Apple Fruit Bud Development and Growth; Analysis and an Empirical Model

Analysis of the information available on apple bud developmentand growth after dormancy leads to an empirical model of growthto full bloom. The analysis and model are set in the frameworkof the physiological mechanisms considered to be responsiblefor dormancy and subsequent bud growth. It is necessary to introducean arbitrary ‘growth unit’ scale to describe theseprocesses quantitatively, which is done by the equation G = A/(I+be^–k(I).P) where G and A are in growth units, the value of k is controlledby a dormancy index I and P is a temperature summation. Themodel fulfils the main requirements laid down for it and thevalues of P at full bloom, derived from controlled environmentwork and field observations, are very similar.     

A Comparison of Two Approaches for Modelling Cassava (Manihot esculenta Crantz.) Crop Growth

Two approaches for modelling the growth and development of cassava,Manihot esculenta Crantz, are described and evaluated. The twomodels differ only in the hypotheses accounting for storageroot growth. In model 1, assimilate allocation to storage rootsis governed by the combined Chanter's (1976: Mathematical modelsin mushroom research and production. PhD Thesis, Universityof Sussex, UK) growth equation; and in model 2 the spill-overhypothesis for assimilate allocation to storage root governsstorage root growth. In both models, canopy photosynthesis generatesthe carbon substrate required for all growth processes. Thegrowth rates of leaves, stems and storage roots are definedby growth equations subject to substrate saturation kinetics.A key feature of both models is that the growth demands of thestem, fibrous roots and storage roots are related to leaf demandrates. Allocation to stems and branches was modelled by meansof a modified logistic growth equation which includes all theparameters and variables (number of nodes, internode lengths,stem density, stem modulus of elasticity and branch tensilestrength) that define the limits of the load bearing capacityof the shoot's supportive structures. The correlation coefficientsfor determination of yield prediction for the models werer =0.898,P =0.0385 (model 1) and r =0.954, P =0.0117 (model 2). For agrowth season of 290 d (after which leaf area index equals zeroand crop growth ceases), both models simulate the sigmoidaltransition from the lag to exponential phase of crop growth.Both models are equally well corroborated by observed data;however, model 1 has greater explanatory power. Copyright 2000Annals of Botany Company Allocation, simulation, model, crop growth, cassava, Manihot esculenta Crantz.     

Simulations of the Ontogeny of Spongiophyton, a Devonian Plant

Mathematical representations of the cellular organization anddimensions of Spongiophyton Krusel, a Middle Devonian thallophytewere projected by means of a computer to simulate patterns ofdevelopment and organization. Extrapolation of the cellularpatterns observed on the surface of the fossil may be comparedwith those derived from living plants of which the ontogenycan be directly observed. Spongiophyton is compared in thisrespect with the growth of Protosalvinia (an Upper Devonianplant of enigmatic affinity), Pellia (a thallose liverwort)and Cutleria (a brown alga). The growth pattern of Spongiophytondeveloped by computer shows a closer similarity to that of thepseudoparenchymatous alga Cutleria than to the truly parenchymatousPellia or the fossil Protosalvinia. Computer simulations ofthe growth process throw light on the affinity of Spongiophytonwhich cannot be derived from direct observation of the fossil.Broader applications of computer simulations of tissue organizationand gross morphology are suggested with regard to the studyof living and fossil plants.     

