Applications of Finite Element Analyses to Problems in Plant Morphology

Methods of describing the geometry and position of cells bymeans of the finite method are applied to selected extant (Fucus,Cutleria, and Calypogeia) and fossil plant genera (Protosaloinia,Spongiophyton, and Parka). The gross morphology and some aspectsof the ontogeny of these six genera are simulated by means ofcomputer; the pseudo- and parenchymatous tissue organizationsare mathematically characterized. Simulated representationsof living (Fucus and Cutleria) and fossil algae (Protosalcinia,Spongio phyton, and Parka) are shown to be distinctively differentfrom those of the bryophytes. The application of the finiteelement method to problems of plant morphology makes possiblethe dynamic simulations of some aspects of growth and developmentin living plants, and the extrapolation of missing stages inthe ontogeny of fossil plants.     

Organic chemistry of Protosalvinia (Foerstia) from the Chattanooga and New Albany Shales

Vertical samplings of Protosalvinia, a thalloid Upper Devonian alga from the Chattanooga and New Albany Shales, are chemically analyzed and correlated with the organic chemical constituents isolated from associated shale matrices. Normal, saturated acids (n-C₈ to n-C₃₆n-paraffins (C₁₀ to C₃₆), showing an odd carbon-number preference, branched-chain alkanes, and vanadyl porphyrins isolated from Protosalvinia vary in their concentrations with depth of burial and with the dominant associated morphology of Protosalvinia, i.e., P. arnoldii, P. ravenna, P. furcata. Organic constituents of shales, in general, reflect those detected in thalli; relative concentrations, molecular diversity, carbon chain-lengths and maxima of compounds extracted from both shale and fossil material are similar. Pristane, phytane and porphyrins are probably derived from a chlorophyllous organism, while δ¹³C data corroborate a photosynthetic system operating in the primary biosynthesis of shale geochemistry. Crude-oil extracts of Protosalvinia-rich strata contain higher alkane and lower aromatic hydrocarbon concentrations than those of an average crude oil. Chemical variations among forms of Protosalvinia suggest biochemical differences in original plant composition rather than diagenetic transitions; field observations of morphological trends seen in vertical samplings may be used in crude extrapolations of the organic chemical compositions of shale strata.     

Chemical examinations of some non-vascular Paleozoic plants

The organic chemical constituents of compression fossils ofNematothallus,Spongiophyton, Orestovia andEohostimella are identified and compared with those isolated from living and fossil forms ofBotryococcus (a green alga) andTaeniocrada (a vascular plant fossil). The range and maxima in the carbon numbers observed in the normal, saturated acids isolated fromNematothallus, Orestovia, andSpongiophyton are similar to those of fossilBotryococcus, while those acids contained within compression fossils ofEohostimella are similar to the hydrocarbon composition ofTaeniocrada. Isoprenoid, branched hydrocarbons and steroids identified fromNematothallus, Orestovia, andSpongiophyton suggest these genera have algal affinities, while the presence of thick cuticles and in some cases cutin-like compounds appear to show adaptation to a terrestrial environment. Phenolic compounds retained within rock matrices associated withEohostimella are similar to those isolated fromTaeniocrada suggesting chemical, as well as morphological parallels with the land plant habit. These data are interpreted as indicating an early polyphyletic exploitation of the terrestrial habitat during the Paleozoic.     

A Model for Growth and Self-thinning in Even-aged Monocultures of Plants

A theoretical model is derived from simple postulates to describethe rates of growth and mortality of plants in populations ofdifferent densities. The growth rate is described by a modificationof the logistic growth differential equation in which the increasein weight of an individual plant depends on its area, s_i ratherthan on its weight. The effective area for growth of a plantis reduced by an empirical function, f(s_i) with two terms: oneterm expresses the constraint imposed upon the increasing totalarea of plants by the limited physical area of the plot; theother term allows for a competitive advantage or disadvantagefor plants of varying sizes. Depending on the value of the parametercontrolling the relative competitive advantage term, intrinsicvariability between plants can be amplified or suppressed. Anindividual plant dies if the f(s_i) results in a negative growthrate for that plant. Computer simulations of the growth andsurvival of plants at different population densities were run.The results exhibit characteristics that appear realistic uponcomparison with published data: a survival of the fittest occurringduring thinning; a line of slope close to –3/2 boundingthe graphs of log weight versus log density; and the occurrenceof bimodality, associated with subsequent mortality, on frequencydistribution of log weight. computer logistic model, growth differential equation, density-effect, competition, mortality, self-thinning     

