Chloramphenicol Inhibition of Salt Absorption by Intact Plants

The influence of chloramphenicol on the accumulation of calciumand rubidium by intact barley plants has been investigated.The uptake of both ions during 24 hrs. was reduced by exposureto the inhibitor for 24 hrs. before the uptake period. The maineffect was on the fractions of the ions which reached shootsand on those present in roots in non-exchangeable forms. Chloramphenicolalso reduced transpiration, but to a considerably smaller extent. The primary effect of chloramphenicol on salt uptake appearsto be on the mechanisms of active transport which convey ionsacross the root. Since chloramphenicol does not affect the uptakeof oxygen, it appears that the active accumulation of saltsis not directly mediated by the electron transfer in respiration.The results are compatible with the existence of a linkage betweensalt absorption and protein synthesis; the nature of this linkageis at present unknown.     

Restoration of Photosynthesis in Pot-Bound Tobacco Plants

Premature senescence is observed in pot-bound tobacco plants(Nicotiana tabacum L. cv. xanthii) and this is shown to be accompaniedby gross accumulation of leaf starch and a marked decline inphotosynthesis, ribulose- 1, 5-bisphosphate (RuBP) carboxylaseactivity, and soluble protein content. Starch content, uptakeof CO₂ by leaf discs, and the activity of RuBP carboxylase inwhole leaf extracts were measured daily following transfer ofrestricted plants to larger pots. Starch declined rapidly, whilstphotosynthetic activity was fully restored within a period ofseveral days, and frequently exceeded the maximum rates measuredin non-restricted plants. This overcompensation, which couldbe related to availability of carbohydrates accumulated as starch,is discussed in relation to the well-established horticulturalpractice of ‘potting on’.     

The Organic Acid Metabolism of Swede 'Root' Tissue

Data are recorded on the quantitative changes in the contentof succinic, malic and citric acids of discs of washed ‘root’tissue of ‘swede’ (Brassica napus), subjected toexperimental treatments involving the addition of succinate,malate, citrate, -ketoglutarate, pyruvate and malonate. Theresults are interpreted as showing the acids to be associated,in part at least, with the operation of an active Krebs cycle.It is suggested that they are also involved, by providing carbonskeleton material, in the enhanced protein synthesis resultingon washing discs of swede tissue and treating washed discs withphosphate buffer.     

The Effect of Bud Position on Branch Growth and Bud Abscission in Quercus petraea (Matt.) Liebl.

The time at which a bud began to expand was related to its positionnot only on an individual shoot but also within the crown. Thedistribution of buds and branches on the shoot was uneven; theshoot tip, where they were densely clustered, was termed the‘whorl; and the remainder of the shoot, where they werewidely spaced, the ‘interwhorl’ stem. In spring,the terminal bud started expanding before the ‘whorl’buds which preceded the ‘interwhorl’ stem buds;completion of the flush of growth, determined by the end ofleaf expansion, occurred in the reverse order, ‘interwhorl’> ‘whorl’ > terminal. Similarly bud expansionstarted at the top of the crown and progressed downwards, andthe first shoots to complete their flush were at the bottomof the crown. Approximately 60% of the buds on each shoot beganexpanding in spring but only about half of these formed branches.Bud abscission began in May and by Sep. 45% of buds originallypresent had abscised. Most of-the buds that did not abscisewere the small buds at the base of the shoot that were not originallyassociated with a leaf. Approximately 42% of ‘whorl’buds and 28% of MnterwhorP stem buds formed branches. ‘Whorl’branches were approx. 60% longer that ‘interwhorl’stem branches; buds on the lower surface of the shoot producedlonger branches than those on the upper surface. The implicationsof the results for the development of crown form and selectionof superior oak are discussed. Quercus petraea, oak, buds, branches, crown form     

Effects of Flooding and Drainage and their Alternation on the Growth and Uptake of Nutrients by Rice (Oryza sativa L., indica, var. IR-8)

