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The properties of two strains of carrot (Daucus carota) callus are presented. One has a very low acid invertase activity which is accompanied by differences in morphology and metabolic rate, but not in growth rate. We conclude that one of the main functions of plant acid invertases is in controlling the levels of sugars which, by interaction with hormones, affect differentiation, both morphological and biochemical. The effect of tris on sucrose metabolizing enzymes, and the cause of the "sucrose effect" are considered.

The growth of the fruit of two varieties of almond (Prunus dulcis (Mill.) D. A. Webb) was studied from anthesis (week 0) to maturity (week 32). The dimensions, fresh weight, moisture content, anatomy and chemical composition of the pericarp, testa, embryo, endosperm and nucellus are recorded diagrammatically, graphically and by micrographs for one variety. Of the two ovules present at flowering only one normally developed further. By 12 weeks after flowering the whole fruit had reached full size. The space enclosed by the pericarp was filled by nucellus until week 10, with subsequent enlargement of both endosperm and embryo. From week 16 to week 20 the embryo increased to full size with a concurrent decrease in the size of the endosperm. Sixteen weeks after flowering, the embryo began to accumulate protein and lipid, little of which originated from either the nucellus or endosperm. The embryo contained no starch or reducing sugar but up to 3 % sucrose in the early stages which decreased as lipid and protein increased. Starch and sucrose levels were high in the testa at week 16 but subsequently dropped, starch more rapidly than sucrose. The role of the testa in transport of metabolites to the embryo is discussed.

The activities of enzymes involved in starch metabolism were measured at intervals during tuberization and the early stages of tuber growth in Solanum tubersum grown in water culture under controlled environmental conditions. Starch synthase, ADPglucose pyrophosphorylase, UDPglucose pyrophosphorylase and phosphorylase activities all increased during tuber development, the most pronounced increases occurring in the activities of ADP-glucose pyrophosphorylase and phosphorylase. The activity ratio ADPglucose pyrophosphorylase/phosphorylase was lowest in slow growing tubers and hightest in fast growing tubers. In addition, high sugar concentrations in fast growing tubers and low sugar concentrations in slow growing tubers suggested that enzyme levels might be influenced by sugar concentration. The activities of starch synthase, phosphorylase and ADPglucose pyrophosphorylase were increased 2–2.5 fold by the presence of 100 mM K+. It is concluded that the major enzyme changes occur as a consequence of tuber initiation and that starch accumulation is controlled, at least in part, by the activities of ADPglucose pyrophosphorylase and phosphorylase.

Soluble ADPglucose: α-1,4-glucan α-4-glucosyltransferase from potato tubers (Solanum tuberosum L.) was partially purified by chromatography on DEAE-cellulose. The enzyme transferred glucose from ADPglucose to several glucan primers. In addition, the enzyme synthesized glucan in the absence of added primer in a reaction mixture containing sodium citrate and bovine serum albumin. The rate of synthesis of glucan in the absence of primer was half the rate found with amylopectin as primer and was linear with time in 0·5 M sodium citrate. The unprimed product was a methanol precipitable glucan with principally α-1,4-linkages and some branches which were cleaved by glucoamylase. The enzyme showed unprimed activity after treatment of both the enzyme and reaction mixtures with glucoamylase.

ADP-glucose:α-1,4 glucan-4-glucosyl transferase was extracted from spinach leaves and separated by gradient elution on a DEAE-cellulose column. Fractions I and II gave equal activity with amylose, amylopectin, or glycogen as a primer while the activity of fraction III with glycogen as primer was only 25% of the activity observed with amylose or amylopectin as primer. Glucan synthesis in the absence of primer was found in fraction III. This activity was stimulated over 1000-fold by bovine plasma albumin and high salt concentrations. The radioactive unprimed product was a glucan with principally α-1,4 linkages and some α-1,6 linkages.

A relatively simple and inexpensive apparatus has been developed for the rapid determination of the surface contamination of dried vine fruits by grit. Up to 80 measurements can be made in an 8-hour day by a semi-skilled operator. Grit is separated from samples (200 g) of dried fruit by sieving, and grit particles greater than 50 μm diameter are collected on a small sieve. After separation of organic matter and grit in a saturated solution of potassium carbonate the height of grit in a tube of diameter 2 mm gives an index of the grit content of the fruit. Values obtained with the gritometer show significant correlation with values obtained using a previously accepted slower method.

Untreated berries of Vitis vinifera and berries treated with commercial dipping solution were dried in the dark, full shade or in the sun. Dipping treatment increased the drying rate. The major pigments, namely, chlorophyll a, chlorophyll b, pheophytin a, pheophorbide a and the carotenoids, decreased in all treatments where berries received light. Only the chlorophylls and carotenoids decreased in berries dried in the dark, but not to the same extent as in berries exposed to light during drying. Pigment loss was not directly related to berry moisture content. Berries dried in the dark remained green while berries dried in the light changed to brown if untreated or pale golden-brown if treated with commercial dipping solution. In situ removal of the magnesium from the magnesium porphyrin compounds demonstrated that the green coloration was due to the chlorophylls and chlorophyllides.

