Showing papers in "Plant Physiology in 1967"
TL;DR: Gibberellic acid enhances the synthesis of alpha-amylase in isolated aleurone layers of barley-seeds and enhances the formation of ribonuclease which increases linearly over a 48 hour period.
Abstract: Gibberellic acid enhances the synthesis of α-amylase in isolated aleurone layers of barley-seeds (Hordeum vulgare var. Himalaya). In the presence of 20 mm calcium chloride the amount of enzyme obtained from isolated aleurone layers is quantitatively comparable to that of the half-seeds used in earlier studies. After a lag period of 6 to 8 hours enzyme is produced at a linear rate. Gibberellic acid does not merely trigger α-amylase synthesis, but it is continuously required during the period of enzyme formation. Enzyme synthesis is inhibited by inhibitors of protein and RNA synthesis. Small amounts of actinomycin D differentially inhibit enzyme release and enzyme synthesis suggesting 2 distinct processes. Gibberellic acid similarly enhances the formation of ribonuclease which increases linearly over a 48 hour period. During the first 24 hours the enzyme is retained by the aleurone cells and this is followed by a rapid release of ribonuclease during the next 24 hour period. The capacity to release the enzyme is generated between 20 and 28 hours after the addition of the hormone. Ribonuclease formation is inhibited by inhibitors of protein and RNA synthesis. These inhibitors also prevent the formation of the release mechanism if added at the appropriate moment.
585 citations
TL;DR: The molecular requirements for ethylene action were investigated using the pea straight growth test and it is suggested that CO(2) delays fruit ripening by displacing the ripening hormone, ethylene, from its receptor site.
Abstract: The molecular requirements for ethylene action were investigated using the pea straight growth test. Biological activity requires an unsaturated bond adjacent to a terminal carbon atom, is inversely related to molecular size, and is decreased by substitutions which lower the electron density in the unsaturated position. Evidence is presented that ethylene binds to a metal containing receptor site. CO2 is a competitive inhibitor of ethylene action, and prevents high concentrations of auxin (which stimulate ethylene formation) from retarding the elongation of etiolated pea stem sections. It is suggested that CO2 delays fruit ripening by displacing the ripening hormone, ethylene, from its receptor site. Binding of ethylene to the receptor site is also impeded when the O2 concentration is lowered, and this may explain why fruit ripening is delayed at low O2 tensions.
570 citations
TL;DR: The method of evaluating cold injury in woody plants by the use of triphenyl tetrazolium chloride has been refined to eliminate bias associated with visual differentiation between varying degrees of tetrazoium reduction and to predict tissue survival at a later date.
Abstract: The method of evaluating cold injury in woody plants by the use of triphenyl tetrazolium chloride has been refined to eliminate bias associated with visual differentiation between varying degrees of tetrazolium reduction and to predict tissue survival at a later date. An advantage of the method described here is that a small amount of tissue (50-100 mg) is required; this, therefore, allows for hardiness determinations at precise locations on the plant. The high correlation between cold injury and triphenyl tetrazolium chloride reduction may be due to cofactor and substrate limitations rather than inactivation of dehydrogenases.
472 citations
TL;DR: The influence of nitrate, urea, and ammonium nitrogen nutrition on the cation-anion balance and the organic acid content of the plant has been considered and the effects of these different nitrogen forms on both the pH ofThe plant and the nutrient medium and its consequences discussed.
Abstract: An investigation was carried out to study the cation-anion balance in different tissues of tomato plants supplied with nitrate, urea, or ammonium nitrogen in water culture. Irrespective of the form of nutrition, a very close balance was found in the tissues investigated (leaves, petioles, stems, and roots) between total cations (Ca, Mg, K and Na), and total anions (NO 3 − , H 2 PO 4 − , SO 4 −− , Cl − ) total non-volatile organic acids, oxalate, and uronic acids. In comparison with the tissues of the nitrate fed plants, the corresponding ammonium tissues contained lower concentrations of inorganic cations, and organic acids and a correspondingly higher proportion of inorganic anions. Tissues from the urea plants were intermediate between the other 2 treatments. These results were independent of concentration or dilution effects, caused by growth. In all tissues approximately equivalent amounts of diffusible cations (Ca ++ , Mg ++ , K + and Na + ), and diffusible anions (No 3 − , SO 4 −− , H 2 PO 4 − , Cl − ) and non-volatile organic acids were found. An almost 1:1 ratio occurred between the levels of bound calcium and magnesium, and oxalate and uronic acids. This points to the fact that in the tomato plant the indiffusible anions are mainly oxalate and pectate. Approximately equivalent values were found for the alkalinity of the ash, and organic anions (total organic acids including oxalate, and uronic acids). The influence of nitrate, urea, and ammonium nitrogen nutrition on the cation-anion balance and the organic acid content of the plant has been considered and the effects of these different nitrogen forms on both the pH of the plant and the nutrient medium and its consequences discussed.