Continuous flooding of the soil (‘flooded’ treatment)gave best growth of IR-8 variety of rice whereas soil drainedfor 4 weeks and then flooded for 8 (‘drained and flooded’treatment) resulted in poorest growth and chlorotic plants.Plants grown in the continuously drained soil (‘drained’treatment) and those in the soil flooded for 4 weeks and thendrained for 8 (‘flooded and drained’ treatment)showed intermediate growth. There were no differences in therelative water content of plants growing in the various treatments.Analyses of plant tissues showed that a consideration of therelative concentration of Fe, Mn, and P in the shoots is mostclosely related to the performance of rice under various culturalconditions. An increase in the concentration of Fe in the planttissues following flooding was correlated with the best growth(‘flooded’ treatment) unless it was accompaniedby high level of Mn (as in the ‘drained and flooded’treatment) which may have proved toxic, e.g. by interferencewith Fe metabolism as was evidenced by chlorosis. Measurementsof oxidation-reduction potentials, oxygen diffusion rates, andthe concentration of exchangeable and soluble Fe and Mn in thesoils have shown that the ‘drained and flooded’treatment caused the most extreme reducing conditions. Floodingaccompanied by the development of extreme reducing conditionsled to a greater accumulation of Mn in the shoots (‘drainedand flooded’ treatment) whereas flooding accompanied bythe maintenance of oxidizing conditions (‘flooded’treatment) resulted in a lower uptake of Mn. Growth of riceplants for 4 weeks in the drained soil did not fit them forthe reduced conditions which developed during subsequent flooding(‘drained and flooded’ treatment).     

Diurnal Phototropism in Leaves of Lavatera cretica L. under Conditions of Simulated Solar-Tracking

Diurnal laminar reorientation was followed in solar-trackingleaves of Lavatera cretica L. under simulated conditions. Asimulated ‘sun’ was moved over the lamina in a 180?arc in the vertical plane of the mid-vein, at an angular velocityof 15? h^–1 in a regime of 12-h photoperiods. In one groupof plants the petioles of the experimental leaves were arrangedto face ‘sunrise’, while in the other they werearranged to face ‘sunset’. At ‘sunrise’,the laminae in both groups, which were inclined towards theanticipated direction of ‘sunrise’, changed theirelevation towards the rising ‘sun’, resulting inprogressive reduction in the angle of incidence (AI) of lighton the laminar surface (AI= differential between laminar and‘solar’ elevation). As a result, laminar and ‘solar’elevation converged, and laminar reorientation gradually ceased,until the ‘solar’ elevation had passed the normalto the laminar surface (AI=0?). laminar reorientation was thenresumed, but its direction was reversed to follow the directionof ‘solar’ reorientation. During most of the remaining‘day’, laminar elevation (LE) trailed that of the‘sun’ by an average of 11?-14?. Laminar reorientationthen anticipated ‘sunset’ by starting to slow down60 to 90min in advance. During the 12-h dark period, the laminareoriented towards the anticipated direction of the subsequent‘sunrise’. The time-course of nocturnal reorientationwas qualitatively different in the two groups of experimentalplants. The time-course of diurnal phototropism under naturaland simulated conditions is analysed and compared and differencesand similarities between them are discussed. Key words: Diurnal phototropism, solar-tracking, vectorial excitation     

The growing outer epidermal wall: design and physiological role of a composite structure

