Responses of Leaf and Tiller Emergence and Primordium Initiation in Wheat and Barley to Interchanged Photoperiod

The influence of constant (9, 13 and 19 h) and reciprocally-interchangedphotoperiods [at terminal spikelet (TS) or triple mound (TM)]on leaf, tiller and primordium development were examined usingphotoperiod-responsive cultivars of spring wheat, ‘UQ189’ and spring barley, ‘Arapiles’. In bothspecies, constant longer photoperiod reduced the duration fromsowing (S) to double ridge (DR), as expected. However, photoperiodsensitivity was not restricted to this mainly vegetative phase.There was also a marked increase or reduction in the durationof reproductive phases between TS/TM and heading (H) when plantswere transferred to shorter or longer photoperiods respectively,compared with controls. These responses were largely independentof the photoperiod during previous phases although minor effectsof the previous photoperiod were observed. For both species,the time course of leaf emergence was linear, or bi-linear,depending on the final leaf number on the main stem. The rateof leaf emergence was faster for the first six to eight leavesthan for the leaves appearing subsequently. The rate of emergenceof early-formed leaves was independent of photoperiod whereasthe rate of emergence of later leaves varied with photoperiod.Photoperiod also affected the dynamics of tillering. The rateof leaf primordium initiation was little affected by variationin photoperiod, but the rate of spikelet initiation increasedwith increases in photoperiod. The rates of leaf and spikeletprimordium initiation were both substantially higher in barleythan in wheat. The fact that the reproductive phase from TS/TMto H was largely independent of the duration of the previousphase provides evidence that this phase might be geneticallymanipulated to increase the time for floret development andhence grain number. Copyright 2000 Annals of Botany Company Photoperiod, rate of development and leaf emergence, tillering, wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)     

Growth and development of Avena fatua (Wild-oat) in the field

The growth and development of field-grown Avena fatua plants were studied for autumn and spring sowings in two consecutive years. The duration of various growth stages from sowing until anthesis was quantified in terms of thermal time (accumulated degree days) or photothermal time (degree days modified by photoperiod). Base temperatures and photoperiods for developmental phases were estimated as those which minimised the coefficient of variation among sowing dates. Relationships were derived between leaf emergence, canopy height, plant leaf area, and photothermal time. Stem extension and flowering occurred earlier in autumn-sown plants than spring-sown plants. Autumn-sown plants produced more leaves on the main stem, and had greater leaf area and above-ground biomass at anthesis than spring-sown plants.     

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.     

Leaf primordia initiation,leaf emergence and tillering in wheat (Triticum aestivum L.) grown under low-phosphorus conditions

In two simultaneous experiments we examined the effects of phosphorus (P) supply on leaf area development in wheat (Triticum aestivum L.) grown in sand with nutrient solutions. In Experiment 1 we studied leaf emergence, leaf elongation, tiller emergence, shoot growth, and P uptake under four levels of P supply (mM) 0.025 (P1), 0.05 (P2), 0.1 (P3), and 0.5 (P4), and. In Experiment 2 there were two levels of P supply, P1 and P4, and we examined the effects of P on leaf primordia differentiation and leaf emergence. The phyllochron was calculated as the inverse of the rate of leaf emergence calculated from the regression of number of leaf tips (PHY-Ltip), Haun index (PHY-Haun), and as the cumulated thermal time between the emergence of two consecutive leaves (PHYtt). The plastochron was calculated from the inverse of the rate of leaf primordia initiation in the apex. P deficiency delayed the emergence of leaves on the main stem and on the tiller 1. Phosphorus deficiency increased the time from emergence to double ridge and anthesis. The final number of leaves was not affected by P. The effects of P on the value of the phyllochron were attributed to both a reduced rate of leaf primordia initiation, and to a reduced leaf elongation rate. P deficiency delayed or even suppressed the emergence of certain tillers. In this work a phosphorus deficiency that reduced shoot growth by 25% at 44 days after emergence significantly modified the structure of the plants by increasing the value of the phyllochron and delaying tillering. These results suggest that any attempt to simulate leaf area development and growth of wheat plants for P-limited conditions should include the effects of the deficiency on leaf emergence.     

