Showing papers in "Planta in 1971"
TL;DR: The findings suggest that auxin induces a proton accumulation in a cell wall compartment and, as a consequence, enzymatic cell wall softening, which may be the last step in the process of cell elongation.
Abstract: 1. Sections of auxin-starved hypocotyls of Helianthus annuus do not show any significant growth rate in water of buffers of pH\>-6. However, in buffers with pH-values of approximately 4, elongation growth is observed; its rate is similar to the rate of auxin-stimulated growth (after 6 h incubation). \3- This phenomenon of acid-induced growth occurs also under anaerobic conditions in contrast to auxin-induced growth (Hager 1962). 2. Intact cell wall aggregates of Helianthus hypocotyls were obtained by complete plasmolysis of hypocotyls in 50% glycerol; cell wall associated enzymes were still active after this treatment, at least in part. While cell walls in solutions of pH\>-6 show only a small plastic extension during the first minute in response to a 50 g stretching force, a constant rate of elongation over longer periods of time (measured up to 1 h) is observed in weakly acid buffers. The highest rate of elongation is observed at about pH 4. This acid-induced plastic extension is completely inhibited by Cu(2+)-ions (5mM); the elongation of cell walls is apparently the consequence of an enzyme-catalysed increase in plasticity having a pH optimum of about 4. The pH optimum of acid-induced cell wall extension observed during stretching of plasmolysed hypocotyls coincides with the pH optimum of acid-induced growth of intact hypocotyl sections (around pH 4). 3. Under anaerobic conditions the growth rate of intact coleoptiles stays unchanged (at a low value) if the sections are incubated in a buffer of pH 5.0. Higher proton concentrations, however, stimulate growth immediately, whereas low proton concentrations are inhibitory (Fig. 7 and 8). The strongest initial growth response is elicited by buffers or acids of pH 3.9 (Fig. 9). Acid-induced growth of coleoptiles with a similar pH optimum is also found under anaerobic conditions. The growth of coleoptile cylinders can be switched on or off by repeatedly changing to acid or basic medium, respectively (under conditions of anaerobiosis) (Fig. 10). IAA-induced growth (aerobic conditions, pH≥5) can also be inhibited immediately by basic buffers or NaOH-solutions, and resumes after the pH value is lowered (Fig. 11). This pH-dependency may be taken as an indication that auxin affects the same reaction which is stimulated by high proton concentrations and which may be the last step in the process of cell elongation. CCCP, known to make membranes permeable for protons, rapidly inhibits the auxin-induced elongation growth (pH 6,5) when applied at a concentration which does not influence respiration; removal of CCCP shows that the growth inhibition by CCCp is partly reversible (Fig. 12). In contrast, acid-induced elongation growth (pH 4) shows inhibition by CCCP not before 10 min after application.-These findings suggest that auxin induces a proton accumulation in a cell wall compartment and, as a consequence, enzymatic cell wall softening. Such an accumulation could be brought about by an auxin-activated, membrane-bound, anisotropic ATPase or ion pump. The notion that ATPases or pumps may be located in the outer layers of the cell membrane is supported by the observation that addition of ATP to coleoptile cylinders under anaerobic conditions results in an immediate stimulation of elongation (Fig. 14). This effect is further enhanced by Mg(2+)-and K(+)-ions (Figs. 15 and 16). Mg(2+) can be partly replaced by Ca(2+). The stimulatory effect of ATP is increased considerably if the coleoptiles are treated with IAA under aerobic conditions prior to ATP addition (Figs. 15 b and 14). ITP, GTP, UTP, and CTP induce elongation growth under anaerobiosis similarly to ATP. In the presence of ITP or GTP the increase in growth rate is maintained over a longer period of time than in the presence of the other nucleoside triphosphates (Fig. 17). IAA, which causes no elongation growth under anaerobiosis (Fig. 13) is also unable to further stimulate the elongation growth induced by ATP, UTP, or CTP under anaerobiosis (Fig. 18); however, if IAA is added after growth has been stimulated by GTP or ITP, a temporary inhibition and, 10 min later, a strong stimulation is noticed (Fig. 19). If the sequence of addition is reversed, -that is, if IAA (without growth effect) and, after 20 min, GTP or ITP are added to the coleoptiles-, the same initial inhibition and subsequent increase of the growth rate is found (Fig. 20). Thus, IAA can stimulate growth of coleoptiles even under anaerobic conditions if GTP or ITP is present at the same time. 4. The results support the following hypothesis (Fig. 21): auxin acts cooperatively with GTP (ITP) as an effector of a membrane-bound, anisotropic ATPase or proton pump. This pump, activated by auxin, utilizes respiration energy (ATP or other nucleoside triphosphates) to raise the proton concentration in a compartment at the cell wall. This event leads to an increase in the activity of enzymes softening cell walls and thus triggers cell elongation. The transport or secretion of protons into the cell wall compartment should be compensated by a flow of cations into the interior of the cytoplasm or by a flow of anions to the cell periphery, thus causing secondary auxin effects.
