Tiller Age Research Articles

Do plants respond to multi‐year disturbance rhythms and are we missing the beat?

Disturbance seasonality and return interval can create complex interactions of direct and indirect effects on species and ecosystems. Fire is a key grassland disturbance, yet long‐term research examining seasonality and return intervals is limited. A 15‐year experiment testing combinations of fire seasonality (summer, fall, spring) and return interval (2, 3, 6‐year) plus non‐burned controls was conducted in northern mixed prairie to evaluate effects on the plant community. Hesperostipa comata is a native C3 bunchgrass and dominant species in northern mixed prairie and previously observed to be fire‐sensitive. Current‐year aboveground biomass results were generally counter to expectations based on short‐term research. Fire increased H. comata biomass with a strong, rhythmic response pattern to a specific fire seasonality‐return‐interval combination (fall fire at 3‐year return intervals) that periodically increased biomass to more than three times that with no fire. Through the first four post‐fire growing seasons, biomass with summer, fall and spring fire across return intervals was 41, 89 and 93% of that with no fire. Afterward, no fire combination produced less biomass than no fire and recurring patterns emerged with large increases in biomass, particularly with fall fire at 3‐year intervals. Peak biomass years were regularly two growing seasons after 3‐year fall fire and occurred across wet, near‐average and dry conditions. We hypothesize that productivity responses were driven by the combination of demographic processes of seedling recruitment and synchronization of multiple tiller age classes. Because short‐term negative effects were reversed and regular patterns only emerged 5 years after study initiation, more long‐term research evaluating fire regimes is recommended to expand upon tests of individual factors over short periods. This suggestion is based on fire research, but likely applies to multiple forms of disturbance and demonstrates how demographic processes can inform responses for individual species and larger ecosystem functions, such as productivity.

Contribution of tiller age category to herbage accumulation of Marandu palisadegrass under two fertilization regimes

Based on the hypothesis that climate and fertilizers influence the proportion of tiller age categories in the canopy and, consequently, in herbage accumulation, the objective of this study was to determine the population density and the contribution of tiller age categories for herbage accumulation of Urochloa brizantha cv. Marandu during the year and in response to phosphate and nitrogen fertilization. The treatments consisted of two fertilization strategies: low and high fertilization and three tiller ages (young, mature and old), evaluated at four times of the year: winter, early and late spring, and summer. The total number of tillers and the proportion of young tillers were higher in late spring and summer. The growth and herbage accumulation rates showed a typical seasonal pattern and were higher in the canopy under high fertilization. Old tillers contributed more to control the total stem growth rate, as well as the canopy senescence rate. The highest percentage of young tillers is related to the high herbage accumulation in the Marandu palisadegrass canopy.

Effect of June Weather on Final Leaf Age and Number of Productive Tillers in Rice Medium Seedlings cv. Akitakomachi.

Effect of June Weather on Final Leaf Age and Number of Productive Tillers in Rice Medium Seedlings cv. Akitakomachi.

Number and morphology of tiller age groups during summer in Marandu palisadegrass pastures previously used under deferred grazing

The relative contribution of young, mature and old tillers in the canopy influences the production and structure of the pasture. The objective with this work was to evaluate the balance between tiller appearance and tiller death (BAL) during spring and early summer, the morphology and percentages of young, mature and old tillers in Brachiaria brizantha cv. Marandu (marandu palisadegrass) with three conditions in late winter: short (24.1 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). Tall and tall/mown pastures presented higher BAL in September and October, respectively. In January, BAL was higher in short and tall/mown pastures than in tall pasture. The tiller number was higher in short pasture, intermediate in tall/mown pasture and lower in tall pasture. The percentage of old tillers was higher in short and tall pastures compared to tall/mown pasture. The percentage of live leaf lamina reduced, while the percentage of dead leaf lamina increased with tiller age. Mowing of the tall marandu palisadegrass pasture in late winter increases the renewal of tillers in the spring and decreases the percentage of old tillers in the summer. The old tillers present worse morphology than young tillers.