Leaf Growth in Cotton (Gossypium hirsutum L.) 1. Growth in Area of Main-stem and Sympodial Leaves

A model is presented for growth of individual and successivemain-stem leaves of cotton, based on a series of indoor experimentsand data sets from the literature. Three variable parametersare used to describe individual leaf growth: relative growthrate of meristematic tissue (R¹), relative rate of approachof final area (R₂) and a ‘position parameter’ (t_0.5)which governs the transition from meristematic to extensiongrowth. Final area of a leaf does not occur in the model asa deterministic quantity but it is a result of the processesduring growth. The model generates successive mainstem leavesand sympodial leaves as an integrated system. Assimilate shortagesoccurring in the plant operate on R₁ leading to the characteristicchange of final leaf area along the mainstem. Gossypium hirsutumL., cotton, leaf growth, relative growth rate, meristematic tissue, extension growth, mathematical model     

Pigmented Plant Tissues in Culture II. Growth, Development and Decline of Chlorophyllous Tissues

During the phase of exponential growth in chlorophyllous calluscultures derived from Haplopappus gracilis, Hypochaeris radicata,and Acer pseudoplatamus, cells double their number on the average,and also their volume, in about 4.3, 6.6, and 9–2 daysrespectively. The two rates decline subsequently but cell expansioncontinues for a short time after division has ceased. With culturesof Oxalis dispar, however, which have an average cell generationtime of about 10 days, there is first a short exponential phasedominated by division, and this is followed by a series of phasesdominated alternately by either division or expansion. Chlorophyll accumulation does not occur in Haplopappus duringthe exponential phase (chlorophyll a decreases) but there isa slow accumulation of caro-tenoids. The bulk of the pigmentsaccumulate during the declining phase of growth mainly afterdivision has ceased. With Hypochaeris and Acer, on the otherhand, accumulation is most intense during the exponential phase,and few pigments are added later. With Oxalis, most of the accumulationoccurs after the exponential phase; carotenoids accumulate untilthe cessation of growth whereas chlorophylls start to declinebefore this. With all species, pigments decline after the cessationof growth. The loss is small in Haplopappus and the tissuesare still bright green when the medium dries out: Hypochaerisand Oxalis, in contrast, eventually become colourless. The data are discussed in relation to the changes in pigmentcontent that accompany the growth and development of a singlecell in each species.     

Proximate developmental mediators of sexual dimorphism in size: case studies from squamate reptiles

Sexual dimorphism in size (sexual size dimorphism; SSD) is nearlyubiquitous, but the relative importance of genetic versus environmentalcontrol of SSD is not known for most species. We investigatedproximate determinants of SSD in several species of squamatereptiles, including three species of Sceloporus lizards andthe diamond-backed rattlesnake (Crotalus atrox). In naturalpopulations of these species, SSD is caused by sexual differencesin age-specific growth. Males and females, however, may oftenshare similar potentials for growth: growth is strongly responsiveto the availability of food, and sexual differences in growthcan be greatly suppressed or completely absent under commonenvironmental conditions in the laboratory. Sexually divergentgrowth is expressed in natural environments because of inherentecological differences between males and females and becauseof potential epigenetic effects of sex-specific growth regulators.In field-active Sceloporus, sexual differences in growth rateare associated with sexual divergence in plasma testosterone.Experiments confirm that testosterone inhibits growth in speciesin which females are larger (for example, S. undulatus and S.virgatus) and stimulates growth in those in which males arelarger (for example, S. jarrovii). Interestingly, however, sexualdivergence in plasma testosterone is not accompanied by divergencein growth in S. jarrovii or in male-larger C. atrox in the laboratory.Furthermore, experimental effects of castration and testosteronereplacement on growth are not evident in captive S. jarrovii,possibly because growth effects of testosterone are supersededby an abundant, high-quality diet. In female-larger S. undulatus,growth may be traded-off against testosterone-induced reproductivecosts of activity. In male-larger species, costs of reproductionin terms of growth are suggested by supplemental feeding ofreproductive female C. atrox in their natural environment andby experimental manipulation of reproductive cost in femaleS. jarrovii. Growth costs of reproduction, however, do not contributesubstantially to the development of SSD in male-larger S. jarrovii.We conclude that the energetic costs of testosterone-induced,male reproductive behavior may contribute substantially to thedevelopment of SSD in some female-larger species. However, despitestrong evidence that reproductive investment exacts a substantialcost in growth, we do not support the reproductive cost hypothesisas a general explanation of SSD in male-larger species.     