391 citations
TL;DR: It was concluded that, although stem characteristics may affect the measurements, pressure chamber determinations were sufficiently close to psychrometer measurements that the pressure chamber may be used for relative measurements of leaf water potentials, especially in sunflower and yew.
Abstract: Leaf water potentials were estimated from the sum of the balancing pressure measured with a pressure chamber and the osmotic potential of the xylem sap in leafy shoots or leaves. When leaf water potentials in yew, rhododendron, and sunflower were compared with those measured with a thermocouple psychrometer known to indicate accurate values of leaf water potential, determinations were within +/- 2 bars of the psychrometer measurements with sunflower and yew. In rhododendron. water potentials measured with the pressure chamber plus xylem sap were 2.5 bars less negative to 4 bars more negative than psychrometer measurements.The discrepancies in the rhododendron measurements could be attributed, at least in part, to the filling of tissues other than xylem with xylem sap during measurements with the pressure chamber. It was concluded that, although stem characteristics may affect the measurements, pressure chamber determinations were sufficiently close to psychrometer measurements that the pressure chamber may be used for relative measurements of leaf water potentials, especially in sunflower and yew. For accurate determinations of leaf water potential, however, pressure chamber measurements must be calibrated with a thermocouple psychrometer.
339 citations
TL;DR: The production of protease by isolated aleurone layers of barley in response to gibberellic acid has been examined, giving some credence to the hypothesis that the effect of gibb Berellic Acid is to promote the simultaneous synthesis and secretion of a group of hydrolases.
Abstract: The production of protease by isolated aleurone layers of barley in response to gibberellic acid has been examined. The protease arises in the aleurone layer and is mostly released from the aleurone cells. The courses of release of amylase and protease from aleurone layers, the dose responses to gibberellic acid and the effects of inhibitors on the production of both enzymes are parallel. As is the case for amylase, protease is made de novo in response to the hormone. These data give some credence to the hypothesis that the effect of gibberellic acid is to promote the simultaneous synthesis and secretion of a group of hydrolases.
283 citations
TL;DR: Peppermint (Mentha piperita L.) was grown in a growth chamber under several combinations of temperature and illumination, and the monoterpenes of each leaf pair were analyzed by gas chromatography, suggesting that the oxidation-reduction level of the monoterspenes reflects the oxidizing state of the respiratory coenzymes of the terpene-producing cells.
Abstract: Peppermint (Mentha piperita L.) was grown in a growth chamber under several combinations of temperature and illumination, and the monoterpenes of each leaf pair were analyzed by gas chromatography. Effects on the monoterpenes could be seen in the new leaves after a few days in the growth chamber. Long-day conditions enhanced growth, with a corresponding increase in the total amount of monoterpenes. Either short nights or cool nights, combined with full light intensity during the day, enhanced the formation of menthone and depressed the accumulation of menthofuran and pulegone. Experiments with interrupted night and with low light intensity indicated that photoperiod, as such, does not directly influence the terpene composition. It is suggested that the oxidation-reduction level of the monoterpenes reflects the oxidation-reduction state of the respiratory coenzymes of the terpene-producing cells, and that this, in turn, depends on the concentrations of respiratory substrates in the cells. This suggestion is based on the likelihood that warm nights cause depletion of respiratory substrates, resulting in oxidizing conditions, while cool nights preserve high levels of respiratory substrates, and thus maintain reducing conditions.
270 citations
TL;DR: Data are consistent with the hypothesis that the expression of the GA effect requires the synthesis of enzyme-specific RNA molecules, and the similarity in the kinetics of inhibition between abscisin and 8-azaguanine or 6-methylpurine on the other suggests that abscillin may exert its action by inhibiting the synthesisOf these enzyme- specific RNA molecules or by preventing their incorporation into an active enzyme-synthesising unit.
Abstract: Gibberellic acid (GA) enhances the synthesis of alpha-amylase and ribonuclease in isolated aleurone layers and this process is inhibited by abscisin. Removal of gibberellic acid in mid-course of alpha-amylase production results in a slowing down of alpha-amylase synthesis, suggesting a continued requirement of GA for enzyme synthesis. This is paralleled by a continuous requirement for RNA synthesis. Addition of 6-methylpurine or 8-azaguanine in mid-course results in an inhibition of alpha-amylase synthesis within 3 to 4 hours. However, actinomycin D added in mid-course is almost without effect. This is not due to its failure to enter the cells, because it does inhibit (14)C-uridine incorporation at this stage. Addition of abscisin to aleurone layers which are synthesizing alpha-amylase results in an inhibition of this synthesis within 2 to 3 hours. Cycloheximide on the other hand inhibits enzyme synthesis immediately upon its addition. These data are consistent with the hypothesis that the expression of the GA effect requires the synthesis of enzyme-specific RNA molecules. The similarity in the kinetics of inhibition between abscisin on the one hand and 8-azaguanine or 6-methylpurine on the other suggests that abscisin may exert its action by inhibiting the synthesis of these enzyme-specific RNA molecules or by preventing their incorporation into an active enzyme-synthesising unit.
