The Effect of Temperature on the Initiation of Leaf Primordia in Developing Potato Sprouts

Kirk, W W., Davies, H. V. and Marshall, B. 1985. The effectof temperature on the initiation of leaf primordia in developingpotato sprouts.—J. exp. Bot. 36: 1634–1643. Initiation of leaf primordia in potato sprouted out of soilin light was an asymptotic function of thermal time and thebase temperature for the process was 3.6 °C. The parametervalues of the asymptotic function were universal for cv. MarisPiper. The estimated rate of leaf primordium initiation decreasedlinearly from 0.033 leaf pnmordia (K day)^–1 when abouteight leaf primordia were present to zero after a maximum numberof 24 leaf primordia had been initiated. The decrease in rateof development with increasing number of primordia may be dueto depletion of mother tuber resources. The transition of theapex from a vegetative to a reproductive state was not the factorlimiting the initiation of additional leaf primordia. Key words: Potato, Solanum tuberosum L., leaf primordia initiation, temperature, thermal time, development     

The Relationship Between the Distribution of Periclinal Cell Divisions in the Shoot Apex and Leaf Initiation

Periclinal cell divisions in vegetative shoot apices of Pisumand Silene were recorded from serial thin sections by mappingall the periclinal cell walls formed less than one cell cyclepreviously. The distribution of periclinal divisions in theapical domes corresponded to the distributions subsequentlyoccurring in the apices when the young leaf primordia were forming.In Pisum, periclinal divisions were almost entirely absent fromthe I₁ region of the apical dome for half a plastochron justafter the formation of a leaf primordium and appeared, simultaneouslyover the whole of the next potential leaf site, about half aplastochron before the primordium formed. In Silene periclinaldivisions seemed to always present in the apical dome at thepotential leaf sites and also round the sides of the dome wherethe ensheathing leaf bases were to form. Periclinal divisionstherefore anticipated the formation of leaf primordia by occuring,in Pisum about one cell cycle and in Silene two or more cellcycles, before the change in the direction of growth or deformationof the surface associated with primordial initiation. Pisum, Silene, planes of cell division, orientation of cell walls, leaf primordia, shoot apical meristem, plastochron     

Determination and Differentiation of Leaf and Petal Primordia in Impatiens balsamina

The development of primordia as leaves, petals, or as organsintermediate between leaves and petals can be regulated by photoperiodin Impatiens. In intermediate organs only some parts of theorgan differentiated as petal, and then only in some cell layers.Allometric measurements of primordium shape suggested that intermediateorgans may begin development as petals, and that their intermediatecharacter at maturity resulted from a switch of some parts ofthe organs from petal to leaf development when the primordiawere between 0.5 and 1 mm long. In reverted apices made to re-flower,primordia were not completely determined as leaves until theywere about 750 µm long. Determination typically occurredfirst at the tips and last at the bases of these primordia.The determination of primordia as leaves or petals in Impatiensis discussed in relation to primordium determination in otherspecies. It is suggested that the lack of commitment to flowermay result in relatively late primordium determination in Impatiens. Impatiens balsamina, determination, differentiation, leaf and petal development, flowering, reversion     

Effect of Sucrose on Starch Accumulation in and Adventitious Bud Formation on Embryos of Picea abies

Adventitious buds were initiated on embryos of Picea abies (L.)Karst. after a pulse treatment with cytokinin. The initial stagesof bud formation could take place on culture medium lackingsucrose, but sucrose was required for further development ofmeristematic centres into bud primordia and buds. Sucrose atone per cent was optimal for adventitious bud formation. Embryoscultured on media containing sucrose started to accumulate starchduring the first day. Starch accumulation occurred especiallyin the cortex cells where starch grains were frequently presentin the chloroplasts. The starch accumulation increased withhigher sucrose concentrations in the culture medium. Embryoscultured on medium lacking sucrose did not accumulate starchbefore the formation of meristematic centres. Starch accumulationwas never observed in meristematic cells from which adventitiousbud primordia developed. Picea abies (L.) Karst., Norway spruce, adventitious bud, starch accumulation, sucrose concentration     