508 citations
TL;DR: Advantages of mesophyll protoplasts as the source of clones as well as implication of the plating technique for genetical studies are discussed.
Abstract: A technique was developed to derive cell and plant clones from isolated mesophyll protoplasts of tobacco. The protoplasts, plated on a fully defined agar medium, divided and grew actively forming visible colonies after one month of culture. Efficiency of colony formation depended on cell density and light condition during incubation. Under standard conditions, 60% of plated protoplasts formed colonies. Upon transfer onto suitable media, these colonies differentiated shoots and roots, and eventually regenerated whole plants. Advantages of mesophyll protoplasts as the source of clones as well as implication of the plating technique for genetical studies are discussed.
468 citations
TL;DR: Large areas of the lower epidermis of full-grown leaves of Polypodium vulgare (and Valerianella locusta) are normally separated from the mesophyll by an extensive subepidermal airspace and would appear to be able to reduce their transpiration through an increase in diffusion resistance of the stomata during decreasing humidity in the ambient air, without changing the water status of the whole leaf.
Abstract: Large areas of the lower epidermis of full-grown leaves of Polypodium vulgare (and Valerianella locusta) are normally separated from the mesophyll by an extensive subepidermal airspace. Epidermal stripes were prepared for experiments to simulate these conditions in order to investigate stomatal reactions. They were placed with their inner surface in contact with an airspace of uniformly high humidity. The outer surface was treated with air of varying degrees of humidity. The stomatal reactions were observed by microscope and the opening of the guard cells determined photographically. Treatment of the outer side of the epidermis with dry air led to a rapid closing of the stomata, whilst moist air caused opening. This induction of opening and closing movements could be repeated up to 15 times with the same stoma by changing the degree of humidity. Neighbouring groups of stomata showed different apertures according to their individual humidity conditions. The degree of aperture of the stomata depended on the water potential of the ambient air and also on the humidity conditions in the subepidermal airspace. The cause of this stomatal behaviour could lie in the “peristomatal transpiration”. In this way, the guard cells are able to function as “humidity sensors” which “measure” the difference in water potential inside and outside the leaf. Their aperture thus is controlled by their individual transpiration conditions. This controlling mechanism could be very important for the water economy of plants. They would appear to be able to reduce their transpiration through an increase in diffusion resistance of the stomata during decreasing humidity in the ambient air, without changing the water status of the whole leaf.
420 citations
TL;DR: Import of K and Cl into the guard cells and loss of both elements from theGuard cells become observable 1 or 2 min after light is turned on or off, both when histochemical methods and the electron-probe microanalyzer are used for detection.
Abstract: When stomates of Zea mays open K and Cl migrate from the subsidiary cells into the guard cells; when the stomates close both elements return to the subsidiary cells. Subsidiary cells function as reservoirs for K and Cl. Import of K and Cl into the guard cells and loss of both elements from the guard cells become observable 1 or 2 min after light is turned on or off, both when histochemical methods and the electron-probe microanalyzer are used for detection. Each stomatal complex of maize contains on the average 10±3×10-13 gram equivalents (eq) of K and 4±1×10-13 eq of Cl. Guard cells accumulate K in the light and CO2-free air at an average rate of 10×10-15 eq K per minute, and Cl at approximately half that rate.