255 citations
TL;DR: The expression of a circadian rhythm of conidiation by timex, a strain of Neurospora crassa, is inhibited by growth in continuous white light, and the action spectrum suggests that a carotenoid or flavin compound may be the photoreceptor, but does not allow one to determine conclusively whether the receptor is indeed a carOTenoid, flavin, or some other unrelated pigment.
Abstract: The expression of a circadian rhythm of conidiation by timex, a strain of Neurospora crassa, is inhibited by growth in continuous white light. The action spectrum for this effect has a strong peak (with minor subpeaks) in the blue region of the visible spectrum, and a broad shoulder in the near ultraviolet. This action spectrum suggests that a carotenoid or flavin compound may be the photoreceptor, but does not allow one to determine conclusively whether the receptor is indeed a carotenoid, flavin, or some other unrelated pigment. Two lines of evidence suggest that a carotenoid is not the photoreceptor. First, the in vivo absorption spectrum of timex (representing the sum of the spectra of the individual pigments present, predominantly carotenoids) has peaks at wavelengths 10 to 20 mmu longer than those of the action spectrum peaks. Second, an albino-timex has normal photosensitivity, a situation requiring that the photoreceptor, if carotenoid, be a quantitatively minor constituent of the total carotenoid complement.The magnitude and direction of phase-shift resulting from a standard dose of white light given at different times in the daily cycle of timex varies in the manner reported for other organisms. Additional phase-shift experiments have shown that there are no major transients in the attainment of a new equilibrium after a phase-shifting perturbation, and that 2 light reactions (rapidly and slowly saturating) may be involved in the phase-shift response.
220 citations
TL;DR: It is concluded that ethylene participates in the geotropic response of roots, but not that of stems.
Abstract: Low concentrations of indole-3-acetic acid inhibit the growth of pea root sections by inducing the formation of the growth regulator, ethylene gas. Ethylene is produced within 15 to 30 minutes after indole-3-acetic acid is applied and roots begin to swell immediately after they are exposed to the gas. Carbon dioxide competitively inhibits ethylene action in roots, impedes their geotropic response, and partially reinstates auxin inhibited growth. It is concluded that ethylene participates in the geotropic response of roots, but not that of stems.
186 citations
TL;DR: The heterogeneity of the peroxidases in peas was examined by starch gel electrophoresis, and the band patterns in corresponding organs from different varieties were far more alike than were the patterns in the different organs within each variety.
Abstract: The heterogeneity of the peroxidases in peas was examined by starch gel electrophoresis. Comparisons were made between tall and dwarf cultivars and among organ systems developed in light and darkness. Isoperoxidase bands could be grouped as cathodic, anodic and near-neutral (at pH 9.0) types. The cathodic set stained well with guaiacol oxidation products whereas some anodic bands reacted preferentially with 2,6-dimethoxyphenol. Some near-neutral bands were aceto-carmine positive and may have been organellar. Each organ had a characteristic isozyme pattern, and the band patterns in corresponding organs from different varieties were far more alike than were the patterns in the different organs within each variety. Ontogenetic changes were marked in all 3 organ systems, principally in the cathodic bands. The effect of light on isozymal patterns was quantitative rather than qualitative, possibly influencing the isoperoxidases secondarily via its effect upon organ physiology and development.
TL;DR: Exposure of etiolated seedlings to a single dose of red light caused a transient decrease in ethylene production and a corresponding increase in plumular expansion, suggesting that the ethylene intervenes as a regulator in the phytochrome control of plumularansion.
Abstract: The production of ethylene by etiolated pea epicotyls (Pisum sativum L., cv. Alaska) is confined to the plumule and plumular hook portion of the epicotyl, and occurs at a rate of about 6 mul.kg(-1).hr(-1). Such a rate is sufficient to give physiologically active concentrations of ethylene within the tissue. Exposure of etiolated seedlings to a single dose of red light caused a transient decrease in ethylene production and a corresponding increase in plumular expansion. Far-red irradiation following the red light treatment decreased the red effect to the level achieved by the far-red alone, suggesting that the ethylene production mechanism is controlled by phytochrome and thus that the ethylene intervenes as a regulator in the phytochrome control of plumular expansion.
TL;DR: That remiioval of the pollinia per se is not responsible for floral fading is indicated bv experiments with Phalcanopsis Pamiiala, which have showun that disturbance of the connection between the rostelluii and the upper surface of the sticky disk with which it is in intimate contact.
