Modification of growth habit of Majestic potato by growth regulators applied at different times

The effect of gibberellic acid, CCC (2-chloroethyltrimethylammonium chloride) and B 9 (N-dimethylaminosuccinamic acid) was studied on growth of potato plants in pots. Growth was analysed on four occasions and changes in habit defined in terms of internode lengths, leaf areas and growth of lateral branches. Soaking seed pieces for 1 hr. in GA solution caused six internodes to elongate greatly, an effect not prevented by CCC applied when the shoot emerged from the soil. The effects on internode extension were determined by the length of the interval between GA treatment and CCC treatment. Treatment at emergence with CCC shortened all internodes and more CCC applied 4 weeks later had no effect. Late application of CCC or B9 shortened the top two lateral branches, usually very long in untreated plants. The regulators affected leaf growth differently from internode growth: usually growth regulators had less effect on leaf growth. Effects on growth depended on when the regulators were applied. Treatment with GA alone inhibited bud development at higher nodes than in untreated plants; when followed by late treatment with CCC, lateral growth at higher nodes was also less. CCC retarded development of lateral branches especially when applied early. B9 had a similar effect to CCC applied late. When regulators retarded growth of lower laterals, upper laterals often grew more than in untreated plants. Treatments did not affect the number of leaves on the main stem at first but later GA hastened senescence. GA increased the number of leaves on lateral stems, and the effect was enhanced by CCC. CCC alone increased the number of first- and second-order lateral leaves. GA lengthened and CCC shortened stolons. The effect of CCC persisted throughout the life of the plant. CCC or B 9 shortened stolons whenever applied. CCC hastened tuber initiation but slowed tuber growth. CCC at first retarded formation of lateral tubers but had no effect on the ultimate numbers of lateral and terminal tubers. The value of E (net assimilation rate) did not alter with time. CCC applied at emergence increased E, probably because it hastened tuber initiation and temporarily increased sink capacity. Although tubers formed earlier with CCC, their growth was slower and their demand for carbohydrate was also less. The increase in second-order laterals in CCC-treated plants indicates that they utilize carbohydrate that would normally go to tubers. This experiment also demonstrates that crowding leaves by shortening stems did not diminish E, possibly because another over-riding process (bigger sinks) offsets the effect of shading.     

Mixed Compound of DCPTA and CCC Increases Maize Yield by Improving Plant Morphology and Up-Regulating Photosynthetic Capacity and Antioxidants

DCPTA (2-diethylaminoethyl-3, 4-dichlorophenylether) and CCC (2-chloroethyltrimethyl- ammonium chloride) have a great effect on maize growth, but applying DCPTA individually can promote the increase of plant height, resulting in the rise of lodging percent. Plant height and lodging percent decrease in CCC-treated plants, but the accumulation of biomass reduce, resulting in yield decrease. Based on the former experiments, the performance of a mixture which contained 40 mg DCPTA and 20 mg CCC as active ingredients per liter of solution, called PCH was tested with applying 40mg/L DCPTA and 20mg/L CCC individually. Grain yield, yield components, internode characters, leaf area per plant, plant height and lodging percent as well as chlorophyll content, chlorophyll fluorescence, enzymatic antioxidants, membranous peroxide and organic osmolyte were analyzed in two years (2011 and 2012), using maize hybrid, Zhengdan 958 (ZD 958) at density of 6.75 plants m^-2. CCC, DCPTA and PCH were sprayed on the whole plant leaves at 7 expanded leaves stage and water was used as control. Compared to control, PCH significantly increased grain yield (by 9.53% and 6.68%) from 2011 to 2012. CCC significantly decreased kernel number per ear (by 6.78% and 5.69%) and thousand kernel weight (TKW) (by 8.57% and 6.55%) from 2011 to 2012. Kernel number per ear and TKW increased in DCPTA-treated and PCH-treated plants, but showed no significant difference between them. In CCC-treated and PCH-treated plants, internode length and plant height decreased, internode diameter increased, resulting in the significant decline of lodging percent. With DCPTA application, internode diameter increased, but internode length and plant height increased at the same time, resulting in the augment of lodging percent. Bending strength and puncture strength were increased by applying different plant growth regulators (PGRs). In PCH-treated plants, bending strength and puncture strength were greater than other treatments. Compared to control, the bending strength of 3rd internode was increased by 14.47% in PCH-treated plants in 2011, increased by 18.40% in 2012, and the difference was significant. Puncture strength of 1st, 3rd and 5th internode was increased by 37.25%, 29.17% and 26.09% in 2011 and 34.04%, 25% and 23.68% in 2012, compared to control. Leaf area and dry weight per plant reduced significantly in CCC-treated plants, increased in DCPTA-treated and PCH-treated plants from 2011 to 2012. Chlorophyll content and chlorophyll fluorescence improved with CCC and DCPTA application. Due to the additive effect of DCPTA and CCC, PCH showed the significant effect on chlorophyll content and chlorophyll fluorescence. Compared to control, total enzyme activity (SOD, POD, CAT, APX and GR) and soluble protein content increased, malonaldehyde (MDA) and hydrogen peroxide (H₂O₂) content reduced in PCH-treated plants. The transportation of soluble sugar from leaf to kernel improved significantly at the late silking stage. The research provided the way for the further use of DCPTA and CCC into the production practice.     