183 citations
TL;DR: It is concluded that the wax-filled stomatal antechambers reduce the rate of transpiration by about two thirds but reduce the rates of photosynthesis by only about one third.
Abstract: The distribution of wax tubes on the leaf surfaces is described, especially the presence of wax tubes in the antechambers of the stomata. The extra resistances which the wax-filled antechambers add to the other resistances in the pathway for diffusion of water vapour and of carbon dioxide are calculated. We conclude that the wax-filled stomatal antechambers reduce the rate of transpiration by about two thirds but reduce the rate of photosynthesis by only about one third. Thus wax-filled stomatal antechambers are excellent antitranspirants.
175 citations
TL;DR: The treated cotyledons of cucumber plants grown in the dark for 7 days were treated with various concentrations of cytokinins for 14 h and then moved into light and had up to 450% more chlorophyll than the water controls.
Abstract: Cotyledons of cucumber plants grown in the dark for 7 days were treated with various concentrations of cytokinins for 14 h and then moved into light. After 3 h the treated cotyledons had up to 450% more chlorophyll than the water controls. This suggests that cytokinins have an important role in the formation of chlorophyll. The increase in chlorophyll level was proportional to cytokinin concentration and was apparent at concentrations as low as 0.001 mg/l. Sensitivity to cytokinins depended on the age of the cotyledons and the time of exposure to light. Gibberellic acid, indoleacetic acid, adenine and sucrose did not cause a similar increase in chlorophyll levels. This effect of cytokinins on chlorophyll formation is valuable as a simple, rapid bioassay for cytokinins.
145 citations
TL;DR: A β-glucanase-free preparation of amyloglucosidase is employed to hydrolyse starch to glucose; this is subsequently estimated by the glucose oxidase technique.
Abstract: A specific enzyme method is described for the routine estimation of starch in small quantities (10–30 mg) of dried leaf tissue. A β-glucanase-free preparation of amyloglucosidase is employed to hydrolyse starch to glucose; this is subsequently estimated by the glucose oxidase technique. The method gives result which agree closely with those obtained by a specific iodine-precipitation method.
135 citations
TL;DR: Results are consistent with the localization of auxin transport sites at the plasma membrane of plant cells and appear to be strong KM between 10-8 and 10-7 M) but non-covalent.
Abstract: Plasma membrane-rich fractions were prepared from maize coleoptiles by low-shear homogenization and differential and sucrose-gradient centrifugation. Plasma membrane fragments were identified using a specific cytochemical stain based on phosphotungstic acid prepared in chromic acid. In a comparison of 10 different cell fractions of varying plasma membrane content, the N-1-napthylphthalamic-acid (NPA)-binding activity of the fractions was directly proportional to the content of plasma membrane. The NPA binding appears to be strong K M between 10(-8) and 10(-7) M) but non-covalent. NPA is known to inhibit auxin transport efficiently and quickly. Thus, the results are consistent with the localization of auxin transport sites at the plasma membrane of plant cells.
131 citations
TL;DR: The protein-carbohydrate body was identified by silver-hexaminestaining; this was not caused by carbohydrate but by some component which stained green in toluidin blue and which also occurred in cell walls in a thin band adjacent to the cytoplasm.
Abstract: Cytochemical methods have been used in conjunction with light and electron microscopy to determine the nature of the inclusions in aleurone grains of barley aleurone layers. Two kinds of inclusions were found: (1) Globoids within globoid cavities which were not enclosed by a membrane: the globoids stained red with toluidin blue due to the presence of phytin, and with lipid stains; (2) Protein-carbohydrate bodies which stained green with toluidin blue. The characteristics of globoids and protein-carbohydrate bodies as seen in the electron microscope are described in detail using both glutaraldehyde- and permanganatefixed tissues. The protein-carbohydrate body was identified by silver-hexaminestaining; this was not caused by carbohydrate but by some component which stained green in toluidin blue and which also occurred in cell walls in a thin band adjacent to the cytoplasm. The characteristics of both bodies are discussed in relation to apparent confusion in their identities in previous electron-microscope studies.
