14C-Studies on Apple Trees. I. The Effect of the Fruit on the Translocation and Distribution of Photosynthates

The presence of fruits affects the translocation and distribution of photosynthates from apple leaves to other organs of the tree. An attempt has been made to study the relationship in greater detail by following the distribution of ¹⁴C introduced in the form of ¹⁴CO₂ on shoots with and without fruits, respectively. Determinations of the ¹⁴C-content were made on different parts of the shoot sampled at varying intervals after the introduction of the tracer. The ^l4C-labelling and the content of sorbitol and sugar in the leaves were determined by means of paper chromatography. A total of nearly 90 per cent of the ¹⁴C taken up by the leaves can be transferred to a fruit close by, the majority during the first 4 to 5 days following the addition of the ¹⁴C. The content of ¹⁴C in the leaves is reduced more rapidly in shoots with fruits than in those without. Young leaves retain more of the added ¹⁴C than do fully developed ones. The greatest changes with time are found in the methanol-soluble ¹⁴C-compounds. Immediately following application, the leaves contain 58 to 80 per cent of the ¹⁴C added in sorbitol, 7 to 9 per cent in sucrose, and 1 to 4 per cent in the form of glucose. Within 5 days after the introduction of ¹⁴C the amount of ¹⁴C-sorbitol is reduced very considerably, while in certain cases the amount of ¹⁴C-glucose increases. The ¹⁴C-sorbitol content was higher in leaves from shoots without fruits than in those from fruit-bearing shoots, and this applied also to the total contents of sorbitol and of glucose.     

14C-Studies on Apple Trees. VII. The Early Seasonal Growth in Leaves, Flowers and Shoots as Dependent upon Current Photosynthates and Existing Reserves

The young leaves' consumption proper of photosynthates and their contribution to the growth of flowers, fruits and shoots by exposing spurs and shoots to ¹⁴CO₂ at the earliest stages of the growth period in apple trees (Malus X domestica) were studied. By a parallel determination of the growth intensity in various organs an attempt is made to evaluate their relative dependence on current photosynthates and on reserves from inside the tree. The proper fixation of ¹⁴C by growth in the exposed leaves is high in the earliest phases of growth. The fixation of ¹⁴C is considerable in the flowers, including the petals, immediately prior to flowering, in intensely growing fruits, and in the woody parts of the current year's shoots, when the main part of the terminal growth has been completed. Under conditions of high intensity of growth in an organ, the total fixation by growth in the parts studied may amount to as much as 80–90% of the ¹⁴C absorbed. Only in the very earliest phases of development does the growth of flowers and shoots appear to be based to a greater extent on materials supplied from reserves than from current photosynthesis. Quantitatively the greater part by far of the total new growth in fruits and shoots appears to be based on materials from current photosynthesis.     

14C-Studies on Apple Trees. VIII. The Seasonal Variation and Nature of Reserves

The nature, seasonal variation and mobilization of reserves in Malus × domestica have been studied by means of ¹⁴C, carbohydrate analyses and extractions of xylem sap. Following exposure to ¹⁴CO₂ in the autumn, the majority of the ¹⁴C absorbed is found in the root. During the winter and in particular the spring the amounts of ¹⁴C in the top and root are reduced to approximately 40 per cent of the autumn values; in the root the amount of dry matter was also considerably reduced. In the tops, most of the ¹⁴C absorbed was found as methanol (80 %)-soluble ¹⁴C which also showed the greatest seasonal reduction; sorbitol, sucrose or glucose in particular are responsible for the decrease in concentration within this fraction. Maximum values for methanol-insoluble ¹⁴C were found in March. In the root, the highest values for absolute changes were found for methanolinsoluble ¹⁴C. Hydrolysis of this fraction showed considerable activity in glucose. In the root there was also considerable activity in a precipitated fraction of the methanol extract. Eluates of xylem sap from apple branches contained primarily sorbitol, the highest concentration of which was found at the beginning of March. For a tree with a dry matter weight of about 300 g, the utilization of reserves from the tree in the spring was calculated to be at least 13 g of dry matter. However, only a minor part (less than 25 per cent) of the latter appears to serve as building material for new growth.     

