Description and Model of the Architecture of Four Genotypes of Determinate Autumn-sown White Lupin (Lupinus albus L.) as Influenced by Location, Sowing Date and Density

The structure of four new autumn-sown determine genotypes ofwhite lupin, grown with a combination of sowing dates and plantdensities at four locations in France was studied in 1990/91and 1991/92. Plant architecture was characterized in terms ofthe number of first-order branches produced and the distributionof leaves on these branches and how they varied with the numberof mainstem leaves and the position of the branch on the mainstem. The variation in the number of mainstem leaves on determinegenotypes was satisfactorily described by an earlier model developedfor indeterminate genotypes using the intensity of vernalizationrelative to accumulated temperature above 3°C as input.However the architecture of the first-order branches, definedby their number and the total number of leaves per branch ateach subtending position on the mainstem, differed and was influencedby genotype, location and sowing date. In four determinate genotypes,these two characters were positively correlated, and correlatedwith the number of leaves on the mainstem. Increasing densityfrom 10 to 40 plants m^-2 reduced the number of branches andtheir total number of leaves. Pruning 15 leaves from the mainstemat the beginning of stem elongation did not influence the developmentof the first-order branches. There appeared to be a functionalrelationship between the number of leaves on the mainstem andthe number of branches established very early in the growingseason. The profiles of number of leaves on the first-order brancheson the mainstem with branch position were modelled using twosub-models, one describing the mean number of leaves on thebranches actually present, and the second describing the frequentlyof occurrence of a branch at a particular position on the mainstem.Of the five model parameters, one, representing the minimalnumber of branches present on the plant, was correlated withthe number of first-order branches. Genotype, location, sowingdate and density affected the shape of the profiles.Copyright1993, 1999 Academic Press While lupin, Lupinus albus L., determine growth, architecture, model, branch     

Redistribution of Nutrient Elements from Cotyledons of Two Species of Annual Legumes During Germination and Seedling Growth

The distribution of dry matter and various mineral nutrientsbetween testa and embryo of seeds of Lupinus albus and L. angustifoliusis described It was found that lupin seeds at either end ofa pod contained less dry matter and minerals than seeds in themiddle of the fruit. The transport of dry matter, N, P, K, S,Ca, Mg, Na, Fe, Zn, Mn and Cu from cotyledons of parent seedsof both species to the seedling axis was measured from germinationto the time of cotyledon death. N, P, K and S were retrievedfrom cotyledons with over 90 per cent efficiency, dry matter,Mg, Na, Fe, Zn, Mn and with 59–90 per cent efficiency,and Ca with 26–31 per cent efficiency. There was littlechange in the efficiency of nutrient retrieval from cotyledonswhen seedlings were grown in different culture media. Both speciesshowed a linear relationship between the loss of each elementand dry matter throughout the experiment, and a similar proportioningbetween root and shoot of the amount of a specific nutrientmobilized from cotyledons of parent seeds. Lupinus albus L., Lupinus angustifolius L., lupin, transport, of dry matter and mineral nutrients     

Winter Growth of Autumn-sown White Lupin (Lupinus albus L.) Main Apex Growth Model

The winter growth of winter white lupin (cv. Lunoble) was investigated.Over three consecutive years, 1987–1989, it was sown atdifferent times at Lusignan (France) and in 1989, at nine differentlocations with various sowing times. The production of primordia,the vernalization requirements and the final number of leaveson the main stem were related to field measurements of dailymaximum and minimum temperatures. A statistical model for the main apex growth with a system oftwo equations was developed, with a threshold level for leafprimordia production at 3°C. The number of leaf primordiaproduced by a vegetative apex (y) in terms of the cumulativesums of temperature over 3°C (x) followed the curvilinearregression y = 4.76+ 0.0268x + 0000015 6x². The upper and lowertemperature limits for vernalization were estimated as 14 and1°C respectively. The vernalization requirements of a vegetative apex (y) decreasedwhen the number of initials produced (x) increased accordingto the negative exponential regression y = exp (7.2— 0.02626.x). The two equations were used for the prediction of the finalnumber of leaves of a lupin crop. The predictive accuracy ofthe model was checked against independent data. The agreementbetween observed and predicted final leaf number was often close,but some deviations did occur with low leaf number. The modeldescribed most of the growth phenomena which occur during thephase sowing to floral initiation of the main stem of a winterlupin crop, and its possible uses are discussed Lupinus albus L, white lupin, growth, model, vernalization, primordia, apex, thermal time     