Background: The cells of growing plant organs secrete an extracellular fibrouscomposite (the primary wall) that allows the turgid protoplaststo expand irreversibly via wall-yielding events, which are regulatedby processes within the cytoplasm. The role of the epidermisin the control of stem elongation is described with specialreference to the outer epidermal wall (OEW), which forms a ‘tensileskin’. Novel Facts: The OEW is much thicker and less extensible than the walls ofthe inner tissues. Moreover, in the OEW the amount of celluloseper unit wall mass is considerably greater than in the innertissues. Ultrastructural studies have shown that the expandingOEW is composed of a highly ordered internal and a diffuse outerhalf, with helicoidally organized cellulose microfibrils inthe inner (load-bearing) region of this tension-stressed organwall. The structural and mechanical backbone of the wall consistsof helicoids, i.e. layers of parallel, inextensible cellulosemicrofibrils. These ‘plywood laminates’ containcrystalline ‘cables’ orientated in all directionswith respect to the axis of elongation (isotropic material).Cessation of cell elongation is accompanied by a loss of order,i.e. the OEW is a dynamic structure. Helicoidally arranged extracellularpolymers have also been found in certain bacteria, algae, fungiand animals. In the insect cuticle crystalline cutin nanofibrilsform characteristic ‘OEW-like’ herringbone patterns. Conclusions: Theoretical considerations, in vitro studies and computer simulationssuggest that extracellular biological helicoids form by directedself-assembly of the crystalline biopolymers. This spontaneousgeneration of complex design ‘without an intelligent designer’evolved independently in the protective ‘skin’ ofplants, animals and many other organisms.     

Plant Morphology: The Historic Concepts of Wilhelm Troll, Walter Zimmermann and Agnes Arber

Recent molecular systematic and developmental genetic findingshave drawn attention to plant morphology as a discipline dealingwith the phenotypic appearance of plant forms. However, sincedifferent terms and conceptual frameworks have evolved overa period of more than 200 years, it is reasonable to surveythe history of plant morphology; this is the first of two paperswith this aim. The present paper deals with the historic conceptsof Troll, Zimmermann and Arber, which are based on Goethe'smorphology. Included are contrasting views of ‘unity anddiversity’, ‘position and process’, and ‘morphologyand phylogeny’, which, in part, are basic views of currentplant morphology, phylogenetic systematics and developmentalgenetics. Wilhelm Troll established the ‘type concept’and the ‘principle of variable proportions’. Hehas provided the most comprehensive overview of the positionalrelations of plant forms. Agnes Arber started from the universaldynamics of life and attempted to describe all structures asprocesses. She paid attention to ‘repetitive branching’,‘differential growth’, and ‘parallelism’.As a result she has recently been rediscovered by developmentalbotanists. Walter Zimmermann rejected any metaphysical influenceon plant form and instead called for objective procedures. Hewas mainly interested in phylogenetic ‘character transformation’and the ‘reconstruction of genealogical lines’.Guided by the example of flower-like inflorescences, a futurepaper will deal with functional and developmental constraintsinfluencing plant forms. Recent morphological concepts (‘trialectical’,‘continuum’/‘fuzzy’, ‘processmorphology’) will be discussed and related to currentmorphological and developmental genetic research. Copyright2001 Annals of Botany Company Plant form, plant morphology, natural philosophy, homology, phylogeny, Goethe, Troll, Arber, Zimmermann, typology, character transformation, differential growth, complementarity     

Factors determining Petal Colour of Baccara Roses III: EFFECT OF THE RATIO BETWEEN CYANIN AND PELARGONIN

The changes in colour and in the pigment concentration of thetwo sides of Baccara rose petals which occur when plants aregrown under various temperature regimes, were examined. Theinner side of the petal is redder and the predominant pigmentis pelargonin whereas the outer petal surface tends to ‘blue’,and, the predominant pigment on this side is cyanin. The cyanin:pelargonin ratio on the outer side of petals increased three-foldunder the influence of low temperatures. The outer surface of petals growing for a long period underlow tempertaures was ‘blue’ when compared with thered petals which had been subjected to low temperatures fora short period. The cyanin: pelargonin ratio of ‘blue’petals was higher than that of red petals. Total pigment contentwas similar in both types of petal. Flowers grown under hightemperatures ‘blued’ without a concomitant fallin the cyaninpel: argonin ratio. Examination of colour solutions in which the ratio between cyaninand pelargonin was varied revealed that the colour of the solutionbecame bluer as this ratio increased. We suggest that the ‘blueing’ of Baccara rose petalsis caused primarily by a dilution of the cyanin content, butwhen the ratio between cyaniri and pelargonin increases sharply,‘blueing’ may also occur in dark flowers in whichthe total pigment content did not diminish.     

