Growth and Senescence of the Successive Leaves on a Cocksfoot Tiller. Effect of Nitrogen and Cutting Regime

The effects of nitrogen supply and cutting regime on the morphologicalcharacteristics (leaf appearance and expansion rates, leaf growthduration, leaf lifespan) of a cocksfoot sward were studied overthree growing seasons to gain a better understanding of thechanges in tiller characteristics (length and age of laminae,number of leaves per tiller) over time and in different seasons.We show that, for a given regrowth, the lamina expansion rateat the tiller level depended on herbage nitrogen status, butthe time course of its components differed according to nitrogensupply. When nitrogen was supplied, leaf appearance was fasterbut also decreased faster. In other words, the length of successivelaminae increased faster when nitrogen was supplied. The samewas true for the growth duration of the laminae and their lifespan.These changes resulted from the length of the sheaths from whichthe successive laminae emerged. As nitrogen increased cell number,it changed the ratio of lamina length_n+1/sheath length_nmorethan the ratio lamina length_n/sheath length_nat the same insertionlevel. Therefore sheath length increased faster and leaf appearancedecreased faster when nitrogen was supplied. This finding helpsto explain the effects of different heights and frequenciesof cutting in terms of their effects on sheath length. Copyright2000 Annals of Botany Company Nitrogen, defoliation, cocksfoot, sheath     

Leaf and Tiller Production of Prairie Grass (Bromus willdenowii Kunth) and Two Ryegrass (Lolium) Species

A detailed morphological study of three prairie grass cultivars(Bromus willdenowii Kunth) was conducted under ‘vegetative’and ‘reproductive’ growth conditions (short andlong photoperiods) and at different temperatures. Perennialryegrass (Lolium perenne L.) and Westerwolds ryegrass (Loliummuhiflorum Lam.) were compared during vegetative growth. Prairie grass had higher leaf appearance rates (leaves per tillerper day) and lower site filling (tillers per tiller per leafappearance interval) than the ryegrass species. Tillering rates(tillers per tiller per day) were also lower, except under vegetativeconditions at 4C. Low tiller number in prairie grass was notdue to lack of tiller sites but a result of poor filling ofthese sites. Lower site filling occurred because of increaseddelays in appearance of the youngest axillary tiller and lackof axillary tillers emerging from basal tiller buds. In prairiegrass, no tillers came from coleoptile buds while only occasionallydid prophyll buds develop tillers. Low tiller number in prairiegrass was compensated for by greater tiller weight. Prairiegrass had more live leaves per tiller, greater area per leafand a high leaf area per plant. Considerable variation between cultivars was found in prairiegrass. The cultivar ‘Bellegarde’ had high leaf appearance,large leaves and rapid reproductive development, but had lowlevels of site filling, tillering rate, final tiller numberand herbage quality during reproductive growth. ‘Primabel’tended to have the opposite levels for these parameters, while‘Grasslands Matua’ was intermediate and possiblyprovided the best balance of all plant parameters. prairie grass, Bromus willdenowii Kunth, perennial ryegrass, Lolium perenne L., Westerwolds ryegrass, Lolium multiflorum Lam., temperature, photoperiod, leaf appearance, leaf area, tillering, site filling, tillering sites, yield     

The Effects of Position and Temperature on the Expansion of Leaves of Vicia faba L.

The growth in area of the first eight leaves of broad bean plantswas investigated in growth room experiments. Plants were grownat either 20 or 14 °C or transferred from 20 to 14 °C.Rates of leaf appearance and unfolding increased with temperature.The duration of growth of a leaf increased with leaf numberfor the first five leaves and then remained constant The meangrowth rate declined or remained constant with increasing leafnumber Durations of growth were shorter and growth rates largerat 20 °C than at 14 °C Plants responded immediatelyto the change in temperature Final areas of leaves which expandedafter transfer from 20 to 14 °C were larger than those grownat 20 °C Vicla faba L., broad bean, leaf expansion, temperature responses     