Leaf Growth and Apex Development of Perennial Ryegrass During Winter and Spring

The relationships between rates of leaf extension, leaf appearance,and primordia production on the apex were studied in the fieldduring winter and spring in established swards of four contrastingperennial ryegrass lines (Aurora, Melle, a hybrid selectionfrom a cross between Aurora and Melle and S.24). All four linesshowed an increase in leaf extension rates which commenced whenspikelet primordia were first initiated at the apex. This wassome time after vernalization requirements had been satisfied.In early-flowering lines the stimulus to leaf growth rates occurredearlier than in late-flowering lines. Maximum leaf growth ratesoccurred about the time of double ridge formation, in the middleof the period of spikelet primordia production. The rate andduration of the period of spikelet primordia production variedbetween lines. By the time of flowering, leaf growth rates declinedto values recorded for vegetative plants in the winter. Leafappearance rates followed a similar pattern to leaf growth rates,although the increase in leaf appearance rate was less thanin primordia production or leaf growth rates. Hybrids from across between early- and late-flowering lines showed early enhancementof leaf extension rates due to early initiation of spikeletprimordia production. These high rates of leaf growth were maintainedfor longer, compared with the early-flowering line, as the durationof spikelet production was longer. This illustrates a mechanismfor combining early spring growth with lateness of floweringin ryegrass breeding programmes Leaf growth, apex development, vernalization, initiation, spikelet primordia production, flowering, thermal time, Lolium perenne, perennial ryegrass, spring growth     

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.     

Leaf Emergence of Spring Wheat Receiving Varying Nitrogen Supply at Different Stages of Development

We examined effects of nitrogen (N) supply on leaf emergenceof spring wheat (Triticum aestivum L.) grown in sand with nutrientsolution containing different N concentrations (9NO₃: 1NH₄).In expt 1, the cultivar 'Gamenya' received nutrient solutiontwice weekly containing a constant N supply ranging from 50to 2400 µM N. In expts 2 and 3, cultivars 'Aroona' and'Gamenya' were irrigated hourly with nutrient solution containingeither low (L = 50 µM N) or high (H = 2000 µM N)N supply. In expt 2, the N supply to half of the plants receivingL and H was changed at the double ridge stage of apical development,producing plants receiving LL, LH, HL and HH. In expt 3, N supplywas changed firstly when the main stem apex was vegetative (oneto two leaves) and secondly when the main stem apex was at doubleridge stage (four to five leaves), producing plants receivingLLL, LHL, HLH and HHH. Leaves on the main stem and primary tillerswere counted. Rate of leaf emergence was estimated from regressionof number of leaves against thermal time; the phyllochron wascalculated as 1/ rate of emergence. Severely N-deficient plants (which had at least a 60% reductionin shoot dry weight) had slower rates of leaf emergence (expt1). Fluctuating N supply sometimes, but not always, changedthe rate of leaf emergence (expts 2 and 3). The N supply beforedouble ridge stage had bigger effects on the phyllochron thanthat afterwards (expt 3). The phyllocrons of the main stemswere generally lower than those of tillers, with a greater differencebetween stems in N-deficient plants. Low N supply at the vegetativeapex stage decreased the total number of leaves on the mainstem, while low N supply after double ridge did not.Copyright1994, 1999 Academic Press Nitrogen, stress, spring wheat, Triticum aestivum, leaf emergence, phyllochron, apical development     

Impact of tree leaf phenology on growth rates and reproduction in the spring flowering species Trillium erectum (Liliaceae)

We investigated the impact of overstory tree leaf phenology on growth rates, carbon allocation pattern, and fruit characteristics in the spring flowering species, Trillium erectum (Liliaceae). Air temperature, overstory canopy closure, and T. erectum phenology were monitored at three locations following a latitudinal gradient in Québec, Canada. Northern sugar maple trees leaf out at cooler temperatures than more southern populations, while Trillium development was initiated at the same soil temperature irrespective of the latitude. Therefore, in northern areas, the time between initiation of T. erectum leaf expansion and canopy closure was shorter than in southern areas, which left less time for northern plants to accumulate reserves before canopy closure. Differences in growth patterns were noted between T. erectum populations. From a south-north gradient, investment to reproduction, total plant biomass, and annual growth rate decreased, while specific leaf area and stem height increased, indicating shade acclimation. The length of the high light period in early spring seems to be a determinant for spring flowering plants' growth and reproduction and may explain the northern distribution limit of some of these species.     