Turnover of the Intracellular Mannitol Pool of Fucus spiralis L. (Fucales, Phaeophyta) during Osmotic Shock

13C {¹H} nuclear magnetic resonance spectroscopy has been usedto study the turnover of the low-molecular weight carbohydratemannitol in the marine brown alga Fucus spiralis L. During incubationof plants in seawater medium with ¹³C enriched bicarbonate,all of the NMR-visible ¹³C appeared in mannitol; no significant¹³C-labelling of laminaran was observed in seawater, in a hypo-salineor in a hyper-saline medium. Pulse-chase experiments showedthat intracellular mannitol was subject to turnover (half-time20 h), the rate of carbon assimilation into mannitol being slightlygreater than the dissimilation rate, possibly due to net mannitolsynthesis during growth. Fucus spiralis was conservative in the use of mannitol as anintracellular osmoticum. In a hypo-saline medium, mannitol showedno substantial change while potassium, the major cellular cation,was reduced. In contrast, mannitol increased substantially overa 12 h incubation period in a hyper-saline medium, whereas potassiumcontent remained constant. Mannitol assimilation and dissimilation rates were not affectedsignificantly by transfer to a hypo-saline medium. The increasedmannitol content of plants incubated in a hyper-saline mediumappeared to be due to a significant increase in the mannitolassimilation rate. Key words: Mannitol, Fucus, Phaeophyta, ¹³C-NMR, osmotic adjustment     

Water Relations of Sitka Spruce Seedlings After Root Damage

Sitka spruce[Picea sitchensis(Bong.) Carr] seedlings were subjectedto varying degrees of root damage in a growth room, rangingfrom careful transplanting to exposure of the root system toair for up to 3 h. After replanting, transpiration (E), leafwater potential (₁) and growth of the shoot and root were measuredand observations made on plant survival. Some plants in the root exposure treatments died 20–85days after planting. In plants which eventually died, E wasdepressed directly after treatment, but ₁ showed a variableresponse. In some plants ₁ decreased from —8·0x 10⁵ to —30 x 10⁵ Pa after only 10 days but in othersthere was little change in ₁ for 50 days. In spite of the maintenanceof a high water potential in some of the latter plants for longperiods, no root or shoot growth occurred. In plants which lived, the root damage reduced root and shootgrowth relative to untreated controls, and most treatments stronglydepressed E but had little or no effect on ₁. The changes of E and ₁ in treated plants suggest that the suppressionof E was often independent of ₁ although water stress eventuallydeveloped in some of the severely treated plants. Sitka spruce, Picea sitchensis (Bong.)Carr, water relations, root damage, transpiration, leaf water potential     

Sulphate Uptake in Fucus serratus

The brown alga Fucus serratus Linn has been shown to possessan active sulphate uptake system, which is blocked by the metabolicinhibitors DNP and DCCD, but not by the photosystem II inhibitorDCMU. The affinity of the system for sulphate was 5.9 ? 10^–5M, and a monophasic response to external sulphate concentrationwas found in the range 10^–6–10^–3 M. Sulphateuptake was also inhibited by the Group VI anions selenate andchromate. Short-term kinetic experiments showed an initial hyperbolicuptake of for 20 s probably representing diffusion into the intracellular free spaces of the alga, afterwhich sulphate uptake was linear. The intermediates of the sulphateactivating system, APS and PAPS, appeared in the alga after20 s and cysteine after 1 min. The sulphate intermediary metabolicpools were saturated after 2 min, and radioactivity was linearlyincorporated into the sulphated fucan, fucoidan, after 2 min.A chase period of 15 min confirmed that the sulphate activatingsystem APSPAPS occurs in Fucus serratus.The principal metabolic fate of the assimilated sulphate wasesterification to fucoidan (80% of the total ³⁵S present aftera 1 h pulse) and assimilatory sulphate reduction to the sulphuramino acids was a minor pathway in this alga. The turnover ofsulphate in fucoidan was rapid (t_0.5 20 h) and was much higherthan the corresponding turnover of carbon under optimal photosyntheticconditions. This suggested that a preexisting polymer was sulphated;there was also no evidence for sulphated sugar nucleotides inthe short-term kinetic experiments.     