14C-Studies on Apple Trees. V. Translocation of Labelled Compounds from Leaves to Fruit and their Conversion within the Fruit

Following application of ¹⁴CO₂ to fruit spur leaves, the majority of the ¹⁴C absorbed is transfered to the fruit on the same spur, and the total content of ¹⁴C within the leaf-fruit system as a whole remains virtually constant with time. The considerable reduction in activity in the leaves is accounted for mainly by a decrease in the amount of ¹⁴C-sorbitol, although relatively speaking the decrease in ¹⁴C-sucrose is also considerable. The major part of the activity of the sugar fraction in the conducting tissues between blade and fruit (petiol, spur) is found in sorbitol. Immediately following uptake of ¹⁴C yia the leaves a large part of the activity of the sugar fraction in the fruit is found in sorbitol; but this activity is rapidly reduced, accompanied by an increase in sucrose activity, and over longer periods of time increases in particular in glucose and fruclose activity, and in that of methanol insoluble compounds. The changes in activity distribution in the fruit vary with the variety of fruit and the dates within the growing season. By injecting labelled sorbitol directly into the fruit sorbitol is converted into sucrose, glucose and fructose, while injection of labelled sucrose, glucose and fructose has yielded proof of interconversions between these compounds but no measurable amounts of surbitol. After application of ¹⁴CO₂ directly to the outer skin of the fruit considerably less of the activity is found in sorbitol than is the case in leaves following exposure to ¹⁴CO₂. A minor, but significant, translocation of ¹⁴C away from the fruit was found to take place following the application of labelled ¹⁴C compounds to the fruit. The smallness of the respiratory loss of ¹⁴C in the leaf-fruit system is discussed. It is concluded that in apple trees considerable translocation occurs in the form of sorbitol which in the fruits rapidly converted into other compounds.     

14C-Studies on Apple Trees III. The Influence of Season on Storage and Mobilization of Labelled Compounds

The present paper reports an attempt to elucidate the storage and mobilization processes in 1-year-old apple rootstocks by studying the ¹⁴C content of different parts of the tree following application of ¹⁴CO₂. The translocation of the ¹⁴C taken up from the leaves to other parts proceeds at the highest rate during the first few days after the application of ¹⁴C. The distribution in shoots, trunk and roots after application of ¹⁴C during May, July, August, and in part of September depends in particular upon the intensity of growth in the various parts. From the lime of the application of ¹⁴C until leaf-fall, 40–50 per cent of the ¹⁴C initially absorbed disappears from the tree. After exposure to ¹⁴C during October, and in part of September, a relatively large part of the ¹⁴C applied goes to the root. In this case there is a considerable reduction in the ¹⁴C-conlent from leaf-fall to the following spring after leafing, especially in the root, although relatively speaking reduction is also considerable in the bark of the parts above ground, and it is most pronounced in the methanol (80 %) soluble fraction. The reduction takes place primarily during spring, and comprises, after application during October, for the whole tree 20–25 per cent of the ¹⁴C initially absorbed. Only 13–17 per cent of this amount was recovered in the newly developed shoots and leaves in the following June.     

14C-Studies on Apple Trees. VI. The Influence of the Fruit on the Photosynthesis of the Leaves, and the Relative Photosynthetic Yields of Fruits and Leaves

When paired samples of either intact or detached apple shoots with and without fruits were exposed simultaneuosly to ¹⁴CO₂, the uptake of ¹⁴CO₂ of leaf area was found to be greater in the fruit-bearing shoots, often by a factor of 1.5 or more, although the difference tends to be slight or even non-existent when the experiments follow shortly after a previous dark period. The uptake of ¹⁴CO₂ by photosynthesis in the skin of detached fruits is very slight compared to the simultaneous uptake of ¹⁴CO₂ by the leaves from the same spur, and can hence contribute only slightly to the development of the fruit compared with the supply of assimilates taking place from the leaves to the fruit.     

14C-Studies on Apple Trees. IV. Photosynthate Consumption in Fruits in Relation to the Leaf-Fruit Ratio and to the Leaf-Fruit Position

The photosynthate consumption in apple fruits in relation to the leaf/fruit ratio was studied in sections of branches of the Graasten and Golden Delicious varieties by exposure to ¹⁴CO₂during July and August. A significant, negative correlation was found between the fixation of ¹⁴C in the fruits in terms of percent of the total amount of ¹⁴C absorbed and the leaf/fruit ratio of the branch sections. The leaf area required for the saturation of one fruit was found to be ca. 190 and 230 cm² (14 and 17 leaves) in the case of Golden Delicious, and ca. 400 and 670 cm² (25 and 42 leaves) for Graasten in July and August, respectively, calculated under conditions of large leaf areas per fruit. In such cases a fairly good, reverse proportionality exists between the ¹⁴C fixation in the fruit in terms of percent and the leaf area expressed in multiples of saturation area. At low leaf/fruit ratios, however, the actual saturation area is found to be lower than the theoretically computed one. The translocation of the ¹⁴C assimilated in the leaves of the extension shoots or of spurs without fruits to fruits on other spurs was on the whole promoted by a decreasing leaf/fruit ratio in the parts in question; similarly the greatest transport took place on the side where the leaf/fruit ratio was lowest. The fixation was often greatest in the fruit closest to the treated leaves, hut in a number of cases the value was higher for the second closest or even further removed fruits. In this connection the importance of the size of the fruit and the vascular connections is discussed.     