Regulation of leaf growth of grass by blue light

Changes in light quality occur naturally within a canopy when a plant grows from unshaded to shaded conditions, and the reverse occurs after a cut that reduces shading. These changes in light quality could be responsible for the variation in leaf elongation and appearance rates of grasses. The role of blue light in leaf growth was investigated in tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.). Leaf length was measured daily following a decrease or an increase in blue light to evaluate effects on duration of leaf growth, leaf elongation and the rate of leaf appearance rate. A reduction in blue light increased sheath length by 8 to 14% and lamina length by 6 to 12% for both species. These increases could be reversed by enrichment of blue light. With low blue light treatment, final leaf length was increased due to a greater leaf elongation rate. In tall fescue, but not in perennial ryegrass, this effect was coupled with a greater phyllochron and a longer duration of leaf elongation. Development of successive leaves on a tall fescue tiller were co-ordinated. A decrease in blue light increased the duration of elongation in the oldest growing leaf and also delayed the appearance of a new leaf, maintaining this co-ordination. We conclude that final leaf size and phyllochron for tall fescue can be significantly modified by blue light. Perennial ryegrass appeared less responsive, except for displaying longer sheaths and laminae in low blue light, as also occurred for tall fescue. We hypothesize that leaf length could be regulated by the quality of the light reaching the growing region itself.     

The Effect of Temperature on the Growth of Individual Leaves of Vicia faba L. in the Field

The generalized logistic curve was used to describe the growthof individual leaves in crops of Vicia faba L. Durations of.expansionand mean absolute growth rates were derived from these curves.The duration of expansion was inversely related to temperatureaveraged over four days from unfolding. This relationship wasindependent of leaf position except for the lowest leaves. Theduration of expansion of a leaf was related to the rate of productionof new leaves, the number of expanding leaves remaining relativelyconstant. Absolute growth rates varied with leaf position upto leaf 10. At higher leaves, in the absence of water stress,absolute growth rate was a function of temperature and radiation. Vicia faba L., field bean, leaf growth, temperature     

Effect of the Duration of the Vegetative Phase on Shoot Growth, Development and Yield in Pearl Millet (Pennisetum americanum (L.) Leeke)

Craufurd, P. Q. and Bidinger, F. R. 1988. Effect of the durationof the vegetative phase on shoot growth, development and yieldin pearl millet (Pennisetum americanum (L.) Leeke).–J.exp. Bot. 38: 124–139 The duration of the vegetative phase (DVP) in millet, whichis the major cause of variation in the crop duration, has markedeffects on the number of productive tillers per plant and onmainshoot (MS) and tiller grain yield. Daylength extensionswere used to vary the DVP and the effect on factors affectingpanicle (tiller) number per plant and panicle yield examinedin millet hybrid 841A x J104, grown in the field at Hyderabad,India. Tiller appearance, shoot leaf appearance and leaf area,and stem and panicle growth, in both MS and primary tillers(PTs), were monitored at frequent intervals over the season.At maturity grain yield per shoot was measured The concept of thermal time was used to describe shoot development.The rates of tiller appearance and shoot leaf appearance werelinearly related to thermal time and were not affected by DVPtreatments. The duration of the growth phase from panicle initiationto flowering (GS2) and from flowering to maturity (GS3) was320 and 390 degree days (°Cd), respectively. There was nodifference in rates of leaf or tiller appearance or developmentbetween MS and PTs. Tiller appearance, tiller leaf appearanceand tiller apical development all ceased at the same time inthe later initiated PTs, approximately 550 °Cd from sowing,shortly after rapid stem growth had begun. Tillers that didnot survive were all vegetative or in the early stages of reproductivedevelopment at this time The rate of accumulation of dry matter per plant was similarin all DVP treatments, but in the longer DVP treatments a greaterproportion of the dry matter was partitioned to the MS. Mainshootstem and panicle growth rates were increased by a longer DVP,as was grain yield on the MS, and these were related to increasedMS leaf area. Concurrently, growth rates and yields in laterinitiated tillers were reduced in relation to their leaf areas.Stem growth rate was proportionately increased more than paniclegrowth rate in the longer DVP treatments and this, combinedwith a longer duration of stem growth, resulted in greater stemdry matter at maturity and, therefore, in reduced harvest index.     