Abstract: Blossoms fromii several varieties of orchids fade prematurely when their pollinia are removed or disturbed (2,3,7), and also if the flowers are gassed with ethylene (8, 9, 10), pollinated (3, /7), or treated with an auxin (3, 7). During natural Ifading as well as that induced by removal of the pollinia, ethylene is evolved (2, 3, 9, 10), andtherefore it has ibeen inferred that the gas is the catusative agent. Ethylene evolution also is stimlulated Nvllen plant tissuies are exposed to auXin ( 1, 4), andl wve now )resent evidence that this response is the basis for flower fading1 indtuced by pollination or an,xin application. Blossoms from ['undo Petanboeran or Van(la Rose .M1arie were iplaced wvitlh their cut ends in a beaker of water, and( sealed nudtler a 200 nlm bell jar having a ground glass base anid a side arm closed with a rubber vaccine cap. Otlher flowers svere pollinated, emilasculated (pollinia removed), self-pollinated, or treated with 5 mnm IAA in lanolin or 0.1 mm carboxyl lajbeled '-C-IAA in 0.8 % agar (specific activity 8 mc/mmole) applied to the stigmas, and then the flowers were sealed under a bell jar. Air samples, removed with a hlypodernmic syringe, were analyzed by gas chromatography to determine the ethylene content (4), anid at least every 10 hours the chambers were completely aerated. Ethylene evolution by isolated sepals and petals, columns or lips was measured by incubating each tissue in a 50 ml flask fitted with a vaccine cap. and sampling the air in the flask at hourly intervals. Cutting the floral parts induced a wound response, lasting about 1 hour, during whichi time 1.5 mkdJ of ethylene per gram of cut control tissue 'was produced. Treated cut tissue was only considered to produce ethylene if the total evolution exceeded this value, and if the extra evolution contintued at a nearlv constant rate for at least 4 hours. Intact blossoms were also placed in desiccators and gassed for 3 to 24 hours with 10 ppnm ethylene. In suich cases the flowNers were aerated f'or at least 1 hour 'before ethy;lenle production was measured in order to remiove any ethylene contained within the tissue. The sipread of 1AC-IAA from the stigmas of the flower was determined by excising the 'floral parts from representative blossomiis after 3, 6, and 24 hours and dividing these into pieces as illustrated in figure 3. Each piece was ground with ethanol on a planchet, dried, and counted w ith a 21 % efficient gas flow counter. When blossoms of V. Rose Marie were emasculated, ethylene evolution began after a 10 hour lag period (fig 1), and fading became obvious after an additional. 8 to 12 hours. A similar time course of ethvlene production and fadintg hias been reported for V. Miss Agnes Joaquitin blossoms after renoval of tlieir pollinia (2). whereas F. Petarnioeran, a semiterete of heav\ texture, fades after a considerablv longer lag(fig 2). That remiioval of the pollinia per se is not responsible for floral fading is indicated bv experiments with Phalcanopsis Pamiiala (7) which have showun that disturbance of the connection between the rostelluii (tthe structure supporting the pollinia) and the upper surface of the sticky disk with which it is in intimate contact, suffices to induce the response. There is no indication that this tvpe of fading ,in.volves a release or production of auxin, for it does not result in swelling of the column whereas both auxin application and pollination bring about such an effect. Self ,pollination induces ethylene formation within 1 hour in V. Rose Marie, and flower fading within 8 to 10 bhours (ifig 1). A simil.ar time course was observed with V. Petamboerant even when the flower was pollinated with its own pollinia intact (fig 2). This response was duplicated by applying enough IAA (5 mm) in lanolin paste to fill the stigmatic cavity (figo2), and exactlv the same result was obtained using 0.1 bM '*C-IAA in 0.8 % agar. Other cases .n which the fading response caused by pollination is stimulated by auxin have been reported (3, 7), and led to the suggestion that the large quantity df auxin contained in the pollen is responsible for the pollination effect (7). As auxin stimulates ethylene evolution in these blossoms and other plant tissues within an hour, an(d since ethylene causes floral fading, it is logical to conclude that this is the mlechanismll involved. Auxin induced ethylene formation must also influence the growvth of the column for within 2 hours after application of pollinia or auxin this structure
TL;DR: Radioactively labeled Na(+) absorbed by barley roots was sequestered in an intracellular compartment or compartments ("inner" spaces) in which it was only very slowly exchangeable with exogenous Na(+).
Abstract: Radioactively labeled Na + absorbed by barley roots was sequestered in an intracellular compartment or compartments (“inner” spaces) in which it was only very slowly exchangeable with exogenous Na + . Absorption of this fraction proceeded at a constant rate for at least 1 hour. When the rate of Na + absorption was examined over the range of concentrations, 0.005 to 50 mm, the isotherm depicting the relation showed dual kinetics as follows. Over the range, 0.005 to 0.2 mm, a single Michaelis-Menten term describes the relation between the concentration of Na + and the rate of its absorption. The mechanism of Na + absorption operating over this range of concentrations, mechanism 1 of alkali cation transport, is severely inhibited in the presence of Ca 2+ and virtually rendered inoperative for Na + transport by the combined presence of Ca 2+ and K + . The mechanism is equally effective in Na + transport whether Cl − or F − is the anion, but is somewhat inhibited when the anion is SO 4 2− . Over the high range of concentrations, 0.5 to 50 mm Na + , a second, low-affinity mechanism of Na + absorption comes into play. In the presence of Ca 2+ and K + , this mechanism 2 is the only one to transport Na + effectively, since Na + absorption via mechanism 1 is virtually abolished under these conditions. Anaerobic conditions, low temperature, and the uncoupler, 2,4-dinitrophenol, inhibit Na + absorption both at low and high Na + concentrations.