Vegetative reproduction characteristics of Leymus chinensis in heterogeneous habitats in Songnen Plain, China

The perennial clonal grasses rely mainly on vegetative reproduction to achieve continuous regeneration. Buds and juvenile tillers formed by buds are potential populations for vegetative reproduction. We compared the composition and size of potential population of Leymus chinensis in the enclosure meadow, long-term mowing meadow, enclosing sand-covered meadow, and forest-grassland, with excavation sampling by unit area and using vegetative reproduction generations to classify the age of tillers, rhizomes and various types of buds and juvenile tillers. The results showed that at the end of the growing season, potential population of L. chinensis was composed of rhizome buds and buds of tiller growing upwards at different ages, as well as juvenile tillers on the tillers and rhizomes. Across the four habitats, the potential population of tillers of L. chinensis was composed of 3-4 age classes, and the rhizomes' potential population consisted of four age classes, of which the potential population formed by rhizomes accounted for 68.3% of the total potential population. The potential population produced by 1st age class tillers and rhizomes accounted for 60.2% of the total, which was the main part of the potential population composition and the main source of population renewal. The potential population of tillers was the most abundant in long-term mowing meadow. The potential population of rhizomes was the most abundant in enclosing sand-covered meadow. The vegetative fertility of tillers and rhizomes was the highest in young age. The vegetative fertility of rhizomes was 10.0 times as that of tillers, which dominated the vegetative reproduction of L. chinensis. The potential population composition of L. chinensis varied greatly across different habitats, reflecting the divergent adaptation to habitat variation.

Modeling the leaf angle dynamics in rice plant.

The leaf angle between stem and sheath (SSA) is an important rice morphological trait. The objective of this study was to develop and validate a dynamic SSA model under different nitrogen (N) rates for selected rice cultivars. The time-course data of SSA were collected in three years, and a dynamic SSA model was developed for different main stem leaf ranks under different N rates for two selected rice cultivars. SSA increased with tiller age. The SSA of the same leaf rank increased with increase in N rate. The maximum SSA increased with leaf rank from the first to the third leaf, then decreased from the third to the final leaf. The relationship between the maximum SSA and leaf rank on main stem could be described with a linear piecewise function. The change of SSA with thermal time (TT) was described by a logistic equation. A variety parameter (the maximum SSA of the 3rd leaf on main stem) and a nitrogen factor were introduced to quantify the effect of cultivar and N rate on SSA. The model was validated against data collected from both pot and field experiments. The relative root mean square error (RRMSE) was 11.56% and 14.05%, respectively. The resulting models could be used for virtual rice plant modeling and plant-type design.

Identification of tiller age categories based on morphogenetic responses of continuously stocked marandu palisade grass fertilised with nitrogen

Nitrogen fertilization augments tiller appearance and death, modifying the age profile of tiller population. Tillers from different age categories present distinct responses to environmental factors and management practices characterized by variation in their morphogenetic responses, which interfere in the dynamics of the herbage accumulation process. In that context, rates of leaf appearance and elongation and leaf lifespan were used as indicators to identify tiller age categories of continuously stocked marandu palisade grass managed at 30cm and subjected to nitrogen fertilization regimes using cluster analysis. Analysis was based on the average distance method using combined means of the response-variables studied, and the results used to build a dendogram to illustrate the arrangement of the resulting clusters. Three clusters were identified corresponding to the tiller age categories denominated young (tillers with age between 0 and 60 days), mature (between 60 and 120 days) and old (over 120 days). Discrimination of the tiller age categories according to nitrogen fertilization regime followed the same pattern of clustering. The fact demonstrates consistency and indicates the three age categories as reference for detailed studies regarding the ecophysiology of marandu palisade grass.