129 citations
TL;DR: It is concluded that ABA has a greater effect on ion uptake into guard cells than into the leaf tissues as a whole, and evidence from several sources suggests that starch disappearance occurs simultaneously with K+ entry into guard Cells.
Abstract: Abscisic acid (ABA) at a concentration of 100 μm reduced the mean stomatal aperture on isolated epidermis of Commelina communis from 9.5 to 3.1 μm. This closure resulted from a fall in osmotic pressure of the guard cells from 14.1 to 9.8 bars; the osmotic pressure of the subsidiary cells did not change significantly. Histochemical tests showed that the potassium concentration in guard cells was reduced by ABA-treatment, while the starch content of the chloroplasts increased. ABA was found to exert a significant effect on Rb86 uptake into leaf discs, but this was relatively small in magnitude. It is concluded that ABA has a greater effect on ion uptake into guard cells than into the leaf tissues as a whole.
117 citations
TL;DR: Gas analysis of leaves treated with ABA or DCMU allows one to distinguish effects on the stomatal apparatus from inhibition of photosynthesis and to conclude that ABA acts on stomata directly.
Abstract: Closure of stomata caused by low (10-7M) concentrations of abscisic acid (ABA) is specific for cis-trans ABA, and is initiated within 5 minutes. Upon withdrawal of the hormone supply, reopening starts within 5 minutes. Gas analysis of leaves treated with ABA or DCMU allows one to distinguish effects on the stomatal apparatus from inhibition of photosynthesis and to conclude that ABA acts on stomata directly.
TL;DR: Nitrogen, which was growth-limiting in a synthetic medium, had to be consumed completely before conjugation could start, and Agglutinability was not constitutive in heterothallic strains.
Abstract: Conjugation was studied in Schizosaccharomyces pombe using liquid media. Nitrogen, which was growth-limiting in a synthetic medium, had to be consumed completely before conjugation could start. Conjugation was preceded by sexual agglutination. Agglutinability was not constitutive in heterothallic strains. It only developed when cells of h (+) and h (-) mating type were grown in mixed culture for at least 2.5 hr before the start of conjugation.
TL;DR: New techniques are described which permit the quantitative analysis of microgram quantities of abscisic acid in plant extracts by gas chromatography by using 2-trans-abscisal acid as an internal standard.
Abstract: New techniques are described which permit the quantitative analysis of microgram quantities of abscisic acid in plant extracts by gas chromatography. Presumptive methyl abscisate peaks on gas chromatograms are positively identified by photosensitised isomerisation to methyl 2-trans-abscisate. Losses of abscisic acid during pre-purification are corrected by using 2-trans-abscisic acid as an internal standard.
TL;DR: The long, dead-end extracellular channels in the basal cell of Spartina appear comparable to surface specializations seen in the secreting epithelium of animal cells which carry out solute-linked water transport.
Abstract: The salt gland in Spartina foliosa is composed of two cells, a large basal cell and a smaller, dome-shaped cap cell which is located on a neck-like protrusion of the basal cell. There is no cuticular layer separating the salt gland from the mesophyll tissue. The basal cell has dense cytoplasm which contains numerous mitochondria, rod-like wall protuberances, and infoldings of the plasmalemma which extend into the basal cell and partition the basal cell cytoplasm. The protuberances originate on the wall between the basal and the cap cells and are isolated from the basal-cell cytoplasm by the infoldings of the plasmalemma. While the cap cell has no partitioning membrane system or wall protuberances, it resembles the basal cell by having dense cytoplasm and numerous mitochondria.The basal cell seems to be designed for efficient movement of ions toward the cap cell. The long, dead-end extracellular channels in the basal cell of Spartina appear comparable to surface specializations seen in the secreting epithelium of animal cells which carry out solute-linked water transport. The number of mitochondria and their close association with the plasmalemma extensions suggest that they have an important role in the transfer of ions through the basal cell.The accumulated ions would move into the extracellular spaces along an osomotic gradient where the accompanying passive flow of water would move the ions into the cap-cell wall and from there the solution would pass out through the pores in the cuticle.