Effects of CCC and GA on internodal development of barley

Summary The effect of applying (2-chloroethyl)trimethylammonium chloride (CCC) or gibberellic acid (GA) as foliar sprays on internodal development of barley was studied. CCC applied to the whole plant at main tiller leaf stages 1, 2 or 3 decreased shoot elongation, and prevented elongation of internode 6 (internode 5 subtended the head). CCC at all stages delayed senescence of the lower leaves. CCC sprayed at all 6 leaf stages and GA sprayed at main tiller leaf stages 1, 2, 3 or 4 reduced plant height at maturity. GA treatment at leaf stages 2, 3 or 4 initially stimulated internodal elongation; elongation of later developed internodes was inhibited resulting in shorter plants at maturity. Only the treatment with GA at leaf stages 5 and 6 resulted in increased plant height.     

Structural changes in the vacuole and cytoskeleton are key to development of the two cytoplasmic domains supporting single-cell C<Subscript>4</Subscript> photosynthesis in <Emphasis Type="Italic">Bienertia sinuspersici</Emphasis>

Bienertia sinuspersici Akhani has an unusual mechanism of C₄ photosynthesis which occurs within individual chlorenchyma cells. To perform C₄, the mature cells have two cytoplasmic compartments consisting of a central (CCC) and a peripheral (PCC) domain containing dimorphic chloroplasts which are interconnected by cytoplasmic channels. Based on leaf development studies, young chlorenchyma cells have not developed the two cytoplasmic compartments and dimorphic chloroplasts. Fluorescent dyes which are targeted to membranes or to specific organelles were used to follow changes in cell structure and organelle distribution during formation of C₄-type chlorenchyma. Chlorenchyma cell development was divided into four stages: 1—the nucleus and chloroplasts occupy much of the cytoplasmic space and only small vacuoles are formed; 2—development of larger vacuoles, formation of a pre-CCC with some scattered chloroplasts; 3—the vacuole expands, cells have directional growth; 4—mature stage, cells have become elongated, with a distinctive CCC and PCC joined by interconnecting cytoplasmic channels. By staining vacuoles with a fluorescent dye and constructing 3D images of chloroplasts, and by microinjecting a fluorescence dye into the vacuole of living cells, it was demonstrated that the mature cell has only one vacuole, which is traversed by cytoplasmic channels connecting the CCC with the PCC. Immunofluorescent studies on isolated chlorenchyma cells treated with cytoskeleton disrupting drugs suspended in different levels of osmoticum showed that both microtubules and actin filaments are important in maintaining the cytoplasmic domains. With prolonged exposure of plants to dim light, the cytoskeleton undergoes changes and there is a dramatic shift of the CCC from the center toward the distal end of the cell.     