Winter Growth of Autumn-sown White Lupin (Lupinus albus L.) Main Apex Growth Model

The winter growth of winter white lupin (cv. Lunoble) was investigated.Over three consecutive years, 1987–1989, it was sown atdifferent times at Lusignan (France) and in 1989, at nine differentlocations with various sowing times. The production of primordia,the vernalization requirements and the final number of leaveson the main stem were related to field measurements of dailymaximum and minimum temperatures. A statistical model for the main apex growth with a system oftwo equations was developed, with a threshold level for leafprimordia production at 3 °C. The number of leaf primordiaproduced by a vegetative apex (y) in terms of the cumulativesums of temperature over 3 °C (x) followed the curvilinearregression y = 4.76 + 00268x + 00000156x². The upper and lowertemperature limits for vernalization were estimated as 14 andI °C respectively. The vernalization requirements of a vegetative apex (y) decreasedwhen the number of initials produced (x) increased accordingto the negative exponential regression y = exp (7.2 + 002626.x). The two equations were used for the prediction of the finalnumber of leaves of a lupin crop. The predictive accuracy ofthe model was checked against independent data. The agreementbetween observed and predicted final leaf number was often close,but some deviations did occur with low leaf number. The modeldescribed most of the growth phenomena which occur during thephase sowing to floral initiation of the main stem of a winterlupin crop, and its possible uses are discussed. Lupinus albus L., white lupin, growth, model, vernalization, primordia, apex, thermal time     

The Development of Desiccation-tolerance and Maximum Seed Quality During Seed Maturation in Six Grain Legumes

‘Physiological maturity’, i.e. the time when seedsreach their maximum dry weight during development, occurredwhen maturation drying on the parent plant in the field hadreduced seed moisture content to approximately 60 per cent infaba bean (Vicia faba L.), lentil (Lens culinaris Medic.), chickpea(Cicer arietinum L.), white lupin (Lupinus albus L.), soya bean(Glycine max [L.] Merr.) and pea (Pisum sativum L.) The onsetof desiccation-tolerance, i.e. the ability of seeds to germinatefollowing harvest and rapid artificial drying, coincided withphysiological maturity, except in pea where it occurred a littleearlier at about 70 per cent moisture content. Maximum seedquality as determined by maximum viability, minimum seedlingabnormalities and maximum seedling size occurred in pea, chickpeaand lupin when seeds were harvested for rapid drying at physiologicalmaturity; but for maximum seed quality in the other speciesmaturation drying had to proceed further - to about 45 per centmoisture content in soya bean and to about 30 per cent moisturecontent in lentil and faba bean seed crops. Much of this variationamongst the six species, however, was due to differences inthe variation in maturity within each seed crop. Results forindividual pods showed that peak maturity, i.e. maximum seedquality following harvest and rapid artificial drying, was achievedin all six species once maturation drying had reduced the moisturecontent of the seeds to 45–50 per cent. In pea, faba beanand soya bean there was a substantial decline in viability andan increase in seedling abnormalities when harvest was delayedbeyond the optimal moisture content for harvest.     

The Role of the Stem in Phloem Loading of Minerals in Lupinus albus L. cv. Ultra

Collections of phloem sap made over a 40-day period from a varietyof locations on nodulated white lupin plants (Lupinus albusL. cv. ultra) showed considerable enrichment with K⁺ and Mg²⁺in the phloem streams destined for the shoot apices or fruitsrelative to the streams arising from the leaflets (up to 5.5times). Sodium showed enrichment in the streams destined forthe roots (up to 2.5 times) but only when present in the watersupply at a high level (3 mM). The stem, in view of its centrallocation in the transport pathway, is seen as an organ capableof redistributing minerals in the phloem independently of photosynthate. Lupinus albus L., lupin, phloem loading, magnesium, potassium, sodium, mineral elements     

Seed Germination and Radicle Growth of a Halophyte, Kalidium caspicum(Chenopodiaceae)