TL;DR: It is shown that transpiration and assimilation are equally sensitive to change of stomatal aperture when the internal resistance to assimilation is equal to an effective resistance to evaporation which exists because of the coupling of heat and vapour exchanges between leaf and atmosphere.
Abstract: The ways in which transpiration and assimilation depend on stomatal aperture are compared. It is shown that transpiration and assimilation are equally sensitive to change of stomatal aperture when the internal resistance to assimilation is equal to an effective resistance to evaporation which exists because of the coupling of heat and vapour exchanges between leaf and atmosphere. Generally the ratio of transpiration to assimilation changes with stomatal aperture in a manner which is determined by the relative magnitude of these resistances and on temperature. Some possible implications in relation to the optimal behaviour of stomata are discussed.
TL;DR: Results showed that the water potential of red-light-treated embryos was lower than that of dark-treated ones, the difference being equivalent to the potential of a 0.30 molal mannitol solution.
Abstract: Redlight is known to increase the growth potential in the embryo of photodormant lettuce seed, enabling it to overcome the resistance offered by the seed coats (particularly the endosperm) or by an osmotically active medium. Determinations of the water potential of lettuce embryos germinating in osmoticum. carried out with a modified gravimetric technique which eliminates errors intro, duced by solute penetration into cellular osmotic space, showed that the water potential of red-light-treated embryos was lower than that of dark-treated ones, the difference being equivalent to the potential of a 0.30 molal mannitol solution. The force necessary for the radicle to penetrate the seed coats, measured directly, was found to be equivalent to the osmotic potential of 0.16 to 0.38 molal mannitol. Thus red light, acting through phytochrome, induces in photodormant lettuce embryos a decrease in water potential which is equal to that which is required for germination. A mechanism for this phytochrome-induced decrease in water potential is discussed.
TL;DR: Geoperception in roots may be a function of pressure exerted differentially by amyloplasts on the ER-complex, and may bring about geotropic equilibrium.
Abstract: In the root cap of Lepidium sativum a complex of multiple rough endoplasmic reticulum develops above the morphological lower transverse cell walls during ontogenesis of the columella cells ("statocysts"). The cisternae of the ER-complex are preferentially oriented parallel to the transverse walls. In normal vertical exposure of the roots the amyloplasts ("statoliths") lie above the ER-complex. They do not touch the plasma membrane, but possibly they press against the ER-complex and thereby bring about geotropic equilibrium.In each storey of the root cap the transverse walls together with their ER-complexes have a parabolic shape. Therefore the surface areas of the central ER-complexes form a right angle and those of the peripheral ER-complexes an acute angle with the organ axis.Owing to the shape of the whole ER-complex within each storey, the amyloplasts in the physically upper peripheral columella cells do not press against the membranes of the ER in the case of horizontal exposition. On the other hand in the physically lower part the amyloplasts are still situated above the ER-complex and can press on the ER.Geoperception in roots may be a function of pressure exerted differentially by amyloplasts on the ER-complex.
TL;DR: In the earliest stages of germination the raffinose family oligosaccharides are metabolised both in the endosperm and in the cotyledons of the seed but there is no change in the appearance, amount or composition of the main carbohydrate reserve, a galactomannan localised in theendosperm.
Abstract: Seeds of Trigonella foenum-graecum are examined light microscopically and by chemical analysis at different stages of germination. In the earliest stages of germination the raffinose family oligosaccharides are metabolised both in the endosperm and in the cotyledons of the seed but there is no change in the appearance, amount or composition of the main carbohydrate reserve, a galactomannan localised in the endosperm. About 18 hours after the emergence of the radicle the endosperm galactomannan begins to be mobilised. In a period of 24 hours the polysaccharide is completely degraded and the breakdown products, mainly galactose and mannose, are absorbed by the cotyledons in which sucrose increases and starch is formed. Mobilisation of the galactomannan is accompanied by the formation in the endosperm of a dissolution zone the form of which implies that the aleurone layer is involved in the degradation process.