Experimental and Analytical Studies of Pteridophytes: XXIX. The Effect of Progressive Starvation on the Growth and Organization of the Shoot Apex of Dryopteris aristata Druce

Observations on shoot apices of Dryopteris aristata maintainedunder conditions of progressive starvation for periods of upto a year are recorded. Changes in the size of the shoot apexand leaf primordia, in the rates of inception and developmentof leaf primordia, and in phyllotaxis, are described and discussed.     

TheAfGene Regulates Timing and Direction of Major Developmental Events during Leaf Morphogenesis in Garden Pea (Pisum sativum)

The wildtype leaf of the garden pea possesses proximal pairsof leaflets and distal pairs of tendrils in the blade region.Theafila (af) mutation causes leaflets to be replaced by compound(branched) tendrils. We characterized the morphological variationin leaf form along the plant axis and leaf development in earlyand late postembryonic leaves onafilaplants to infer the roleof theAfgene. Leaf forms are more diverse early in shoot ontogenyonafilaplants.Afinfluences pinna length and pinna branchingin addition to pinna type. Pinna initiation in the proximalregion ofafilaleaf primordia is basipetal and delayed comparedto wildtype plants. In addition, pinna development in the proximalregion ofafilaleaves occurs for a longer period of time thanon wildtype leaf primordia. Therefore,Afregulates the timingand direction of leaf developmental processes in the proximalregion of the leaf, but has little effect on the distal region.These data support the heterochronic model of pea leaf morphogenesisproposed by Luet al. (International Journal of Plant Science157:311–355, 1996).Copyright 1999 Annals of Botany Company. afila,Fabaceae, garden pea, heterochrony, leaf morphogenesis,Pisum sativum.     

Surgical Experiments on the Differentiation of Vascular Tissue in the Shoot Apex of Carrot (Daucus carota L.)

Surgical techniques were applied to the shoot apex of carrot(Daucus carota L.) to test the interpretation that provasculartissue is the initial stage of vascular differentiation andto localize the sources of the influences that control its differentiation.If the apex is isolated laterally by vertical incisions leavingit at the summit of a plug of pith tissue, vascular differentiationproceeds normally and an independent vascular system is formedin the pith plug. If all leaf primordia are systematically suppressed,provascular tissue continues to differentiate as an acropetalextension of the pre-existing vascular system but no furtherdifferentiation occurs. When the apex is isolated laterallyand all leaf primordia are suppressed, provascular tissue continuesto be formed acropetally and is extended basipetally into thepith plug by redifferentiation of pith cells, but no furtherdifferentiation occurs. This tissue reacts positively to histochemicaltests for esterase indicating its vascular nature. If only oneleaf primordium is allowed to develop on an isolated shoot apex,its vascular system develops normally and extends basipetallyinto the pith plug, but there is no extension of provasculartissue into the pith plug. These results support the interpretationthat the initial stage of vascular differentiation is controlledby the apical meristem but that further maturation of vasculartissue depends upon influences from developing leaf primordia.Copyright 2000 Annals of Botany Company Provascular tissue, differentiation, carrot (Daucus carota L.), shoot apex, surgical techniques, leaf primordia     

The Initiation, Growth, and Emergence of Leaf Primordia in Fragaria

The leaf initiation rate in Fragaria vesca (var. ‘RoyalSovereign’) has been compared with the elongation rateof the leaf primordia at different seasons. Certain conceptionsof growth correlation within the bud are presented. Experimentson the nature of elongation and emergence of primordia are described,and the causes of emergence are discussed.     