Rates of Leaf and Tiller Production in Young Spaced Perennial Ryegrass Plants in Relation to Soil Temperature and Solar Radiation

In an experiment designed to investigate the rate of leaf appearanceand tiller production in young spaced plants of three clonesof perennial ryegrass grown in the field, it was found thatthe rate of leaf appearance per tiller increased linearly withmean soil temperature up to approx. 14 °C. The rate of productionof tillers in relation to the rate of leaf appearance (sitefilling) appeared to be virtually independent of weather conditions.In plants which were adequately established, but still relativelysmall, site filling was equal to or exceeded the theoreticalsteady state; all the tiller buds which were being formed weredeveloping into visible tillers. Thus the relative rate of tillerproduction was controlled by the rate of leaf appearance. Inlarger plants site filling was less complete, and site redundancieswere probably caused by within-plant competition for light atthe tiller bases. Lolium perenne L., perennial ryegrass, tillering, leaf production, solar radiation, soil temperature     

Measuring the RGR of Individual Grass Plants

Vegetative growth of grasses was analysed by dry mass increaseof growing leaves.Holcus lanatuswas grown in a controlled environmentand leaf extension rates of leaf numbers 5–10 of the maintiller were monitored daily. Leaf appearance and leaf extensionrates (LER) of leaves 5–7 enabled the prediction of thefinal length and dry mass of leaf 8 during its growth. A linearincrease of leaf mass per unit leaf length (LML) of leaf 8 wasobserved during growth. After harvest the daily increase indry mass of growing leaves was calculated from the LER and correspondingincrease in LML. The relative growth rate (RGR) of the maintiller showed day-to-day fluctuations and was gradually reducedby 50% over a 16-d period. The RGR of the shoot was maintainedby tillering. The RGR of a single (grass) plant can be calculatedfrom four parameters only: LER, LML, leaf appearance and tillering.Variation of RGR over a period can be reconstructed after harvestand the impact of these four parameters on RGR can be established.Copyright1998 Annals of Botany Company. Relative growth rate, grass, leaf growth,Holcus lanatus.     

Mineral Depletion and Leaf Senescence in Soya Bean as Influenced by Foliar Nutrient Application During Seed Filling

Senescence, as judged by the time courses of leaf lamina photosynthesis,soluble protein and chlorophyll contents, was studied in relationto mineral redistribution in field-grown soya beans [Glycinemax (L.) Merr] to investigate the hypothesis that the depletionof nutrients m the leaves by the developing seeds is the causeof soya bean senescence. A mineral nutrient solution was appliedto the canopy during the seed-filling period, and the effectson senescence and mineral depletion of the leaves were determinedin three cultivars, at two leaf positions, weekly from beginningof seed filling through physiological maturity. The onset of senescence occurred shortly after the beginningof rapid seed filling Photosynthetic rate declined about 60per cent within 3 weeks. Protein dropped by 52 per cent andchlorophyll by 48 per cent over the same period. Foliar nutrient application, at a rate previously shown to givesignificant yield increases in soya beans, increased the concentrationsof N, P and K in the leaf laminae, but tended only to delaytheir decline and failed to either delay the onset or alterthe course of senescence. The results of this experiment seem to indicate that, undernormal growth conditions, the events of senescence in the soyabean are not causally related to the N, P or K concentrationsof the leaf laminae Glycme max (L.) Merr., soya bean, nitrogen, phosphorus, potassium, leaf protein, chlorophyll, photosynthesis, foliar nutrient application, mineral depletion, leaf senescence     