Effects of gibberellin on the cellular dynamics of dwarf pea internode development

This study analysed the dynamics of cell production and extension, and how these were affected by applied gibberellic acid (GA₃), during internode development in dwarf peas (Pisum sativum L. cv. Meteor). Image analysis was used to obtain cell number and length data for entire cell columns along the epidermis, the two outermost cortical layers, and the pith, from internode 7, over a time period covering the whole of the internode's growth phase. For a few days following the inception of an internode at the shoot apex, little further growth occurred, and there was no significant effect of GA₃ on cell division or cell extension. The subsequent growth of the internode was stimulated more than fourfold by GA₃ as a result of the production of more than twice the number of cells, which were twice as long. At least 96.5% of the cells of the mature internode were actually formed within the internode itself during this period of growth, demonstrating that the internode cells themselves represent the morphogenetic site of response to GA₃. Mitoses and cell extension occurred along the full length of the internode throughout its development. The daily changes in cell numbers were modelled by the Richards function, and manipulations of the fitted functions to reveal time trends of absolute and specific cell production rates were performed for each stem tissue. The increase in cell numbers in the +GA₃ plants was brought about by an increase in the rate of cell production, over a shorter time interval; specific cell production rates declined continuously from initial rapid rates in the +GA₃ epidermis and pith, but declined more slowly in the cortex. The control (−GA₃) epidermis and cortex cells exhibited a constant specific cell production rate (i.e. purely exponential) for several days. Cell extension rates were calculated so as to compensate for the size-reduction effects of concurrent cell division. These calculations confirmed that `real' cell extension rates were higher in the +GA₃ internodes. Models of the cellular controls of internode growth, based on the estimated dynamics of cell division and extension, are discussed. Received: 1 July 1997 / Accepted: 30 July 1997     

Unequal chromosome division and inter-genomic translocation occurred in somatic cells of wheat–rye allopolyploid

Newly synthesized wheat–rye allopolyploids were investigated by genomic in situ hybridization, over the first, second, third and fourth allopolyploid generations. Inter and intra chromosome connections were observed in 12 root-tip cells of CA4.4.7 (S₂ generation), and translocations between wheat and rye chromosomes were also detected in five root-tip cells. In root-tip cells of CA4.4.7.5 and CA4.4.7.2.2 (S₃ and S₄ generation), the chromosome connections occurred again, a dissociative small rye segment was detected in seven cells of CA4.4.7.5. In plants MSV6.1 and MSV6.5 (S₁ generation), almost half of the root-tip cells contained 13 rye chromosomes and the rest held 12 rye chromosomes, and all the cells of the two plants contained 42 wheat chromosomes. Five pairing configurations of rye chromosomes, including 5 II + 3 I, 6 II + 1 I, 6 II, 5 II + 2 I and 4 II + 4 I, were observed in pollen mother cells of the two plants. The two plants’ progeny, including S₂, S₃, and S₄ generation plants, contained 42 wheat chromosomes and 12 rye chromosomes. Therefore, the inter chromosome translocation and unequal chromosome division could occur in somatic cells of wide hybrids. The unequal chromosome division in somatic cell could induce chromosome elimination at the early stages of allopolyploidization.     

The Effect of Parental Genotypes of Rye Lines on the Development of Quantitative Traits in Primary Octoploid Triticale: Plant Height

When breeding the primary spring octoploid triticale derived from crosses of various inbred rye lines to wheat Chinese Spring, the effects of the rye genotype and growth conditions on the plant height and proportion of the first, second, and final (pedicle) internodes to the entire stem length were studied. Two triticale groups were examined: homozygotes for the dominant (Ddw1) and recessive (ddw1) alleles of the gene responsible for short stem in rye. In the short stem triticale lines carrying the Ddw1 alleles, the plants were 20 cm shorter on average than those in the ddw1-carrying lines, and the distribution of the two triticale groups overlapped significantly. In both groups, the lines significantly differing in plant height could be differentiated, because of allelic diversity of the additional genes controlling this trait along with the Ddw gene. In most triticale lines, especially in theDdw1-carrying ones, the plant height was much reduced under unfavorable growth conditions. At the same time, a short-stem line was isolated, which is characterized by ecological plasticity, like the maternal wheat cultivar. In the triticale studied, the stem structure depended on the short-stem rye genotype. The two-year study showed that in the triticale carrying the dominant allele of this gene, the first internode is significantly extended, whereas the upper (pedicle) internode is reduced, which increases plant lodging resistance. The differences revealed between the rye lines as well as their effect on the quantitative triticale traits are discussed in view of a variant of the hybridological analysis, which had been previously proposed for identification and mapping of the correspondent rye genes.     

