Final Leaf Research Articles

Prediction of leaf rust severity and yield loss in wheat based on environmental factors

Six commercial bread wheat (Triticum aestivum L.) cultivars were evaluated against leaf rust (Puccinia triticina) at two different locations in Egypt during three successive growing seasons, i.e., 2016/2017, 2017/2018 and 2018/2019. Correlation between eight weekly environmental factors: solar radiation, total precipitation, average wind speed, maximum wind speed, minimum air temperature, maximum air temperature, minimum relative humidity and maximum relative humidity to leaf rust severity (%) and yield losses (%), was determined using stepwise regression analysis. Predictive models for each tested cultivar for final leaf rust severity (%) and yield losses using environmental data were determined. Generally, maximum relative humidity was positively correlated with final leaf rust severity (%). Significant correlation between yield losses (%) and the two factors, i.e., final leaf rust severity (%) and maximum relative humidity, was also found in this study. Meanwhile, negative correlation was found between final leaf rust severity (%) and yield losses (%) and the two environmental factors, i.e., solar radiation and minimum relative humidity. The effectiveness of tested models was estimated by using R2 values for all models, and these models were validated to predict leaf rust severity (%) and yield loss.

Morphogenesis of Cynodon cultivars fertilized with nitrogen

To evaluate the biomass flow of two cultivars of Cynodon (Tifton 85 grass and vaquero grass) fertilized with increasing levels of nitrogen (N) (control – without nitrogen; 200; 400 and 600 mg dm-3) under greenhouse conditions, this study was carried out, in a completely randomized design, with factorial arrangement. Forages were examined during three regrowth cycles, with results presented as mean values of the cycles. In the analysis of the effect of nitrogen fertilization, the Tifton 85 grass showed an increasing response to nitrogen levels for the leaf elongation rate (LER). The vaquero grass had a quadractic response for the LER with increasing levels of N. As for the stem elongation rate, there was an increasing linear response in both grasses according to increasing levels of N. The leaf senescence rate (LSR) of the Tifton 85 grass has been enhanced by nitrogen fertilization. The vaquero grass revealed a quadractic response for this variable LSR with nitrogen fertilization, with a minimum value of 0.96 cm tiller-1 day-1 with nitrogen level of 42.5 mg dm-3. The phyllochron and the total number of leaves of both grasses have been influenced by nitrogen fertilization, with downward and upward linear responses, respectively, with increasing levels of nitrogen. For the final mean leaf length (MLL) of both forages, we verified an increasing response with increasing levels of nitrogen. Tifton 85 grass and vaquero grass presented similar LER in the absence of nitrogen, but higher values were observed for the fertilized Tifton 85 grass. The fertilization using nitrogen leads to positive responses of the biomass flow of Tifton 85 grass and vaquero grass under the conditions of the present study.

Elucidating the regulatory roles of microRNAs in maize (Zea mays L.) leaf growth response to chilling stress.

MAIN CONCLUSION: miRNAs control leaf size of maize crop during chilling stress tolerance by regulating developmentally important transcriptional factors and sustaining redox homeostasis of cells. Chilling temperature (0-15°C) is a major constraint for the cultivation of maize (Zea mays) which inhibits the early growth of maize leading to reduction in leaf size. Growth and development take place in meristem, elongation, and mature zones that are linearly located along the leaf base to tip. To prevent shortening of leaf caused by chilling, this study aims to elucidate the regulatory roles of microRNA (miRNA) genes in the controlling process switching between growth and developmental stages. In this respect, hybrid maize ADA313 seedlings were treated to the chilling temperature which caused 26% and 29% reduction in the final leaf length and a decline in cell production of the fourth leaf. The flow cytometry data integrated with the expression analysis of cell cycle genes indicated that the reason for the decline was a failure proceeding from G2/M rather than G1/S. Through an miRNome analysis of 321 known maize miRNAs, 24, 6, and 20 miRNAs were assigned to putative meristem, elongation, and mature zones, respectively according to their chilling response. To gain deeper insight into decreased cell production, in silico, target prediction analysis was performed for meristem specific miRNAs. Among the miRNAs, miR160, miR319, miR395, miR396, miR408, miR528, and miR1432 were selected for confirming the potential of negative regulation with their predicted targets by qRT-PCR. These findings indicated evidence for improvement of growth and yield under chilling stress of the maize.