Effects of temperature, light, NaCl and polyethylene glycol(PEG)-6000 on seed germination and radicle growth in a halophyticshrub, Kalidium caspicum(L.) Ung.-Sternb. were investigated.When seeds were incubated in deionized water at constant temperaturesbetween 10 and 30°C, the percentage germination in the darkexceeded 75%; light suppressed seed germination at alternatingtemperatures. Incubating seeds with a hypersaline solution ofNaCl for 30 d had no adverse effect on their germinability.The percentage germination of seeds incubated with a –0.8MPa NaCl solution was 73, 80 and 54% at 10, 20 and 30°C,respectively, but all radicles died before their length exceeded5 mm. In contrast, when seeds were incubated with a –0.8MPa PEG solution at 20°C, 68% of seeds germinated, and 95%of the emerging radicles survived beyond 5 mm. The high sensitivityof small radicles of this species to salinity indicated thatsalt must be removed from the soil surface for seedling establishment.Copyright2000 Annals of Botany Company Chinese desert, radicle growth, germination, halophyte, Kalidium caspicum, salinity     

A Biochemical and Cytochemical Study of the Cuticle-associated Peroxidases in Lupinus

A biochemical and cytochemical study of peroxidases (EC 1.11.1.7 [EC] )associated with the outermost cell layers of Lupinus albus hypocotylshas been performed. Cytochemical investigations showed thatin the epidermis of lupin hypocotyls, peroxidatic activitiescould be detected mainly at the level of the endoplasmic reticulum,Golgi apparatus, ground substance of the cytoplasm, intercellularspaces between adjacent epidermal cells, and in the cuticlelayer. No peroxidatic reactions were seen at the level of eitherthe radial or the tangential walls. The cuticle peroxidaticreaction was due to two acidic isoperoxidases, also found incell walls of vascular tissues, and was further characterizedthrough a study of its catalytic activities. These studies showedthat cuticle-associated peroxidases were able to oxidize genistein,but unable to oxidize ascorbic acid. These results suggest thatextracellular peroxidases associated with the outermost celllayers of lupin hypocotyls are involved more in the metabolismof isoflavones of the cuticle layer than in the growth responsesof the whole organ. Epidermal cell, cuticle, peroxidase cytochemistry, genistein oxidation, Lupinus albus     

The Rate of Morphogenesis of Embryos and Seeds in Four Species of Grain Legumes

Comparative embryo development has been studied histologicallyin Lupinus albus, Lupinus mutabilis, Vicia faba, Pisum sativumand Latkyrus latifolius. The detailed histology of the stagesof embryo formation up to the early differentiation of tissuesof the seed is reported. The rate of embryogenesis has beentimed through 15 stages of development from anthesis and comparativerates of tissue formation established between the species. Themain observation was the slow rate of morphogenesis of embryosand seeds in Lupinus albus in comparison with the very rapidrate observed in Pisum sativum. A long period at the globularembryo stage, when embryo morphogenesis was inactive contributedto the extended development time of embryos and seeds in Lupinusalbus. Slow differentiation of reproductive tissues in L. albusdetermines late maturity in seeds and pods. Lupinus albus, white lupin, L. mutabilis, tarwi, Vicia faba, faba bean, Pisum sativum, pea, Lathyrus latifolius, everlasting pea, embryo development     

Oxygen Diffusion in Lupin Nodules: I.VISUALIZATION OF DIFFUSION BARRIER OPERATION

Root nodules of Lupinus albus (L.) cv. Multolupa were subjectedto short- and medium-term stresses by lowering rhizosphere temperaturefrom 25 to 16°C (2 h), detopping plants (3 h), darkeningplants (21 h) or exposing roots to 20 mol m^–3 KNO₃ for4 d. All experimental treatments produced increases in oxygendiffusion resistance, compared with control plants. These correlatedwith structural changes in the nodule cortex, which is describedin detail for the first time. The most noticeable change isthe occlusion of intercellular spaces by a glycoprotein whichwas identified using the monoclonal antibody MAC236. This glycoproteinwas also found surrounding bacteria in intercellular spacesof the cortex of control nodules. Key words: Oxygen diffusion resistance, glycoprotein, nodules, nitrogen fixation, Lupinus albus     

Biosynthesis, accumulation and secretion of isoflavonoids during germination and development of white lupin (Lupinus albus L.)