Experimental and Analytical Studies of Pteridophytes: XXXIII. The Experimental Induction of Buds from Leaf Primordia in Dryopteris aristata Druce

When a young leaf primordium of Dryopteris aristata is isolatedon a plug of tissue at any time prior to the formation of alenticular apical cell, the tissue may be induced to developas a solenostelic bud instead of a leaf. The result dependson the rate of leaf development. In some apices, leaf determinationmay take place during the first plastochrone; in others it maybe postponed until the end of the third plastochrone. Isolationof very young primordia by deep incisions in close proximityto the primordium may result in the cessation of meristematicgrowth and the formation of parenchyma. The vascular structureof the isolated primordia and the phyllotaxis of the inducedbuds are described, and the significance of the findings isdiscussed.     

Growth and Histological Changes During Transition to Dormancy in the Regeneration Buds of Hordeum bulbosum L.

Growth and histological changes in a regeneration bud of Hordeumbulbosum during transition to dormancy were studied. Activeformation of new-leaf primordia on the elongating apex accompaniedby arrest of cell division in the lower leaf primordia characterizedthe first period. When activity subsequently in the distal partof the bud decreased, exillary buds and root primordia werestill actively being produced in its basal part.     

Leaf and Flower Development in Pea (Pisum sativum L.): Mutants cochleata andunifoliata

The stipule mutant cochleata(coch) and the simple-leaf mutantunifoliata(uni) are utilized to increase understanding of the controlof compound leaf and flower development in pea. The phenotypeof the coch mutant, which affects the basal stipules of thepea leaf, is described in detail. Mutant coch flowers have supernumeraryorgans, abnormal fusing of flower parts, mosaic organs and partialmale and female sterility. The wild-type Coch gene is shownto have a role in inflorescence development, floral organ identityand in the positioning of leaf parts. Changes in meristem sizemay be related to changes in leaf morphology. In the coch mutant,stipule primordia are small and their development is retardedin comparison with that of the first leaflet primordia. Thediameter of the shoot apical meristem of the uni mutant is approx.25% less than that of its wild-type siblings. This is the firsttime that a significant difference in apical meristem size hasbeen observed in a pea leaf mutant. Genetic controls in thebasal part of the leaf are illustrated by interactions betweencoch and other mutants. The mutantcoch gene is shown to changestipules into a more ‘compound leaf-like’ identitywhich is not affected by thestipules reduced mutation. The interactionof coch and tendril-less(tl) genes reveals that the expressionof the wild-type Tl gene is reduced at the base of the leaf,supporting the theories of gradients of gene action. Copyright2001 Annals of Botany Company Pisum sativum, garden pea, leaf morphogenesis, compound leaf, leaf mutants, flower morphology     

Leaf Determination in the Fern Osmunda cinnamomea--A Reinvestigation

Earlier studies of leaf determination in the fern Osmunda cinnamomeaL., using the technique of excision and sterile culture, indicatedthat the apices of incompletely determined leaf primordia areconverted into shoot apices after isolation. Subsequently otherworkers questioned this interpretation, suggesting that a primordiumis determined as a leaf shortly after its inception and thatany shoot which arises from it is an adaxial adventitious bud.Because of the importance of this distinction in the interpretationof determination, the phenomenon has been reinvestigated byscanning electron microscopy and histological methods. Sincefixation for electron microscopy was inconsistence, the workwas performed on the primordia using resin models formed indental plastic moulds. Our data, on explanted P3, P4, and P5leaf primodia, provide strong confirmation for the interpretationthat the leaf apex is indeed converted to a shoot apex in incompletelydetermined primodia after explantation. This new evidence formsthe basis for interpreting leaf determination in this experimentalsystem.Copyright 1993, 1999 Academic Press Leaf determination, in vitro, surface replica, scanning electron microscopy, Osmunda cinnamomea L., cinnamon fern     

Effects of Developing Leaves on Stelar Pattern Development in the Shoot Apex of Matteuccia struthiopteris