Uptake and Metabolism of Sugars by Suspension cultured Catharanthus roseus Cells

p. 186, right column line 11 ‘27.2 KBq’ change to‘37.2 MBq’ p. 187, left column line 8 ‘27.2 KBq’ change to‘37.2 MBq’ line 10 ‘13.6 KBq’ change to ‘18.6 MBq’ line 11 ‘13.6 KBq’ change to ‘18.6 MBq’ line 21 ‘89%’ change to ‘80%’ right column line 24 ‘CLC-NH₄’ change to ‘CLC-NH₂’ P. 189, Table 1 appeared incorrectly: it should appear as indicated.     

The Polarity of the Cell-wall of Valonia

Further evidence is presented to show that the systems of orientationof cellulose fibrils in the cell-walls of Valonia and Dictyosphaeriamay be described by reference to two ‘poles’ uponwhich these orientation systems converge. The ‘poles’are real structural features of the wall.     

How do migrating daphnids cope with fish predation risk in the epilimnion under anoxic conditions in the hypolimnion?

The vertical distribution of Daphnia in experimental tubes isinfluenced by fish kairomone concentration in the ‘epilimnion’and oxygen conditions in the ‘hypolimnion’. Daphnidstrade off reduced predation mortality in a refuge against disadvantagesdue to unfavourable oxygen conditions.     

Reply to 'In defence of the Cell Quota model of micro-algal growth' by M. R. Droop

Droop’s defence of the Cell Quota model shows that itis statistically superior to the ‘Chemical Reaction’(CR) model for modelling of the internal nutrient content ofcells at a range of dilution rates in a chemostat. As Droopconcludes, saturating functions like a rectangular hyperbolaappear to be a more appropriate choice of function for algalgrowth/nutrient content than power law curves. Droop finisheswith an interesting speculation as to the reason why algal growthand surface absorption chemistry might share common functionalforms.     

The Use of Random and Contiguous Quadrats in the Study of the Structure of Plant Communities

Artificial ‘communities’ of discs have been constructedand sampled by random throws of quadrats of different sizesand by a grid of contiguous quadrats. The use of a grid opens the way to more detailed study of thenature of the non-random distribution of species in the field,especially to the detection of mosaic patterns not normallyrevealed by subjective methods.     

The Effects of Salinity upon Galactosyl-Glycerol Content and Concentration of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in the major alcohol-soluble, low molecular weight carbohydratesof P. purpurea, O--D-galactopyranosyl-(1-2)-glycerol (‘floridoside’)and O--D-galactopyranosyl-(1-1)-glycerol (‘isofloridoside’),have been examined in response to salinity variation. ‘Floridoside’is shown to vary in absolute amount, increasing in hypersalineand decreasing in hyposaline media. ‘Isofloridoside’content per cell does not change in a similar manner. Responsesare almost identical under light or dark conditions, ‘floridoside’changes being complete within 24 h. Decreasing the externalwater potential using ionic and non-ionic solutes has the sameeffect upon galactosyl-glycerol content. The amount of ‘floridoside’synthesized, and degraded under hypersaline and hyposaline conditionsrespectively is shown to be insufficient to restore cell volumeto its original value. It is therefore suggested that the primaryfunction of ‘floridoside’ increases in concentratedsea-waters is that of a compatible solute, serving to protectthe cell during periods when the external salt content is increaseddramatically.     

