The Rate of Growth and Partitioning of Assimilates in Young Grass Plants: A Mathematical Model

A model describing the increase in weight with time of younggrass plants is formulated. The parameters are the relativegrowth rates of the root and shoot systems; k, the ratio ofthe relative growth rate of the root system relative to thatof the shoot system; b, the weight of the root system when thatof the shoot system is unity, and u the rate of increase inweight of the whole plant per unit of shoot system per unitof time, k and b are the constants in the allometric formula,r = bs^k where r and are the weights of the root and shoot systems.The model enables the effect of changes in the distributionof assimilates between the root and shoot systems upon the rateof growth of the plant to be assessed. Data from a number ofexperiments are analysed in this manner and the significanceof the results discussed.     

Shoot Inversion-induced Ethylene Production in the Diageotropica Tomato Mutant

Shoot inversion was found to inhibit shoot elongation over 24h in the diageotropica (dgt) mutant tomato and its isogenicparent, VNF8, by 55% and 51%, respectively. Previous studieswith normal tomato and other species would suggest that gravitystress-induced ethylene production in the inverted shoot retardselongation. Since exposure of the diageotropic shoot of thedgt mutant tomato to ethylene restores normal upward growth,it might appear that dgt is defective in its capacity to produceethylene. That shoot inversion did stimulate some ethylene productionand that the ethylene action inhibitor, AgNO₃, largely negatedthe inhibiting effect of shoot inversion on elongation in dgtstrongly suggest that the ethylene produced in the invertedshoot was responsible for its retardation of growth. Althoughethylene production in the slower growing dgt was much lessthan that in the faster-growing VNF8, the dgt shoot was foundto be much more sensitive to ethylene. Shoot inversion, ethylene, shoot elongation, diageotropica (dgt), auxin     

Chalcone Synthase Localization in Shoot Apices of Fagopyrum, Brassica and Pisum

Chalcone synthase (CHS), a key enzyme of flavonoid synthesis,was localized in shoot apices of Fagopyrum, Brassica and Pisum.The enzyme was detected in initial cells of the shoot apex,which gives rise to the whole plant body. In Fagopyrum and BrassicaCHS was located in the rib and flank meristems, whereas in theArgenteum mutant of Pisum this enzyme was localized at an earlierstage in the ontogenesis of the shoot. It occurs in a few cellsof the tunica, which gives rise to the protoderm, and then tothe epidermis which contains anthocyanins in these plants. Chalcone synthase, immunogold labelling, promeristem, shoot apex, Brassica, Fagopyrum, Pisum     

Differences in Architecture and Shoot Growth during Stagnant and Extension Growth Phases of Acanthopanax sciadophylloides(Araliaceae)

The shoot growth of a deciduous tree, Acanthopanax sciadophylloidesFranch. et Savat. shows inter-annual intermittent repetitionof two distinctive phases, a stagnant growth phase (S-phase)and vigorous extension-growth (E-phase). To help understandthe differentiation mechanism, shoot development was studiedover time in both shoot phases. S-phase and E-phase shoots weredistinguished from each other by morphological traits: S-phaseshoots are characterized by higher allocation to leaves anda shorter period of stem growth, while E-phase shoots show continuousstem extension over the growing season. Specific leaf area didnot differ between the two phases. This shoot differentiationwas similar to the morphological differentiation of shoots betweenlong vs. short shoots found in some temperate trees. Leavesof both phases were well-dispersed through adjustment of petiolelength and leaf-blade size to reduce mutual shading within ashoot. Stem-wood density of current-year shoots was lower inE-phase compared with S-phase shoots. Leaves produced earlyin the season affected the growth phase of the following year.These results suggest that annual shoot differentiation of A.sciadophylloides was determined during the previous season andreflects leaf productivity in a given habitat during that growingseason. Copyright 2001 Annals of Botany Company Acanthopanax sciadophylloides, Araliaceae, biomass allocation, intermittent shoot growth, leaf display, shoot architecture, shoot differentiation     

The Presentation Time for Shoot Inversion Release of Apical Dominance in Pharbitis nil

The presentation time for shoot inversion release of apicaldominance in Pharbitis nil is between 1 and 1.5 d. Five to 6d of shoot inversion are required for persistent outgrowth ofthe highest lateral bud. Pharbitis nil, apical dominance, shoot inversion, lateral bud growth, presentation time     