TL;DR: Initial changes in these processes preceded the detection of modifications of fine structure; however, each continued with further breakdown of the chloroplasts, and distinct grana could not be detected.
Abstract: Ammonium toxicity resulted in morphological modifications of tomato leaf chloroplasts. The chloroplasts, which are normally flattened around the protoplast periphery, became ellipsoidally rounded and dispersed through the protoplasm. The first apparent effect of plastid degradation was development of many vesicles from the fretwork. Later the grana lamellae swelled, and some disappeared. Eventually, distinct grana could not be detected.Ammonium accumulation, chlorophyll loss, and photosynthetic decrease occurred simultaneously. Initial changes in these processes preceded the detection of modifications of fine structure; however, each continued with further breakdown of the chloroplasts.
TL;DR: Findings support previous conclusions to the effect that the active sites of mechanism 2 have higher affinity for Na(+) than for K(+), whereas the reverse is true for mechanism 1.
Abstract: When barley roots absorb Na(+) at concentrations ranging from 1 to 50 mm, in the presence of low concentrations of Ca(2+) and K(+), absorption of Na(+) is mediated by carrier mechanism 2 of alkali cation transport, mechanism 1 being unavailable for Na(+) transport under these conditions. The absorption isotherm depicting the rate of Na(+) absorption as a function of the external Na(+) concentration, over the 1 to 50 mm range of concentrations, shows several inflections. This stepwise response occurs whether Cl(-) or SO(4) (2-) is the counterion, but actual rates of Na(+) absorption are lower in the latter case.When the concentration of Na(+) is 50 mm, and the concentration of either K(+) or Ca(2+) is increased from nil to 50 mm, the rate of absorption of Na(+) is diminished not as a smooth function of increasing concentrations of the interfering ions but stepwise. Similarly, when the concentration of K(+) is 50 mm, and the concentration of either Na(+) or Ca(2+) is increased from nil to 50 mm, the rate of absorption of K(+) is diminished not as a smooth function of increasing concentrations of the interfering ions but stepwise.Together, this evidence supports the previous conclusion to the effect that mechanism 2 of alkali cation transport possesses a spectrum of carrier sites with different ionic affinities.When both K(+) and Na(+) are presented at equivalent concentrations over the 1 to 50 mm range, mechanism 2 transports Na(+) almost exclusively, and mechanism 1 K(+) almost exclusively. These findings support previous conclusions to the effect that the active sites of mechanism 2 have higher affinity for Na(+) than for K(+), whereas the reverse is true for mechanism 1.
TL;DR: A test was made of how closely the Nernst equation describes the electrochemical equilibrium in seedling tissues and it would appear that the root is the site of regulation of ion uptake in the intact plant although other correlative mechanisms may be involved.
Abstract: The relationships of concentration gradients to electropotential gradients resulting from passive diffusion processes, after equilibration, are described by the Nernst equation The primary criterion for the hypothesis that any given ion is actively transported is to establish that it is not diffusing passively A test was made of how closely the Nernst equation describes the electrochemical equilibrium in seedling tissues Segments of roots and epicotyl internodes of pea (Pisum sativum var Alaska) and of roots and coleoptiles of oat (Avena sativa var Victory) seedlings were immersed and shaken in defined nutrient solutions containing eight major nutrients (K+, Na+, Ca2+, Mg2+, Cl−, NO3−, H2PO4− and SO42−) at 1-fold and 10-fold concentrations The tissue content of each ion was assayed at 0, 8, 24, and 48 hours A near-equilibrium condition was approached by roots for most ions; however, the segments of shoot tissue generally continued to show a net accumulation of some ions, mainly K+ and NO3− Only K+ approached a reasonable fit to the Nernst equation and this was true for the 1-fold concentration but not the 10-fold The data suggest that for Na+, Mg2+, and Ca2+ the electrochemical gradient is from the external solution to the cell interior; thus passive diffusion should be in an inward direction Consequently, some mechanism must exist in plant tissue either to exclude these cations or to extrude them (eg, by an active efflux pump) For each of the anions the electrochemical gradient is from the tissue to the solution; thus an active influx pump for anions seems required Root segments approach ionic equilibrium with the solution concentration in which the seedlings were grown Segments of shoot tissue, however, are far removed from such equilibration Thus in the intact seedling the extracellular (wall space) fluid must be very different from that of the nutrient solution bathing the segments; it would appear that the root is the site of regulation of ion uptake in the intact plant although other correlative mechanisms may be involved
TL;DR: Nonaqueous and aqueous isolation techniques were used to establish that nitrite reductase is localized within the chloroplasts, but that nitrate reduct enzyme and glutamic acid dehydrogenase are not.
