Benzyladenine-Induced Increase in DNA Content per Cell, Chloroplast Size, and Chloroplast Number per Cell in Intact Bean Leaves

Primary leaves of intact bean plants (Phaseolus vulgaris L.)were treated with benzyladenine (BA) at different stages oftheir growth. BA induced a marked increase in DNA content percell in growing leaves where no cell division occurred. BA stimulatedthe chloroplast replication compared with untreated leaves.After the replication period, chloroplast size continued toincrease in BA- treated leaves, but not in untreated controls.     

Effects of Benzyladenine on Chlorophyll, DNA, RNA and Protein Content of Attached Young Bean (Phaseolus vulgaris L.) Leaves

N⁶-Benzyladenine (BA) was applied to intact bean (Phaseolusvulgaris L.) primary leaves at 2 and 6 days after imbibition,when they were in the cell division and post-cell division stages,respectively. BA treatment at day 2 temporarily inhibited an increase in chlorophyllcontent in the following day, but stimulated it in later days.No such inhibition by BA was observed for changes with timein DNA, RNA, and protein content and f. wt. On the other hand,BA treatment at day 6 enhanced RNA and protein content, withoutsignificant influence on DNA and chlorophyll content and f.wt. The mode of cytokinin action on greening in leaves during cell-divisiongrowth seems to be different from that in etiolated cotyledons. Phaseolus vulgaris L., bean, greening, benzyladenine, DNA, RNA, protein     

Studies on the Growth in Culture of Plant Cells: VI. NUCLEIC ACID METABOLISM OF ACER PSEUDOPLATANUS L. CELL SUSPENSIONS

Changes in the nucleic acid content of cell suspension culturesof Acer pseudoplatanus, L. have been investigated. Both RNAand DNA contents rise sharply early in the period of cultureand before any significant increase in cell number. With theonset of rapid cell division there is a rapid decline in DNAcontent per cell to reach the value which persists during thesubsequent period of growth. The high level of RNA establishedat the beginning of the phase of rapid cell division, declinesgradually as growth proceeded. More detailed investigation ofthe RNA revealed no signficant changes, during the 3-week periodof culture, in either its base composition or in the relativeamounts of its different constituent molecular species.     

Leaf Growth in Phaseolus vulgaris: I. Growth of the first pair of leaves under constant conditions

The growth of the first pair of leaves of Phaseolus vulgaris(French bean) has been studied during germination and followingemergence of the seedling. The leaves are well developed inthe embryo and, at 22.5° C, show an exponential increasein fresh weight, dry weight, and leaf area up until about eightdays from planting. Cell division commences about two days afterplanting and is exponential for a short period. Considerablechanges in cell volume occur during the period over which celldivision occurs. Cell division ceases soon after emergence andunfolding, when the leaf has reached only 17 per cent of itsfinal area. Cessation of cell division is followed by a phaseof growth which is due entirely to cell expansion. The significanceof these findings is discussed in relation to recent work onother genera.     

Regulation of RNA synthesis in plant cell culture: delayed synthesis of ribosomal RNA during transition from the stationary phase to active growth

Ribosomal RNA synthesis was studied during the early phases of growth activation in a cell suspension culture derived from peanut (Arachis hypogaea, L.) cotyledon. Upon dilution from stationary phase, these cells show a characteristic lag of 3 days before the commencement of cell division. An analysis of the nature of RNA synthesized during this early period of growth showed that the cells obtained immediately upon dilution from stationary phase synthesize primarily messenger RNA and essentially no ribosomal RNA. The synthesis of ribosomal RNA is delayed for about 24 hr after which it rises sharply resulting in a 2- to 3-fold accumulation of ribosomal RNA per cell during the subsequent 24-hr period. Both the messenger RNA and the ribosomal RNA were characterized by their cellular localization; by sucrose and CsCl gradient analyses, and by the determination of their base ratios.It would appear that a major facet of the lag phase in the cell growth is the diversion of a significant part of the RNA biosynthetic apparatus from the synthesis of messenger RNA to that of ribosomal RNA.     