14C-studies on Apple Trees. IX. Seasonal Changes in the Formation of Fruit Constituents and their Subsequent Conversions

The formation and subsequent conversions of ¹⁴C-labelled compounds were followed in fruits of Malus domestica cvs. Golden Delicious and Cox's Orange Pippin after labelling proximate leaves with ¹⁴CO₂ at different times during the growing season. A few hours after labelling of the leaves, the larger share of fruit ¹⁴C was detected in sorbitol. This share descreased rapidly except in the late autumn. When labelling about 1 July (c. 1 month after bloom), 40–60% of the fruit ¹⁴C was permanently fixed in the methanol and water insoluble fraction. 25% or more was primarily found in organic acids, but this declined during the season to a few per cent. When labelling at the end of July, the dominating feature was the establishment of a peak of temporarily insoluble ¹⁴C, returning back to the soluble form through October and November. This was particularly pronounced in‘Cox's Organe Pippin'. Labelling with ¹⁴C at the end of August and at the end of September yielded increasing amounts of ¹⁴C in sugars. The labelling of fructose predominated, but as the autumn progressed the amount of label in sucrose increased. This was due to a conversion from ¹⁴C-compounds of older origin as well as to a larger share of the imported assimilates turning into sucrose at this time of the year. During prolonged storage of harvested fruits at 3°C, ¹⁴C in fructose increased at the expense of ¹⁴C in sucrose.     

Distribution of Soluble 14C-Labelled Assimilates as Related to Distribution of 14C-Benzyladenine in Shoot Tips of Hedera helix

The relationship between benzyladenine and assimilate distributions in shoot tips of English Ivy (Hedera helix L.) was studied. Exogenous applications of benzyladenine resulted in small amounts of the hormone moving to the apical meristem. The large part of the recovered benzyladenine was found in the young leaves of the shoot tip. Benzyladenine increased the amount of ¹⁴C-labelled assimilates in the shoot tip, but the distribution pattern of those assimilates within the tip was like that of the untreated control.     

Studies on Cassava, Manihot utilissima. II. Biosynthesis of Asparagine-14C from 14C-labelled Hydrogen Cyanide and its Relations with Cyanogenesis

Seeds and seedlings of Manihot utilissima were analysed for cyanogenic glycosides und free amino acids, with special reference to valine and isoleucine which serve as precursors of the aglycone moieties of linamarin and lotaustralin. Seeds contained traces of valine and isoleucine but no glycosides, whereas seedlings contained high concentrations of these amino acids and glycosides. Illumination of seedlings led to a steep increase in the concentration of glycosides followed by a decrease without excretion of detectable HCN. Seeds accumulated asparagine, while seedlings accumulated both asparagine and glutamine in the storage and transport of nitrogen. Seedlings incorporated 13.2 per cent of label from valine-¹⁴C(U) and 2.4 per cent of label from isoleucine-¹⁴C(U)into linamarin and lotaustralin, respectively. In both cases, appreciable amounts of label were also incorporated into asparagine. 49 per cent of label from H¹⁴CN was incorporated inio asparagine in which ca. 98 per cent of total radioactivity was located in the amide-carbon atom. The different patterns of labelling which occurred during the assimilation of H¹⁴CN and ¹⁴CO₂ showed that cyanide metabolism did not proceed via CO₂, and that M. utilissima contains an efficient enzyme-system which catalyses the conversion on high concentrations of HCN into asparagine, which subsequently enters different metabolic pools involved with respiration, protein and carbohydrate syntheses. Cyanogenesis in M. utilissima appears lo be directly influenced by available pools of valine and isoleucine, and the metabolism of HCN released from linamarin and lotaustralin by the action of linamarase may be directly related to respiratory and synthetic processes by way of the incorporation of HCN as a unit into asparagine.     

Production of [14C]Acetylcholine and [14C]Carbon Dioxide from [U–14C]Glucose in Tissue Prisms from Aging Rat Brain

Abstract: Production of [¹⁴C]acetylcholine and ¹⁴CO₂ was examined by using tissue prisms from neocortex, hippocampus, and striatum from rats aged approximately 5 months, 13 months, and 27 months. [¹⁴C]Acetylcholine synthesis in the striatum showed highly significant decreases with age for measurements in the presence of both 5 m m - and 31 m m -K⁺, contrasting with the lack of significant change in ¹⁴CO₂ production in this region. The neocortex and hippocampus showed only small changes, especially when comparison was made between 13-month and senescent animals. Measurements of the release of [¹⁴C]acetylcholine and influence of atropine on this release confirmed the relative stability with age of the cholinergic system in the neocortex.     