Fractionation of Nitrogen Isotopes during the Uptake and Assimilation of Ammonia by Plants

Two varieties (Nihonbare and Koshihikari) of rice plants (Oryzasativa L.) were grown hydro-ponically with two levels (20 and100 mg N liter ^–1) of ammonia. Variations in levels ofnatural abundance of ¹⁵N (¹⁵N) were analyzed in the ammoniaand organic nitrogen of shoots and roots, as well as in theammonia in the culture solution. There was substantial fractionationof nitrogen isotopes during the uptake of ammonia. When plantsabsorbed a large proportion of ammonia from a solution witha low concentration, less negative ¹⁵N values in plants andhigh positive ¹⁵N values in the ammonia remaining in solutionwere observed. The reverse was found when a smaller fractionof ammonia was absorbed from a solution with a higher concentrationof ammonia. The ^l5N values of ammonia in shoots and roots werehigher than in the respective constituent organic nitrogen,suggesting the fractionation of nitrogen isotopes during theassimilation of ammonia. Wild-type and mutant cells of the cyanobacterium(blue-green alga) Synechococcus PCC 7942 were grown in nitrate-or ammonia-containing medium as the source of nitrogen. Fractionationof nitrogen isotopes during the uptake of nitrate was limited,whereas that during the uptake of ammonia was considerable. ¹ In this report, the term ammonia refers indiscriminately toboth NH₃ or NH₄⁺. (Received June 13, 1991; Accepted September 12, 1991)     

An Extension of the Logistic Model of Plant Growth

The kinetics of growth of Dactylis glomerata L. were studiedunder controlled temperature and nutritional conditions at threelevels of irradiance (35·55 and 85 W m^–s). Thedry weights of the root and shoot parts of the plants were measuredeach week between the fourth and eleventh weeks after sowing. The growth kinetics were found to be dependent on the levelof irradiance, but no significant differences in the root: totaldry weight ratio were observed. To characterize the effect of illuminance, the experimentalgrowth curves were analysed initially using the logistic model,the adequacy of which is discussed. An extension of the logisticmodel is proposed, represented by the kinetic equation dM/dt= kM, with < 1 and where M is the dry weight of the plant.It is shown that this relationship allows a distinction to bemade between two kinds of plant material according to theirfunctions in the growth process. Dactylis glomerata L., illuminance, growth curves, kinetic analyses, logistic model, shoot:root ratio, partition of assimilates     

A Rapid Method for the Determination of the Leaf Area of Oxalis corniculata L. and Tephrosia purpurea (Linn.) pers.

A rapid simple method has been described for the determinationof leaf area of Oxalis corniculata L. (Oxalidaceae) and Tephrosiapurpurea (Linn.) pers. (Leguminoseae) by evaluating area = a²x0.866and a²x0.335 respectively for the two plants, where a representsa single linear measurement. The relation has been derived afterintegrating the equation of the curve r² = a² cos 2 coveringthe area of each leaflet. Areas of a large number of leaflets have been determined withthe help of two methods (1) Planimeter method, (2) Evaluationmethod. The significance of the difference between the two valuesfor a particular leaf has been statistically examined and itappears that the former method can be replaced by the latterin the case of these plants.     