The influence of pruning on wasp inhabitants of galls induced by Hemadas nubilipennis Ashmead (Hymenoptera: Pteromalidae) on lowbush blueberry

The efficacy of pruning methods for managing blueberry stem galls caused by the chalcid wasp, Hemadas nubilipennis (Ashmead), was studied in five commercial lowbush blueberry (Vaccinium angustifolium Aiton) fields in Nova Scotia, Canada, between October 1999 and May 2000. Blueberry fields were mowed in the fall, and burning treatments were subsequently applied either in the fall or the spring. Three treatments were compared: mowing only, mowing plus fall burning, and mowing plus spring burning. Galls collected from the mow plus spring-burn treatment had the least wasp emergence of the three treatments, while the total number of galls was not affected by treatment. Wasp mortality, not gall destruction, is why wasp emergence is reduced in burn treatments. More galls were located and, for the burn treatments, higher wasp emergence was seen from galls found within the leaf litter than those above it. Five co-inhabitants emerged from blueberry stem galls in this study. Three, Eurytoma solenozopheriae (Ashmead), Sycophila vacciniicola (Balduf), and Orymus vacciniicola (Ashmead) are commonly found associates. The other two, Eupelmus vesicularis (Ritzius) and Pteromalus spp., are new records for Nova Scotia. O. vacciniicola is likely an inquiline because it is the largest wasp emerging from galls, and there was a positive relationship between its emergence and that of H. nubilipennis. Larger gall size improved H. nubilipennis emergence from mow and spring-burn galls. After a field has been mowed in the fall, we recommend a spring burn to reduce gall populations and the threat of product contamination.     

The Influence of Genes for Vernalization Response on Development and Growth in Wheat

Studies were made of the influence of genes for vernalizationresponse on the growth and development of four near-isogeniclines of bread wheat (Triticum aestivum L.). The duration from sowing of flower initiation, terminal spikeletformation and ear emergence all increased with increasing vernalizationresponse. There was a close positive relationship between thedays from sowing to flower initiation and from sowing to earemergence, indicating that the duration of either phase of developmentis a useful measure of relative vernalization when daylengthdoes not limit the rate of development. Total spikelet number per ear and the duration of spikelet initationincreased with increasing vernalization response and there wasa correspondingly higher rate of spikelet initiation in thetwo lines with stronger vernalization response. Most of the differences in growth between the lines were associatedwith diferences in development caused by the vrn genes. Maximumtotal above-ground dry matter and total leaf area per plantincreased with increasing vernalization repsonse but relativegrowth rate and leaf area per plant were not significantly differentbetween the lines. There were no differences in net assimilationrate between the four lines until 40 d from sowing; thereafterit decreased, with the greatest decrease in the line with thestrongest vernalization response. Flower initiation, terminal spikelet formation, spikelet initiation, ear emergence, growth rate     

小麦不同蘖位叶片出生的两段线性模式及其品种、播期效应

叶片出生动态是小麦生长发育进程及其协调状况的重要表现,研究发现,小科叶片出生与播后累积ＧＤＤ（ｆｇｒｏｗｉｎｇ ｄｅｇｒｅｅ ｄａｙｓ ａｆｔｅｒ ｓｏｗｉｎｇ）的关系遵循两段（阶段Ⅰ快于阶段Ⅱ）线性模式,护颖分化期为两段模式的分界点,这一规律在正常发育的冬性和春性品种的７主茎及分蘖中表现一致,冬性品种播期１（９月３０日）、播期３（３月２日）的主茎及冬、春性品种各播期的Ｔ３分蘖,因生长发育异常而”     

Phenological and growth patterns of the Mediterranean oak Quercus suber L.