The effects of temperature on leaf growth of sugar beet varieties

Leaf growth of nine varieties of sugar beet (Beta vulgaris L.) was studied at constant temperatures of 7, 11, 15 and 20·C, using generalised logistic curves fitted to the data to estimate the parameters of growth. The rate of leaf appearance increased linearly with temperature and was the same in all varieties. There were differences between varieties in the weighted mean rates of expansion of leaf area per plant (ā), the temperature coefficient of ā and the leaf area duration (D); these differences were caused more by differences in rates of expansion and final sizes of individual leaves than by differences in rates of leaf production. The growth of the first six leaves produced by each plant was examined in detail. The greater size of successive leaves of plants and genotypic differences between comparable leaves were more attributable to differences in the rate than differences in the duration of leaf expansion. Increasing temperatures increased leaf size because they accelerated the rate of expansion more than they shortened the duration of the expansion phase. It is inferred that all effects arose through differences in the initial sizes of leaves before they unrolled from the shoot apex. Dry matter production was proportional to D but was partitioned more to the storage root at the colder temperatures. This may have been related to the differential effects of temperature on cell division and expansion and the relative contribution of these two processes to the final sizes of the leaves and storage root.     

The Production of Leaves and Stolon Branches on Established White Clover Cuttings in Relation to Temperature and Soil Moisture in the Field

Successive sets of cuttings of three white clover genotypeswere raised in a 15 °C growth room and transferred to thefield at 14 d intervals over the course of a year. Rates ofleaf appearance (leaves per stolon growing point per unit time)were found to be closely correlated with 10 cm soil temperatures.Petiole lengths, and weights of the lamina+petiole increasedin May and decreased towards the end of August, but also exhibiteda marked response to a mid-season water deficit. In the conditionsof the experiment (i.e. in the absence of competition from neighbouringplants) the vast majority of axillary buds developed into visiblebranches at all times of the year. There was, however, an increasein the nodal age at which bud development was first observedin winter. Deferred bud development was also observed, particularlyin one genotype, during periods characterized by dry soil surfaceconditions. The results are discussed in relation to observedpatterns of stolon branching in sward conditions. White clover, Trifolium repens, axillary bud development, branching, growing points, leaf appearance rate, petiole length, soil moisture, soil temperature     

Analysis of the Nitrogen Response of Leaf Extension in Lolium temulentum Seedlings

Lolium temulentum seedlings were grown on a nutrient mediumcontaining NH₄NO₂ at 0, 0·1, 0·5, 1·0 and4·3 mmoll^–1 as the sole N source. Relative andabsolute extension rates, maximal leaf size, duration of extensiongrowth, rate of leaf appearance and plastochron index were determinedfrom the parameters of Richards functions fitted to lengthsof laminae measured at intervals after sowing. The final lengthof leaf I was relatively insensitive to N whereas mean relativeextension rate was increased and duration of growth decreasedwith increasing NH₄NO₂ concentration. Leaves 2 and 3 enlargedprogressively with N at concentrations up to 1·0 mmoll^–1but were unresponsive thereafter. There was no significant correlationbetween final length and mean relative extension rate for leaves1 to 3. Leaves 4 to 6 continued to show increasing length beyond1·0 mmoll^–1 N and final length was significantlycorrelated with mean relative extension rate. Increasing N increasedthe rate of leaf appearance by decreasing the duration of leafextension and plastochron. These results are discussed in relationto the control of leaf and N turnover. Lolium temulentum, rye grass, leaf extension, nitrogen, Richards function, growth analysis     

The role of the sheath tube in the development of expanding leaves in perennial ryegrass

A possible morphogenic effect of leaf sheaths on subsequent leaf development was investigated by varying sheath tube (pseudostem) length in plants of perennial ryegrass (Lolium perenne) cv. Talbot by either incising longitudinally or excising the distal portion of the sheath tube, while leaving the basal length of the tube intact. The tube was maintained at predetermined lengths by incising and excising new growth daily. The youngest rapidly expanding leaf was allowed to grow through the tube and was measured when fully expanded. Reducing tube length by excision or by incision from 60 mm to just above the cowl leaf on the apex reduced lamina length by 87% and 77% respectively. Over all tube lengths, laminae in incised treatments were almost twice as long as those in excised treatments. Sheath length followed a similar pattern. The effect on developing leaves of artificially extending sheath tubes (previously excised to 15 mm) to 30 or 45 mm with foil was similar to that of initially excising sheath tubes to 30 or 45 mm. The shorter the sheath tube (reduced by incision) through which the leaves had to grow, the shorter the cells, especially in the laminae. The estimated cell number per row along the length of the laminae ranged from 190 in tillers (shoots) with a very short tube (just above the cowl leaf) to 454 in intact control tillers. It is concluded that the sheath tube has a morphogenic influence on the development of subsequent leaves due to the change in environment of the leaf lamina on appearance, affecting both cell elongation and cell division.     

