-containing grinding medium at -20°C. The whole isolation process is simple and consistently produces about 20% nuclear yield with reasonable purity. Histone extraction from this nuclear fraction by the H2SO4-EtOH method is superior to other methods examined. The extracted Acer histones exhibit a typical histone pattern on polyacrylamide gels, and the major fractions are identified as H1, H2A, H2B, H3 and H4 (in sequence from the anode to the cathode end on the gel); their molecular weights are respectively 24,500, 13,500, 13,300, 12,800 and 11,000, Both the H3 and H4 histones of Acer cells are identical with those of calf thymus in terms of their mobilities on acid-urea and SDS gels. Identification of the Acer histone fractions has been assisted by a newly developed differential staining method which stains the 5 major histone fractions of calf thymus in 5 different colours. The total extracted Acer histone fraction contains 22% of basic amino acids, and the ratio of lysine to arginine is 2.6 which is higher than that for calf thymus and is probably due to the low content of arginine in Acer H2A. The Acer histones have been shown to be synthesized in the cytoplasm and then transported into the nucleus. The synthesis occurs throughout the cell cycle but reaches its maximum rate while INA is being synthesized. Histone samples obtained from both asynchronous and synchronous cultures at intervals during the progress of their growth show uniform electrophoretic patterns on the gels, suggesting that the Acer histones are generally homogeneous and that any modification of the histones probably affects only a very small proportion of the total histones. The possible existence of such modified histone derivatives and their functions remains to be investigated. Directions along which the present studies could be developed are discussed.

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