High-Throughput Phenotyping of Dynamic Canopy Traits Associated with Stay-Green in Grain Sorghum

Drought is a recurring phenomenon that puts crop yields at risk and threatens the livelihoods of many people around the globe. Stay-green is a drought adaption phenotype found in sorghum and other cereals. Plants expressing this phenotype show less drought-induced senescence and maintain functional green leaves for longer when water limitation occurs during grain fill, conferring benefits in both yield per se and harvestability. The physiological causes of the phenotype are postulated to be water saving through mechanisms such as reduced canopy size or access to extra water through mechanisms such as deeper roots. In sorghum breeding programs, stay-green has traditionally been assessed by comparing visual scores of leaf senescence either by identifying final leaf senescence or by estimating rate of leaf senescence. In this study, we compared measurements of canopy dynamics obtained from remote sensing on two sorghum breeding trials to stay-green values (breeding values) obtained from visual leaf senescence ratings in multienvironment breeding trials to determine which components of canopy development were most closely linked to the stay-green phenotype. Surprisingly, canopy size as estimated using preflowering canopy parameters was weakly correlated with stay-green values for leaf senescence while postflowering canopy parameters showed a much stronger association with leaf senescence. Our study suggests that factors other than canopy size have an important role in the expression of a stay-green phenotype in grain sorghum and further that the use of UAVs with multispectral sensors provides an excellent way of measuring canopy traits of hundreds of plots grown in large field trials.

Morphogenetic, physiological, and productive of forage peanut responses to shading

Abstract: The objective of this work was to evaluate the morphogenetic, structural, physiological, and productive traits of forage peanut (Arachis pintoi) subjected to different levels of artificial shading in the field. The 'Amarillo MG-100' forage peanut was planted in April 2015, and the evaluations were carried out from May 2017 to April 2018. The treatments were: 0, 30, 45, and 75% of artificial shading. There was no significant effect of shading on the morphogenetic traits of forage peanut. Shading increased final leaf length and canopy height and decreased the leaf area index and number of stolons. Photosynthesis, transpiration rate, stomatal conductance, chlorophyll b, and leaf temperature increased quadratically as a function of shading. There was a linear positive effect on the growing cycle length and a quadratic effect on the production of dry matter mass, with the maximum at 30% shade. Forage peanut harvested at 95% light interception (11-cm height) shows adaptation to shading up to 45%, with increased leaf size, canopy height, photosynthetic rate, stomatal conductance, transpiration rate, and chlorophyll b. In addition, plants at 30% shading show a higher yield than those growing under full sun.

Morphological characteristics of the leaf blade and the variety of dill morphotypes

Relevance. Common dill (Anethum graveolens L.) is an annual plant of the celery family (Apiaceae). It has alternated variously repeatedly pinnatisected simple leaves character- ized by a number of morphological features including color, presence of waxy bloom, size and density of the final segments, size and shape of the leaf blade. Leaves on different nodes of the same plant can be variable. Environment conditions of plant cultivation also affect some morphological characteristics of the leaf (inc. size of the leaf and its final segments). But, under the same conditions each variety of dill possess a certain set of morphological features that determine the variety identity. In recent years, dill varieties with new morphological features of the leaf blade have emerged, and it is important to evaluate and classify the existing morphologic diversity of the plant.Methods. Several methods are currently used to describe morphological features of dill leaves structure: developed by VIR (All-Russian Institute of Plant Genetic Resources), UPOV, the plant approbation manual, description of leafy vegetables in “Cultivated Flora” compendium. There are similarities and differences between the methods in description of characteristics and their grouping according to the extent of the characters. In this study the current methods for description of the morphological features of dill leafs were compared. The described morphological evaluation of the dill varieties was carried out at 2016–2018 in open field in the Research Institute of Vegetable Crop Breeding (LLC), in the “Gavrish-Slobodskoy” Plant Breeding Center (Pavlovskaya Sloboda, Istrinsky district, Moscow region).Results. As a result, it was revealed that the UPOV method more comprehensively describes the morphological characteristics of dill leaf blade. This method can be extended in the following direction: Establish groups according to the length of leaf, using leaf blade length without petiole: small leaf blade – 5-12 cm, medium – 12-25 cm, large – 25- 40 cm; Establish new character: a density of leaf segments (in parts of the 2nd order) and identify the following groups: thin (up to 5 segments), medium density (6-15 segments), and dense (16 or more segments) arrangement of the segments; Establish new character: segment length, grouping it according their actual length: up to 1 cm – short, from 1 to 1.5 cm – medium, and more than 1.5 cm – long leaf segments. According to the evaluated leaf morphological characteristics: size, color, presence of waxy bloom, “leaf patterns”, the dill plants are very diverse. Two dill morphotypes can be distinguished by presence or absence of waxy bloom, 3 morphotypes by the leaf shape (diamond-shaped, elongated, triangular), and 27 morphotypes – by location and size of the final leaf segments.