Effect of Root and Shoot Meristem Temperature on Shoot to Root Dry Matter Partitioning and the Internal Concentrations of Nitrogen and Carbohydrates in Maize and Wheat

Maize (Zea mays L.) and spring wheat (Triticum aestivum L.)were grown in nutrient solution at uniformly high air temperature(20 °C), but different root zone temperatures (RZT 20, 16,12 °C). To manipulate the ratio of shoot activity to rootactivity, the plants were grown with their shoot base includingthe apical meristem either above (i.e. at 20 °C) or withinthe nutrient solution (i.e. at 20, 16 or 12 °C). In wheat, the ratio of shoot:root dry matter partitioning decreasedat low RZT, whereas the opposite was true for maize. In bothspecies, dry matter partitioning to the shoot was one-sidedlyincreased when the shoot base temperature, and thus shoot activity,were increased at low RZT. The concentrations of non-structuralcarbohydrates (NSC) in the shoots and roots were higher at lowin comparison to high RZT in both species, irrespective of theshoot base temperature. The concentrations of nitrogen (N) inthe shoot and root fresh matter also increased at low RZT withthe exception of maize grown at 12 °C RZT and 20 °Cshoot base temperature. The ratio of NSC:N was increased inboth species at low RZT. However this ratio was negatively correlatedwith the ratio of shoot:root dry matter partitioning in wheat,but positively correlated in maize. It is suggested that dry matter partitioning between shoot androots at low RZT is not causally related to the internal nitrogenor carbohydrate status of the plants. Furthermore, balancedactivity between shoot and roots is maintained by adaptationsin specific shoot and root activity, rather than by an alteredratio of biomass allocation between shoot and roots.Copyright1994, 1999 Academic Press Wheat, Triticum aestivum, maize, Zea mays, root temperature, shoot meristem temperature, biomass allocation, shoot:root ratio, carbohydrate status, nitrogen status, functional equilibrium     

The Effects of Plant Density on Shoot and Leaf Lamina Angles in Lolium multiflorum and Paspalum dilatatum

The effects of plant density on shoot and leaf lamina zenithangles (i e the angles with respect to the vertical) were investigatedin Lolium multiflorum and Paspalum dilatatum plants grown inpots either outdoors or in a glasshouse Tillers appeared abovethe ligule of their subtending leaf with a small zenith anglebut, in plants grown at low densities, gradually adopted a morehorizontal position In plants grown at high densities this gradualincrease in shoot zenith angle with age was strongly reducedThe average shoot zenith angle at a given time was lower (ie tillers were more erect) at high, compared to low plant densitiesShoot number per plant and average shoot zenith angle per plantwere directly related In P dilatatum plants the leaf lamina remained nearly horizontalat any plant density This observation indicates that the movementof the leaf lamina, pivoting at the point of attachment to theleaf sheath, compensated the movement of the shoot, pivotingat the base of the leaf sheath-tube Shoot angle responses to plant density would place leaf laminaeat different heights within the canopy, affecting their abilityto compete for light and their susceptibility to wind impactand herbivore grazing Foliage architecture, Lolium multiflorum Lam, Paspalum dilatatum Poir, plant density, neighbour effects, shoot angle, leaf angle     

Relationships Between Nitrogen and Water Concentration in Shoot Tissue ofMolinia caeruleaDuring Shoot Development

Plants ofMolinia caeruleawere supplied with either a low (0.2mol m^-3) or high (10 mol m^-3) supply of nitrogen over two growingseasons. A total of 14 destructive plant harvests were made:when plants were in an over-wintering state prior to the secondseason; immediately following bud burst; and on 12 further occasionsthroughout the second season. The relationships between shootnitrogen concentration on a dry mass basis, shoot water contentand plant developmental stage were investigated. Shoot nitrogenconcentration on a dry mass basis fell as the growing seasonprogressed. In contrast, the concentration of nitrogen in tissuewater after bud burst showed only a slight reduction. The concentrationof nitrogen both on a dry mass basis and in tissue water wasgreater for plants receiving the higher supply of nitrogen.Shoot water content was highest immediately following bud burstthen declined as the season progressed, with plants receivingthe low nitrogen supply having slightly greater shoot watercontents. It was concluded that the decline in shoot nitrogenconcentration ofM. caeruleaon a dry mass basis as the mass increasedwas mainly explained by changes in shoot water content. Theobserved increase in the rate of decline of both shoot nitrogenconcentration and water content with increased shoot mass coincidedwith the cessation of leaf tissue production and was thereforedue to a switch from the production of leaves to other tissues.Copyright1999 Annals of Botany Company Molinia caerulea(L.), purple moor grass, nitrogen, water content, shoot development.     