Analysis of the effects of parental genotypes of rye lines on the development of quantitative traits in primary octaploid triticale. Plant height

When breeding the primary spring octoploid triticale derived from crosses of various inbred rye lines to wheat Chinese Spring, the effects of the rye genotype and growth conditions on the plant height and proportion of the first, second, and final (pedicle) internodes to the entire stem length were studied. Two triticale groups were examined: homozygotes for the dominant (Ddw1) and recessive (ddw1) alleles of the gene responsible for short stem in rye. In the short stem triticale lines carrying the Ddw1 alleles, the plants were 20 cm shorter on average than those in the ddw1-carrying lines, and the distribution of the two triticale groups overlapped significantly. In both groups, the lines significantly differing in plant height could be differentiated, because of allelic diversity of the additional genes controlling this trait along with the Ddw gene. In most triticale lines, especially in the Ddw1-carrying ones, the plant height was much reduced under unfavorable growth conditions. At the same time, a short-stem line was isolated, which is characterized by ecological plasticity, like the maternal wheat cultivar. In the triticale studied, the stem structure depended on the short-stem rye genotype. The two-year study showed that in the triticale carrying the dominant allele of this gene, the first internode is significantly extended, whereas the upper (pedicle) internode is reduced, which increases plant lodging resistance. The differences revealed between the rye lines as well as their effect on the quantitative triticale traits are discussed in view of a variant of the hybridological analysis, which had been previously proposed for identification and mapping of the correspondent rye genes.     

CONTROL OF THE INTERNODAL INTERCALARY MERISTEM OF CYPERUS ALTERNIFOLIUS

In the growing culm of C. alternifolius, surgical removal of parts indicated that the stimulus for the prolonged activity of the internodal intercalary meristem (IM) came from the matured leaves and upper internode and that buds were not involved in maintaining internodal growth. Decapitation of the culm resulted in cessation of internodal extension. Various growth regulators were applied to the decapitated internode, and both the total extension and growth rates were analyzed statistically. Gibberellin A₃ (GA) and benzyladenine (BA) substituted for the excised parts in their effect on internodal extension. Indoleacetic acid (IAA) had little effect. (2-chloroethyl) trimethylammonium chloride (CCC) inhibited internodal growth, and its effects were reversed by GA. IAA was antagonistic to BA but not to GA. BA and GA were somewhat antagonistic. The quantitative effects of growth regulators on epidermal and ground parenchyma cell length and number of interstomatal cells were examined. Extension induced by GA was due to both cell division and cell elongation in the IM. Cells were longer, and fewer stomates differentiated than in the control. In internodes induced to extend by GA + BA cell division, cell length, and stomate differentiation were similar to the control. The results indicate that prolonged internodal IM activity is maintained by cytokinins and gibberellins coming from the matured upper portions of the culm. Changes in the levels of these regulators during growth presumably result in the histological gradient in the internode.     