Molecular networks regulating cell division during Arabidopsis leaf growth.

Leaves are the primary organs for photosynthesis, and as such have a pivotal role for plant growth and development. Leaf development is a multifactorial and dynamic process involving many genes that regulate size, shape, and differentiation. The processes that mainly drive leaf development are cell proliferation and cell expansion, and numerous genes have been identified that, when ectopically expressed or down-regulated, increase cell number and/or cell size during leaf growth. Many of the genes regulating cell proliferation are functionally interconnected and can be grouped into regulatory modules. Here, we review our current understanding of six important gene regulatory modules affecting cell proliferation during Arabidopsis leaf growth: ubiquitin receptor DA1-ENHANCER OF DA1 (EOD1), GROWTH REGULATING FACTOR (GRF)-GRF-INTERACTING FACTOR (GIF), SWITCH/SUCROSE NON-FERMENTING (SWI/SNF), gibberellin (GA)-DELLA, KLU, and PEAPOD (PPD). Furthermore, we discuss how post-mitotic cell expansion and these six modules regulating cell proliferation make up the final leaf size.

Effect of shading and canopy height on pasture of Andropogon gayanus in silvopastoral system

In silvopastoral systems (SPS) canopy height and the existence of shaded and non-shaded environments can provide changes in plant development. The objective in this study was to evaluate the effect of shading and canopy height on morphogenic, structural and biomass production characteristics of Andropogon gayanus in an SPS. It was adopted a completely randomized design in a 2 × 3 factorial scheme, with four replications, being two luminosity intensities (shaded and non-shaded within a SPS) and three canopy heights (45, 55 and 65 cm). The studied area was used for 21 years in SPS and grazed by goats. The luminosity in the A. gayanus canopy in shaded areas was reduced by 40% in comparison to the non-shaded area in the SPS. There was effect of the interaction between heights and environments on the dry forage biomass, with higher values in non-shaded areas and in higher canopy heights. The leaf/stem ratio, as well as the leaf percentage did not differ between the environment luminosities and canopy heights, whereas the number of tillers was lower in the shaded areas, also where final leaf length was higher. The shade from Tabebuia sp. in SPS does not compromise the growth of A. gayanus. In SPS A. gayanus should be managed at a canopy height of 65 cm in order to present higher yield and maintain its sustainability.

Responses of Vallisneria natans (Lour.) Hara to the combined effects of Mn and pH.

Aquatic plants play a vital role in maintaining the health and stability of ecosystems and in ecological restoration of contaminated water bodies. Herein, a 21-day-long laboratory-scale experiment was designed to explore the growth and physiological responses of Vallisneria natans (Lour.) Hara (V. natans) to the combined effects of manganese (Mn, 5, 20, and 80 mg L-1) and pH (pH 4.0, 5.5, and 7.0). Our results showed the combined toxicity intensity was closely related to Mn concentration and the toxicity exhibited by Mn gradually strengthened with the decrease of pH level. High concentration of Mn stress significantly reduced plants leaf area, final leaf number, photosynthetic pigment content, RGR (relative growth rate) and biomass accumulation, but significantly increased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2). At the same time, V. natans plants can resist the adverse stress by activating the antioxidant defense system, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and polyphenol oxidase (PPO) activities. Besides, V. natans tended to adjust the biomass allocation strategy and transferred more energy to the subsurface and the ramets and stolons parts under the combined stress. This experiment also showed that the increasing pH within a certain range could largely improve the removal rate of Mn (at highest by 84.28%). This may indicate the V. natans plant species can act as a promising tool for the Mn phytoremediation in aquatic environments which needs to be further explored by longer cycle field studies.

E2FB Interacts with RETINOBLASTOMA RELATED and Regulates Cell Proliferation during Leaf Development.