Allometric Root/Shoot Relationships and Predicted Water Uptake for Desert Succulents

Root morphology, shoot morphology, and water uptake for Agavedeserti and Ferocactus acanthodes of various sizes were studiedusing allometric relationships (y = ax^b) and a previously developedwater uptake model. Shoot surface area increased with shootvolume with an exponent b of 0.75 for both species. Root lengthand the ground area explored by the roots increased with shootsurface area with b's of 0.72 for A. deserti and 0.92 for F.acanthodes. Various sized individuals had about the same ratioof root length to explored ground area, with higher values occurringfor A. deserti. Predicted water uptake averaged over the exploredground area was approximately constant over a 10⁴-fold rangein shoot surface area, suggesting that shoot size confers nointraspecific competitive advantage for water uptake. For theroot lengths per explored ground area observed in the field,water uptake was predicted to be 85 per cent of maximal; wateruptake could be increased by the production of more rain roots.When differences in shoot volume were accounted for by allometry,small plants had relatively less shoot surface area and relativelymore root length per shoot volume than did large plants, whichmay be important for the water relations of seedling establishment. Agave deserti, Ferocactus acanthodes, allometry, desert succulents, root distribution, root length, seedling growth, seedling establishment, shoot surface area, shoot volume, water uptake     

Preformation of Node Number in Vegetative and Reproductive Proleptic Shoot Modules of Persea (Lauraceae)

The numbers of nodes on single flush terminal and axillary shootmodules were determined in a range of Persea species and cultivars.They were compared with node numbers in apical and axillarybuds to investigate whether preformation or neoformation ofnodes occurred. Mean number of nodes on terminal shoots was14 for vegetative shoot modules and 21 for reproductive shootmodules, and was similar across species, cultivars, rootstocks,locations and climates. In the cultivar 'Hass', numbers of nodeson axillary shoot modules were variable, and lower than thosefor primary shoot modules forming the dominant growth axis ofannual growth modules. There was a mean of 12 nodes for vegetativeproleptic shoot modules, 15 for reproductive proleptic shootmodules and six for sylleptic shoot modules, which were invariablyvegetative. All nodes were preformed within both apical andaxillary proleptic buds. This was not the case in syllepticbuds, which burst contemporaneously with extension of the parentaxis. The majority (63%) of reproductive buds formed indeterminatecompound inflorescences. They carried six basal bud scales,six axillary inflorescences and their subtending bracts, andup to nine true leaves.Copyright 1994, 1999 Academic Press Persea Clus., avocado, Persea americana Mill., bud morphology, shoot growth, preformation, prolepsis     

Spike initiation in Plantago ovata Forssk.

Histological studies on Plantago ovata indicated that spikeinitiation occurs from neither the shoot apex nor the axilsof young leaves. The first detectable inflorescence primordium,noticed in the axils of older leaves, gives rise to spike primordiumat later stages of development. Plantago ovata Forssk., inflorescence initiation, shoot apex     

Basal Plate Tissue in Narcissus Bulbs and in Shoot Clump Cultures: Its Structure and Role in Organogenic Potential of Single Leaf Cultures