Use of the Expolinear Growth Model to Analyse the Growth of Faba bean, Peas and Lentils at Three Densities: Predictive Use of the Model

The expolinear equation for crop growth (Goudriaan and Monteith,Annalsof Botany66: 695–701, 1990; Goudriaan, 1994. In: MonteithJL, Scott RK, Unsworth MH, eds.Resource capture by crops.Nottingham:Nottingham University Press, 99–110) has the potentialto predict growth under specified environmental conditions.The choice of suitable parameters is discussed and tested usingdata from field experiments with faba bean, peas and lentils(Ishag and Dennett,Annals of Botany82: 497–505. 1998).It is suggested that suitable parameters for predicting cropgrowth are the fraction of solar radiation intercepted at emergence,the extinction coefficient for solar radiation, the maximumfraction of radiation intercepted, the maximum relative growthrate and the maximum crop growth rate for a crop interceptingall the incident radiation. In the experiments considered, thedifferences in growth patterns were due mainly to differencesin the maximum relative growth rate associated with differencesin temperature.Copyright 1998 Annals of Botany Company Expolinear equation, grain legumes, crop growth rate, crop density, relative growth rate, growth modelling, faba bean,Vicia fabaL., peas,Pisum sativumL., lentils,Lens culinarsMedic.     

Respiratory aspects of Rhodotorula mucilaginosa

The absorption spectrum of intact cels of Rhodotorula mucilaginosaexhibits three absorption peaks for carotenoids and a Soretband for cytochrome(s). The difference spectrum between thereduced and oxidized states indicates there are components ofcytochrome b, c(c₁) and a+a₃. However, the respiratory aspectof this strain differs significantly from that of baker's yeast,Saccharomyces cerevisiae. The respiratory capacity is strikinglyenhanced in the transition from the lag to the logarithmic phaseof growth, and is accompanied with a special increase in cytochromeoxidase. Addition of TMPD (plus ascorbate) in the presence ofglucose barely affects oxygen consumption of the cells duringthis period, whereas it markedly affects consumption in oldercells. Sodium azide slightly inhibits respiration in the courseof growth, except during this limited transitional period. Azide-insensitiverespiration is also seen in the mitochondrial fraction preparedfrom cells grown to the stationary state. A similar situationis found with antimycin A. Morphological investigations were carried out electron-microscopicallyon the cells of different growth stages. (Received September 16, 1969; )     

Morphometric Analysis of the Growth of Phsp70-ipt Transgenic Tobacco Plants

The effect of introducing a supplementary ipt-gene into thegenome of Nicotiona tabacum L. cv. Petit Havana SR 1 is studiedon the morphological plant development. The ipt-gene, accountingfor the biosynthesis of cytokinins, was coupled to the heat-induciblehsp70- promoter from Drosophila melanogaster. Besides the influenceof the hormonal changes involved, the effects of the experimentalconditions are examined, namely the in vitro growth conditionsfor selecting transformed plants and the heat treatment to induceipt-gene expression. The phenotype of the plants is determined by the tissue sensitivityto three factors: (1) heat treatment reduces stem elongationand diameter growth; (2) in vitro pre-cultivation also reducesstem elongation; and (3) expression of the ipt-gene stimulatesdiameter growth, induces debudding of the axillary shoots andinhibits root development. In addition, axillary bud developmentindicates that in vitro cultivation affects ipt-gene expression. Key words: Cytokinin, heat treatment, in vitro cultivation, ipt-gene, morphology     

Some observations on the urea-degrading enzyme of the diatom Cyclotella cryptica and the role of nickel in its production