Cell cycle entry and quiescence are regulated by the E2F transcription factors in association with RETINOBLASTOMA-RELATED (RBR). E2FB is considered to be a transcriptional activator of cell cycle genes, but its function during development remains poorly understood. Here, by studying E2FB-RBR interaction, E2F target gene expression, and epidermal cell number and shape in e2fb mutant and overexpression lines during leaf development in Arabidopsis (Arabidopsis thaliana), we show that E2FB in association with RBR plays a role in the inhibition of cell proliferation to establish quiescence. In young leaves, both RBR and E2FB are abundant and form a repressor complex that is reinforced by an autoregulatory loop. Increased E2FB levels, either by expression driven by its own promoter or ectopically together with DIMERIZATION PARTNER A, further elevate the amount of this repressor complex, leading to reduced leaf cell number. Cell overproliferation in e2fb mutants and in plants overexpressing a truncated form of E2FB lacking the RBR binding domain strongly suggested that RBR repression specifically acts through E2FB. The increased number of small cells below the guard cells and of fully developed stomata indicated that meristemoids preferentially hyperproliferate. As leaf development progresses and cells differentiate, the amount of RBR and E2FB gradually declined. At this stage, elevation of E2FB level can overcome RBR repression, leading to reactivation of cell division in pavement cells. In summary, E2FB in association with RBR is central to regulating cell proliferation during organ development to determine final leaf cell number.

Assessment of Possible Use of Potentilla fruticosa L. (Rosaceae, Magnoliopsida) for Bioindication of the Natural Environment Status in the Area of the Eastern Ural Radioactive Trace

Журнал принимает на русском и английском языках статьи, представляющие результаты научных исследований в различных областях теоретической и прикладной экологии. Приоритет отдается научным статьям, основанным на явно сформулированных гипотезах.

Redox homeostasis in the growth zone of the rice leaf plays a key role in cold tolerance.

We analysed the cellular and molecular changes in the leaf growth zone of tolerant and sensitive rice varieties in response to suboptimal temperatures. Cold reduced the final leaf length by 35% and 51% in tolerant and sensitive varieties, respectively. Tolerant lines exhibited a smaller reduction of the leaf elongation rate and greater compensation by an increased duration of leaf growth. Kinematic analysis showed that cold reduced cell production in the meristem and the expansion rate in the elongation zone, but the latter was compensated for by a doubling of the duration of cell expansion. We performed iTRAQ proteome analysis on proliferating and expanding parts of the leaf growth zone. We identified 559 and 542 proteins, of which 163 and 210 were differentially expressed between zones, and 96 and 68 between treatments, in the tolerant and sensitive lines, respectively. The categories protein biosynthesis and redox homeostasis were significantly overrepresented in the up-regulated proteins. We therefore measured redox metabolites and enzyme activities in the leaf growth zone, demonstrating that tolerance of rice lines to suboptimal temperatures correlates with the ability to up-regulate enzymatic antioxidants in the meristem and non-enzymatic antioxidants in the elongation zone.

Morphogenic and structural characteristics and chemical composition of grass aruana, submitted to nitrogen fertilization

This study aimed at evaluating the morphogenic and structural characteristics of Panicum maximum Jacq. cv. Aruana, as well as its chemical composition after submitting it to different nitrogen levels. The experiment was performed by adopting a randomized block design which included four treatments (0, 75, 150 and 225 kg ha-1 of N) and three replications, in 100 m2 plots. Twice a week, for the 63 days of regrowth, the morphogenic characteristics were determined and estimated, after which the chemical composition was assessed. The aruana grass revealed a quadratic and positive response to the nitrogen fertilization, and showed a remarkable rise in the elongation rates, leaf appearance and senescence, besides the number of live leaves per tiller and final leaf length. However, the nitrogen fertilization reduced the phyllochron and leaf life in the aruana grass, implying the direct effect of nitrogen on the flow of tissues. A quadratic and positive effect of the nitrogen fertilization was observed for the dry mass production, from 5,840.80 kg ha-1 for plants lacking the nitrogen fertilization to 8,862.55 kg ha-1 for those fertilized with 225 kg ha-1 of N. Thus, while the nitrogen fertilization positively affected both tillering and morphogenesis, the N doses used in this study were insufficient to induce any change in the chemical composition of the aruana grass.

Multiple steps of leaf thickening during sun-leaf formation in Arabidopsis.