A combination of ¹⁴C labelling experiments of white lupin seedlings(Lupinus albus L.) and high pressure liquid chromatography oftissue extracts indicated active biosynthesis of isoflavonoidsduring the first 2–4 d of seed germination. These weresynthesized mostly as glucosides and to a lesser extent as aglycones,with trace amounts of prenylated derivatives. There was a generaldecrease in total isoflavonoids during later stages of germination(c. until d 13), which may be ascribed to their turnover and/orexudation into the rhizosphere. In addition, exudation of isoflavonoidsby lupin seeds germinated under sterile conditions continuesfor 12 d with a preferential release of monoprenylated compounds.The relationship between the specific developmental events duringseed germination and the accumulation of certain groups of isoflavonoidsis discussed in relation to their possible role in the growthprocesses of lupin. Key words: Isoflavonoids, glucosides, aglycones, prenylated derivatives, root exudates, white lupin     

Analysis of Branching in Spring-sown White Lupins (Lupinus albusL.): The Significance of the Number of Axillary Buds

Plant density and sowing date were shown to affect branchingin spring-sown white lupin (Lupinus albusL.), but the responsevaried among environments. The patterns of primary and secondarybranching in the cv. Lublanc were studied as a function of boththe number of axillary buds and the plant growth rate. Fieldexperiments that used a wide range of sowing dates and plantdensities to alter plant architecture were conducted over 5years, and these were supplemented with data from additionalglasshouse and growth cabinet experiments. The number of axillary buds on the main stem or primary branches,which determined the potential number of branches, increasedlinearly with the number of nodes. In situations where all axillarybuds did not produce branches, it was found that the numberof primary and secondary branches produced was related to theplant growth rate at the beginning of branch elongation. Knowledgeof the number of axillary buds improved the analysis of theinteraction between cultural practices and environmental conditionson plant architecture. The variability of branching potentialamong genotypes was discussed. Lupinus albus; branches; axillary buds; growth; sowing date; plant density     

Modelling of quinolizidine alkaloid net flows in Lupinus albus and between L. albus and the parasite Cuscuta reflexa: new insights into the site of quinolizidine alkaloid synthesis

The present work reveals new and completely different conclusionsabout the alkaloid economy of symbiotically fed Lupinus albusand L. albus parasitized by Cuscuta reflexa in the study periodof 43–55 d after sowing of lupin. Net flows of alkaloidswithin lupin and between host and parasite were calculated usingthe molar ratio of alkaloid nitrogen: total nitrogen combinedwith known net flows of nitrogen in the transport fluids andanalysing alkaloid accumulation in plant organs by HRGC. Incontrast to previous studies, quinolizidine alkaloids were predictedto be synthesized mainly in the root of L. albus and to be predominantlytransported via xylem to the apical plant shoot organs. Parasitismby C. reflexa for 12 d induced a decline of alkaloid contentin the host L. albus up to 53% compared to control plants andalkaloid synthesis was halved—apparently due to a shortageof the precursor lysine. In spite of an additional decreasein nitrogen levels at the second harvest, the host-parasitesystem showed a1.3-fold higher alkaloid content than the controlplants, 63% of the total alkaloids being attracted by Cuscuta.This indicates (a) restriction of catabolic processes withininfected lupins, (b) a massive shift of nitrogen metabolismin the direction of alkaloids and (c) an enormous sink potentialof Cuscuta for nitrogenous compounds. Although xylem was foundto be the main translocation system for alkaloids, the modellingof alkaloid flows predicts Cuscuta to derive only 4.5% of itstotal alkaloid supply from the xylem and 95.5% from the phloem.By analogy with nitrogen flows, this finding requires xylemphloemtransfers which were assumed to occur within the stem axis oflupin. A similar proportion regarding the contribution of xylemand phloem to the supply of Cuscuta was obtained for the netflows of two selected alkaloids, lupanine and 13     

High pH Causes Disintegration of the Root Surface in Lupinus angustifolius L.

The effect of high pH on the morphology and anatomy of the rootsof lupin (Lupinus angustifolius L. cv. Yandee) and pea (Pisumsativum L. cv. Dundale) was examined in buffered solution. Themorphology and anatomy of lupin roots were markedly altered,and root growth was reduced by increasing solution pH from 5·2to 7·5, whereas pea roots were unaffected. In lupin roots,pH 7·5 caused disintegration of the root surface andimpaired root hair formation. Lupin roots grown at pH 7·5also had decreased cell lengths but increased cell diameterin both the epidermis and the cortex in comparison to rootsgrown at pH 5·2. High pH reduced cell volume greatlyin the epidermis, to a lesser extent in the outer cortex andnot at all in the inner cortex. It appears that in lupins, theprimary detrimental effects of growth at pH 7·5 is reducedlongitudinal growth of cells near the root surface with a consequentreduction in elongation of the cells in inner cortex.Copyright1993, 1999 Academic Press Lupinus angustifolius L., Pisum sativum L., high pH, root morphology, root anatomy     