Translocation of 14C-dieldrin from small droplets on cotton leaves

Dieldrin (HEOD) spread from dried residues formed from droplets of emulsions and crystalline suspensions applied to the upper surfaces of cotton leaves (Gossypium species). The amounts of radiolabelled insecticide reaching defined areas of leaf-surface bearing adhesive tape (Sellotape) were measured quantitatively by scintillation counting. Autoradiography supported these results in demonstrating the extent of insecticide movement in the leaf. Up to one-fifth of the applied dose spread more than 8 mm across the leaf surface within a day (lateral movement). Penetration to the lower surface (vertical movement) took place within 4 days, depending on the leaf thickness, which itself was greatly affected by the growing conditions. During this process some dieldrin formed a derivative, possibly a hydroxydieldrin, and some was sorbed at the sites of the lysigenous secretory glands within the leaf. Dieldrin spreads from a deposit (representing that left by a spray droplet) on cotton leaf in all directions to a greater extent and more rapidly than previously supposed.     

Translocation of 14C-Assimilates in Roses

Movement of ¹⁴C-assimilates from young and mature leaves to young rose shoots (Rosa hybrida cv. Marimba) was examined in two developmental stages. In the first stage after bud breaking the young shoot, especially its tip, depends for its supply of assimilates mainly on the mature foliage. At this stage young leaves are powerful sinks and retain 97% of their own photosynthates. The translocated 3% move mainly to the roots. At a later stage, just after the appearance of the flower bud, most of the leaves on the shoot become a source. The upper leaves supply assimilates to the flower bud and to the upper part of the stem. The ¹⁴C-assimilates from the lower leaves move in two directions, the larger part being directed downward.     

Translocation of 14C-assimilates in roses

The upper shoot on decapitated rose branches ( Rosa hybrids cv. Marimba) grows faster than lower shoots on the same branch. Transport of radioactive assimilates to the upper shoot is higher than to the lower ones. Darkening of the uppermost shoot resulted in the reduction of growth and ^I4C-assimilate accumulation in the darkened shoot as well as the promotion of growth and ¹⁴C transport to the lower 2 shoots, thereby rendering dominance to the second shoot. Benzyladenine treatment to the uppermost shoot reversed the effect of darkening and restored the apical control of this shoot.     

The Effect of Dichlorophenyldimethylurea on Light-Stimulated 22Na+, 42K+ and 86Rb+ Absorption in Different Tissues of Phaseolus vulgaris Leaves

The light-stimulated absorption of ⁸⁶Rb⁺ by Phaseolus vulgaris L. leaf slices was found to be sensitive to dichlorophenyldimethylurea in air as well as in nitrogen, whereas light-stimulated ²²Na⁺ absorption in nitrogen was not sensitive to this inhibitor. The absorption of ²²Na⁺ is not affected by light in air. The absorption of ⁴²K⁺ is enhanced by a dichlorophenyldimethylurea-insensitive light effect under anaerobic conditions and further increased by light in the absence of the inhibitor. Light-enhanced ⁴²K⁺ absorption in air was also inhibited by dichlorophenyldimethylurea. Previous work showed that light-stimulated ⁸⁶Rb⁺ and ⁴²K⁺ absorption by Phaseolus vulgaris leaf slices is restricted to the guard cells. The present results are discussed with reference to the effect of light on stomatal opening.     

Studies on the uptake of (14C) amino acids derived from both dietary (14C) protein and dietary (14C) amino acids by rainbow trout, Salmo gairdneri Richardson

Previous studies have shown that rainbow trout fed on diets containing whole protein have superior growth rates compared to fish fed on diets of similar amino acid composition but containing a high proportion of free amino acids. The influence of several nutritional factors on the uptake of radioactivity from food pellets containing either [U-^I4C] protein or [U-¹⁴C] amino acids into the systemic blood of trout has been investigated. The time taken for radioactivity in the free amino acid fraction of blood to reach a peak after a meal containing [U-¹⁴C] protein had been given was much shorter, and the level of radioactivity in the blood higher, in trout with almost empty stomachs than in fish with almost full stomachs; uptake of radioactivity into blood amino acids was also more rapid and reached much higher concentrations when pellets containing [U-¹⁴C] amino acids were fed than when [U-¹⁴C] protein was fed. Incorporation of radioactivity into blood protein continued for a much longer period and reached higher levels when a pellet containing [U-¹⁴C] protein was fed than when a pellet containing [U-¹⁴C] amino acids was fed. Previous dietary history (low or high protein intake) did not appear to affect the rate of absorption of amino acids from either protein or free amino acid pellets. The uptake rates from pellets containing free amino acids could be slowed by mixing the dietary amino acids with albumin. The distribution, postabsorption, of radioactivity in the different fractions of blood and liver suggested that incorporation of carbon residues into glycogen and lipid from an amino acid diet was greater than from a protein diet. The converse was true of incorporation of radioactivity into tissue protein.     