SummaryPlant morphological and physiological traits exhibit plasticity in response to light intensity. Leaf thickness is enhanced under high light (HL) conditions compared with low light (LL) conditions through increases in both cell number and size in the dorsoventral direction; however, the regulation of such phenotypic plasticity in leaf thickness (namely, sun‐ or shade‐leaf formation) during the developmental process remains largely unclear. By modifying observation techniques for tiny leaf primordia in Arabidopsis thaliana, we analysed sun‐ and shade‐leaf development in a time‐course manner and found that the process of leaf thickening can be divided into early and late phases. In the early phase, anisotropic cell elongation and periclinal cell division on the adaxial side of mesophyll tissue occurred under the HL conditions used, which resulted in the dorsoventral growth of sun leaves. Anisotropic cell elongation in the palisade tissue is triggered by blue‐light irradiation. We discovered that anisotropic cell elongation processes before or after periclinal cell division were differentially regulated independent of or dependent upon signalling through blue‐light receptors. In contrast, during the late phase, isotropic cell expansion associated with the endocycle, which determined the final leaf thickness, occurred irrespective of the light conditions. Sucrose production was high under HL conditions, and we found that sucrose promoted isotropic cell expansion and the endocycle even under LL conditions. Our analyses based on this method of time‐course observation addressed the developmental framework of sun‐ and shade‐leaf formation.

Changes in leaf appearance and developmental phases associated with breeding progress in six-rowed barley in the Pannonian Plain

Abstract The aim of this study was to analyze traits of leaf appearance and phenological development related to grain yield gain in winter barley cultivars released over the past 50 years. Field trials with 15 six-rowed winter barley cultivars were conducted during two growing seasons. The main leaf appearance and developmental traits were studied. The duration of the emergence-anthesis and emergence-physiological maturity phases decreased by 2.35 and 2.16 GDD yr-1, respectively. The duration of the stem elongation-anthesis phase was 10% longer in modern cultivars. The results showed no clear trend of improvement in final leaf number and phyllochron. The duration of the stem elongation-anthesis phase was positively related with grain number and yield. Constant improvements in grain number and grain weight by fine manipulation of the crop developmental phases could represent an essential strategy for further increases in barley grain yield potential.

Molecular markers and phenotypic characterization of adult plant resistance genes Lr 34, Lr 46, Lr 67 and Lr 68 and their association with partial resistance to leaf rust in wheat

Thirty-nine wheat genotypes were studied to estimate their partial resistance levels to leaf rust at Behira governortae during three growing seasons, i.e. 2016/2017, 2017/2018 and 2018/2019. In these genotypes, partial resistance was characterized using final leaf rust severity (FRS %) and area under disease progress curve (AUDPC). Of the tested genotypes, only three wheat varieties; Giza 171, Misr 3 and Sohag 5 showed complete resistance. Further, 28 of the 39 genotypes had partial resistance as they revealed low and/or moderate values of FRS (%) and AUDPC (not exceeding 30% and 300, respectively). The other eight varieties were fast rusting, as they displayed the maximum values of FRS (%) and AUDPC. The four monogenic lines; Lr 34, Lr 46, Lr 67 and Lr 68 were identified in the wheat varieties using linked molecular markers; csLV34, Xgwm259, CFD71 and csGSR. Phenotypic results of the wheat varieties were confirmed by molecular marker analysis.

Architectural Response of Wheat Cultivars to Row Spacing Reveals Altered Perception of Plant Density.

Achieving novel improvements in crop management may require changing interrow distance in cultivated fields. Such changes would benefit from a better understanding of plant responses to the spatial heterogeneity in their environment. Our work investigates the architectural plasticity of wheat plants in response to increasing row spacing and evaluates the hypothesis of a foraging behavior in response to neighboring plants. A field experiment was conducted with five commercial winter wheat cultivars possessing unique architectures, grown under narrow (NI, 17.5 cm) or wide interrows (WI, 35 cm) at the same population density (170 seeds/m2). We characterized the development (leaf emergence, tillering), the morphology (dimension of organs, leaf area index), and the geometry (ground cover, leaf angle, organ spreading, and orientation). All cultivars showed a lower number of emerged tillers in WI compared to NI, which was later partly compensated by lower tiller mortality. Besides, the upper leaf blades were larger in WI. Finally the leaf area index at flowering showed little difference between WI and NI treatments. The rate of leaf emergence and the final leaf number were higher in WI compared to NI, except for one cultivar. Around the start of stem elongation, pseudo-stems were more erect in WI, while around the time of flowering, stems were more inclined and leaves were more planophile. Cultivars differed in their degrees of responses, with one appearing to prospect more specifically within the interrow space in WI treatment. Altogether, our results suggest that altering interrow distance leads to changes in the perceived extent of competition by plants, with responses first mimicking the effect of a higher plant density and later the effect of a lower plant density. Only one cultivar showed responses that suggested a perception of the heterogeneity of the environment. These findings improve our understanding of plant responses to spatial heterogeneity and provide novel information to simulate light capture in plant 3D models, depending on cultivar behavior.