Abstract: Greenhouse grown seedlings of corn (Zea mays L.) and foxtail (Setaria faberii Herrm.) were used as source material in determining the intracellular localization of nitrate reductase, nitrite reductase, and glutamic acid dehydrogenase, Nonaqueous and aqueous isolation techniques were used to establish that nitrite reductase is localized within the chloroplasts, but that nitrate reductase and glutamic acid dehydrogenase are not. Nonaqueous isolation gives distribution patterns of nitrite reductase which are the same as those observed for NADP-dependent 3-phosphoglyceraldehyde dehydrogenase but which differ drastically from the patterns observed for pyruvic acid kinase. The distribution patterns for nitrate reductase are the same as those of pyruvic acid kinase. The techniques used do not eliminate the possibility that nitrate reductase and pyruvic acid kinase are localized on the external chloroplast membrane.The data obtained establish that glutamic acid dehydrogenase of green leaves is localized within the mitochondria.
TL;DR: The hypothesis that the normal supply of root cytokinins is important in shoot metabolism is supported, as well as the differences in response to kinetin of stressed and control discs, which suggest a lower endogenous level of cytokinin in the stressed discs.
Abstract: The capacity of tobacco ( Nicotiana rustica ) leaf discs to incorporate l-leucine 14 C into proteins was measured. Leaf discs were obtained from plants which experienced soil water depletion, or which were exposed to a saline or osmotic stress in the root medium. The stresses were brief of relatively short duration and water potential did not decrease below 4 bars in the root media. Leaf discs were sampled 2 hours after stress removal, achieved by reirrigation, or replacement of saline and osmotic solutions with normal nutrient solution. Plants were always turgid when leaves were sampled. All stressed tissues showed reduced capacity to incorporate l-leucine 14 C into protein. The reduction was about 50% and could not be attributed either to reduced uptake into the discs, or to possible isotopic dilution. Incorporation decreased progressively with leaf age in control discs as well as in stressed leaf discs. At all ages tested, incorporation in stressed discs was lower than that of the control. Full recovery of incorporation capacity in stressed discs was obtained when discs were sampled 72 hours after stress removal but not earlier. Kinetin pretreatment prior to incubation with labelled leucine partially restored incorporation in stressed discs. The differences in response to kinetin of stressed and control discs suggest a lower endogenous level of cytokinins in the stressed discs. The results were qualitatively similar regardless of the kind of stress given to the plants during pretreatment. This supports the hypothesis that the normal supply of root cytokinins is important in shoot metabolism.
TL;DR: The mitochondria isolated from dark-grown mung bean hypocotyls oxidize succinate, l-malate, and externally added reduced nicotine adenine dinucleotide (NADH) with good respiratory control.
Abstract: The mitochondria isolated from dark-grown mung bean hypocotyls oxidize succinate, l-malate, and externally added reduced nicotine adenine dinucleotide (NADH) with good respiratory control. While the pattern of respiration resembles that of animal mitochondria, there are 4 basic differences between the respiratory properties of mung bean and animal mitochondria: A) the ability to oxidize NADH, B) the pattern of succinate and malate oxidation, C) the rate of oxygen uptake, and D) the adenosine-5′-diphosphate to oxygen ratios. The apparent `Km9 for malate of mung bean mitochondria is about one order higher than that expected from malic dehydrogenase in animal mitochondria, whereas the affinity for phosphate is about 5 times higher with plant mitochondria than rat-liver mitochondria. While the half-maximal stimulation of respiration by adenosine-5′-diphosphate is practically identical to that of animal mitochondria, higher concentrations of adenosine-5′-diphosphate cause some decrease in its stimulating action.
TL;DR: It is suggested that peanut spherosomes are principal sites of lipid storage but not of lipid degradation.
Abstract: Spherosomes of cotyledons of germinating peanuts (Arachis hypogea L.) were examined by electron microscopy and found to be particles about 1.0 to 2.0 μ in diameter bounded by a limiting membrane. Isolated spherosomes appear similar to spherosomes in situ. The isolated spherosomes are composed of 98.1% total lipids, 0.77% phospholipid and 1.27% protein by dry weight. The amounts of protein and phospholipid associated with the isolated spherosomes are sufficient to account for limiting membranes. Spherosomes amply account for the lipid in a peanut cotyledon. The activity of lipase and fatty acyl-Coenzyme A synthetase is not associated with the isolated spherosomes. This suggests that peanut spherosomes are principal sites of lipid storage but not of lipid degradation.
TL;DR: The rate and pathways of atrazine metabolism are important in determining the tolerance of plants to the herbicide and the influence of this pathway in determining tolerance of Plants to Atrazine is discussed.