Effects of Temperature and Water Potential on Germination, Radicle Elongation and Emergence of Mungbean

Controlled environment experiments were performed to determinethe effects of temperature and water potential on germination,radicle elongation and emergence of mungbean (Vigna radiata(L.) Wilczek cv. IPB-M79-17-79). The effects of a range of constant temperatures (15–45°C) and water potentials (0 to –2.2 MPa) on germinationand radicle elongation rates were studied using an osmoticumtechnique, in which seeds were held against a semi-permeablemembrane sac containing a polyethylene glycol solution. Linearrelationships were established between median germination time(Gt₅₀) and water potential at different temperatures, and betweenreciprocal Gt₅₀ (germination rate) and temperature at differentwater potentials. Germination occurred at potentials as lowas –2.2 MPa at favourable temperatures (30–40 °C),but was fastest at 40 °C when water was not limiting, withan estimated base temperature (T_b) of about 10 °C. Subsequentradicle elongation, however, was restricted to a slightly narrowertemperature range and was fastest at 35 °C. The conceptof thermal time was used to develop an equation to model thecombined effects of water potential and temperature on germination.Predictions made using this model were compared with the actualgermination obtained in a related series of experiments in columnsof soil. Some differences observed suggested the additionalimportance of the seed/soil/water contact zone in influencingseed germination in soil. Seedling emergence appeared to reflectfurther the radicle elongation results by occurring within anarrower range of temperatures and water potentials than germination.Emergence had an estimated T_b of 12.6 °C and was fastestat 35 °C. A soil matric potential of not less than about–0.5 MPa at sowing was required to obtain 50% or moreseedling emergence. Key words: Germination, temperature, water potential     

An Analysis of the Effects of Temperature and Light Integral on the Vegetative Growth of Pansy cv. Universal Violet (Violaxwittrockiana Gams.)

Pansies (Viola xwittrockiana Gams.) cv. Universal Violet weresown on five dates between Jul. and Dec. 1992 and placed insix temperature-controlled glasshouse compartments set to providemean temperatures between 6.5 and 30 °C. Shoot dry weightand leaf number were recorded. A model was constructed, to analysethe effects of light and temperature on dry matter accumulation,which assumed that relative growth rate (RGR) declined linearlywith thermal time accumulated from sowing, reflecting ontogeneticdrift. Furthermore, it assumed that RGR was a semi-ellipsoidfunction of temperature, rising to an optimum of 25.3 °Cand declining thereafter, and a positive linear function oflight integral. When fitted to data collected in this studythe model accounted for 94% of the variance in RGR. Independentvalidation using data from four further crops grown in glasshousecompartments at four different set point temperatures showedthat the model could also be used to predict plant dry weightaccurately (r ²=0.98). The rate of mainstem leaf productionwas also linearly related to both light integral and temperature. Pansy; Viola xwittrockiana ; temperature; light integral; dry weight; relative growth rate; leaf number     

Physiological Aspects of Cluster Root Function and Development in Phosphorus-deficient White Lupin (Lupinus albus L.)

Cluster root formation in white lupin (Lupinus albus L.) isinduced mainly by phosphorus (P) starvation, and seems to beregulated by the endogenous P status of the plant. Increasedformation of cluster roots, when indole acetic acid is suppliedto the growth medium of P sufficient plants, and inhibitoryeffects of kinetin application suggest the involvement of endogenousphytohormones (auxins and cytokinins), which may act in an antagonisticmanner in the P-starvation response. Phosphorus deficiency-inducedadaptations of white lupin, involved in P acquisition and mobilizationof sparingly available P sources, are predominantly confinedto the cluster roots, and moreover to distinct stages duringtheir development. Increased accumulation and exudation of citrateand a concomitant release of protons were found to be mainlyrestricted to mature root clusters after prolonged culture (3–4weeks) under P-deficient conditions. Inhibition of citrate exudationby exogenous application of anion channel antagonists such asethacrynic- and anthracene-9-carboxylic acids may indicate involvementof an anion channel. Phosphorus deficiency-induced accumulationand subsequent exudation of citric acid seems to be a consequenceof both enhanced biosynthesis and reduced turnover of citricacid in the cluster root tissue, indicated by enhanced expressionof sucrose synthase, fructokinase, phosphoglucomutase, phosphoenol-pyruvatecarboxylase, but reduced activity of aconitase and slower rootrespiration. The release of acid phosphatase and of phenoliccompounds (isoflavonoids) as well as the induction of a putativehigh-affinity P uptake system was more highly expressed in juvenile,mature and even senescent cluster regions than in apical zonesof non-proteoid roots. An AFLP-cDNA library for cluster root-specificgene expression was constructed to assist in the identificationof further genes involved in cluster root development. Copyright2000 Annals of Botany Company Acid phosphatase, auxin, citric acid, cluster roots, cytokinin, Lupinus albus L., P acquisition, P uptake, root exudates     