Light microscopy demonstrated that the apparently amorphous,achlorophyllous tissue at the base of in vitro shoot clump cultureof Narcissus was comparable in structure to the basal plateof Narcissus bulbs. Both had very complex vascularisation andsmall, densely packed parenchymatous cells. In shoot clump cultures, primordia were produced by meristematiczones at the surface of this achlorophyllous tissue, very closeto the base of leaves. Single leaf units excised from the invitro shoot clump cultures with a wedge of basal achlorophylloustissue were highly organogenic when used as secondary explantsfor in vitro culture of Narcissus. No organogenesis occurredin the absence of the leaf base and achlorophyllous (basal plate)tissue and little organogenesis occurred unless the leaf baseand basal plate tissue were immersed in the culture medium (i.e.explants inoculated into liquid medium or upright in agar-solidifiedmedium). After two 5-week culture passages in liquid medium, more thanfive leaves were produced per leaf base inoculated. Thus rapidmicropropagation of Narcissus can be achieved using only thebase of single leaf units excised from shoot clump cultures.Copyright1993, 1999 Academic Press Anatomy, basal plate, bulb, in vitro, leaf culture, Narcissus, organogenesis     

Pattern of Shoot Growth in Zizyphus mauritiana and Z. oenoplia

Shoot polymorphism and patterns of sylleptic branching and shoottip abscission in two Zizyphus species are reported. Z. mauritiana(ber) produced three types of proleptic shoots: vigorous, normaland spur-type, by reiteration or following pruning;Z. oenopliahad only one type of shoot. Both species revealed up to thirdorder sylleptic branching on the vigorous proleptic shoots witha characteristic pattern and rhythm. Bud dormancy breaking chemicalsgiven as pre-pruning foliar sprays in ber, did not alter thepattern of sylleptic branching. Zizyphus oenoplia produced morefirst and second order sylleptic branches compared to Z. mauritiana.All main axes and 97% of first order sylleptic branches ofZ.mauritiana abscised their apical buds during summer, but inZ. oenoplia all main axes and 54% of first order sylleptic branchesremained active. Shoot tip abscission was almost complete onthe higher order sylleptic branches of both species. Activefirst order branches in Z. oenoplia were confined to the tophalf of the shoot. Both species had a few dormant apical budsduring the summer on their sylleptic branches, emerging mostlyfrom the middle portion of the shoot. Some of the most vigorousfirst order branches of Z. oenoplia, which had dormant apicalbuds during summer, showed a change in the frequency of syllepticbranching when they resumed growth following monsoon showers.These characteristic growth and branching patterns may haveadaptive value for canopy development under arid and semi-aridconditions. Copyright 1999 Annals of Botany Company Ber, branching pattern, shoot polymorphism, shoot tip abscission, sylleptic branching, Zizyphus mauritiana, Zizyphus oenoplia.     

High-frequency Organogenesis from Direct Seed Culture in Lathyrus

Culture conditions were developed for inducing a high frequencyof direct shoot morphogenesis and whole plant regeneration incultures of intact seedlings of Lathyrus cicera L., L. ochrus(L.) DC., L. sativus L., and L. tingitanus L. The procedureof shoot regeneration involved culturing of whole, mature seedson MS medium containing cytokinins, or thidiazuron (TDZ), asubstituted phenylurea with cytokinin-like activity. Differentiationof shoots occurred without an intervening callus phase fromthe cotyledonary node and surrounding tissues of the intactseedlings developed from seeds germinated on media containingkinetin, BAP or TDZ. An average of 19·0, 15·8,28·8 and 43·0 shoots were regenerated at optimalconcentrations of 50·0, 50·0 and 80·0 µMBAP in L. cicera, L. tingitanus, L. ochrus and L. sativus, respectively.TDZ enhanced the shoot formation at the concentration of 10µM to an average of 33·1 and 33·7 shootsper seedling in L. cicera and L. tingitanus and at 50 µM,to 57·4 shoots per seedling in L. sativus. Regeneratedshoots developed roots on a modified MS medium containing 2·5µM NAA and the surviving plantlets were transferred tosoil. Histological studies revealed de novo formation of shoot budsfrom the epidermal or subepidermal cells of the basal and nodalregion of multiple epicotyls. Several meristematic centres consistingof actively-dividing cells developed in the subepidermal celllayer of the nodal tissue and adjacent areas within 7 d of seedculture on a cytokinin- or TDZ-supplemented medium. The patternof the development of these meristematic centres and shoot developmentwas similar in all four species.Copyright 1993, 1999 AcademicPress Seed culture, direct shoot morphogenesis, Lathyrus, thidiazuron, grass pea, vetch ochrus     

Spectral Transmission and the Aerial Profile in Mature Stands of Mercurialis perennis L.