The Concept of Minimum Leaf Number

Several quotations of minimum leaf numbers for floral initiationare given in the literature, but it was thought desirable toobtain further evidence that they do represent, as claimed byPurvis and Gregory for rye, obligatory vegetative growth precedingthe attainment of Klebs's Blhreife. The effects of mineral starvationon leaf number, as in Purvis's original experiments, were thereforetested with Xanthium, Eupatorium adenophorum, and Celosia argentea.In each of these, near-constant leaf numbers are characteristicof plants induced to flower rapidly by continuous short-daytreatment. In each, treatments such as starvation which retardvegetative growth do somewhat reduce the numbers. In Xanthiumindeed, the concept of Blhreife is superfluous, for the 8 leavesto be accounted for could be explained as the primordia presentin the seed plus the extra leaves initiated during daylengthinduction. For the other two plants, on the other hand, thesum of these is still many short of the required number, andfor them a concept of Blhreife expressed by leaf number is retained,but with the admitted doubt whether all factors controllingtheir flowering are yet known.     

Dasyclad-like problematic fossils from the lower Cambrian of North Greenland

The problematic fossil Kordesphecia nyeboensis gen. et sp. nov. from the lower Cambrian of North Greenland resembles the slightly younger, putative dasycladalean alga Amgaella Korde, 1957 in terms of its spirally arranged rhombic cells and central cavity. It differs in adding new cells through the sequential addition of roofing plates (‘shingles’) to pre-existing cell rows rather than encrusting lateral branches in dasycladalean fashion, in which character it seems comparable to the contemporaneous Lenaella Korde, 1959) from Siberia of unknown affinity. Kordesphecia is classified as incertae sedis but may be a stem-group dasycladalean.     

Effect of Inhibitors on the Formation of Stereoisomers in the Biosynthesis of {beta}-Carotene in Dunaliella bardawil

An assay system was developed in which the effects of inhibitorsof ß-carotene biosynthesis in Dunaliella bardawilcould be tested. Since D. bardawil can be induced to accumulateover 10% of its dry weight as ß-carotene, it is particularlysuitable for such studies. Norflurazon a desaturation inhibitor,caused the accumulation of phytoene, or of phytoene and phytofluene,depending on the concentration employed. J-334, a substituted6-methylpyrimidine which also inhibits desaturation, causedthe accumulation of ß-zeacarotene, -carotene and phytoenein different proportions, depending on the concentration employed.The cyclization inhibitors, nicotine, CPTA and MPTA, severelyaffected the growth and survival of the alga, and their effectscould therefore not be studied directly. However, their actionwas observed indirectly by following the transformation of phytoenein norflurazon-pretreated phytoene-rich algae. Under these conditions,presence of the cyclase inhibitors caused the transformationof phytoene to lycopene, rather than to ß-carotene.The accumulated ß-carotene or the intermediates ß-zeacarotene,lycopene, -carotene, phytofluene and phytoene in D. bardawilwere all composed of two stereoisomers, tentatively assignedas the all-trans stereoisomer (55%) and the 9-cis stereoisomer(45%). This suggests that the isomerization reaction which leadsto the production of the presumed 9-cis isomers occurs earlyin the pathway of carotene biosynthesis, at or before phytoene,with no isomerization during the further transformations leadingto ß-carotene. (Received January 29, 1990; Accepted May 9, 1990)     

Active uptake of inorganic carbon by Chlorella saccharophila is not repressed by growth in high CO2

Regulation of transport of dissolved inorganic carbon (DIC)in response to CO₂ concentration in the external medium hasbeen compared in two closely-related green algae, Chlorellaellipsoidea and Chlorella saccharophila. C. ellipsoidea, whengrown in high CO₂, had reduced activities of both CO₂ and transport and DIC transport activitieswere increased after the cells had acclimated to air. However,high CO₂-grown C. saccharophila had a comparable level of photosyntheticaffinity for DIC to that of air-grown C. ellipsoidea and thiswas accompanied by a capacity to accumulate high internal concentrationsof DIC. The high photosynthetic affinity and the high intracellularDIC accumulation did not change in cells grown in air exceptthat the occurrence of external carbonic anhydrase (CA) in air-grownC. saccharophila stimulated the intracellular DIC accumulationin the absence of added CA. These data indicate that activeDIC transport is constitutively expressed in C. saccharophila,presumably because this alga is insensitive to the repressiveeffect of high CO₂ on DIC transport. This strongly supportsthe existence of a direct sensing mechanism for external CO₂in Chlorella species, but also indicates that external CA isregulated independently of DIC transport in Chlorella species. Key words: Carbonic anhydrase, Chlorella, CO₂-insensitive, DIC transport, wild type     