The urea-degrading enzyme of Cyclotella cryptica was testedin crude cell-free extracts for effects from chemical reagentsknown to distinguish between urease and ATP:urea amidolyase.Inhibition of the enzyme by hydroxyurea and its indifferenceto added ATP, Mg²⁺ or K⁺ avidin or biotin clearly characterizedthe enzyme as urease (EC 3.5.1.5 [EC] ). The Cyclotella urease wasunaffected by thiourea addition, as was also the growth of thediatom in the presence of this substrate analogue. Indirectevidence was obtained from growth studies of the diatom andcorresponding urease production showing that the enzyme: (i)contains Ni²⁺ tightly bound to an apoprotein; (ii) is producedconstitutively even from growth on nitrate and does not requireextracellular urea for its synthesis, although quantitativelythe activity is greatest from growth on urea. It is concludedthat Cyclotella urease is a Ni²⁺ constitutive enzyme similarin many respects to those previously reported from Phaeodactylumtricornutwn and Tetraselmis maculata.     

Nutrient-Limited Growth Rates: Roles of Nutrient-Use Efficiency and of Adaptations to Increase Uptake Rate

When stressed by low nutrient availability, young sunflowerplants (Helianthus annuus) showed responses seen in many otherspecies: increases in root uptake capacity (V^max, l/K_m), root:shoot ratio, and putative nutrient-use efficiency, nUE=l/(tissuenutrient content). A straightforward mechanistic model is derivedfor relative growth rate (RGR) in solution culture in termsof these factors. A linear regression based on the model indicatesa negative role for nUE, which violates a premise of the model.A revised model proposes that primary adaptations are only inuptake rate and growth or nutrient allocations, and these actthrough the photosynthetic utility of nutrient. The tissue nutrientcontent and associated nUE become dependent quantities. Thepredictions for RGR, as tested by linear regression, are improved.The model predicts that nUE can increase as external solutionconcentration decreases, but decreases with increased uptakeadaptations in one given environment. The decrease in nUE compromisespotential gains in RGR from uptake adaptations, and makes increasesin root: shoot ratio a nearly insignificant contributor to earlyRGR. The model and associated regression analyses are generalizedfor additional adaptations such as increased root fineness andfor different quantitative ways that a nutrient may limit photosynthesis.The model and analyses are also generalized to plant growthin soil and growth without functional balance between root andshoot. Key words: Relative growth rate, Helianthus annuus, nutrient stress, nutrient use efficiency, functional balance     

A Model for Mortality in a Self-thinning Plant Population

A model for mortality process in a self-thinning plant populationis proposed. It considers the spacial process but does not requirepositional information of each individual plant due to the assumptionsthat plants with interacting neighbours all greater than themselvesare the first to die and neighbours' sizes are mutually independentat each growth stage. Mortality of plants of size x at age t,M(t, x), is given as M(t, x) = m{P(t, x)}ⁿ where P(t, x) isthe proportion of plants of size greater than x at age t, andm and n are parameters. This model fits data from an experimentalplantation of Abies sachalinensis and will be useful for furtherdevelopment of the theoretical study of plant population growth. Abies sachalinensis Fr. Schm., self-thinning, mortality, size distribution, neighbourhood effect, spacial process model     

The Relative Growth Rates of Three Plankton Diatoms in Relation to Underwater Radiation and Temperature

Relative growth rates of three freshwater plankton diatoms-Asterionellaformosa, Fragilaria crotonensis, and Tabellaria flocculosa var.asterionelloides-are described from cultures suspended at variousdepths and during several seasons in the lake Windermere. Seasonalvariation in rates recorded near the surface (i m. depth) isinterpreted in terms of seasonal changes in temperature anddaylength. Rates recorded for Asterionella and Fragilaria aregenerally similar, but are approximately twice the rates obtainedwith Tabellaria. Depth profiles of relative growth rates areof similar form in all species, and normally show lightsaturationnear the surface. The shape of profiles for Asterionella isin good agreement with estimates of photosynthesis integratedover the growth periods. The parallelism between photosyntheticand relative growth rates of Asterionella is further illustratedfrom laboratory experiments: an approximate interconversion,under certain conditions, is given.     