Changes in the Pollen Grain Wall of Linum grandiflorum following Compatible and Incompatible Intraspecific Pollinations

The exine surrounding the colpal furrows in the pollen grainsof Linum grandiflorum is rapidly degraded following the twocompatible pollinations between ‘pin’ and ‘thrum’types of flower and also following the incompatible pollinationbetween ‘thrum’ and ‘thrum’. In allthese pollinations the pollen germinates normally. Exine isnot degraded in the incompatible pollination between ‘pin’and ‘pin’. In this pollination the pollen does notswell or germinate. The exine degradation is restricted to thecolpal regions. Hydration of the pollen grain by buffer solutionwithout contact with the stigma also stimulates the degradationof the exine. The erosion of the exine reveals a fibrous, PAS-positivematrix which follows the original contours of the exine. Vesicles are discharged into the intinc following pollination;these appear to contribute their contents to the intine-likewall which eventually invests the pollen tube. The observations are interpreted by assuming:

1. 1. an enzyme situatedwithin the pollen and localized underthe colpi; this enzymeis active after hydration;
2. 2. the degradation is a means bywhich colpal furrows are enlargedto permit the emergence ofthe pollen tube;
3. 3. the degradation process both by bufferand on the stigmais purely the consequence of hydration andis only secondarilyrelated to incompatibility through the ‘pin’by‘pin’ pollination not permitting hydration ofthepollen.

     

Properties of Mitochondria Prepared by Two Different Isolation Procedures From the Cotyledons of Germinating Bean Seedlings

Mitochondria from 1-day-old bean cotyledons were isolated bya ‘slow’ isolation procedure involving a wash andby a ‘rapid’ procedure. The mitochondria isolatedby the ‘rapid’ procedure were more tightly coupledthan those isolated by the ‘slow’ procedure. Anexogenous supply of cytochrome c or NAD was shown to improvethe activity of mitochondria isolated by the ‘slow’procedure, but not those isolated by the ‘rapid’procedure. The phosphorylative abilities of the latter weremuch greater than the former and were retained for longer periods.It was found that there was a leakage of NAD out of the mitochondria.     

Effects of Inorganic Phosphate on the Utilization of Sucrose by Suspension-cultured Catharanthus roseus Cells

The metabolic fate of [U-¹⁴C]sucrose in suspension culturesof Catharanthus roseus cells was monitored for 96 h after thecells were transferred to fresh complete (‘+Pi’)or to phosphate-deficient Murashige and Skoog (‘–Pi’)medium. Sucrose was hydrolysed extracellularly to glucose andfructose. The rate of uptake of sugars by the cells was 1.5–3times higher in ‘+Pi’ culture than in ‘–Pi’culture. Little difference in the rate of incorporation of radioactivityinto the ethanol-soluble fraction was found between the ‘+Pi’and ‘– Pi’ cultures during the initial 24h of culture, but after 48 h the rate in ‘ +Pi’cultures was higher than that in ‘–Pi’ cultures.Incorporation of radioactivity into ethanol-insoluble macromoleculeswas always significantly higher in the cells in ‘+Pi’cultures than in those in ‘–Pi’ cultures.The results suggest that Pi strongly affects the utilizationof sugars by cultured plant cells through the stimulation oftransport of sugars as well as through the activation of metabolism. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, sucrose, transport, metabolism     

The Occurrence of Translocated Antibiotics in Expressed, Plant Sap

The details of a convenient laboratory press are presented anda procedure by which plant sap is readily obtained is described.The pressing procedure has been shown to release 53–74per cent. of the total plant water as expressed sap. Preliminary observations on the uptake and translocation ofantibiotics by higher plants obtained by examining expressedsap are described. It is shown that the assay of expressed sapprovides a measure of the griseofulvin and chloramphenicol concentrationin leaves of plants grown in solutions of these antibioticsthat does not differ significantly from the value obtained bythe assay of water extracts. Extraction of leaves from plants grown in griseofulvin solutionswith organic solvents demonstrates a much greater antibioticcontent than is indicated by the assay of expressed sap. Toexplain this difference a ‘free’ antibiotic fraction,obtainable in expressed sap or water extracts, and a ‘bound’fraction recovered from the leaf only by organic solvent extractionare postulated.     