1. A phosphatase that hydrolyses sucrose phosphate (phosphorylated at the 6-position of fructose) was isolated from sugar-cane stem and carrot roots. With partially purified preparations fructose 6-phosphate, glucose 6-phosphate, fructose 1-phosphate, glucose 1-phosphate and fructose 1,6-diphosphate are hydrolysed at between 0 and 2% of the rate for sucrose phosphate. 2. The activity of the enzyme is increased fourfold by the addition of Mg2+ ions and inhibited by EDTA, fluoride, inorganic phosphate, pyrophosphate, Ca2+ and Mn2+ ions. Sucrose (50mm) reduces activity by 60%. 3. The enzyme exhibits maximum activity between pH6·4 and 6·7. The Michaelis constant for sucrose phosphate is between 0·13 and 0·17mm. 4. At least some of the specific phosphatase is associated with particles having the sedimentation properties of mitochondria. 5. A similar phosphatase appears to be present in several other plant species.

As part of an investigation of the growth of tomato plants supplied with either nitrate or ammonium nitrogen (6), leaves were assayed for NAD4 and NADP. Anderson and Vennesland (1) assayed NAD and NADP in various green tissues and reported recoveries between 50 % and 85 % of NAD and NADP added to spinach leaf extracts. Very low levels of NAD and NADP were recorded for tomato leaf extracts. These low levels were attributed to losses of NAD and NADP in the additional purification steps necessary with tomato leaf material for removal of other compounds absorbing at 340 mIy. The method reported here provides an improved procedure for the assay of NAD and NADP in tomato leaf extracts.

Temperatures in the chilling range (from about 12° to 0°C) markedly inhibit photosynthetic electron transport, carboxylation and translocation in susceptible plants. A similar inhibition for starch synthesis is reported for the chilling-sensitive plants, avocado, maize and sweet potato. Arrhenius plots for soluble and starch grain-bound forms of starch synthetase from chilling-sensitive plants showed a change in slope (discontinuity) at about 12°C. The chilling-resistant potato maintained a constant energy of activation from 23°C to 3°C for both forms of enzyme. The discontinuity in chilling-sensitive plants was abolished by high concentrations of tert-butyl alcohol, but not Triton X-100 or phospholipase A. The existence of an enzyme-lipid interaction within amylose molecules is suggested. The phospholipid, lysolecithin, may be uniquely involved in the control of starch biosynthesis and degradation.

Sucrose phosphate phosphohydrolase (sucrose phosphatase, EC 3.1.3.24) catalyses specifically the hydrolysis of sucrose phosphate which is phosphorylated at the 6 position of the fructose moiety releasing sucrose and Pi (Hawker, Hatch 1975). It is involved in the pathway of sucrose synthesis in higher plants together with the enzyme sucrose phosphate synthase (EC 2.4.1.14).

1. By using EDTA in reaction mixtures it was possible to determine the activity of sucrose phosphate synthetase in freshly prepared leaf extracts without the complications caused by sucrose phosphatase. 2. EDTA was found also to increase the activity of sucrose phosphate synthetase by as much as 100%. 3. High sucrose phosphate synthetase activities were found in leaf preparations in which sucrose phosphatase was inhibited by EDTA. By contrast with previous reports, the activities were sufficient to allow sucrose synthesis in leaves during photosynthesis to occur via sucrose phosphate. 4. Sugar-cane plants having different rates of photosynthesis also had different activities of sucrose phosphate synthetase in their leaves. 5. It is suggested that the activity of sucrose phosphate synthetase in leaves may play a role in the control of the rate of photosynthesis.

TWO ADENOSINE DIPHOSPHOGLUCOSE: alpha-1,4-glucan alpha-4-glucosyl-transferases were extracted from kernels of waxy maize harvested 22 days after pollination and separated by gradient elution from a diethylaminoethyl-cellulose column. Both fractions could utilize amylopectin, amylose, glycogen, maltotriose and maltose as primers. The rate of glucose transfer from adenosine diphosphoglucose to rabbit liver glycogen of fraction II was 78% of the rate of glucose transfer to amylopectin, but with fraction I the rate of transfer of glucose to rabbit liver glycogen was 380% of that observed to amylopectin. Glucan synthesis in the absence of added primer was found in fraction I in the presence of 0.5 m sodium citrate and bovine serum albumin. The unprimed product was a methanol-precipitable glucan with principally alpha-1,4 linkages and some alpha-1,6 linkages, and its iodine spectrum was similar to that of amylopectin.