Benzyladenine-induced increase in DNA content per chloroplast in intact bean leaves

Benzyladenine (BA) treatment was found to induce chloroplast DNA (ctDNA) synthesis after it had stopped in primary leaves of light-grown intact bean plants (Phaseolus vulgaris L.). The leaves were treated with BA from 7 days after sowing. Chloroplasts were isolated and the ctDNA content per chloroplast was determined. Chloroplast division occurred until 13 days after sowing in untreated leaves. BA stimulated the division keeping the level of ctDNA content per chloroplast the same as that in the untreated controls. After the division period, the ctDNA content per chloroplast increased in BA-treated leaves, but not in controls. Consequently, ctDNA per leaf (or per cell) increased immediately after the beginning of BA treatment, but remained constant in the control leaves.     

Growth and cell division of Mycobacterium avium

The rates of cell division and of protein, DNA and RNA synthesis upon transition of Mycobacterium avium to and from rich medium were examined. The changes in cell morphology (elongation) were also examined by optical and electron microscopy. Upon transfer from poor to rich medium, the rate of synthesis of RNA increased rapidly, followed by an increase in protein synthesis within 3 h and by an increase in DNA synthesis within 7 h; cell division began after a lag of about 10 h. Upon transfer from rich to poor medium, the preshift rates for protein and DNA synthesis changed to postshift rates after 3 h and 7 h, respectively; RNA synthesis stopped immediately, there was a transient fall in total RNA, and synthesis was resumed at a new rate only after 24 h. After the period of adjustment to new medium, the bacteria entered the postshift growth in which cell size, the increase in cell mass (absorbance at 650 nm) and viable counts, and the rates of synthesis of protein, DNA and RNA were constant. Ultrastructural examination of elongated cells during the adjustment period showed that they had septa at different stages of formation, but no evidence of fragmentation was found. It was concluded that cell division in M. avium was by binary fission, and that the notion of a life-cycle was not supported by present findings.     

The Effect of Rooting Space on Whole Plant and Leaf Growth in Brussels Sprouts (Brassica oleracea var. gemmifera)

Seedlings of Brassica oleracea var. gemmifera DC. (Brusselssprouts) were grown in four pot sizes over a 4-week period.Whole plant, stem, root and foliage d. wts and foliage area,together with specific leaf area, leaf area ratio and numberof leaves initiated were reduced by restricting rooting space.Individual leaves showed similar reductions in d. wt and area,with the effect being more pronounced in later-formed leaves.Cell counts and measurements on the epidermis and palisade mesophylllayers of the first four leaves showed that the reduction ingrowth was due to reduced cell division. Cell numbers in thefirst-formed leaf were halved over the range of pot sizes used,and there was a progressively greater reduction in cell numbersin later-formed leaves. There was some tendency for cell sizeto decrease with decreasing rooting space, but this was notgeneral and was most marked between plants grown in the twosmallest pot sizes. Brassica oleracea var. gemmifera, Brussels sprouts, rooting space, growth analysis, leaf growth, cell numbers, cell sizes     

Phage formation in Staphylococcus muscae cultures. XI. The synthesis of ribonucleic acid,desoxyribonucleic acid,and protein in uninfected bacteria

1. The synthesis of ribonucleic acid, desoxyribomicleic acid, and protein in S. muscae has been studied: (a) during the lag phase, (b) during the early log phase, and (c) while the cells are forming an adaptive enzyme for lactose utilization. 2. During the lag phase there may be a 60 per cent increase in ribonucleic acid and protein and a 50 per cent increase in dry weight without a change in cell count, as determined microscopically, or an increase in turbidity. 3. During this period, the increase in protein closely parallels the increase in ribonucleic acid, in contrast to desoxyribonucleic acid, which begins to be synthesized about 45 minutes after the protein and ribonucleic acid have begun to increase. 4. The RNA N/protein N ratio is proportional to the growth rate of all S. muscae strains studied. 5. While the RNA content per cell during the early log phase depends upon the growth rate, the DNA content per cell is fairly constant irrespective of the growth rate of the cell. 6. Resting cells of S. muscae have approximately the same RNA content per cell irrespective of their prospective growth rate. 7. While the cells are adapting to lactose, during which time there is little or no cellular division, there is never an increase of protein without a simultaneous increase in ribonucleic acid, the RNA N/protein N ratio during these intervals being approximately 0.15. 8. Lactose-adapting cells show a loss of ribonucleic acid. The purines-pyrimidines of the ribonucleic acid can be recovered in the cold 5 per cent trichloroacetic acid fraction, but the ribose component is completely lost from the system. 9. The significance of these results is discussed in relation to the importance of ribonucleic acid for protein synthesis.     