The Influence of the Plant Growth-regulator, 2-Methyl-4-Chlorophenoxyacetic Acid, on the Metabolism of Carbohydrate, Nitrogen and Minerals in Solanum lycopersicum (Tomato)

The effects of the foliar application of phytocidal concentrationsof 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in totaldry weight, and in ‘available carbohydrate’ (starch,‘total’ and ‘reducing’ sugars), totalnitrogen, phosphorus, potassium, calcium, and magnesium of ‘tops’and roots of tomato plants have been followed over a periodof 14 days following spraying. There were two main treatments—‘nutrient’(nutrient supply to roots continued after spraying) and ‘water’(distilled water only supplied to roots after spraying) and‘water’ (distilled water only supplied to rootsafter spraying)—the sub-treatments consisting of ‘MCPA’versus ‘no-MCPA’ for each of the main treatments.Twelve different times of sampling were used. In analysing the present data, the quantity ‘residualdry weight’ (total dry weight less ‘available carbohydrate’),which was originally introduced by Mason and Maskell as a basisof reference for analyses of plant organs in short-period experimentsnot involving appreciable growth, has been used as an estimateof the permanent structure of plant growth. This new use ofthe ‘residual dry weight’ basis has brought outimportant features which were obscured when the data were leftin their primary form (as percentages of total dry weight oramounts per plant). Growth, as measured by increase in ‘residual dry weight’,was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acidshortly after spraying, in both the presence and the absenceof nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, netassimilation rate (estimated as rate of increase in total dryweight per gram ‘residual dry weight’ of the ‘tops’)was greatly diminished while uptake of total nitrogen and ofP₂O₅ (estimated as increase in total nitrogen or of P₂O₅ ofthe whole plant per day per 1 g. ‘residual dry weight’of the roots) appeared to undergo a similar but much smallerdiminution. It seemed probable, however, that in the presenceof MCPA a larger proportion of the carbohydrate actually formedwas utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletionof ‘available carbohydrate’ as a result of MCPAtreatment, this fraction showing a steady increase in all treatmentsthroughout the experiment. The rate of increase was, however,much reduced by MCPA treatment. The ‘tops’ presentedmuch the same picture as the whole plant, but for the rootsthe situation was quite different. While the roots of the ‘no-MCPA’plants and also of the ‘MCPA-water’ plants showeda steady increase in available carbohydrate, those of the ‘MCPA-nutrient’plants rose only very slightly (from the initial value of 8mg. per plant to about 10 mg.) during the first 2 days, andthen in the next 2 days declined to a value (about 6 mg.) belowthe initial and remained at this low level for the rest of theexperiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyaceticacid in the presence of nutrient may be due to depletion ofthe ‘available carbohydrate’ supplies in the roots,which is shown to be brought about, in part, by reduced transportfrom the tops, and partly by the relatively greater utilizationof the carbohydrate present. These results offer an explanationfor the facts that plants showing vigorous growth are more easilykilled by MCPA and that perennial plants, particularly thosewith storage tissues in their roots, are more resistant. Further,they suggest the useful practical application that MCPA treatmentshould be given when the carbohydrate reserves of the rootsare at a minimum. For perennial plants, conditions might beexpected to be optimal for the application of MCPA in late spring,at a time when the first ‘flush’ of growth is slowingdown and before any appreciable new reserves of carbohydratehave been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid preventedthe net synthesis of starch, but still permitted an appreciablenet formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effecton the uptake of potassium, calcium, or of magnesium. The lackof effect on potassium is contrasted with the previous observationby Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrationsof MCPA, applied over a relatively long period to the rootsof tomato plants, specifically depressed the uptake of potassium.