Effects of the fungal endophyte, Neotyphodium lolii, on net photosynthesis and growth rates of perennial ryegrass (Lolium perenne) are independent of In Planta endophyte concentration

• Background and Aims Neotyphodium lolii is a fungal endophyteof perennial ryegrass (Lolium perenne), improving grass fitnessthrough production of bioactive alkaloids. Neotyphodium speciescan also affect growth and physiology of their host grasses(family Poaceae, sub-family Pooideae), but little is known aboutthe mechanisms. This study examined the effect of N. lolii onnet photosynthesis (P_n) and growth rates in ryegrass genotypesdiffering in endophyte concentration in all leaf tissues. • Methods Plants from two ryegrass genotypes, Nui D andNui UIV, infected with N. lolii (E+) differing approx. 2-foldin endophyte concentration or uninfected clones thereof (E–)were grown in a controlled environment. For each genotype xendophyte treatment, plant growth rates were assessed as tilleringand leaf extension rates, and the light response of P_n, darkrespiration and transpiration measured in leaves of young (30–45d old) and old (>90 d old) plants with a single-chamber openinfrared gas-exchange system. • Key Results Neotyphodium lolii affected CO₂-limited ratesof P_n, which were approx. 17 % lower in E+ than E– plants(P < 0·05) in the young plants. Apparent photon yieldand dark respiration were unaffected by the endophyte (P >0·05). Neotyphodium lolii also decreased transpiration(P < 0·05), but only in complete darkness. There wereno endophyte effects on P_n in the old plants (P > 0·05).E+ plants grew faster immediately after replanting (P < 0·05),but had approx. 10 % lower growth rates during mid-log growth(P < 0·05) than E– plants, but there was noeffect on final plant biomass (P > 0·05). The endophyteeffects on P_n and growth tended to be more pronounced in NuiUIV, despite having a lower endophyte concentration than NuiD. • Conclusions Neotyphodium lolii affects CO₂ fixation,but not light interception and photochemistry of P_n. The impactof N. lolii on plant growth and photosynthesis is independentof endophyte concentration in the plant, suggesting that theendophyte mycelium is not simply an energy drain to the plant.However, the endophyte effects on P_n and plant growth are stronglydependent on the plant growth phase.     

Stigma-surface Esterase Activity and Stigma Receptivity in Some Taxa Characterized by Wet Stigmas

Stigma-surface esterase activity and stigma receptivity througha sequence of developmental stages of the pistil have been studiedin four taxa characterized by having wet stigmas — Petuniahybrida, Nicotiana tabacum, Crinum defixum and Amaryllis vittata.The style is solid in the first two and hollow in the lattertwo taxa. In all the taxa, stigma—surface esterase couldbe detected in a thin surface layer (pellicle) from a very earlystage of pistil development, irrespective of the presence orabsence of the exudate. However, the taxa showed variation instigma receptivity. In Petunia and Nicotiana, stigmas from pistilsof all the stages supported pollen germination and tube growth.In Amaryllis and Crinum, stigmas of only the mature pistils,when the exudate is present on the stigma, supported normalpollen germination and tube growth. It is inferred that in taxacharacterized by a wet stigma and solid style, the factors requiredfor pollen germination are present from an early stage of pistildevelopment and the exudate per se is not involved in pollengermination. In taxa characterized by a wet stigma and hollowstyle, however, the pellicle does not carry the factors requiredfor pollen germination and tube growth; they appear to be presentin the exudate. Petunia hybrida Vilm, Nicotiana tabacum L., Crinum defixum, Ker-Gawl, Amaryllis vittata Ait., tobacco, pollination, pollen germination, stigmatic exudate, stigma receptivity, stigma-surface esterase, esterase activity     