Abstract: Metabolism of the herbicide 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) was investigated in resistant corn (Zea mays L.) and sorghum (Sorghum vulgare Pers.), intermediately susceptible pea (Pisum sativum L.), and highly susceptible wheat (Triticum vulgare Vill.) and soybean (Glycine max Merril.). This study revealed that 2 possible pathways for atrazine metabolism exist in higher plants. All species studied were able to metabolize atrazine initially by N-dealkylation of either of the 2 substituted alkylamine groups. Corn and wheat, which contain benzoxazinone, also metabolized atrazine initially by hydrolysis in the 2-position of the s-triazine ring to form hydroxyatrazine. Subsequent metabolism by both pathways resulted in the conversion of the parent atrazine to more polar compounds and eventually into methanol-insoluble plant residue. No evidence for s-triazine ring cleavage was obtained.Both pathways for atrazine metabolism appear to detoxify atrazine. The hydroxylation pathway results in a direct conversion of a highly phytotoxic compound to a completely non-phytotoxic derivative. The dealkylation pathway leads to detoxication through one or more partially detoxified, stable intermediates. Therefore, the rate and pathways of atrazine metabolism are important in determining the tolerance of plants to the herbicide. Both quantitative and qualitative differences in atrazine metabolism were detected between resistant, intermediately susceptible, and susceptible species. The ability of plants to metabolize atrazine by N-dealkylation and the influence of this pathway in determining tolerance of plants to atrazine are discussed.
TL;DR: Results were interpreted to mean that the bordered pits on the tracheids of gymnosperms function to isolate the freezing sap in each tracheid so that the expansion of water upon freezing not only eliminates any existing tension but also develops positive pressure in the sap.
Abstract: Freezing of stem sections and entire twigs of hemlock (Tsuga canadensis) has been demonstrated to occur without increasing the resistance to the movement of water through the frozen part after rewarming. This was interpreted to mean that freezing did not produce cavitation in the xylem sap even though A) the sap was unquestionably frozen; B) it contained dissolved gases; and C) it was under tension before freezing and after. Freezing stem sections of some other evergreen gymnosperms during the summer again produced no evidence for cavitation of the xylem sap. On the other hand, freezing stem sections of some angiosperms invariably increased the resistance to sap flow leading to wilting and death in a few hours when the sap tension was at normal daytime values at the time of freezing. These results were interpreted to mean that the bordered pits on the tracheids of gymnosperms function to isolate the freezing sap in each tracheid so that the expansion of water upon freezing not only eliminates any existing tension but also develops positive pressure in the sap. Dissolved gases frozen out of solution may then be redissolved under this positive pressure as melting occurs. As the bubbles are reduced in size by this ice pressure developed in an isolated tracheid, further pressure is applied by the surface tension of the water against air. If the bubbles are redissolved or are reduced to sufficient small size by the time the tension returns to the sap as the last ice crystals melt, then the internal pressure from surface tension in any existing small bubbles may exceed the hydrostatic tension of the melted sap and the bubbles cannot expand and will continue to dissolve.
TL;DR: It is established that a fully active photosystem I can be associated with single unfolded thylakoids and the complete photosynthetic electron transport system including the oxygen evolving apparatus of photosystem II, on the other hand, appears to require a close packing of at least 2 thylAKoids.
Abstract: Photosynthetic reactions of whole leaves and isolated chloroplasts from various mutants of Nicotiana tabacum have been correlated to the lamellar structure seen in electron micrographs of the chloroplasts. In this way it could be established that a fully active photosystem I can be associated with single unfolded thylakoids. The complete photosynthetic electron transport system including the oxygen evolving apparatus of photosystem II, on the other hand, appears to require a close packing of at least 2 thylakoids. The unusual high capacity for photosynthesis observed earlier for leaves of certain aurea mutants is reflected by a correspondingly high activity of the isolated chloroplasts in the Hill reaction. These chloroplasts contain extended areas where 2 thylakoids touch by forming simple lamellar overlappings instead of the familiar stacks of lamellar discs.
TL;DR: Some microscope observations of the protein bodies of the cotyledon cells of the soybean (Glycine max) are described, together with changes in their appearance which occur on germination.
Abstract: Some microscope observations of the protein bodies of the cotyledon cells of the soybean (Glycine max) are described, together with changes in their appearance which occur on germination. Density gradient centrifugation permits the isolation of protein bodies from soymeal. They contain about 70% of the protein of the bean. Only 1 protein could be detected in them: glycinin, the major soybean protein.The protein bodies were fractionated to light and heavy fractions. The former contained 97.5% protein, the latter 78.5%. RNA, phytic acid and lipids were also present. The 2 fractions probably differ only in the extent of contamination by other cell fragments.
TL;DR: Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake and appear to be associated with the low-salt component of ion uptake.
Abstract: Excised roots of barley (Hordeum vulgare, var. Campana) were incubated in KCl, K(2)SO(4), CaCl(2), and NaCl solutions at concentrations of 10(-5) to 10(-2)n. Changes in substrate solution pH, cell sap pH, and organic acid content of the roots were related to differences in cation and anion absorption. The pH of expressed sap of roots increased when cations were absorbed in excess of anions and decreased when anions were absorbed in excess of cations. The pH of the cell sap shifted in response to imbalances in cation and anion uptake in salt solutions as dilute as 10(-5)n. Changes in cell sap pH were detectable within 15 minutes after the roots were placed in 10(-3)n K(2)SO(4). Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake. Changes in organic acid content in response to differential cation and anion uptake appear to be associated with the low-salt component of ion uptake.