TL;DR: Apical dominance in Xanthium strumarium was influenced by the quality of illumination received at the end of the photoperiod, and the involvement of the red/far-red regions of the spectrum was apparent.
Abstract: Apical dominance in Xanthium strumarium was influenced by the quality of illumination received at the end of the photoperiod. The involvement of the red/far-red regions of the spectrum was apparent. The persistence of the effects was partially dependent on the age of the individual buds concerned. Plants receiving 30 minutes of illumination from tungsten lamps after a 16-hour photoperiod from fluorescent tubes failed to branch, whereas plants given an identical photoperiod, both in terms of day-length and photosynthetically available light energy, but lacking the far-red from tungsten lamps, branched profusely.The influence of the spectral distribution of illumination on the levels of cytokinins and abseisic acid in the plant, and the correlation with the degree of branching, is presented and discussed. The cytokinin content was much higher in inhibited than released buds. The cytokinins present were probably not able to particinate in bud growth because of an accumulation of inhibitors resembling abscisic acid. The concentration of the inhibitors in inhibited buds was 50 to 250 times that occurring in all other plant parts examined.
TL;DR: The presence of numerous pits containing plasmodesmata in the inner tangential wall of the tertiary endodermis in barley roots is demonstrated by electron microscopy.
Abstract: The presence of numerous pits containing plasmodesmata in the inner tangential wall of the tertiary endodermis in barley roots is demonstrated by electron microscopy. The pit floor is covered by a thin layer of material which is continuous with and resembles the tertiary wall. The plasmodesmatal pore is constricted at its ends so that the plasmalemma lining the pore is appressed to the desmotubule. The frequency of plasmodesmata and their cross-sectional area is estimated, and phosphate and water fluxes through them are calculated on the assumption that they represent the only communication between the cortex and the vascular tissue. The pressure gradient across the ends of the plasmodesmata necessary to support the observed water flux is calculated for limiting cases of the pore radius and the viscosity of the fluid passing through the pore.
TL;DR: Observations on the relative abundance and distribution of peroxisomes in leaves of grasses with high CO2-photorespiration versus those with low are consistent with the published biochemical data on the levels and Distribution ofPeroxisomal enzymes in representatives of plants with high and low CO2, and may help explain the differences in apparent photorespiratory levels between these two groups of plants.
Abstract: A comparative study was made of the ultrastructure, distribution and abundance of leaf microbodies in four species of “temperate” grasses with high and four “tropical” grasses with low CO2-photorespiration. The temperate grasses were all festucoid; the tropical grasses included two panicoid species and two chloridoid. Comparisons of relative abundance were made by computing the average numbers of microbody profiles per cell section.
TL;DR: Isolated epidermal strips of Commelina communis L. showed progressively smaller stomatal openings when incubated in abscisic acid solutions ranging in concentration from 10-8 to 10-4 M.
Abstract: Isolated epidermal strips of Commelina communis L. showed progressively smaller stomatal openings when incubated in abscisic acid solutions ranging in concentration from 10-8 to 10-4 M. The effects were reproducible and did not appear to be affected by the presence of auxin, gibberellic acid or kinetin. This specificity suggests that this method may prove valuable as a quick, sensitive bioassay for abscisic acid and other related compounds which might be used as antitranspirants on field crops. The fungal toxin fusicoccin, previously reported to cause increased stomatal opening on intact leaves, partially reversed the closure induced by abscisic acid.
TL;DR: It is concluded that in this system ultraviolet irradiation is required in order to change the cells in such a way as to allow a physiological effectiveness of the phytochrome system.