A developmental study of the normal shoot apex of Matteucciastruthiopteris suggested that patterned stelar differentiationis initiated immediately beneath the single layer of promeristemand occurs prior to the initiation of the youngest leaf primordium.A developmental study in which all leaf primordia were suppressed,with or without lateral isolation of the terminal meristem byvertical incisions, has confirmed this interpretation of stelardifferentiation. Experimentally-induced changes in the tissueimmediately below the promeristem were reflected in the resultingmature structure of the stele. Failure of leaf gap initialsto differentiate, if all leaf primordia were suppressed at theincipient stage, resulted in a mature stele without leaf gaps.Similarly the disappearance of pith mother cells after severalweeks of leaf removal was associated with the formation of astele without pith. Leaf influence was further assessed by allowingone primordium to develop while all others were suppressed.The developing leaf had a small promoting effect on caulinevascular tissue differentiation but its major impact on theexpansion of the parenchymatous tissues of the stele. Characteristicprotoxylem and protophloem failed to differentiate when allleaves were suppressed and, when leaf was allowed to develop,formed only in relation to the leaf.Copyright 1995, 1999 AcademicPress Leaf influence, vascular pattern formation, experimental surgery, shoot apex development, protoxylem, protophloem, Matteuccia struthiopteris     

Initiation of Procambial Strands in Axillary Buds of Dactylis glomerata L., Secale cereale L., and Lolium perenne L.

In axillary buds of Dactylis glomerata L., Secale cereale L.,and Lolium perenne L., the first two procambial strands of theprophyll and the median strand of the first normal leaf areinitiated in the bud in isolation from the vascular system ofthe parent axis. They rapidly form connections with the vascularsystem of the parent axis, presumably by downward extension,as is the case of the strands of leaf primordia on the mainaxis.     

Rates of Leaf Initiation and Leaf Growth in Agropyron repens (L.) Beauv.

Rates of leaf initiation, emergence, and growth have been measuredduring the period between the production of one and of ten matureleaves on the primary shoot of Agropyron repens. There is aprogressive decline in the growth rate of successively formedleaves so that at the time of formation of the next leaf primordiumeach primordium is smaller than its predecessor at a comparablestage of development. There is also a trend towards a diauxicpattern of growth with a lag phase apparently coinciding withthe transition from apical to intercalary growth of the youngleaf. Up to the six-leaf stage the rate of leaf formation exceedsthe rate of emergence and leaf primordia accumulate on the shootapex. Thereafter the rate of emergence exceeds the rate of formation.These changes in rates of leaf formation and growth are interpretedin terms of competition for assimilates between expanding leavesand leaf primordia, and between the primary and axillary shootapices.     

Shoot Axillary Bud Morphogenesis in Kiwifruit (Actinidia deliciosa)

The annual cycle of kiwifruit [Actinidia deliciosa(A. Chev.)C. F. Liang et A. R. Ferguson var.deliciosacv. Hayward] shootaxillary bud (first-order axillary bud, FOAB) morphogenesisis described. FOABs developed quickly with the majority of budscales and leaf primordia present approx. 125 d after budbreak(dab). Mature FOABs had, on average, 23.2 bud scales and leafprimordia. Most second-order axillary structures were also presentapprox. 125 dab. During the growing season, the second-orderstructures developed into second-order axillary buds (SOABs)or remained as simple, dome-shaped meristems (SDSMs). At maturity,nearly all FOABs had four SOABs and, on average, 12.4 SDSMs.Most SDSMs were fused to the subtending leaf primordia, butsome SDSMs developed so that they were ‘free’ fromthe subtending leaf primordia. Third-order axillary meristems(third-order SDSMs) were observed in the axils of most SOABs,and, on average, there were 20.6 per FOAB. Our observationson the development of second-order axillary structures are consistentwith evocation in kiwifruit occurring earlier than the generally-acceptedtime of late summer. Actinidia deliciosa; bud morphogenesis; development; flowering; evocation     