Physiological Responses of Phytoflagellates to Dissolved Organic Substrate Additions. 2. Dominant Role of Autotrophic Nutrition in Pyrenomonas salina (Cryptophyceae)

The enhancement of algal growth by organic substrate assimilationis a common laboratory observation, yet few studies have addressedthe interaction of dissolved organic compounds and environmentalfactors for controlling the relative contribution of heterotrophyand autotrophy to the nutrition of these algae. The effectsof light intensity and glycerol addition on the growth, cellvolume, pigmentation, and carbon uptake of the facultative heterotroph,Pyrenomonas salina Santore, were examined. Glycerol additionto cultures growing at a limiting light intensity increasedthe growth rate, increased the average cell volume and cellularstarch content, decreased the cellular phycoerythrin to chlorophyll ratio, and had no effect on the CO₂ fixation rate cell^–1.Glycerol addition to cultures growing at a moderate light intensitythat was saturating for photo-autotrophic growth increased theaverage cell volume and cellular starch content but had no effecton the CO₂ fixation rate cell^–1. The results indicatethat autotrophy was the major process for carbon acquisitionduring the growth of P. salina, but that carbon acquisitionfrom glycerol catabolism also was used to partially supportgrowth of the alga at the limiting light intensity. In addition,glycerol presumably was used to fulfill the energy and/or reductantrequirements of the alga, and to increase the reserve carbohydrate(starch). ¹ Current address and address for correspondences: Horn PointEnvironmental Laboratories, University of Maryland, PO Box 775,Cambridge, Maryland 21613, U.S.A. (Received October 29, 1990; Accepted May 31, 1991)     

Derivation of Pressure-Volume Curves by a Non-Linear Regression Procedure and Determination of Apoplastic Water

Data from pressure-volume (PV) analysis may be submitted totransformation I [i.e. leaf water potential (₁) versus inverserelative water content (1/R)] or to transformation II (i.e.1/₁ versus R). This may cause an essential distortion of theerror structure especially in transformation II due to the relativelylarge range which is to be covered by the 1/₁ ratio. Similarly,logarithmic transformation of leaf turgor potential (_P) whenderiving the sensitivity factor of elasticity (ß)by linear regression from values of In _p and 1/R may distortthe error structure. In order to investigate the magnitude ofthe distortion effect on parameters derived from PV analysisby regression a non-linear regression procedure was comparedwith the common linear procedure when calculating _p from ßin the turgid region and leaf osmotic potential (_P) in boththe turgid and non-turgid region. As test plants we used fieldgrown species of spring barley (Hordeum distichum L., cvs Gunnarand Alis). The results show that transformations and applicationof linear regression procedures distort the error structureof _p more than the error structure of _', which was only slightlyaffected. However, we recommend the use of the non-linear procedurein both cases. Furthermore, from PV analysis, obtained by thermocouple hygrometryon living and killed leaf tissue, respectively, we derived themathematical basis for calculating the apoplastic water fraction(R_a). R_a was 0.15 at R= 1 and decreased with dehydration. The equations describing the relation between and R and between_p and R were extended to take into account the apoplastic waterfraction. Key words: Apoplastic water, distortion errors, non-linear regression, pressure-volume curves     

Stable carbon isotopes and the metabolism of the terrestrial Devonian organism Spongiophyton

Devonian fossils of Spongiophyton have been identified as a terrestrial evolutionary intermediate between algae and vascular land plants on the basis of their dichotomously branched, tubular morphology, thick cuticles, and the scattered distribution of surface pores. Our understanding of their physiology is, however, severely limited, but may be increased through the use of stable carbon isotope measurements. One such study led to the hypothesis that Spongiophyton carried a carbon isotope (δ¹³C) signature characteristic of lichens ( Jahren et al., 2003 Geology 31 , 99–102). Here, we outline three difficulties with accepting this idea and report independent isotopic measurements of Spongiophyton fossils from Canada and Ghana. Our results show that the isotopic discrimination of analogous tissues of Spongiophyton, extant lichens, liverworts and mosses are statistically indistinguishable. We suggest therefore that claims to have definitively identified lichen metabolism are premature, and cannot be sustained.     