Abstract: Ultraviolet light was demonstrated to stimulate flavone glycoside synthesis in Petroselinum cell suspension cultures. The data presented suggest the involvement of phytochrome in this response: Flavone glycoside formation resulting from 1 h of ultraviolet irradiation was increased by subsequent continuous far-red light irradiation. However, the ultraviolet effect was reduced by a subsequent irradiation with 10 min of far-red. This far-red effect was fully reversed by a sub-sequent irradiation with 10 min of red. Red and far-red irradiations were ineffective without ultraviolet preirradiation. It is concluded that in this system ultraviolet irradiation is required in order to change the cells in such a way as to allow a physiological effectiveness of the phytochrome system.
TL;DR: Ethylene was found to be required for the release or secretion of cellulase from the cytoplasm to the cell wall in bean-petiole abscission-zone explants, adding to its previously known action in accelerating senescence and cellulase synthesis in abscissions.
Abstract: Ethylene was found to be required for the release or secretion of cellulase from the cytoplasm to the cell wall in bean-petiole abscission-zone explants. This is an addition to its previously known action in accelerating senescence and cellulase synthesis in abscission.
TL;DR: Cytochemical methods have been used to study the distribution of acid phosphatase, esterase, ribonuclease, amylase and protease activity in the stimulated and unstimulated leaf glands of Pinguicula grandiflora, P. vulgaris, and P. caudata, showing that these glands are involved in resorption as well as secretion.
Abstract: Cytochemical methods have been used to study the distribution of acid phosphatase, esterase, ribonuclease, amylase and protease activity in the stimulated and unstimulated leaf glands of Pinguicula grandiflora, P. vulgaris, P. lusitanica, and P. caudata. Two gland types are present, stalked and sessile. The stalked glands bear a muco-polysaccharide secretion droplet, and are concerned with capture of the prey; the sessile glands are specialised for digestion. In unstimulated glands of both classes, acid phosphatase, esterase and ribonuclease activity is associated with the anticlinal walls of the head cells, which have a characteristic spongy inner surface, comparable with that of transfer cells. Acid phosphatase and esterase activity was also detected in the vacuoles of the head cells of the sessile glands. Substrate film tests showed that amylase is readily released from the stalked glands but not from the sessile ones, while in contrast proteolytic activity is mainly associated with the sessile glands.
TL;DR: Suspension cultures of Haplopappus gracilis accumulated anthocyanin when grown in defined media with 4.5×10-6M 2,4-D and were observed to divide without loss of pigmentation, demonstrating that cells differentiated with respect to anthocianin production undergo mitosis.
Abstract: Suspension cultures of Haplopappus gracilis accumulated anthocyanin when grown in defined media with 4.5×10(-6)M 2,4-D. Transfer of cells to media with 10(-5)M kinetin or benzyladenine and no auxin or 10(-7)M NAA for 6 days resulted in increased anthocyanin concentration of the cells but the total amount of pigment was unaffected due to differences in growth rates. The cultures yielded up to 35 mg pigment per gram dry weight.Cells grown in batch culture in media with 10(-5)M kinetin and with 10(-7) M NAA or 5×10(-5)M NAA sampled and analyzed daily grew at the same rate. The concentration of anthocyanin differed, being lower in cells at 5×10(-5)M NAA. After 6 days there was a rapid increase in pigment formation, and by 14 days the concentration of anthocyanin in cells in the two media were the same.When the cells were cultured in 3.5-1 phytostats and 600 ml culture was replaced daily with 600 ml medium, anthocyanins accumulated when the NAA concentration was 10(-7)M but not at 10(-6)M. At 10(-7)M NAA the cultures remained pigmented and anthocyanin accumulation could be restored after a temporary loss of pigmentation due to an earlier, higher auxin concentration. The changes in concentration of phenylalanine ammonia-lyase did not correspond to changes in the rate of anthocyanin accumulation. The enzyme showed a maximum 4-8 h after inoculation of cells to fresh media. Cells grown on agar plates and rich in anthocyanin were observed to divide without loss of pigmentation, demonstrating that cells differentiated with respect to anthocyanin production undergo mitosis.
TL;DR: In this paper, the development of increased activities of ribulosediphosphate carboxylase (EC 4.7.1.19) in greening bean leaves was completely inhibited by D-threo chloramphenicol but unaffected by L-threeo chlorAMPhenicol, where both specific and unspecific (both isomers) inhibition occurred.