The effect of the wheat Ph1 locus on chromatin organisation and meiotic chromosome pairing analysed by genome painting

The Ph1 locus in wheat influences homo(eo)logous chromosome pairing. We have analysed its effect on the behaviour and morphology of two 5RL rye telosomes in a wheat background, by genomic in situ hybridisation (GISH), using rye genomic DNA as a probe. Our main objective was to study the effect of different alleles of the Ph1 locus on the morphology and behaviour of the rye telosomes in interphase nuclei of tapetal cells and in pollen mother cells at early stages of meiosis. The telosomes, easily detectable at all stages, showed a brightly fluorescing chromomere in the distal region and a constriction in the proximal part. These diagnostic markers enabled us to define the centromere and telomere regions of the rye telosomes. In the presence of functional copies of Ph1, the rye telosomes associated at pre-leptotene, disjoined and reorganised their shape at leptotene, and became fully homologously paired at zygotene – pachytene. In plants without functional alleles (ph1bph1b), the rye telosomes displayed an aberrant morphology, their premeiotic associations were clearly disturbed and their pairing during zygotene and pachytene was reduced and irregular. The Ph1 locus also influenced the behaviour of rye telosomes in the interphase nuclei of tapetal cells: in Ph1Ph1 plants, the rye telosomes occupied distinct, parallel-oriented domains, whereas in tapetal nuclei of ph1bph1b plants they were intermingled with wheat chromosomes and showed a heavily distorted morphology. The results shed new light on the effect of Ph1, and suggest that this locus is involved in chromosome condensation and/or scaffold organisation. Our explanation might account for various apparently contradictory and pleiotropic effects of this locus on both premeiotic associations of homologues, the regulation of meiotic homo(eo)logous chromosome pairing and synapsis, the resolution of bivalent interlockings and centromere behaviour. Received: 27 April 1998; in revised form: 5 August 1998 / Accepted: 11 August 1998     

Antifreeze proteins are secreted by winter rye cells in suspension culture

During cold-acclimation, winter rye ( Secale cereale L) leaves secrete antifreeze proteins (AFPs) into the apoplast. The AFPs bind to ice and modify its growth, which is easily observed in vitro . However, it is not yet known whether in planta AFPs interact with ice or whether they exert cryoprotective effects. These experiments are difficult to conduct with intact plants, so the aim of this work was to determine whether AFPs are produced in response to cold temperature in cell culture and to examine their function by using suspension cells. We showed that suspension cells secreted three of the six known winter rye AFPs into the culture medium during acclimation at 4°C. These AFPs were not present in washed suspension cells, thus indicating that they are not firmly bound to the cell walls. In order to examine the function of extracellular AFPs, non-acclimated (NA) winter rye suspension cells and protoplasts isolated from NA winter rye leaves were then frozen and thawed in the presence of AFPs extracted from cold-acclimated winter rye leaves. The AFPs had no effect on the survival of NA protoplasts after freezing; however, they lowered the lethal temperature at which 50% of the cells are killed by freezing (LT₅₀) of NA suspension cells by 2.5°C. We conclude that low above-zero temperatures induce winter rye suspension cells to secrete AFPs free in solution where they can protect intact suspension cells, but not protoplasts, from freezing injury, presumably by interacting with extracellular ice.     

Gibberellin and auxin contents and ethylene production in the hypocotyls of green and etiolated bean plants treated with chlorocholine chloride

The effect of CCC treatment on the GA and IAA contents of the hypocotyls of green and etiolated bean plants and on their distribution was studied. In the treated plants the GA content of the hypocotyls was higher than that of the control. On the application of CCC the distribution of the hormone content within the organ altered: in the basal part of the hypocotyls of the treated plants the hormone content increased. In the hypocotyls of the treated plants the IAA content was less than in the controls and it was accumulated in the basal part. The ethylene production of the aplcal and basal parts of the hypocotyls proved to be correlated with their IAA content. Presented at the International Symposium “Plant Growth Regulators” held on June 18–22, 1984 at Liblice, Czechoslovakia.     