Enhanced Model for Photophobic Responses of the Blue-Green Alga, Phormidium uncinatum

An improved computer-based mathematical model of photophobicresponses in the blue-green alga, Phormidium uncinatum, hasbeen used to simulate the behavior of the alga under variouslight and dark conditions. Under high light intensities, themodel predicts the induction of step-up phobic responses. Thisnovel result could be varified experimentally in vivo. Appropriatefeatures have been incorporated to simulate the effects of ionophoresand the application of external electrical fields; results ofthe computer simulation and in vivo experiments are compared.Several parameters of the model have been varied to specifythe range in which phobic responses are permitted. These parametersallow conclusions to be drawn on the functional correlates inthe living organism. (Received July 13, 1982; Accepted October 9, 1982)     

Levels of {beta}-Glucan and Lignin in Elongating Internodes of Deepwater Rice

Partial submergence or treatment with either ethylene or gibberellicacid (GA₃ induces rapid growth in deepwater rice (Oryza sativaL.). We correlated the synthesis of two cell wall componentswith two phases of internodal elongation, namely (13,14)-ß-glucanformation with cell elongation and lignification with differentiationof the secondary cell wall and cessation of growth. The contentof ß-glucan was highest in the zone of cell elongationin internodes of air-grown plants and plants that were inducedto grow rapidly by submergence. In the intercalary meristemand in the differentiation zone of the internode, ß-glucanlevels were ca. 70% lower than in the zone of cell elongation.The outer cell layers, enriched in epidermis, contained moreß-glucan in submerged, rapidly growing internodesthan in air-grown, control internodes. The ß-glucancontent of the inner, parenchymal tissue was unaffected or slightlylowered by submergence. The epidermis appears to be the growth-limitingstructure of rapidly growing rice internodes. We hypothesizethat elevated levels of ß-glucan contribute to elongationgrowth by increasing the extensibility of the cell wall. Lignificationwas monitored by measuring the content of lignin and the activitiesof two enzymes of the lignin biosynthetic pathway, coniferylalcohol dehydrogenase (CAD) and phenylalanine ammonia-lyase(PAL), in growing and non-growing regions of the internode.Using submerged whole plants and GA₃-treated excised stem segments,we showed that lignin content and CAD activity were up to sixfoldlower in newly formed internodal tissue of rapidly growing ricethan in slowly growing tissue. No differences were observedin parts of the internode that had been formed prior to inductionof growth. PAL activity was reduced throughout the internodeof submerged plants. We conclude that lignification is one ofthe processes that is suppressed to permit rapid growth. ¹ This work was supported by the National Science Foundationthrough grants No. DCB-8718873 and DCB-9103747 and by the Departmentof Energy through grant No. DE-FGO2-90ER20021. M.S. was therecipient of a fellowship from the Max Kade Foundation.     

Carbon Isotope Ratios of Epidermal and Mesophyll Tissues from Leaves of C3 and CAM Plants

The ¹³C values for epidermal and mesophyll tissues of two C₃plants, Commelina communis and Tulipa gesneriana, and a CAMplant, Kalancho daigremontiana, were measured. The values forthe tissues of both C3 plants were similar. In young leavesof Kalancho, the epidermis and the mesophyll showed S13C valueswhich were nearly identical, and similar to those found in C3plants. However, markedly more negative values for epidermalcompared to mesophyll tissue, were obtained in the mature Kalancholeaf. This is consistent with the facts that the epidermis ina CAM leaf is formed when leaves engage in C₃ photosynthesisand that subsequent dark CO₂ fixation in guard cells or mesophyllcells makes only a small contribution to total epidermal carbon. (Received January 27, 1981; Accepted May 14, 1981)