Benzyladenine-Enhanced Growth of Attached Young Bean Leaves. Studies with Inhibitors of Nucleic Acid and Protein Synthesis

Benzyladenine (BA) stimulated division but not expansion ofmesophyll cells and repressed chlorophyll accumulation in attachedyoung bean leaves. Even in the presence of fluorodeoxyuridine(FUdR) or mitomycin C which causes complete suppression of BA-inducedincrease in DNA content, BA increased RNA and protein contentsand fresh weight, but decreased chlorophyll accumulation. Moreover,BA n the presence of FUdR induced marked cell expansion. Inthe presence of a-amanitin (AM), BA did not produce any changein DNA content, fresh weight or cell size. All of the BA effectswere observed even in the presence of fluorouracil (FU) plusthymidine (TdR). AM and cycloheximide added 0–12 h effectively inhibitedBA-stimulated cell division but showed no effect if added at18 h. FU plus TdR added 0–18 h had almostno effect onthe cell number at 24 h. These results indicate that BA stimulates the mRNA synthesisnecessary for induction of cell division, and that the synthesisof cytoplasmic rRNA is not always necessary for BA-stimulatedcell division, and moreover, that BA stimulates expansion growthof cells in which DNA synthesis is suppressed. (Received August 16, 1982; Accepted March 31, 1983)     

Epidermal Cell Division and the Coordination of Leaf and Tiller Development

Initiation and development of grass leaves and tillers are oftendescribed individually with little attention to possible interrelationshipsamong organs. In order to better understand these interrelationships,this research examined epidermal cell division during developmentaltransitions at the apical meristem of tall fescue (Festuca arundinaceaSchreb.). Ten seedlings were harvested each day for a 9-d period,and lengths of main shoot leaves and primary tillers were measured.In addition, numbers and lengths of epidermal cells were determinedfor 0·5 mm segments along the basal 3 mm of each leafand tiller. Primordia development and onset of rapid leaf elongationwere characterized by an increase in the number of cells perepidermal file with mean cell length remaining near 20 µmper cell. After the leaf had lengthened to 1-1·5 mm,cells near the leaf tip ceased dividing and increased in length,at which time leaf elongation rate increased rapidly. Liguleformation, marking the boundary between blade and sheath cells,occurred prior to leaf tip emergence above the whorl of oldersheaths, while the earliest differentiation between blade andsheath cells probably began when leaves were < 1 mm long.Major transitions in leaf and tiller development appeared tobe synchronized among at least three adjacent nodes. At theoldest node, cessation of cell division in the leaf sheath wasaccompanied by initiation of cell division and elongation inthe associated tiller bud. At the next younger node the ligulewas being initiated, while at the youngest node cell divisioncommenced in the leaf primordium, as elongation of a new leafblade began. This synchronization of events suggests a key rolefor the cell division process in regulating leaf and tillerdevelopment.Copyright 1994, 1999 Academic Press Festuca arundinacea Schreb., tall fescue, cell division, leaf initiation, tillering, ligule development     