Dynamics of structural traits in two competing C3grass species: influence of neighbours and nitrogen

AbstractThis work analysed the regulatory structural mechanisms involved in the competitive interactions between the annual grassBromus willdenowiiKunth. (BW = prairie grass) and the perennial C3grassDactylis glomerataL. (DG= orchardgrass) during pasture establishment. Four combinations of species (pureBW, pureDG,DGflanked byBWandBWflanked byDGplants), with and without winter nitrogen fertilization, were factorially arranged in a randomized complete block design. Data were recorded at two organization levels: tillers (three tiller age cohorts) and target plants. Annual neighbours caused a decrease in the number of living leaves in tillers of intermediate age of both species. This structural regulatory mechanism led to a decrease in tiller number per plant and, therefore, restricted the development of horizontal space occupation. Annual neighbours did not cause an increase in tiller size, measured as lamina length or pseudostem height, but decreased root biomass. As a consequence, annual neighbours did not lead the hierarchy in light capture, but limited species radical colonization and competitive ability for soil resources. Winter nitrogen fertilization only affected tiller size in older tillers. These findings emphasize the importance of the cultural decisions, as sowing densities and nitrogen fertilization, to optimize pasture floristic composition.

Suplementação como estratégia de produção de carne de qualidade em pastagens tropicais

O manejo do pastejo e a suplementação estratégica permitem maximizar a produção de carne bovina em pastagens de forma sustentável. A intensidade de pastejo influencia diretamente o crescimento individual, taxas de aparecimento e mortalidade de perfilhos, a determinar o acúmulo de forragem e a estrutura do dossel. Dessa forma, nas águas, é função do manejo do pastejo adequar a frequência e intensidade de desfolhação para que o animal possa colher forragem com idade fisiológica e valor nutritivo adequados. A idade e tamanho dos perfilhos determinam a proporção de tecidos de suporte lignificados que reduzem a digestibilidade da forragem. No período seco, o manejo do pasto e a estratégia de diferimento, ao final do período das águas, são determinantes na obtenção de forragem de melhor valor nutritivo. Assim, o manejo das pastagens visa, primeiramente, à produção de forragens com altos teores de fibra potencialmente digestíveis. A partir de então, a caracterização da quantidade e qualidade da forragem são primordiais à adequação dos nutrientes fornecidos, via suplementos, para otimizar a utilização dos recursos forrageiros basais. A suplementação da dieta dos animais em pastejo, com concentrado, permite aumentar o desempenho dos animais, o que reduz a idade de abate e melhora a qualidade da carcaça e da carne obtida, além dos benefícios na preparação dos animais terminados em confinamento. Portanto, o manejo do pastejo e a suplementação da dieta dos animais permitem aumento de produtividade e maior qualidade dos produtos.

Morphogenetic and structural characteristics of guinea grass tillers at different ages under intermittent stocking

The objective of this research was to assess morphogenetic and structural characteristics of tillers of guinea grass cv. Tanzania at different ages. The pastures of guinea grass were managed in six pasture conditions related to the combination of three frequencies (90, 95, and 99% light interception) and two post-grazing heights (25 and 50 cm). In these six pastures conditions, three tiller ages were evaluated (young, mature, and old). The design was of completely randomized block with three replications. Young tillers exhibited higher leaf appearance rate and leaf elongation rate and, consequently, higher final leaf length and number of live leaves than mature and old tillers, regardless of the pasture condition. On pastures managed with 90 or 95% light interception associated with a post-grazing height of 25 cm, old tillers presented longer leaf lifespan than young and mature ones. There is a progressive reduction in the vigor of growth of pastures of guinea grass cv. Tanzania with advancing tiller age.