Morphogenesis and tiller density of Aruana grass managed at different heights under sheep grazing

This study aimed to assess the morphogenic characteristics and tiller density of Aruana grass managed at different heights under sheep grazing. Aruana grass was managed at four mean heights (12, 15, 20, and 25 cm) distributed in a randomized block design with three replications, totaling 12 paddocks of 250 m² each. Twenty-four crossbred Dorper x Santa Inês lambs, with mean age and weight of 60 ± 15 days and 16.69 ± 2.70 kg, respectively, were randomly distributed in the treatments. Five tillers were demarcated per paddock for measuring morphogenic variables. A representative area in the paddock was used for counting the number of tillers. No differences (P > 0.05) were observed for leaf appearance rate, leaf elongation rate, stem elongation rate, leaf senescence rate, final leaf length, and leaf life span between the assessed heights. Phyllochron was longer at the height of 25 cm when compared to 15 and 20 cm (19.35, 12.11, and 12.75 days, respectively). The number of live leaves was higher at heights of 12, 15, and 20 cm when compared to 25 cm (3.99, 4.35, 4.15, and 2.86, respectively). The number of basal and aerial tillers presented no variation (P > 0.05) between canopy heights. Management heights from 15 to 20 cm allowed a higher number of live leaves and a shorter phyllochron in Aruana grass pastures managed for sheep. Canopy height management did not influence other morphogenic characteristics and tiller density.

Combinations of elemental sulfur with demethylation inhibitor fungicides for management of late leaf spot (Nothopassalora personata) of peanut

Management of demethylation inhibitor (DMI) fungicide resistance in Nothopassalora personata, the cause of late spot of peanut (Arachis hypogaea), is a challenge in peanut production areas of the southeastern United States. Field experiments were conducted in Tifton, GA in 2017 and 2018, and in Plains, GA and Blackville, SC in 2018 to determine the effects of mixtures of micronized elemental sulfur with DMI fungicides, cyproconazole, and a premixture of prothioconazole plus tebuconazole on late leaf spot in fields with DMI-resistant populations of N. personata. Application of sulfur alone provided little reduction in final levels of defoliation compared to the nontreated control. However, mixtures of elemental sulfur with either cyproconazole or the premix of prothioconazole + tebuconazole provided the control that was superior to either of the DMI treatments alone. Greater than additive effects on final leaf spot severity were observed in all trials for mixtures of one or both of the DMI fungicide treatments and sulfur. Greater than additive effects on standardized area under the defoliation progress curve were observed for both DMI fungicide treatments with sulfur in trials at Tifton and Plains, GA. The results suggest that the addition of micronized elemental sulfur to DMI fungicides has potential to improve leaf spot control in fields where the efficacy of DMI fungicides alone is not adequate.

Stochastic population model of Zea mays L.

We propose a minimalist stochastic population model of maize, focused on the description of the maize vegetative stages (seedlings with different number of leaves) involved in the propagation of vector-borne diseases. This model was parameterized from laboratory and field experiments and from observational field studies for multiple hybrids and different weather and soil conditions, taking into account only temperature as input variable. We propose three different submodels to estimate the distribution of the Final Leaf Number NFLN in the plants and to estimate the tassel initiation probability. The first submodel (submodel A), with a fixed NFLN, is adaptable to any particular hybrid, the second and third submodels allow to simulate plants with an empirical NFLN distribution according to bibliographic averages (submodel B) or according to a Poisson Process (submodel C). The three submodels are able to describe the temporal development of populations and events. A good agreement is observed between the development times predicted by the model and the values obtained from laboratory experiments at constant temperature, field experiments carried out in Brazil and Australia and observational studies performed in Argentina. This model may be improved and coupled to leaf growth models and leaf area estimation models to be able to estimate not only the temporal development of populations and events but also the temporal development of the leaf area by plant, which is believed to be related to the carrying capacity of maize specialists insects, vectors of maize diseases.