Studies on Certain Aspects of Senescence in Nicotiana plumbaginifolia Sps

Senescence of Nicotiana plumbaginifolia VIV. (Solanaceae) wasstudied in normal, in deflowered, and in defruited plants. Removalof flowers and fruits delayed senescence, inhibited growth ofthe bolted axis and branches, and promoted the formation ofleaves on them. An increase of dry weight of leaves occurreddue to these operations and the rate of increase was a maximumin deflowered plants. Increase in dry weight was accompaniedby an increase in laminar area and this was most pronouncedin deflowered plants. Changes in total chlorophyll level ofrosette and axial leaves in deflowered, defruited, and controlplants could not, however, be correlated with dry-weight changes.Results of biochemical analyses showed that total basic proteinand RNA increased initially in leaves of deflowered and defruitedplants and during this period dry weight, total chlorophylllevel, and laminar area also increased. During later periodsthe basic protein and RNA levels declined and the rate of declinewas slowest in deflowered plants.     

Development of the Fifth Leaf is Indicative for Whole Plant Performance at Low Temperature in Tomato

In the search for early-detectable selection criteria for growthat low temperature conditions in tomato, first the initiationand growth of individual leaves was analysed. Scanning electronmicroscopy revealed that the first four primordia had alreadydeveloped during the germination period at 25°C. The primordiumof the fifth leaf, however, was initiated after the transferof seedlings to the experimental conditions. The increase inlength of the first three leaves, and to a lesser extent ofthe fourth leaf, was considerably smaller in comparison withthat of later formed leaves. Moreover, the morphology of thefirst three to four leaves was deviant, whereas the others showedthe normal compound leaf architecture. All these results indicatedthat the fifth leaf was the earliest formed leaf with growthcharacteristics that might reflect the growth potential of thewhole plant. Development of the fifth leaf was tested as a marker for wholeplant growth. At three temperature, 18, 15 and 12°C, growthresponses of the fifth leaf were similar to that of whole plantsin four tomato genotypes: Line A, Line B, Premier and MXXIV-13.Significant differences in relative growth rate of dry weightof whole plants and fifth leaves (RGR_W)and of leaf area of thefifth leaves (RGR_LA between two fast growing and two slow growinggenotypes were found. No genotype by temperature interactionfor RGR_W and RGR_LA was found, indicating that the effect oftemperature decrease was similar for the four genotypes. The structure of the mature fifth leaf of one fast and one slowgrowing genotype, Line A and MXXIV-13, was analysed. For bothgenotypes, leaves were small and thick at low temperature, 12°C.The total number of epidermis and palisade parenchyma cellsper leaf was smaller but the size of the cells developed at12°C was larger than at 18°C. Consequently, the slowgrowth at 12°C was due to a low rate of cell division. Atboth temperatures, the fifth leaf to MXXIV-13 was smaller comparedto that of line A. Since the size of the cells were similar,the smaller leaf size was due to lower number of leaf cells. The results confirm the suitability of the growth, especiallyexpressed as RGR_LA , of the fifth leaf as a nondestructive marketfor vegetative development of tomato at low temperature. Growthdifferences between genotypes were mainly reflected by differencesin cell number of leaves, which might be correlated with geneticallydetermined differences in cell number of leaf primordia.Copyright1993, 1999 Academic Press Lycopersicon esculentum Mill. genotypes, plant growth, selection criteria, low temperature, leaf initiation, leaf development, RGR, leaf structure, cell expansion     

Nucleic Acid, Protein, and Starch Synthesis in Developing Cotyledons of Pisum arvense L.

During the cell-division period of cotyledon development inPisum arvense L. cell volume increases slightly but nuclearvolume shows little variation and the DNA content remains atthe 2C to 4C level. During the main period of cell expansionthere is a close correlation between cell volume, nuclear volume,and nuclear DNA content, the nuclei of the largest storage cellsfinally attaining the 64C level. The rate of RNA synthesis increasesseveral days after the increase in DNA has begun and at thesame time accumulation of reserve protein and starch begins.RNA and starch synthesis apparently cease some time before maturationbut protein synthesis continues until the seeds are ripe. Cotyledondevelopment was found to comprise two distinct phases: an initialphase of cell division and differentiation during which DNA,RNA, and protein per unit volume of cell decline; and a phaseof reserve accumulation in which DNA per unit volume of cellremains constant but RNA and protein per unit volume increase,starch synthesis is initiated, and all the cotyledon cells assumethe properties of storage cells.     