Leaf and tiller dynamics in two competingC3grass species: influence of neighbours and nitrogen on morphogenetic traits

AbstractThe objective of this work was to analyse the competitive interactions betweenBromus willdenowiiKunth. (BW = prairie grass) and a perennialC3grassDactylis glomerataL. (DG = cocksfoot) through morphogenetic traits, during pasture establishment. Four combinations of species (pureBW, pureDG,DGflanked byBWandBWflanked byDGplants), with and without winter nitrogen fertilization, were factorially arranged in a complete random block design. Data were recorded on three tiller age cohorts of the central target plant: the main stem and those that appeared 20 and 30 days after fertilization (daf). Leaf elongation rate (LER) of the older tillers was the only variable affected by nitrogen addition. Annual neighbours, which showed higherLERthan perennial ones, caused a decrease in leaf lifespan in the younger tillers and a delay in the leaf appearance rate on the main stem and on 20‐daf tillers, and the tiller appearance rate. Annual neighbours controlled leaf and tiller dynamics and therefore restricted the vertical and horizontal space occupation of the target plant. These results reinforce the advantage of using a low seeding rate for the annual species to avoid negative effects on perennial grass establishment and persistence.

Structural characteristics of tiller age categories of continuously stocked marandu palisade grass swards fertilized with nitrogen

The objective of this experiment was to evaluate the structural characteristics of young, mature and old tillers on continuously stocked marandu palisade grass maintained at 30 cm and fertilized with nitrogen. Treatments corresponded to three nitrogen application rates (150, 300 and 450 kg/ha of N) plus control (no fertilization) and were assigned to experimental units (1,200-m2 paddocks) according to a completely randomized block design, with four replications. Measurements were performed during fall/winter 2007 and summer 2008. During summer, young tillers showed longer leaves and shorter stems relative to old tillers. During fall/winter, young and old tillers showed shorter leaves, while mature and old tillers showed longer stems. Tiller age interfered with the number of leaves per tiller mainly through variations in the number of expanding and senescing leaves during both fall/winter and summer. The structural characteristics of individual tillers are affected by plant age, with nitrogen favouring the production of leaf tissue in young tillers during summer.

Morphogenesis on age categories of tillers in marandu palisadegrass

Knowledge regarding morphogenetic characteristics has contributed to the understanding of plant responses to variations in climatic conditions and management practices. However, the original framework has been developed for temperate grass species, and indicates no ontogenetic effect on the expression of morphogenetic traits. Similar information for tropical grass species is scarce, but not less important. This experiment aimed at evaluating the influence of tiller age on the morphogenetic characteristics of continuously stocked marandu palisadegrass swards maintained at 30 cm and fertilized with nitrogen (N). Treatments corresponded to three nitrogen application rates (150, 300 and 450 kg ha-¹ of N) plus the control (no fertilization) and were assigned to experimental units (1,200 m² paddocks) according to a complete randomized block design, with four replications. The following response variables were measured during autumn/winter (Jun. to Jul. 2007) and summer (Feb. to Mar. 2008): leaf appearance rate (LAR), leaf elongation rate (LER) and the age profile of the tiller population. In general, LAR and LER were higher on young (< 2 months old) relative to mature (2 to 4 months old) and old (> 4 months old) tillers during both autumn/winter and summer. During autumn/winter swards were mainly comprised of old tillers (> 4 months old), the opposite happening during summer, when they were mainly comprised of young tillers. Overall, there was no N effect within tiller age categories. Tiller age was an important factor interfering with the morphogenetic responses of marandu palisadegrass, indicating that there is an ontogenetic effect on plant morphogenesis that should be considered further in future studies of this nature

Morphogenetic and structural characteristics of tillers of guinea grass of different age and grazing severities

The objective of this research was to evaluate the effects of tiller age on morphogenic and structural characteristics of guinea grass cv. Mombaca subjected to intermittent stocking and three stubble heights: 30 cm, 50 cm and 50-30 cm. Stubble heights were assigned to experimental units in a completely randomized block design with three replicates. Grazing was performed when canopy intercepted 95% of light incidence. Leaf appearance rate, leaf elongation rate and number of live leaves per tiller were higher in the summer when compared with the winter. Contrarily, stem elongation rate, phyllochron and leaf lifespan were lower in the summer when compared with the winter. During the summer, young tillers had higher leaf appearance and elongation rates when compared with the older ones. Young and mature tillers had the highest values of live leaves per tiller in the summer. There was no difference between summer and winter for the final length of leaf blade between tillers of the same age, except in mature tillers, which had higher final leaf length during the summer. Senescence rate of leaves was higher in young tillers, followed by mature and old tillers. Age of tiller affects morphogenic and structural characteristics of pasture, showing that young tillers have better growth compared with mature and old tillers