Tracer studies of gas circulation in Nuphar: 18O2 and 14CO2 transport

The objective of this study was to investigate the behaviour of different legumes against salinity and water stress, thus trying to discover simultaneous adaptations to both stresses. The nitrogen fixation, transpiration, predawn leaf water potential, and stomatal response of Medicago sativa L. (cvs. Tierra de Campos and Aragon), Trifolium repens L. (cv. Aberystwyth S-184) and T. brachycalycinum Katzn. et Morley (= T. subterraneum L. cv. Clare) were compared at three levels of stress (0.05, 0.3 and 0.5 MPa of either NaCl or polyethylene glycol 6000) in nutrient solution. The plants were stressed for three days and then returned to control nutrient solution. The changes in the parameters analyzed were dependent on the proportion of stress treatments and the nature of the species, always being greater in plants from PEG than from NaCl solutions. Transfer of lucerne and subclover plants from NaCl at 0.05 MPa to a non-saline medium resulted in an increase of nitrogen fixation above the level of the non-salinized control plants, especially significant in lucerne. Analysis of possible inorganic impurities in commercial PEG suggest that such type of impurities are not responsible for the toxic effects reported. Plant damage resulting from PEG treatment was apparently due to penetrations of PEG (as determined qualitatively by using the tetraiodinebismuthic acid technique) or low-molecular organic impurities into the plant. – The results are discussed as part of the adaptation of the different species to salinity and water stress. The best performance was given by "Tierra de Campos".     

Alterations in the Production of 14CO2 and [14C]Acetylcholine from [U-14C]Glucose in Brain Subregions Following Transient Forebrain Ischemia in the Rat

Abstract: The production of ¹⁴CO₂ and [¹⁴C]acetylcholine from [U-¹⁴C]glucose was determined in vitro using tissue prisms prepared from the dorsolateral striatum (a region developing extensive neuronal loss following ischemia) and the paramedian neocortex (an ischemia-resistant region) following 30 min of forebrain ischemia and recirculation up to 24 h. Measurements were determined under basal conditions (5 mMK⁺) and following K⁺ depolarization (31 mM K⁺). The production of ¹⁴CO₂ by the dorsolateral striatum was significantly reduced following 30 min of ischemia for measurements in either 5 or 31 mM K⁺ but recovered toward preischemic control values during the first hour of recirculation. Further recirculation resulted in ¹⁴CO₂ production again being reduced relative to control values but with larger differences (20–27% reductions) detectable under depolarized conditions at recirculation times up to 6 h. Samples from the paramedian neocortex showed no significant changes from control values at all time points examined. [¹⁴C]Acetylcholine synthesis, a marker of cholinergic terminals that is sensitive to changes in glucose metabolism in these structures, was again significantly reduced only in the dorsolateral striatum. However, even in this tissue, only small (nonstatistically significant) differences were seen during the first 6 h of recirculation, a finding suggesting that changes in glucose oxidation during this period were not uniform within all tissue components. The results of this study provide evidence that in a region susceptible to ischemic damage there were specific changes during early recirculation in the metabolic response to depolarization. This apparent inability to respond appropriately to an increased need for energy production could contribute to the further deterioration of cell function in vivo and ultimately to the death of some cells.     

Metabolism of [14C]ss-glucose and [14C]-acetate by lettuce embryos during early germination

The metabolism of ['⁴C]-labelled glucose and acetate has been investigated during the early germination - before radicle emergence - of lettuce ( Lactuca sativa L., cv. Val d'Orge) embryos. Similar amounts of radioactivity from both substrates were evolved as C., or incorporated into organic acids, amino acids and proteins. A large part of the [¹⁴C]-glucose was also incorporated into sucrose and polysaecharides, and a small part into the glycerol moiety of lipids. Acetate was massively incorporated into lipids, and only slightly into neutral compounds. These results show that both glucose and acetate can be utilized as respiratory substrates during early germination of lettuce embryos. Various biosynthetic pathways leading to amino acids, proteins, polysaecharides and lipids are active during this period.