Temporal and Spatial Development of the Cells of the Expanding First Leaf of Arabidopsis thaliana (L.) Heynh

The three-dimensional quantitative leaf anatomy in developingyoung (9–22 d) first leaves of wild type Arabidopsis thalianacv. Landsberg erecta from mitosis through cell and leaf expansionto the cessation of lamina growth has been studied. The domainsof cell division, the relative proportion of the cell typespresent during development and the production of intercellularspace in the developing leaf have been determined by image analysisof entire leaves sectioned in three planes. Mitotic activityoccurs throughout the youngest leaves prior to unfolding andcell expansion is initiated firstly at the leaf tip with a persistentzone of mitotic cells at the leaf base resulting in a gradientof development along the leaf axis, which persists in the olderleaves. Major anatomical changes which occur during the developmentare, a rapid increase in mesophyll volume, an increase in thevein network, and expansion of the intercellular spaces. Thepattern of cell expansion results in a 10-fold variation inmesophyll cell size in mature leaves. In the youngest leavesthe plan area of mesophyll cells varies between 100 µm²and 400 µm² whereas in mature leaves mesophyll cells rangein plan area from 800 µm² to 9500 µm². The volumesof mesophyll tissue and airspace under unit leaf area increase3-fold and 35-fold, respectively, during leaf expansion. Thevolume proportions of tissue types mesophyll:airspace:epiderrnal:vascularin the mature leaf are 61:26:12:1, respectively. This studyprovides comparative information for future identification andanalysis of leaf development mutants of Arabidopsis thaliana. Key words: Arabidopsis, quantitative leaf anatomy, leaf expansion, image analysis     

Retardation and Reversal of Senescence in Bean Leaves by Benzyladenine and Decapitation

During the early stages of growth when the primary leaves ofbeans (Phaseolus vulgaris L., cv. Kinghorn) are expanding, thereis an increase in chlorophylls, carotenoids and protein levelsas well as superoxide dismutase (SOD), catalase and peroxidaseactivities. However, following the initiation of flowering onday (d) 21 there is a steady decrease in all of these parametersexcept levels of peroxidase activity, and by d 35 the primaryleaves are also showing pronounced morphological symptoms ofsenescence. Following the onset of senescence, primary leaveswere also leaking and showed increased levels of malondialdehyde(MDA). In addition, there was an increase in the lipid phasetransition temperature of a membrane fraction consisting predominantlyof chloroplast membranes, which reflected the formation of gelphase lipid. By d 56, the leaves had abscinded. A single applicationof benzyladenine (BA) to the primary leaves or decapitationof the shoot above the primary leaf on d 9 retarded all of thesesenescence symptoms, with decapitation being more effectivethan BA. On d 35 when the primary leaves were pale green-yellow, a singleapplication of BA to the leaves or decapitation of the shootabove them reversed the symptoms of senescence. Decapitationwas more effective than BA as a means of reversal, causing chlorophyll,carotenoid and protein levels to rise to values higher thanthose present in the control leaves. Decapitation also reversedthe senescence-related changes in membrane phase properties,decreased membrane leakiness and reduced lipid peroxidation. (Received August 22, 1983; Accepted January 26, 1984)     

Growth of the Stem of Agropyron repens (L.) Beauv

The growth rate of the stem of Agropyron repens (L.) Beauv.begins to decline when the sixth foliage leaf has expanded butthe relative growth rate declines throughout the period betweenthe production of one and ten mature leaves. On an absolutetime scale there is a progressive decline in growth rate ofsuccessively formed stem (node-internode) units. On a plastochronscale the relative growth rate of successive stem units declineswithin the apical region but increases behind the apex. Thedecline in the apical region is related to a decrease in therate of cell division and in the later formed stem units thereis no significant increase in cell number from the time of theirformation by the apex until the internode is initiated duringtheir fourth plastochron. These changes are related to concurrentchanges in the size of the shoot apex and in rates of leaf growth.     