Day/night temperature environment affects cell elongation but not division in Lilium longiflorum Thunb

Lilium tongiflorum Thunb. cv. ‘Nellie White’ plantswere grown in different day/night temperature (DT/NT) environmentsto determine the anatomical basis for differential responsesof stem elongation to DT and NT. Lilium plants were forced in1986 and 1987 under 25 and 12 different DT/NT environments,respectively, with temperatures ranging from 14 to 30 °C.Parenchyma and epidermal cell length and width were measuredin stem tissue (1987) and epidermal cell length and width weremeasured in leaf tissue (1986). Total cell number per internodeand vertical cell number per internode were calculated. Stemparenchyma and stem and leaf epidermal cell length increasedlinearly as the difference (DIF) between DT and NT increased(DIF = DT —- NT), i.e. as DT increased relative to NT.DIF had no effect on stem parenchyma width, stem and leaf epidermalcell width, or cell number per internode. Data suggested thatstem elongation responses to DIF are elicited primarily througheffects on cell elongation and not division. Key words: Thermoperiodism, thermomorphogenesis, stem elongation, DIF, cell division, cell elongation, leaf expansion     

Intercellular Transport in Plants: II. CYCLOSIS AND THE RATE OF INTERCELLULAR TRANSPORT OF CHLORIDE IN CHARA

The effect of streaming speed on intercellular transport ofchloride has been studied using pairs of internodal cells ofChara. The rate of transport was measured by that fraction ofthe chloride that entered one internode which was transportedout of it into the cells of the node and the next internode.The speed of cytoplasmic streaming was altered by treating thefirst cell with cytochalasin B. The relative rate of intercellular transport depended markedlyon the streaming speed at all speeds up to those found in untreatedcells. The chloride influx into the treated cell did not dependon the streaming speed. It is concluded that the rate of intercellular transport oflow molecular weight solutes in Chara will be normally limitedby the rate at which cytoplasmic streaming brings solute tothe plasmodesmata, rather than by the diffusion permeabilityof the plasmodesmata. This conclusion may well apply to othercharophyte plants, and could in principle apply to higher plants.     

Abscisic Acid and Apical Dominance in Phaseolus coccineus L. The Role of Tissue Age

Abscisic acid (ABA) applied to the decapitated second internodeof runner bean plants enhanced outgrowth of lateral buds onlywhen internode stumps were no longer elongating. Applied toelongating internodes of slightly younger plants, ABA causesinhibition of bud outgrowth. Together with 10^–4 M indol-3-ylacetic acid (IAA), ABA stimulated internode elongation and interactedadditively in the inhibition of bud outgrowth. A mixture of10^–5 M ABA and 10^–6 M gibberellic acid (GA₃ ) causedsimilar effects on internode growth as IAA + ABA, but was mutuallyantagonistic in effect on growth of the lateral buds. Abscisic acid, apical dominance, gibberellic acid, indol-3yl acetic acid, Phaseolus coccineus, bean     

Annexin A4 Is Involved in Proliferation,Chemo-Resistance and Migration and Invasion in Ovarian Clear Cell Adenocarcinoma Cells

Ovarian clear cell adenocarcinoma (CCC) is the second most common subtype of ovarian cancer after high-grade serous adenocarcinomas. CCC tends to develop resistance to the standard platinum-based chemotherapy, and has a poor prognosis when diagnosed in advanced stages. The ANXA4 gene, along with its product, a Ca⁺⁺-binding annexin A4 (ANXA4) protein, has been identified as the CCC signature gene. We reported two subtypes of ANXA4 with different isoelectric points (IEPs) that are upregulated in CCC cell lines. Although several in vitro investigations have shown ANXA4 to be involved in cancer cell proliferation, chemoresistance, and migration, these studies were generally based on its overexpression in cells other than CCC. To elucidate the function of the ANXA4 in CCC cells, we established CCC cell lines whose ANXA4 expressions are stably knocked down. Two parental cells were used: OVTOKO contains almost exclusively an acidic subtype of ANXA4, and OVISE contains predominantly a basic subtype but also a detectable acidic subtype. ANXA4 knockdown (KO) resulted in significant growth retardation and greater sensitivity to carboplatin in OVTOKO cells. ANXA4-KO caused significant loss of migration and invasion capability in OVISE cells, but this effect was not seen in OVTOKO cells. We failed to find the cause of the different IEPs of ANXA4, but confirmed that the two subtypes are found in clinical CCC samples in ratios that vary by patient. Further investigation to clarify the mechanism that produces the subtypes is needed to clarify the function of ANXA4 in CCC, and might allow stratification and improved treatment strategies for patients with CCC.     