The Morphogenesis of Regeneration Buds in Hordeum bulbosum L.--A Perennial Grass

The tillering phase in Hordeum bulbosum L. is terminated whenthe newly-formed axillary buds no longer emerge as tillers,but differentiate into dormant regeneration buds. The patternof development of the axillary buds differs during the tilleringphase and the post-tillering phase. During the former, accumulationof leaf primordia corresponds to the age of the bud, i.e., leafnumber per bud increases basipetally along the shoot. Duringthe post-tillering phase, leaf number per bud decreases basipetallyfrom the base of the future bulb internode. This transitionis brought about by an acceleration in the rate of accumulationof leaf primordia which is more sustained in the buds situatedcloser to the base of the bulb internode. These positional differencesin the morphogenesis of the regeneration buds are reflectedin their physiological responses during the relaxation of dormancyand activation of the buds.     

Acclimation of Photosynthate Partitioning and Photosynthetic Rates to Changes in Length of the Daily Photosynthetic Period

Pangola, soya bean and spinach plants were grown in long andshort day photosynthetic periods. Reciprocal shifts betweenlong and short day grown plants were made to study acclimationin the rate of leaf starch synthesis with change in daylength.The rate of leaf starch accumulation is a function of the lengthof the daily photosynthetic period. Acclimation, that is a changein partitioning with a change in length of the photosyntheticperiod, occurs in a variety of species. Acclimation in the rateof starch accumulation occurs rapidly in pangola and is apparentlycomplete the day after a change in length of the daily photosyntheticperiod. Soya bean and spinach leaves require a few days in thenew environment for an acclimation to occur. Digitaria decumbens Stent., Glycine max (L.) Merr., Spinacia oleracea L., pangola, soya bean, spinach, specific leaf weight, starch, photosynthesis     

Leaf Primordium Initiation and Expanded Leaf Production are Co-ordinated through Similar Response to Air Temperature in Pea (Pisum sativumL.)

Accurate prediction of the timing of leaf area development isessential to analyse and predict the responses of crops to theenvironment. In this paper, we analyse the two processes determiningthe chronology of leaf development—initiation of leafprimordia by the shoot meristem and production of expanded leavesout of the shoot tip—in several pea (Pisum sativumL.)cultivars in response to air temperature and plant growth rate.Contrasting levels of air temperature and plant growth rateduring leaf development were induced by a wide range of sowingdates and plant densities in glasshouse or field experiments.Full leaf expansion was found to occur one phyllochron afterfull leaf unfolding, whatever the leaf nodal position. Primordiuminitiation and expanded leaf production rates presented similarquantitative responses to air temperature (linear response andcommonx-intercept), whatever the plant growth rate, cultivaror period of cycle. As a consequence, they were co-ordinatedand the numbers of initiated primordia or expanded leaves wereeasily deduced from simple visual observation of leaf unfolding.The change, over time, of the numbers of initiated leaf primordiaand fully expanded leaves correlated with cumulated degree-days,with stable relationships in a wide range of environmental conditions.Two phases, with different production rates, had to be considered.These results allowed us to predict accurately the beginningand the end of individual leaf development from daily mean airtemperatures. The relationships obtained here provide an effectiveway of analysing and predicting leaf development responses tothe environment. Pisum sativumL.; pea; number of leaf primordia; number of leaves; temperature; modelling     

Leaf Ontogeny in Digitaria eriantha

The shoot apex consists of two layers, the dermatogen and thehypodermis. The leaf primordia arise through periclinal divisionswithin these two layers on the side of the apex. Further divisionsof the dermatogen push the little protuberance upward and togetherwith divisions the hypodermis add internal tissues of the youngleaf. When the median and lateral bundles of the primordia arisein Digitaria eriantha they are isolated from the vascular supplyof the rest of the plant. The median strand, the first to form,and the first order laterals form at the disc of insertion ofthe primordium. The other laterals form higher up in the primordium.These strands extend both acropetally and basipetally to linkwith the vascular supply of the rest of the plant. Digitaria eriantha, apical meristem, leaf primordium, vascular bundle, orange G, tannic acid, iron alum