The phenology of Quercus suber L., a dominant species of the montados in the Iberian Peninsula, was studied for 2 years in southwest Portugal. The seasonal progression of phenological events was analyzed in seven trees. Selected branches were examined monthly for shoot elongation, leaf number, branching, flowering, and fruiting. Radial stem growth and specific leaf weight were also studied. Active growth was observed from early spring to early summer. Reserves accumulated during winter and high photosynthetic activity in early spring apparently supported this strong development. The growth flush started with stem radial increment, which seemed to be impaired by spring rainfall. Male inflorescence production was the next phenological event. Old leaves were shed during new twig and leaf emergence. Shoot elongation and the number of new leaves produced were well correlated with the previous-year shoot's length, and were not clearly related to climatic factors. Radial growth resumed in autumn at a lower rate than in the previous spring, a possible consequence of a reserve depletion due to lower photosynthetic production in summer and investment on fruit maturation, which was complete by late autumn. Premature and excessive new leaf production were apparently subjected to self-pruning strategies related to the development of each tree's crown. Younger cork-oaks produced shorter and fewer shoots per module, and more sclerophyllous leaves than the older ones. A high intra-specific variability was observed in all the results.     

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.     

Growth and Dry-weight Distribution in Callistephus chinensis as Influenced by Lighting Treatment

Plants of two cultivars of Callistephus chinensis (Queen ofthe Market and Johannistag) were grown in 8 h of daylight perday with one of the following treatments given during the 16h dark period: (a) darkness—‘uninterrupted night’,(b) I h of light in the middle of the dark period—a ‘nightbreak’, (c) I min of light in every hour of the dark period—‘cycliclighting’, (d) light throughout—‘continuouslight’. The plants receiving uninterrupted dark periods remained compactand rosetted in habit with small leaves, while leaf expansion,stem extension, and flower initiation were promoted in all threeillumination treatments (b, c, d). Although these three treatmentsproduced similar increases in leaf area, continuous light wasthe most effective for the promotion of both stem growth andflower initiation while cyclic lighting was generally more effectivethan a I-h night break. Continuous light also caused more dry matter to be divertedto stems at any given vegetative dry weight and it was shownthat the stem weight ratio of both varieties was correlatedwith stem length.     

A functional-structural model of elongation of the grass leaf and its relationships with the phyllochron

The emergence of a regular phyllochron from the dynamic processes of leaf initiation, leaf elongation and whorl construction suggests causal relationships between leaf elongation and leaf emergence. This paper presents a hypothesis as to how the ontogeny of the growth zone of leaves is triggered by emergence events, and implements it in a dynamic model of leaf elongation. Two different experiments, presenting two contrasted cases of relationships between leaf emergence and kinetics of leaf elongation, were analysed and interpreted with the model in terms of the functioning of the growth zone. Analysis of elongation kinetics revealed that the hypothesis allows for several contrasted elongation patterns that were observed, and for a regular phyllochron emerging from the variable dynamic of elongation. The model was able to simulate these patterns, and helped to identify the mechanisms underlying the key points of the analysis. The hypothesis is not demonstrated, but its coherence and robustness are established, which should inform a renewal of the modelling of leaf elongation in architectural models.     

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     

Studies of Growth and Development in the Genus Fragaria: IV. Winter Growth

The initiation and growth of leaf primordia has been followedduring four winters, and similar rates were obtained in eachseason. When allowance is made for temperature differences,these rates are at a much lower level than during the activegrowing season. In this respect winter dormancy involves a physiologicalchange resulting in a lower level of activity rather than acomplete cessation of activity. Leaf emergence and expansion,on the other hand, is completely stopped during the winter;this appears to be the result of photoperiodic induction bythe shortening days of August and September and is not primarilydependent on the fall in temperature.     