RECRUITMENT AND GROWTH OF THE BLUE-RAYED LIMPET, HELCION PELLUCIDUM (L.), IN SOUTH EAST IRELAND

This account reports on recruitment, growth and population structureof the macroherbivorous gastropod Helcion pellucidum (L.) onan exposed rocky shore in S.E. Ireland, with particular referenceto the pellucidum form. Recently settled Helcion spat were foundinitially on living crustose lithothamnia in pools and on openrock, on the lower shore, during February-April and subsequentlyrecruited to macro-algal fronds. By May they were found in abundanceon Mastocarpus stellatus and Laminaria spp. Helcion was markedlyseasonal in its occurrence on Mastocarpus, being most abundantduring May-August. A complementary pattern was evident on growingHimanthalia receptacles, with limpets abundant from July onwards.It is suggested that Helcion may migrate from Mastocarpus toHimanthalia as they grow. Data on growth rates are presentedfor Helcion in the various habitats studied. Growth rates werehighest on the Laminaria spp. (Received 21 February 1992; accepted 8 June 1992)     

Regression Smoothers for Estimating Parameters of Growth Analyses

The objective of regression smoothers is to obtain predictedvalues of a dependent variable and its first derivative fromempirical data without having to assume any particular functionalrelationship between the dependent and independent variables.An early variant of this type of analysis, specifically naturalB-splines, was first applied to growth analyses by Parsons andHunt in 1981 (Annals of Botany 48 : 341–352, 1981). Theobject of this paper is to describe and evaluate two recentadvances in this area (cubic spline smoothers and loess smoothers)in the context of plant growth analysis and compare them tonaturalB -splines. The accuracies of these methods are evaluatedusing simulated data of a type that normally causes difficultieswith other methods. A bootstrap procedure is described thatimproves the estimate of the optimal smoother parameter. Itis shown that these smoothers can capture even subtle changesin relative growth rate. The method is then applied to growthdata ofHolcus lanatus. B -splines; cubic spline smoothers; growth analyses; Holcus lanatus ; loess; relative growth rate; RGR     

A Model for Plant and Crop Growth, Allowing for Competition for Light by the use of Potential and Restricted Projected Crown Zone Areas

Relations for competition for light are developed and used ina plant growth model applicable to the isolated plant, to plantsin even-aged monoculture and to plants in mixed-aged monoculture.In an isolated plant, it is assumed that a leaf area, proportionalto the plant mass, is contained within a crown whose projectedzone area is proportional to plant mass to the 2/3 power. Self-shadingprogressively reduces the specific growth rate. If light werethe sole limiting resource and were constant, one can derivea growth equation, dw/dt = rw[1 - exp (-KW^1/3)]KW^1/3, which,integrated, gives w^1/3 = K^-1 ln {1 + [exp (KW^1/3₀)-1] exp (rt/3)}.It approximates, initially, to a particular case of the Richards(1959) empirical growth equation. In even-aged evenly-spaced monocrops competing only for light,it is assumed that the zone areas merge at canopy closure, andgrowth then follows the expolinear equation of Goudriaan andMonteith (1990), giving a continuous function based on groundcover. For mixed-aged monocrops, we assume a phase of canopyclosure that affects the younger plants earlier than the olderones. Under varying environmental conditions in the field, plant growthmay be affected by other factors in addition, e.g. temperature.In the growth conductance model of Aikman and Scaife (1993),the shading expressions are applied to the light-dependence. Data from two sowings of cabbage and carrot in even-aged andmixed-aged monocrops were used to test the model. The parametervalues derived from the even-aged monocultures predict the growthrates in the mixed-aged monocultures better than models whichassume uniform canopies.Copyright 1994, 1999 Academic Press Growth, model, monocrop, even-aged, mixed-aged, PAR, density, competition, light, shading, zone area, ground cover, temperature, carbon dioxide, expolinear, carrot, Daucus carota L., cabbage, Brassica oleracea L