Field studies of leaf development and expansion in the leek (Allium porrum)

An analysis of leek leaf development and expansion was carried out over three seasons using field-grown plants of three varieties which were directly sown at different dates or transplanted from controlled conditions. In all cases, successive leaves appeared (tip visible) at equal intervals of accumulated temperature. Detailed analysis of a single sowing in 1985 showed that the regularity of leaf appearance was a consequence of the coordinated response to accumulated temperature of leaf initiation (plastochron 100°C days > 0°C) and leaf blade and sheath extension. For each successive leaf, an additional 32°C days were required between initiation and appearance to allow for the linear increase in ‘sheath’ height, giving a phyllochron of 132°C days. Direct measurement of leaf extension before and after leaf appearance, and of the length of the leaf extension zone, confirmed that the rate of leaf extension, in terms of accumulated tempeature, was constant, and independent of leaf number. However, there were differences between seasons and between varieties in the responses of leaf appearance, leaf extension and ‘sheath’ length to accumulated temperature. It was concluded that the simple ontogenetic increase in leaf dimensions, which was a feature of all the crops studied, was a consequence of the progressive increase in the duration of leaf expansion.     

The Development of the Runner-bean Leaf with Special Reference to the Relation between the Sizes of the Lamina and of the Petiolar Xylem: II. The Normal Development of the Bean Leaf

The development of the first pair of leaves of the Runner-bean(Phaseolus multiflorus Willd.) has been investigated from theunfolding of the leaves to the end of lamina expansion. Thegrowth of the petiole is relatively fast and ceases first. Extensiongrowth of the lamina continues longer. In the growth of thexylem, the average area of the vessels formed increases mostmarkedly at an early developmental stage. Vessel number maycontinue to increase after lamina growth has ceased. Both thenumber of vessels and the xylem area per unit area of laminadiminish as the leaf matures.     

Studies on the Expansion of the Leaf Surface: II. THE INFLUENCE OF LIGHT INTENSITY AND DAYLENGTH

The parts played by constant amounts of visible radiation perday and its two components—daylength and intensity—ininfluencing the growth of Cucumis sativus have been investigated.The amount of radiation per day had a far greater influencethan either of its components per se. Nevertheless, small significanteffects of photoperiod were found, leaf expansion and dry weightincrease being greatest at daylengths between 10 and 15 hr.rather than with longer days which, with similar daily totals,would be expected to give the greatest amounts of assimilation. Rates of leaf production and appearance were greatest with thehighest amounts of radiation, but the rates of expansion ofindividual leaves and their maximum areas were greatest withintermediate amounts of radiation. This response resulted inan optimum curve relating the leaf surface and the dry weightattained after a given period to radiation. The amount of radiationgiving the maximum leaf surface and dry weight decreased withage and with external nutrient supply, but at any one age washigher for increase in dry weight than for increase in leafsurface; stem and root tissues responded more to high radiationthan did the leaf surface. The net assimilation rate was a linearfunction of visible radiation over the range of 15–120cal. cm.^-2 day^-1 explored, the highest value of radiation usedrepresenting the intensity at which photosynthesis would beexpected to be maximal over a 12–15 hr. day. The inhibitory effect of high radiation on leaf expansion andthe resultant influence on the growth of the plant are explainedin terms of the number and intensity of ‘sinks’for carbohydrate and mineral nutrients within the plant.     