Tuberization in Potato at High Temperatures: Responses to Gibberellin and Growth inhibitors

The responses of potato plants (Solanum tuberosum L., cv. Sebago)to high temperatures (32 day/28 C night or 32/18 °C) andgibberellin are similar, in that they promote haulm growth andsuppress tuber production, whereas low temperatures (22/18 °C)abscisic acid and CCC have the opposite effect, promoting tuberproduction and reducing the growth of the haulms. The inhibitoryeffect of the high temperatures on tuber production, under aphotoperiod of 14 h, was almost completely reversed in theseexperiments by the application of CCC, and partly reversed byABA. Single-leaf cuttings from plants grown at the various temperaturesand chemical treatments responded in the same way as the wholeplant. It is suggested that both haulm growth and tuber initiationare influenced by a common hormonal control, and that temperatureexerts its influence by altering the balance between the levelsof endogenous gibberellins and inhibitors. These substancesapparently act directly on the stolon tip, rather than throughtheir general influence on haulm growth. Solanum tuberosum L., potato, tuberization, temperature response, gibberellin, abscisic acid, 2-chloroethyltrimethylammonium chloride (CCC)     

Influence of Cytoplasmic Streaming and Turgor Pressure Gradient on the Transnodal Transport of Rubidium and Electrical Conductance in Chara corallina

In order to study the transnodal transport of Rb⁺ in internodalcells of Chara corallina, a low-temperature loading system wasestablished to separate the loading process from the transportprocess. Tandem cells, consisting of internode-node-internode,were isolated from algal plants. Treatment of a single internodewith 100 mM RbCl at 5°C for 30 min caused an accumulationof 43 mM Rb⁺ in the cytoplasm of this cell (= source cell),but no Rb⁺ was found in the other internode (= sink cell) ofthe tandem cells. In 40 min after a return to 25°C, about12% of the Rb⁺ loaded in the source cell was transported intothe sink cell. The apparent transnodal permeability of Rb⁺ wascalculated to be 4.6 x 10^–7 m.s^–1. Under the assumptionthat the total cross-sectional area of plasmodesmata occupies10% of the nodal area, the diffusion coefficient of RbCl throughplasmodesmata was calculated to be 2.3 x 10^–11 m².s^–1which is about 1% of the free diffusion coefficient in water(2 x 10^–9m².s^–1). The transnodal transport of Rb⁺ was intimately correlated withthe rate of cytoplasmic streaming. The rate of streaming inboth the source and sink cells was varied either by treatingthe cells with cytochalasin B (CB) or by lowering the temperature.The transport rate correlated with the streaming rate irrespectiveof the method used. Since the level of ATP was not influencedby CB or low temperature, the transnodal transport is assumedto be the result of passive diffusion process through plasmodesmata. A turgor pressure gradient across the node decreased both thenodal electrical conductance and the transnodal transport ofRb⁺. By contrast, the exposure of both internodal cells to asolution of sorbitol had no effect on either of them. A turgorpressure gradient of 240 mOsm decreased the transport of Rb⁺in the first hour to 3% of the control, while it decreased thenodal conductance to about 50%. The increase in the electricalresistance occurred on the junction side between the node andthe internode that was treated with sorbitol. Cytochalasin Ehad no effect on the nodal electrical resistance. It is assumedthat plasmodesmata are equipped with a valve-like mechanismwhich is sensitive to the gradient of turgor pressure acrossthe node and is not regulated by an actomyosin system. (Received February 15, 1989; Accepted April 20, 1989)     

Effetti Morfologici,Anatomici Ed Ultrastrutturali Indotti Dai Ritardanti Di Crescita Su Plantule Di Pisum Sativum L. Var. « Gloria Di Quimper » Cultivate in Soluzione Nutritizia