The passage of light through mature stands of the woodland perennialherb Mercurialis perennis L. is investigated. Less than 3 percent of each of seven discrete wavelengths in the visible wavebandreach the herb layer in the sites considered. Percentage transmissionof the 750 nm wavelength was far greater, and the proportionof this light passing deep into the herb profile increased astotal light transmission decreased. Mean specific leaf area of M. perennis is negatively correlatedwith shoot height and weight. Leaf area/shoot increases exponentiallywith shoot height, but linearly with shoot weight. Shoot leafweight ratio remains virtually constant over a range of shootsizes, but shoot leaf area ratio is negatively correlated withshoot height and shoot weight. Most leaf pairs are borne between10–30 cm above ground level and 71 per cent of the totalleaf area occurs between 15–30 cm above ground. Averageleaf area/leaf pair increases from the lowest layers in theprofile upwards except for the highest strata where many leavesare not fully expanded. Chlorophyll content of leaves, expressedon either a weight or an area basis, increases from the bottomto the top of the herb profile; the ratio of chlorophyll a:bdoes not alter through the stand.     

Effect of Assimilate Supply on Development and Growth Potential of Axillary Buds in Roses

The effect of assimilate supply on axillary bud developmentand subsequent shoot growth was investigated in roses. Differencesin assimilate supply were imposed by differential defoliation.Fresh and dry mass of axillary buds increased with increasedassimilate supply. The growth potential of buds was studiedeither by pruning the parent shoot above the bud, by graftingthe bud or by culturing the bud in vitro. Time until bud breakwas not clearly affected by assimilate supply during bud development,Increase in assimilate supply slightly increased the numberof leaves and leaf primordia in the bud; the number of leavespreceding the flower on the shoot grown from the axillary budsubstantially increased. No difference was found in the numberof leaves preceding the flower on shoots grown from buds attachedto the parent shoot and those from buds grafted on a cutting,indicating that at the moment of release from inhibition thebud meristem became determined to produce a specific numberof leaves and to develop into a flower. Assimilate supply duringaxillary bud development increased the number of pith cells,but the final size of the pith in the subsequent shoot was largelydetermined by cell enlargement, which was dependent on assimilatesupply during shoot growth. Shoot growth after release frominhibition was affected by assimilate supply during axillarybud development only when buds sprouted attached to the parentshoot, indicating that shoot growth is, to a major extent, dependenton the assimilate supply available while growth is taking place.Copyright1994, 1999 Academic Press Assimilate supply, axillary bud, cell number, cell size, defoliation, development, growth potential, meristem programming, pith, Rosa hybrida, rose, shoot growth     

Shoot Growth and Mortality Patterns of Urtica dioica, a Clonal Forb

The growth and mortality patterns of the clonal forb Urticadioica were investigated at the level of the individual shootin two growing seasons, 1991 and 1992, in a natural stand. Shootheight and diameter at ground level of each shoot tagged inspring were measured repeatedly five times during the growingseason. Dry weights of these repeatedly measured shoots wereestimated using an allometric relationship between dry weight,height and diameter of harvested shoots. A large decrease inshoot density occurred with stand development from the beginningof the growing season in both the years: (1) shoot survivalrate was about 30% at the end of the growing season; (2) shootmortality rate per 10 x 10 cm subplot between censuses was positivelydependent on shoot density per subplot; (3) the mortality rateof individual shoots was negatively dependent on shoot size(height, diameter and weight) at each growing stage, suggestingone-sided competition between living and dying shoots; (4) shootsize (height, diameter and weight) variability in terms of thecoefficient of variation and skewness decreased in accordancewith shoot mortality. Symmetric competition between living shootswas detected by regression analysis based on a model for individualshoot growth considering the degree of competitive asymmetry.However, the competitive effect on individual shoot growth wasvery small (nearly absent). The mortality pattern of Urticadioica indicates that shoot self-thinning occurred from theearly growing stage as in non-clonal crowded monospecific stands,and contrasts with many clonal plants where shoot self-thinningrarely occurs or, if any, is confined only to a short periodof the later growing stage. The pattern of growth and competitionbetween living shoots of Urtica dioica contrasts with non-clonalcrowded plants undergoing intense competition (usually asymmetric)between individuals, but is a common feature of many clonalplants where shoot competition is supposed to be reduced by'physiological integration' between shoots. These form a newpattern not reported yet for clonal plants. It is pointed outthat clonal plants show a wider spectrum of the growth, competitionand mortality patterns of shoots than non-clonals. Some possiblemechanisms for the pattern of Urtica dioica are discussed.Copyright1995, 1999 Academic Press Shoot competition, diffusion model, individual shoot growth, shoot self-thinning, shoot size variability, Urtica dioica L     