The influence of temperature on leaf development and growth in potatoes in controlled environments

Three controlled environment experiments were conducted at different temperatures to determine the relation between temperature and leaf development and growth in the potato (cv. Maris Piper). Developmental stages are defined for the appearance and duration of leaf extension in the potato and comparisons made with other temperate zone crops. The rate of leaf appearance was linear over the temperature range (9–25°C) and above 25°C there was no further increase in the rate. The temperature coefficient for the rate of appearance of leaves was 0.032 leaves (degree days)^-1 using a base temperature of 0°C. The duration of extension of an individual leaf decreased with increase in temperature up to 25°C such that the thermal duration was constant at 170 degree days using a base temperature of 0°C for leaf positions 4–10 on the main stem. At higher leaf positions the thermal duration was similar or greater. The advantages and limitations of controlled environment work as a parallel to field experimentation are discussed.     

Estimation of Potential Tiller Production and Site Usage During Tall Fescue Canopy Development

Tiller appearance in tall fescue (Festuca arundinacea Schreb.)occurs in an orderly, predictable manner with the potentialfor a high degree of synchronization among tillers on a givenplant. Estimates of potential cumulative tiller production (Tmax)are made for synchronous (Tmax_lx = 2^Lx+1 – 1, where Lxis the axil number of the youngest leaf on the main stem whichbears an emerged tiller) and non-synchronous (Tmax₁ = 2^L–NLAT–1,where L is the number of leaves on the main stem and NLAT thenumber of leaves above the youngest primary tiller at its appearance)conditions. A method for determining the degree of synchronizationand an equation for estimating site usage are also presented.Early in seedling development, site usage of a tall fescue populationwith high tillering capacity was near 90%, and tillering wasregulated largely by rate of tiller site formation. As the canopydeveloped the phyllochron (time between successive leaf appearances)and NLAT increased, slowing the rate of tiller production intemporal terms and in relation to leaf appearance, respectively.Beyond 45 d after planting, site usage decreased rapidly, furtherreducing tiller production. High tiller production appearedto be associated with synchronized tiller appearance, with alack of synchrony being associated with decreased site usage.Tillers formed in prophyll axils were less likely to be in synchronywith other tillers and frequently failed to appear. In contrastwith branching in dicotyledons, apical dominance appears toplay a minor role in regulating tillering in tall fescue Tillerproduction initially appears to proceed at near maximum ratesthen is down-regulated during later development by longer phyllochrons,slower rate of tiller elongation and reduced site usage. Festuca arundinaceaSchreb., tall fescue, tiller production, leaf appearance, site usage, leaf elongation rate, synchronization, phyllochron, canopy development     

Effects of Temperature and Leaf Position on Leaf Area Expansion of Kiwifruit (Actinidia deliciosa) Shoots: Development of a Modelling Framework

This paper describes mathematically the effects of temperatureand position on the expansion of leaves along a kiwifruit (Actinidiadeliciosa) shoot, taking into account shoot morphology. Theleaves were grouped into three zones along the shoot: initialcluster leaves (first zone); the rest of the leaves that werepreformed during the previous season (second zone); and leavesthat were initiated during the current season (third zone).After opening of the initial cluster, the leaves appeared atconstant rates for each of the two temperature treatments considered.The expansion of individual leaves was modelled by a growthfunction with the parameters: final area; duration of the growthwindow; centre of the growth window (timing of expansion); andlower asymptote. Within the first two zones, the pattern ofleaf expansion was affected by nodal position, with basal leaveshaving higher initial rates of expansion than distal leaves.The timing of expansion was linear with respect to the nodalposition within each of the zones, with the slope independentof temperature for the first zone. The slopes of the timingof expansion for the second and third zones depended on temperatureand were correlated for each temperature treatment. Final leafarea was a function of leaf position in the first zone and afunction of timing of leaf expansion for distal leaves startingfrom leaf 10. Temperature had no effect on final leaf area inthe first zone. For the rest of the leaves, temperature affectedfinal leaf area indirectly, through the timing of leaf expansion.The effect of temperature on the growth window of individualleaves within the first zone was less than that for the restof the leaves. However, simulated values for the total leafarea of shoots using the average shoot growth window showedgood agreement with experimental values.Copyright 2001 Annalsof Botany Company Actinidia deliciosa‘Hayward’, shoot development, individual leaf area, temperature effect, positional effects, modelling