Abstract

The effect of the growth retardants on the structure of Pea seedlings coltured in nutritive solution. – The addition of CCC (2-Chloro-ethyltrimethyl ammonium chloride) and AMO 1618 (4-Hydroxyl-5-isopropyl-2 methyl-phenyl-trimethylammonium chloride. 1-piperidine carboxylate) to Pea seedlings (Pisum sativum L. var. Gloria di Quimper) promotes the usual modifications induced by growth retardants on higher plants. CCC appears less effective than AMO 1618; CCC inhibits growth only at 10²-M. concentration, on the contrary 5×10-⁵M. AMO 1618 inhibits strongly the growth of the seedlings both in the light and in darkness. CCC and AMO 1618 operate similarly as far as the inhibition of expansion growth, the increase of the stem diameter, and the decrease of the apical dominance are concerned. 10-²M. CCC stimulates both the growth of roots and the secondary roots formation, on the contrary 2,5×10-⁴M. AMO 1618 inhibits strongly the growth of the roots. AMO 1618 affects more strongly than CCC the expantion growth of the leaves. Leaves of the AMO 1618 treated plants are greener than the control plants. Plants treated with CCC and AMO 1618 are smaller because these chemicals inhibit the expantion growth of the cells. The increase of the stem diameter induced by CCC and AMO 1618 is due to the stimulation of the mitotic activity of the cambium. AMO and CCC induce a decrease of the size of the vessels and the sieve tubes. In the sieve tubes of the treated plants and slime plugs appear near to the sieve plates many slime bodies. AMO and CCC did not affect the mitotic activity of the apical meristems; in fact the plants grown in the presence of the growth retardants, show a normal primary body. AMO and CCC delay the lignification process. Chloroplasts of this Pisum sativum variety show prolamellary bodies associated to a good lamellar system. Starch granules are always present. Starch was never found in the chloroplasts of the treated plants. The general picture of the effects induced by growth retardants in Pea seedlings show so many modifications that it is very difficult to believe, like some Authors suggest, that all the effects produced by growth retardants are due to the inhibition of gibberellin biosynthesis.     

Requirement of Cyclic Adenosine 3′,5′-Monophosphate for the Thermosensitive Effects of Rts1 in a Cyclic Adenosine 3′,5′-Monophosphate-Less Mutant of Escherichia coli

Previous publications showed that a covalently closed circular (CCC) Rts1 plasmid deoxyribonucleic acid (DNA) that confers kanamycin resistance upon the host bacteria inhibits host growth at 42 degrees C but not at 32 degrees C. At 42 degrees C, the CCC Rts1 DNA is not formed, and cells without plasmids emerge. To investigate the possible role of cyclic adenosine 3',5'-monophosphate (cAMP) in the action of Rts1 on host bacteria, Rts1 was placed in an Escherichia coli mutant (CA7902) that lacks adenylate cyclase or in E. coli PP47 (a mutant lacking cAMP receptor protein). Rts1 did not exert the thermosensitive effect on these cells, and CCC Rts1 DNA was formed even at 42 degrees C. Upon addition of cAMP to E. coli CA7902(Rts1), cell growth and formation of CCC Rts1 DNA were inhibited at 42 degrees C. The addition of cAMP to E. coli PP47(Rts1) did not cause inhibitory effects on either cell growth or CCC Rts1 DNA formation at 42 degrees C. The inhibitory effect of cAMP on E. coli CA7902(Rts1) is specific to this cyclic nucleotide, and other cyclic nucleotides such as cyclic guanosine 3',5'-monophosphate did not have the effect. For this inhibitory effect, cells have to be preincubated with cAMP; the presence of cAMP at the time of CCC Rts1 DNA formation is not enough for the inhibitory effect. If the cells are preincubated with cAMP, one can remove cAMP during the [(3)H]thymidine pulse and still observe its inhibitory effect on the formation of CCC Rts1 DNA. The presence of chloramphenicol during this preincubation period abolished the inhibitory effect of cAMP. These observations suggest that cAMP is necessary to induce synthesis of a protein that inhibits CCC Rts1 DNA formation and cell growth at 42 degrees C.