TL;DR: Inhibition of the polar transport system by ethylene could underlie certain responses in which the gas produces symptoms of auxin deficiency.
Abstract: Applied ethylene influences the growth of etiolated pea stem sections cut from untreated plants, but has no effect on 14C-indoleacetic acid uptake, polar transport or destruction. However, the capacity of the polar auxin transport system is markedly reduced in sections cut from plants grown in ethylene, while the velocity of auxin transport is unchanged under these conditions. Inhibition of the polar transport system by ethylene could underlie certain responses in which the gas produces symptoms of auxin deficiency.
TL;DR: The results show that amino acids which on deamination can give rise to intermediates in the pathway of conversion of fat to sucrose are largely converted to Sucrose and the nitrogen transported as glutamine.
Abstract: During germination of the castor bean all of the contents of the endosperm are ultimately transported to the embryo through the cotyledon or respired. A net loss of nitrogen from the endosperm begins about the fourth day, i.e. at the time when embryo growth and fat breakdown are also beginning. Amino acid analysis of the exudate from the cotyledons, still enclosed in the endosperm, showed that the amounts of aspartate, glutamate, glycine, and alanine were very low and that glutamine made up 40% of the amino acids in the exudate.Amino acids labeled with (14)C were applied to intact excised endosperms to follow utilization. Aspartate, glutamate, alanine, glycine, serine, and leucine were converted to sugar to varying extents. Proline, arginine, valine, and phenylalanine were not appreciably converted to sugars. Proline and glutamate were converted to glutamine. When (14)C-glutamate, aspartate, and alanine were added to the outer endosperm of intact seedlings, only sugars and glutamine contained appreciable label in the exudate. When (14)C-valine was added, it was virtually the only labeled compound in the exudate.The results show that amino acids which on deamination can give rise to intermediates in the pathway of conversion of fat to sucrose are largely converted to sucrose and the nitrogen transported as glutamine. Other amino acids released from the endosperm protein are transported intact into the seedling axis. Some carbon from the gluconeogenic amino acids is also transported as glutamine.
TL;DR: The failure to detect Glycolate oxidase, the low level glycolate-(14)C metabolism, and the formation of serine from phosphoglycerate rather than from glycolates are consistent with the concept of an incomplete glycolATE pathway in algae.
Abstract: No glycolate oxidase activity could be detected by manometric, isotopic, or spectrophotometric techniques in cell extracts from 5 strains of algae grown in the light with CO(2). However, NADH:glyoxylate reductase, phosphoglycolate phosphatase and isocitrate dehydrogenase were detected in the cell extracts. The serine formed by Chlorella or Chlamydomonas after 12 seconds of photosynthetic (14)CO(2) fixation contained 70 to 80% of its (14)C in the carboxyl carbon. This distribution of label in serine was similar to that in phosphoglycerate from the same experiment. Thus, in algae serine is probably formed directly from phosphoglycerate. These results differ from those of higher plants which form uniformly labeled serine from glycolate in short time periods when phosphoglycerate is still carboxyl labeled. In glycolate formed by algae in 5 and 10 seconds of (14)CO(2) fixation, C(2) was at least twice as radioactive as C(1). A similar skewed labeling in C(2) and C(3) of 3-phosphoglycerate and serine suggests a common precursor for glycolate and 3-phosphoglycerate. Glycine formed by the algae, however, from the same experiments was uniformly labeled. Manganese deficient Chlorella incorporated only 2% of the total (14)CO(2) fixed in 10 minutes into glycolate, while in normal Chlorella 30% of the total (14)C was found in glycolate. Manganese deficient Chlorella also accumulated more (14)C in glycine and serine.Glycolate excretion by Chlorella was maximal in 10 mm bicarbonate and occurred only in the light, and was not influenced by the addition of glycolate. No time dependent uptake of significant amounts of either glycolate or phosphoglycolate was observed. When small amounts of glycolate-2-(14)C were fed to Chlorella or Scenedesmus, only 2 to 3% was metabolized after 30 to 60 minutes. The algae were not capable of significant glycolate metabolism as is the higher plant. The failure to detect glycolate oxidase, the low level glycolate-(14)C metabolism, and the formation of serine from phosphoglycerate rather than from glycolate are consistent with the concept of an incomplete glycolate pathway in algae.
TL;DR: Invertase inhibitor was extracted from potato tubers and purified nearly 1000-fold and completely inhibited potato tuber invertase and a number of other plant invertases.
Abstract: Invertase inhibitor was extracted from potato tubers and purified nearly 1000-fold. The purification procedure involved precipitation at pH 4.0, fractionation with ammonium sulfate, adsorption on alumina Cγ gel, and gel filtration on Sephadex G-100 and DEAE-Sephadex A-50. The product obtained was homogeneous to electrophoresis on polyacrylamide gel. Exclusion chromatography on Sephadex G-100 indicated a molecular weight of about 17,000. The inhibitor did not inhibit yeast, Neurospora, and several plant invertases. It completely inhibited potato tuber invertase and a number of other plant invertases. Some plant invertases were partially inhibited.