Abstract: The development of increased activities of ribulosediphosphate carboxylase (EC 4.1.1.39) and of phosphoribulokinase (EC 2.7.1.19) in greening bean leaves was completely inhibited by D-threo chloramphenicol but unaffected by L-threo chloramphenicol. This indicates that these enzymes are synthesized by the ribosomes of the developing plastids. A different mechanism appears to be responsible for the development of activity of NADP-dependent triosephosphate dehydrogenase (EC 1.2.1.13) where the D-threo isomer gave 45% inhibition and the L-threo isomer gave 18% inhibition. Thus both specific (D-threo isomer) and unspecific (both isomers) inhibition occurred. It is suggested that the development of NADP-dependent triosephosphate dehydrogenase activity may result from the allosteric activation, in the plastids, of the NAD-dependent enzyme (Muller et al., 1969) which has been synthesized by cytoplasmic ribosomes. Neither isomer inhibited the development of five other enzymes of the photosynthetic carbon cycle namely ribosephosphate isomerase (EC 5.3.1.6), phosphoglycerate kinase (EC 2.7.2.3), triosephosphate isomerase (EC 5.3.1.1), tructosediphosphate aldolase (EC 4.1.2.13) and transketolase (EC 2.2.1.1), but there was a significant stimulation of the activity of transketolase by D-threo chloramphenicol.
TL;DR: A model predicting net photosynthesis of individual plant leaves for a variety of environmental conditions has been developed, based on an electrical analogue describing gas diffusion from the free atmosphere to the sites of CO2 fixation and a Michaelis-Menten equation describingCO2 fixation.
Abstract: A model predicting net photosynthesis of individual plant leaves for a variety of environmental conditions has been developed. It is based on an electrical analogue describing gas diffusion from the free atmosphere to the sites of CO2 fixation and a Michaelis-Menten equation describing CO2 fixation. The model is presented in two versions, a simplified form without respiration and a more complex form including respiration. Both versions include terms for light and temperature dependence of CO2 fixation and light control of stomatal resistance. The second version also includes terms for temperature, light, and oxygen dependence of respiration and O2 dependence of CO2 fixation. The model is illustrated with curves based on representative values of the various environmental and biological parameters. These curves relate net photosynthesis to light intensity, [CO2], [O2], temperature, and resistances to CO2 uptake. The shape of the [CO2]-net photosynthesis curves depends on the total diffusion resistance to CO2 uptake and the Michaelis constant for CO2 uptake. The curves range from typical Michaelis-Menten to Blackman types. The model is combined with a model of leaf energy exchange permitting simultaneous estimation of net photosynthesis and transpiration. The combined model is illustrated with curves relating transpiration to photosynthesis under a wide variety of environmental conditions. Environmental regimes yielding maximum efficiency of water use are identified for the given assumptions and biological parameters.
TL;DR: Heterocysts of aerobically grown Anabaena cylindrica can reduce acetylene in the light, without added cofactors, up to 30% as rapidly as can the intact filaments from which they are derived.
Abstract: Heterocysts of aerobically grown Anabaena cylindrica can reduce acetylene in the light, without added cofactors, up to 30% as rapidly as can the intact filaments from which they are derived.
TL;DR: InCRT1 sucrose caused both a reduction in chloroplast numbers per cell and a suppression of lamellar development in plastids, which was consistent with the observed reduced photosynthetic efficiency of CRT1 calluses grown on sucrose.
Abstract: Substrate levels of sucrose were shown to reduce chlorophyll synthesis in carrot tissue culture strain CRT1 but not in strain CRT2. In CRT1 the effect was shown to be a suppression of greening specifically by sucrose rather than a reducing sugar requirement for chlorophyll synthesis. In CRT1 sucrose caused both a reduction in chloroplast numbers per cell and a suppression of lamellar development in plastids. This effect on chloroplast structure was consistent with the observed reduced photosynthetic efficiency (micromoles CO2 per hour per mg chlorophyll) of CRT1 calluses grown on sucrose.