Age structure and dynamics ofZoysia japonica module population

The age structure of the natural Zoysia japonica clonal population at Qipan Mountain in Huishan Scenic Spot of Shenyang, Liaoning Province, China was studied using the morphological method in 2003 and 2004. The dynamics of leaves were recorded and the dynamics of tiller and rhizome in the growing season were observed. The results indicated that the rhizomes formed in different years changed in color and rigidity. Its internodes produced in autumn became shorter. The number of naked nodes changed with the tiller age. Rhizome and tiller characters were used as a foundation for judging the ages of modules in this study. The longevity of tiller and rhizome was 3 years at most. At the beginning of the growing season, 2-year-old tillers and rhizomes predominated. Then 1-year-old tillers and rhizomes increased rapidly and became dominant in July. The proportion of buds to tillers on quantity was stable at about 30% in the mid-phase of the growing season and rose to about 50% in autumn. The seasonal dynamics of tiller, rhizome and bud was very important to guarantee the sustained existence of the Zoysia japonica population. The turnover of modules was the mechanism of sustaining the rejuvenation of the Zoysia japonica clonal population.

Responses of Bahiagrass to Nitrogen and Defoliation

Pensacola bahiagrass (Paspalum notatum Flgge) swards pretreated with fertilizer nitrogen rates of 0 and 66-99 kg N ha-1 year-1 were exposed to repeated, severe defoliation (i.e., removal of all laminae) of every day (D1), every 2 days (D2), and every 4 days (D4). Responses of the grass were monitored in terms of tiller survival, lamina production and changes in the mass of the stubble-stolon-root system, in an effort to investigate the effects of nitrogen rate and defoliation frequency on defoliation tolerance, to examine differences in survival ability of tillers among tiller age cohorts, and to evaluate contribution of the stubble-stolon-root system to defoliation tolerance. With the progress of defoliation treatments over 12 weeks, the swards degraded with decreasing tiller density, lamina production, and mass of stubble and stolons. Defoliation tolerance in terms of tiller survival was influenced only by defoliation frequency (D1 approximately D2 < D4), with no significant effect of nitrogen fertilizer rate. There were no differences in survival ability of tillers among age cohorts formed before the defoliation treatments, suggesting that all tillers in bahiagrass were able to share energy and nutrients in connecting stolons under severe defoliation. It was confirmed that stolons play a key role in defoliation tolerance in bahiagrass as the main storage organ supporting aboveground parts, whereas the contribution of roots seems nil. DOI:10.2458/azu_jrm_v56i6_hirata

Analysis on age structure ofZoysia japonica (Poaceae) population

The age-structure of natural population ofZoysia japonica in Xiuyan County of Liaoning Province was studied by generational method. The results showed that the highest tiller age class was three, but 1st age class tillers held dominant position with proportions over 95% in each month during the growing seasons. The 2nd age class and 3rd age class tillers were minority in the population. SoZ japonica population was an expanding population. The zero age, class buds on the rhizomes were dominant in buds age structures. The proportion of buds to tillers on quantity in each month was about 30% to 40% and reached the highest at the end of September. The increasing of buds proportion before domancy guaranteed the quantity of tillers in the next spring. The biomass of 1st age class tillers changed with time. The biomass kept increasing from April to July and reached the highest at the end of July and then decreased.