Diverse regulation by sucrose of enzymes involved in storage lipid breakdown in germinating lupin seeds

The regulatory function of sucrose in the activity of lipid-degrading enzymes was investigated in germinating seeds of yellow lupin (Lupinus luteus L.), white lupin (Lupinus albus L.) and Andean lupin (Lupinus mutabilis Sweet). The study was conducted on isolated embryo axes, excised cotyledons and seedlings cultured in vitro for 96 h on medium with 60 mM sucrose or without the sugar. The activity of lipase (lipolysis), acyl-CoA oxidase and catalase (fatty acid β-oxidation) was enhanced in all studied organs cultured on medium without sucrose. The activity of cytosolic aconitase (glyoxylate cycle) was stimulated by sucrose in seedling axes and isolated embryo axes, whereas in seedling cotyledons and excised cotyledons, it was inhibited. The regulatory function of sucrose in phosphoenolpyruvate carboxykinase (gluconeogenesis) was observed only in isolated embryo axes and the activity was lower in carbohydrate deficiency conditions. The peculiar features of storage lipid breakdown in germinating lupin seeds and its regulation by sucrose are discussed.     

Biosynthesis of Volatiles in Brown Boronia Flowers after Harvest: Effect of Harvest Time and Incubation Conditions

Brown boronia flowers (Boronia megastigma)were incubated at25 °C after harvest, increasing the concentration of a solventextracted product by up to 25% (d. wt basis) and floral volatilesby up to 300% (d. wt). Open flowers produced more volatilesduring post-harvest incubation than flower buds, whole flowersproduced more than flowers treated to simulate harvester damage,and fresh flowers produced more than frozen and thawed flowers.Flowers incubated in bags purged with air produced more extractand volatiles than those purged with nitrogen gas; ß-iononewas particularly depleted in nitrogen-purged flowers. Flowersand buds from three successive harvests (68, 82 and 90% openflowers) were incubated at several temperatures for up to 24h. The greatest increase in the concentration of floral extractoccurred in flowers harvested when 90% were open and incubatedfor 4 h at 12 °C, or 14 h at 23 °C. The largest increasein total volatiles occurred in material harvested at 82% openflowers and incubated for 25 h at 12 °C, or 13 h at 23 °C.The concentration of extract and volatiles declined after prolongedpost-harvest incubations. Brown boronia flowers produce volatilesand other components of the floral extract after harvest whenflowers with mature, intact enzyme systems are well suppliedwith oxygen, at temperatures at or below 25 °C. As flowersbecome visibly senescent, their ability to produce volatilesafter harvest declines.Copyright 1998 Annals of Botany Company Boronia megastigma(Nees); brown boronia; essential oils; floral volatiles; ß-ionone; phenology; post-harvest storage.     

Cell Division and Expansion in the Growth of the Leaf

Volumes and numbers of cells were determined at different stagesof development of the fifth leaf of Lupinus albus, and eachof the second pair and the tenth leaf of Helianthus annuus.In the case of the second pair of sunflower leaves the valuescover the whole life of the leaf from initiation to senescence. During both primordial development and the ensuing ‘grandperiod of growth’ division is the determinant of growth.About 10 per cent. of the cells in the fully grown leaf arelaid down before leaf-emergence; the remaining 90 per cent.are formed during unfolding. Division does not cease in thelupin leaf or the second pair of sunflower leaves until theyhave reached half their maximum area. The tenth leaf, on theother hand, is as much as three-quarters fully grown beforedivision ceases. Cell expansion commences soon after leaf initiation and continuesthroughout the life of the leaf. With lupin and the second pairof sunflower leaves there is a fourfold increase in the averagevolume of the cells before emergence from the apical region.During unfolding, there is a further tenfold increase in theaverage volume of the cells of the lupin leaf, and a twentyfoldincrease with the second pair of sunflower leaves. Expansioncontinues after the cessation of division but this further increasein volume is comparatively small. The data are discussed in relation to the ‘two phase’hypothesis of leaf development.