Oxygen Transport in the Salt Marsh Genus Puccinellia with Particular Reference to the Diffusive Resistance of the Root--Shoot Junction and the use of Paraffin Oil as a Diffusive Barrier in Plant Studies

Results are presented which contradict previous reports thatin the graminaceous genus Puccinellia the root-shoot junctionhas a high diffusive resistance which severely restricts oxygentransfer from shoot to root. No such restriction was evidentin P. maritima, P. festuciformis var.festuciformis, and P. festucfformisvar.intermedia(= P. peisonis) and the plants produced well-developedroot systems in permanently flooded soils. The evidence obtainedsupports the view that, whether the root systems are whollyor only partially submerged by soil flooding the shoot is themajor source or entry point for oxygen required by the roots;also, that oxygen passes more readily from shoot to root thanit does through the wall cells of the root base. It is pointed out that paraffin oil is an undesirable productto employ as a diffusion barrier in studies of root aeration. Key words: Puccinellia, Oxygen transport, Diffusive resistance, Polarography     

Independence of Organogenesis and Cell Pattern in Developing Angle Shoots of Selaginella martensii

Angle meristems are mounds of meristematic tissue located atdorsal and/or ventral branch points of the dichotomising stemaxes of many species of Selaginella (Lycophyta). The presentstudy examined the development of ventral angle shoots of S.martensii in response to removal of distal shoot apices (decapitation).Scanning electron microscopy of sequential replicas of developingangle meristems and angle shoots revealed that for the firsttwo pseudowhorls of leaf primordia, particular leaves are notattributable to particular merophytes of the angle meristemapical cell. Individual leaf primordia of the first (outer)pseudowhorl often form from more than one merophyte. Neitherthe shape of the angle meristem apical cell nor the directionof segmentation has any effect on the development of the angleshoot. Additionally, the apical cell of the angle meristem doesnot necessarily contribute directly to either of the new shootapices of the developing angle shoot. The first bifurcationof the angle shoot shows a remarkably consistent relationshipto the branching pattern of the parent shoot. The strong branchof the first angle shoot bifurcation typically occurs towardthe weak side branch of the parent shoot. Anatomical studiesshowed that bifurcation of the young angle shoot involved theformation of two new growth centres some distance away fromthe original angle meristem apical cell; new apical cells subsequentlyformed within these. These results provide additional supportfor the view that cell lineage has little or no effect on finalform or structure in plants.Copyright 1994, 1999 Academic Press Selaginella martensii Spring, Lycophyta, angle meristem, apical cell, shoot apical meristem, leaf primordium, branching, dichotomy, morphogenesis, determination, competence, development, mould and cast technique, replica technique, scanning electron microscopy     

Sensitivity of Floral Shoot Growth, Fruit Set and Early Fruit Size inActinidia deliciosato Local Carbon Supply

The sensitivity of pre-anthesis shoot growth, fruit set andearly fruit size in kiwifruit [Actinidia deliciosa(A. Chev.)C. F. Liang et A. R. Ferguson] to cane girdling and defoliationtreatments was tested, and the results discussed in terms ofshoot carbon balance. The nature and degree of responses obtainedwas dependent on the time of application. When treatments wereapplied soon after budbreak, defoliation initially reduced growth,whereas increasingly severe girdling treatments induced responsesprogressing from stimulation to severe impairment of growthand photosynthetic capability. Similar treatments imposed laterin shoot development produced qualitatively different results.The development of floral tissues on the shoot is shown to besensitive to shoot carbon status during a period close to anthesis,and the significance of this result in relation to fruit heterogeneityat maturity is discussed.Copyright 1998 Annals of Botany Company Actinidia deliciosa, kiwifruit, shoot growth, fruit variability, fruit set, reserves.