Multiple forms of ADP-glucose-alpha-1,4-glucan alpha-4-glucosyltransferase were obtained from spinach leaves by gradient elution from a DEAE-cellulose column. In the presence of high concentrations of some salts and bovine serum albumin, unprimed activity was found in one (transglucosylase III) of the four fractions eluted from the column. In addition to having unprimed activity, transglucosylase III had a lower K(m) for ADP-glucose, a much higher K(m) for oyster glycogen, greater heat sensitivity and lower affinity for maltose, maltotriose and amylopectin beta-limit dextrin than fractions I, II and IV. In addition, the kinetics at low concentrations of amylose, amylopectin and rabbit liver glycogen were non-linear for transglucosylase III. The properties of transglucosylases I, II and IV were generally similar to each other. Rates of the unprimed reaction at physiological concentrations of ADP-glucose were greater than those found for the primed reaction of fraction III. The product formed by the unprimed reaction was a glucan containing principally alpha-1,4 linkages with some alpha-1,6 linkages. The primer, maltose, at a concentration of 0.5m inhibited the synthesis of the unprimed product.

The effects of ethylene gas, 2-chloroethylphosphonic acid, and the auxin, benzothiazole-2-oxyacetic acid, on the ripening of grapes (Vitis vinifera L.) was investigated. Ethylene hastened the start of ripening of Doradillo grapes when it was aplied for 10 days starting midway through the slow growth phase. 2-Chloroethylphosphonic acid applied to Shiraz grapes showed the same effect, but when it was applied earlier, during the second half of the first rapid growth phase or at the start of the slow growth phase of berry development, it delayed ripening. 2-Chloroethylphosphonic acid and benzothiazole-2-oxyacetic acid delayed the ripening of Doradillo grapes, and ethylene partially reversed the effect of benzothiazole-2-oxyacetic acid. The results demonstrate the importance of the slow growth stage in grape berry development and suggest that an auxin-ethylene relationship may be involved in the regulation of grape ripening.

Soluble ADPglucose-alpha-glucan 4-alpha-glucosyltransferase (starch synthetase), ADPglucose pyrophosphorylase, UDPglucose pyrophosphorylase and phosphorylase were assayed in extracts from developing kernels of maize (Zea mays). Normal, waxy and amylose-extender maize at stages of development ranging from 8 days to 28 days after pollination were studied. Shrunken-4 maize at the 22-day stage was also studied. There is adequate activity of both ADPglucose pyrophosphorylase and starch synthetase at all stages of development to account for the synthesis of starch. Thus all starch could be synthesized via the ADPglucose pathway. High levels of UDPglucose pyrophosphorylase and of phosphorylase activities were also found at all stages of development. The possible role of phosphorylase in starch synthesis could not be discounted. The levels of phosphorylase, ADPglucose pyrophosphorylase, starch synthetase, and UDPglucose pyrophosphorylase activities in shrunken-4 kernels were about 20 to 40% of that found in normal maize kernels. It appears that the mutation in shrunken-4 affects the activities of more than one enzyme. The defective starch synthesis seen in this mutant could be due to the low activities of ADPglucose pyrophosphorylase and starch synthetase rather than the low activity of phosphorylase.

The development of callus from immature grape berries of Vitis vinifera L. cvs. Sultana, Muscat Gordo Blanco, Cabernet Sauvignon, Shiraz, Clare Riesling and Rhine Riesling is described. Callus has been successfully subcultured on solid and liquid media.

The growth rate of plants of both spinach (Spinacia oleracea) and sugarbeet (Beta vulgaris) was decreased with low levels of K+ in nutrient solutions. Addition of Na+ at low levels of K+ resulted in growth rates at least as great as those observed with adequate K+. By comparison, bean plants (Phaseolus vulgaris) had only low growth rates when part of the K+ was replaced with Na+. The concentration of starch in spinach leaves was not affected by the K+/Na+ supply, whereas sugarbeet leaves from plants grown on adequate levels of K+ contained nine times more starch than leaves grown on high Na+/low K+ culture solutions. K+, but not Na+, stimulated by about 100% the activity of starch-granule-bound ADPglucose starch synthase from sugarbeet, bean and Atriplex nummularia leaves but not from spinach leaves. Neither ion caused a marked stimulation of the activity of soluble ADPglucose starch synthase, phosphorylase or other enzymes likely to be associated with carbohydrate metabolism. Slices of bean or sugarbeet leaves incubated in 12.5 mM K2SO4, solutions in the light for 8 h contained higher amounts of starch, and slices of bean leaves contained lower amounts of soluble sugars, than similar slices in Na2SO4. There was a considerable efflux of sucrose but not of reducing sugars in the presence of K+ or Na+ ; this efflux was several times higher than in the presence of Ca2+. The results suggest that K+ is essential for the conversion of sugars to starch in some plant species and that ADPglucose starch synthase is the enzyme involved in starch synthesis in the leaves of these species.