Responses of bahiagrass to nitrogen and defoliation

Pensacola bahiagrass (Paspalum notatum Flgge) swards pretreated with fertilizer nitrogen rates of 0 and 66-99 kg N ha-1 year-1 were exposed to repeated, severe defoliation (i.e., removal of all laminae) of every day (D1), every 2 days (D2), and every 4 days (D4). Responses of the grass were monitored in terms of tiller survival, lamina production and changes in the mass of the stubble-stolon-root system, in an effort to investigate the effects of nitrogen rate and defoliation frequency on defoliation tolerance, to examine differences in survival ability of tillers among tiller age cohorts, and to evaluate contribution of the stubble-stolon-root system to defoliation tolerance. With the progress of defoliation treatments over 12 weeks, the swards degraded with decreasing tiller density, lamina production, and mass of stubble and stolons. Defoliation tolerance in terms of tiller survival was influenced only by defoliation frequency (D1 = D2 &lt; D4), with no significant effect of nitrogen fertilizer rate. There were no differences in survival ability of tillers among age cohorts formed before the defoliation treatments, suggesting that all tillers in bahiagrass were able to share energy and nutrients in connecting stolons under severe defoliation. It was confirmed that stolons play a key role in defoliation tolerance in bahiagrass as the main storage organ supporting aboveground parts, whereas the contribution of roots seems nil.

Leaf Blade Dimensions of Rice (Oryza sativa L. and Oryza glaberrima Steud.). Relationships between Tillers and the Main Stem

The effects of genotype and environment on the leaf area index of rice are well documented, but the rules governing leaf area distribution among main stem and tillers are less well understood. This study investigated the ontogenetic patterns of leaf blade area and dimensions on the main stem and tillers of three rice cultivars, IAC47, Javaé (Oryza sativa L.) and CG14 (O. glaberrima Steud.) grown in pots without competition among plants. No differences in phyllochron were observed among culms, but leaves on tillers appeared 0.5 to 0.8 phyllochrons earlier than the genealogically corresponding leaves on the main stem (system of Katayama). Cohorts were thus not fully synchronized. All culms produced their largest leaves soon after panicle initiation (PI), despite differences in tiller age. Leaves that appeared subsequently were smaller owing to reduced length but not width, which remained constant. Three different hypothetical rules governing the behaviour of culms were tested: (1) tillers behave as clones of the main stem; (2) cohorts behave uniformly, and (3) behaviour is determined by leaf position (sum of genealogical leaf and tiller indices). The results were best explained by hypotheses (2) and (3), with leaf blade width and length showing markedly different patterns.

Spikelet numbers, sink size and potential yield in rice

A new plant type (NPT) has been developed at the International Rice Research Institute (IRRI) using tropical japonica germplasm in an attempt to increase yields. In direct contrast to high yielding indicas, which have large numbers of tillers and relatively small panicles, the NPT has large panicles and low tiller numbers. To determine whether the NPT had a higher potential for spikelet production, and possibly yield, than an elite indica, the total number of juvenile spikelets (glumous flower primordia) was determined for plants grown in the field as a crop or widely spaced. The maximum number of juvenile spikelets produced by the temporal pattern of tillers in a hill was recorded at the time of late differentiation of each tiller’s panicle. The number was greater for spaced plants than crop plants and it decreased linearly with tiller age. For crop plants approximately one juvenile spikelet was produced per square centimeter of leaf area. In 1997, a large number of the juvenile spikelets were lost before harvest, that number increased significantly in the wetter year of 1999. To quantify potential yield and its reduction by the loss of spikelets between the juvenile and mature stages, the number of spikelets at harvest and the filled fraction (grains) was determined for each tiller and a simple empirical model of yield was constructed. The model predicted that if all of the juvenile spikelets were to be transformed into grains a potential yield more than double the actual yield would be produced in crops of high yielding indicas or the NPT, suggesting that source strength rather than sink size limited yield in this study. Differences in spikelet number at harvest could be offset by differences in individual grain weight and percentage filling of spikelets. Even in rice crops grown with large applications of fertilizer, at current atmospheric concentrations of CO 2, yields are limited by the supply of resources necessary for the development and synthesis of the grain rather than sink capacity. The potential sink size of the crop is almost double that actually realized, even though the productive tillers of crop plants do not reach their full potential for spikelet production compared with spaced plants.