Simultaneous production of buds on mother and daughter cells of Saccharomyces cerevisiae in the presence of hydroxyurea

Individual budding yeast cells, Saccharomyces cerevisiae, enclosedin small culture chambers were observed through two buddingcycles to examine their behavior during growth and division.In the nutrient medium (YHG medium), the duration of the buddingcycles was 77 min for mother cells and 90 min for daughter cells;a 13-min time lag between the two durations. Continuous exposureof cells to 16 or 32 mM hydroxyurea extended the duration ofthe cycles and increased the volume of the cells, resultingin the formation of abnormally large and equal-sized mother-daughterpairs. Each cell of these pairs subsequently produced buds simultaneously.Stained cell nuclei showed simultaneous nuclear division. Thissynchronous budding on mother-daughter pairs was repeated inthe next budding cycle. The coordination of growth with divisionis discussed in relation to these results. (Received August 11, 1979; )     

Effect of Benzyladenine on Diurnal Changes in DNA Content per Chloroplast and Chloroplast Replication in Intact Bean Leaves

The effect of benzyladenine (BA) on the diurnal changes in DNAand Chl contents per chloroplast and chloroplast replicationin primary leaves of bean plants (Phaseolus vulgaris L.) grownunder a 16 h light/8 h dark cycle was studied. Experiments weremade on primary leaves in the early expansion phase, where celldivision had been completed but chloroplasts were replicating.In untreated controls, chloroplast number, Chl content and freshweight per leaf showed daily periodic changes. Chl content perchloroplast increased in the light period every day, and freshweight per leaf increased most rapidly in the early dark period.Chloroplast number per leaf increased rapidly in the early darkperiod on day 9, though the increase began a little earlierand was less sharp on days 8 and 10. During these periods, DNAcontent per chloroplast was decreasing due to chloroplast divisionas chloroplast DNA (ctDNA) per leaf remained unchanged throughoutthe experimental period. BA induced increases in Chi contentper chloroplast, ctDNA content and fresh weight per leaf within6 h of its application, regardless of whether it was appliedat or 10 h after the beginning of the light period. Applicationof BA at 10 h in the light period shifted the start of chloroplastreplication by 6 h compared to that in untreated controls. However,when BA was applied at the beginning of illumination, the startof chloroplast replication showed the same relative change intime as above. 5-Fluorodeoxyuridine (5-FdU) promptly preventedBA-induced increase in Chl content and chloroplast number perleaf as well as ctDNA content per leaf.     

Adaptation to cycloheximide of macromolecular synthesis in Tetrahymena

Cycloheximide (CHI) at 10 ng/ml partially inhibited protein synthesis in exponential cultures of Tetrahymena Sp. At 20 ng/ml or greater, inhibition was complete. When protein synthesis was inhibited to any extent, cell division ceased immediately. In all instances where measured, synthesis of RNA and DNA also ceased. After a period of delay, cellular functions reinitiated in the order: (i) protein synthesis, (ii) DNA synthesis and, (iii) RNA synthesis and cell division. The delay in cell division was divided into three phases of: I, zero; II, low; and, III, fully recovered rates of exponential protein synthesis. The length of the three phases increased with increasing concentration of CHI Prior growth of cells for one generation in the presence of 7.5 ng/ml CHI (facilitation) eliminated phase I and slightly decreased phases II and III following subsequent challenge with an inhibitory concentration of CHI. Facilitation for six generations further decreased phases II and III. Protein synthesis and cell division were not inhibited during facilitation In the culture, succinate dehydrogenase activity did not increase during the delay but increased normally at the onset of division. In contrast, NADPH-cytochrome c reductase activity continued to increase for an hour after inhibition of protein synthesis, was constant for a period and did not increase again until an hour after reinitiatoin of cell division and RNA synthesis Inhibition of division of all cells was immediate and reinitiation of synthesis and cell division was non-synchronous.