Commercially available plant growth regulators and promoters modify bulk tissue abscisic acid concentrations in spring barley, but not root growth and yield response to drought

Field and lysimeter experiments were conducted in 2002 to investigate the effects of an antigibberellin growth regulator (Moddus, active ingredient trinexapac‐ethyl, Syngenta Crop Protection UK Ltd, Whittlesford, Cambridge, UK) and an auxin‐stimulating (Route, active ingredient zinc ammonium acetate, De Sangosse Ltd, Swaffham Bulbeck, Cambridge, UK) growth promoter on root growth, soil water extraction and the drought response of spring barley. The effects on root growth and distribution were investigated in the field. The effects on the drought response were studied in 1.2‐m‐deep lysimeters packed with a loamy sand subsoil and sandy loam topsoil. Lysimeters were located under a fixed rain shelter, and drought was imposed by withholding irrigation. In both field and lysimeter experiments, growth regulator/promoters were applied to cv. Optic at early tillering according to the manufacturers’ recommendations. After withholding irrigation from lysimeters at Zadoks growth stage (GS) 21 (37 days after sowing), 50% of the profile available water had been depleted by flag leaf emergence (GS 37/39; 62 days after sowing). Drought significantly reduced stem biomass at ear emergence (GS 59; 78 days after sowing) but not leaf or ear dry weight; this was before there was any significant reduction in leaf water potential or stomatal conductance to water vapour. The reduction in stem biomass may reflect a change in partitioning between shoot and root in response to soil drying. When averaged over growth regulator/promoter treatments, drought reduced grain yield by approximately 1 t ha^?1. This was associated with a reduction in both ears per m² and grains per ear. The mean grain weight was not reduced by drought, in spite of significant reductions in stomatal conductance and canopy lifespan post‐anthesis. Route, and to a lesser extent Moddus, significantly increased abscisic acid accumulation in the stem base of droughted plants, and there was some indication of a possible delay in stomatal closure in Route‐treated plants as the soil moisture deficit developed. However, there was no significant effect on the amount of soil water extracted or grain yield under drought. Similarly, in field experiments, neither Route nor Moddus significantly altered total root length, biomass or distribution. There is little evidence from these experiments or in the literature to support the use of antigibberellin or auxin‐simulating growth regulator/promoters to modify root growth and drought avoidance of spring barley.     

Variation in the lag phase and uniformity of the length of the rooting phase prior to adventitious root production in cuttings of Agathis australis

Cuttings of Agathis australis (D. Don) Lindl passed through a well-defined series of morphological changes prior to root emergence. These phases were incorporated into a morphological index which can be used as a guide for the selection of cuttings at known developmental and anatomical stages. After a variable period (lag phase) during which no external change occurred there was an increase in stem diameter a few milimetres above the cut base. This swelling gradually increased in size and isolated bulges developed. Longitudinal splits then arose in the epidermis over the bulges, followed by root emergence through the splits. Root initiation occurred shortly after the sub-basal swelling commenced in cuttings that eventually rooted. Removal of the basal 8 mm of a rooted cutting (which included the roots) usually led to re-rooting of the cuttings. However, if the roots were merely trimmed off, the cutting never formed new roots and always died. The basal region apparently has the capacity to produce only one set of roots. Occasionally the stem diameter continued to increase and the swelling extended to include the basal region. Such cuttings never formed isolated wellings and never rooted.
In general the younger the plant from which the cutting was taken, the shorter the lag phase and the higher the final percentage rooting. Cuttings taken from older plants had a lower rooting percentage and a more variable lag phase, which was related to the time of year the cuttings were taken since root emergence always occurred in spring. Irrespective of the age of the original material there was a constant time period (3–4 weeks) from root initiation to root emergence.     

Coordination between plant and apex development in Hordeum vulgare ssp. distichum

Developmental scales for cereals describe apex and plant morphology separately. In order to link crucial steps of internal and external development, in three varieties of Hordeum vulgare spp. distichum L., sown in autumn and in spring, we recorded plant, leaf and apex stage, following the scales of Zadoks, Haun, and Banerjee and Wienhues, the number of primordia, culm and spike length, and the final number of leaves and spikelets. Primordia initiation was coordinated with leaf appearance and the relative rate was constant for the initiation of productive primordia. The maximum number of primordia was achieved just before the first node became detectable, but development was completed only by those initiated before floret differentiation and internode distension started. The first spikelet was initiated when the third leaf tip became visible, and the last one when plants were at the pseudo stem erection stage and five leaves had still to appear.