The photosynthetic properties of the internal and peripheral tissues of the cherry tomato fruit (Lycopersicum esculentum var. cerasiforme Dun A. Gray) were investipted. Whole fruit and their isolated tissues evolve large aMounts of CO2 in darkness. In the light, this evolution decreases but nevertheless remains a net evolution; 3-(3,4-dichlorophenyl)-1,1-dimethylures abolisbes the effects of light.Incorporation of 14CO2 by leaves and fruit tissues demonstrates that the outer region of the fruit has the highest pbotosynthetic efficiency on a chlorophyll basis; the internal frit tiue, richer in chlorophyll, has a much lower efficiency. The identification of intermedintes following short term incubations with 14CO2 shows that in darkness the fruit accumulates the majority of label in malate. In the light, leaf tissue exhibits a pattern of incorporation characteristic of C-3 metabolism, whereas fruit tissue exhibits a decreased labeling of malate with a concomitant appearance of label in Calvin cyde intermediates. This is in agreement with the levels and types of carboxylating activities demonstrated in vitro; especially noteworthy is the very low nrbulose diphosphate carboxylase activity in the internal fruit tissue. The diameters of green growing fruits which were utilized varied between 4 and 15 mm. Maturing fruits, the diameters of which varied between 15 and 20 mm, were classified in stages "a" through "g" as a function of their color. Thus, stages "a" through "c" represent green to pink and "d" through "g" represent pink to red (cf. refs. 7 and 8 for a more complete description of this system). In most of the experiments presented, the fruit was first cut in two and the two regions of the pericarp were mechanically separated with a spatula. The internal fluidic portion is referred to here as the pulp and the relatively firm external portion is called the flesh. The majority of experiments presented here were performed on green adult fruits of 15 mm diameter. When photosynthetic controls were desired, adult leaves 15 x 25 cm were picked from the same plants as the fruits. All experimental material was harvested between 9 and 11 AM unless otherwise indicated.Carbon Dioxide Gas Exchange Experiments. The tissue to be tested was placed in a thermostated reaction chamber (25 C). White saturating light (400 w -m-2, 400-700 nm) was provided by a xenon lamp (Osram 1001), filtered through 15 cm of water + an anticaloric filter, Balzer Calflex Bl/Kl. Air slightly enriched in CO2 (430 pl/1) was supplied continuously at a constant rate of 9 1/hr and the CO2 concentration in the gas mixture leaving the reaction chamber was determined with an IR gas analyzer.Short Term "4CO2 Incorporations. The plant tissues were physically fragmented as follows: flesh tissue (approximately 200 mg) was cut into about 25 pieces (4 x 4 x 1 mm); the corresponding pulp (approximately 300 mg) was divided into about 15 pieces (4.5 x 3 x 1 mm); half of a foliole was cut into about 100 pieces (4 x 2 x 0.1 mm). The tissue fragments were place...

Previous studies (6, 7) have shown that high PEP' carboxylase activities are found in green tomato fruit tissues; this finding was subsequently confirmed (12). More recently, we demonstrated that the incubation of tomato tissues with "4C-bicarbonate in the light results in the incorporation of radioactivity into malate and RPPC compounds (8). The external pericarp of thE fruit, the flesh, contains a relatively high RuDP carboxylase activity and exhibits a large incorporation of "4CO2 into RPPC compounds. There is also a pronounced labeling of malate, as a result of the very high PEP carboxylase activity of the flesh. In the internal pulp, however, "4C incorporation into RPPC compounds is very low, consistent with the very low RuDP carboxylase activity demonstrated in this tissue (8).In the present report we attempt to correlate malate metabolism and photosynthetic activities in tomato tissues. Precursors differentially labeled with 14C were vacuum-infiltrated into tissues in darkness and the appearance of radioactivity in other metabolic intermediates in the light, especially RPPC compounds, sugars, and starch, was followed. A The results show that only a small rapidly turning over malate pool seems very active. It can originate from the fixation of respiratory CO2 and can be the precursor of RPPC compounds. MATERIALS AND METHODSFruits of the cherry tomato (Lycopersicum esculentum var. cerasiforme Dun A. Gray) were picked at stage a (8). The experiments reported here were performed during the summer when fruits exhibit high photosynthetic activities (8).The extraction and determination of malate in tissues were performed as previously described (3,8).Vacuum-infiltration of Labeled Precursors. Fruit tissues were mechanically separated into the firm outer flesh and the jellylike internal pulp. Four hundred mg of flesh were cut into 0.5-mm cubes and 800 mg of pulp were gently dispersed. '4C-4-or '4C-3-malate or '4C-2-pyruvate, 100 to 200 uCi of each (specific radioactivity 2-10 mCi/mmol), were infiltrated into tissues in darkness with two successive 1-min periods of vacuum. The infiltrated tissues were then rinsed, drained, and finally placed in Petri dishes whose center wells contained a small amount of 40% KOH to trap any CO2 liberated. The incubation vessels were then sealed with adhesive tape and were placed either in white light (40 w/m2) or in darkness at 20 C. The "4CO2 liberated and subsequently trapped by the base was determined by counting small aliquots of KOH in a scintillation counter. The extraction and analysis of labeled metabolic intermediates were performed as previously described (8).

Special culture conditions for Euglena gracilis Z and ZR are described. They induce interactions between the chloroplast and mitochondrial metabolisms leading to paramylon synthesis. When grown in continuous light under pure nitrogen and in the presence of lactate as the sole carbon source, sugar synthesis occurs during the first 24 h of culture with the participation of both mitochondria (using lactate) and of chloroplasts (fixing CO2 from lactate decarboxylation). The activities of ribulose bisphosphate carboxylase, phosphoenolpyruvate carboxylase, and phosphoenolpyruvate carboxykinase are very high and mitochondria and chloroplasts develop then a common network of vesicles in which paramylon grains can be seen. Electron micrographs demonstrate membrane continuity between the two types of organelles. Occasionally the mitochondrial matrix and the chloroplast stroma are separated by only a unit membrane.

Heterotrophically grown Euglena synthesize grains of paramylon, its reserve carbohydrate, in a vesicular complex of mitochondrial origin. A CO2 fixation activity in dark grown Euglena was demonstrated in the mitochondria via paramylon. At the beginning of the exponential phase of growth, the activity of phosphoenolpyruvate carboxykinase increases before the augmentation of paramylon.At the end of the exponential phase, the activity of this enzyme decreases, and low residual levels persist in the transition and stationary phases of growth. The activity of phosphoenolpyruvate carboxylase evolves inversely during the heterotrophic growth of the algae in succinate- or a lactate-containing medium. A compartmentalized scheme of carbon metabolism in mitochondria is presented.

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