Spatial Arrangement Of Plants Research Articles

Physiological quality of soybean seeds under different yield environments and plant density

ABSTRACT Yield potential of agricultural fields associated with plant spatial arrangement could determine the physiological quality of soybean (Glycine max L.) seeds. Thus, this study aimed to evaluate the physiological quality of soybean seeds from different yield environments and plant densities. Experiments were carried out in Boa Vista das Missões-RS, Brazil, during the 2014/2015 growing season. Yield environments were delineated by overlapping yield maps from the 2008, 2009/2010 and 2011/2012 growing seasons. The experimental design was a randomized complete block in a 2 x 5 factorial arrangement with two yield environments (low and high) and five plant densities, with four replicates. Two varieties were tested: Brasmax Ativa RR (10, 15, 20, 25 and 30 plants m-1) and Nidera 5909 RR (5, 10, 15, 20 and 25 plants m-1). After harvested, the seeds were analysed as following: first count index, germination, abnormal seedlings, dead seeds, electrical conductivity, accelerate aging test, root length, hypocotyl length and seedling length. The spatial variability of seed vigor in the production field could be reduced by adjusting plant density, but the adjustment should consider the variety. Harvest according to yield environment is a strategy to separate lots of seeds with higher vigor, originated from high-yield environments.

Spatially designed revegetation—why the spatial arrangement of plants should be as important to revegetation as they are to natural systems

The spatial arrangements of plants, both within and between species, play a key role in natural systems and influence many fundamental ecological processes (e.g. survival, competition, facilitation, pollination, and seed dispersal) and ecosystem functions (e.g. habitat value, erosion, water, and nutrient capture). Despite this knowledge, fine‐scale planting arrangements are rarely considered during restoration plantings, yet manipulation of planting designs has the potential to aid the development of resilient and self‐sustaining ecosystems. Here, we outline how the spatial arrangement of plants can influence processes both at the vegetation level and more broadly at the ecosystem level. The review is focused on woodland systems, but also draws on key examples from grassland ecosystems. Following this synthesis, we identify research gaps in the revegetation literature that could usefully be addressed to help develop this understudied field of research. Finally, we outline components of population and community level arrangements (e.g. spacing, aggregation, community composition) that can be considered during restoration plantings—spatially designed revegetation—which are likely to lead to improved ecological outcomes of woodland and grassy woodland revegetation.

Aquatic Plant Diversity in Italy: Distribution, Drivers and Strategic Conservation Actions.

Italy is recognized as one of the prominent hot spot areas for plant diversity at regional and global scale, hosting a rich range of ecosystems and habitat types. This is especially true considering aquatic habitats, which represent a major portion of the total water surfaces in the Mediterranean region. Nevertheless, only a scant attention was paid to clarify the species richness of aquatic plant and its contribution to the total diversity at the country scale, despite such plants are seriously threatened at multiple scales. This paper provided the first comprehensive inventory of aquatic plants at the whole country scale, collecting data on species’ distribution, trends, and explanatory determinants of species richness. We confirmed the key contribution of Italy to the regional and global aquatic plant diversity with a total of 279 species recorded since 2005, equal to the 88.5%, 55.9% and ∼10% of the richness estimated at European/Mediterranean, Palearctic and global scale, respectively. Ten species are considered extinct in the wild [among which Aldrovanda vesiculosa L., Caldesia parnassifolia (Bassi ex L.) Parl., Helosciadium repens (Jacq.) W.J.D. Koch, and Pilularia globulifera L.], four were doubt [among which Luronium natans (L.) Raf., Utricularia intermedia Hayne, and U. ochroleuca R.W. Hartman.], and eight were erroneously reported in the past, among which Isoëtes lacustris L., Myosotis rehsteineri Wartm., and Ranunculus aquatilis L. Only 18 species – mainly helophytes (14) – were present in all the 20 Italian regions, whereas hydrophytes showed most scanty regional frequencies. Temperature, latitude, area and water resources availability are the main drivers of aquatic plant spatial arrangement and diversity. Furthermore, the number of inhabitants per km2 well described the number of “lost species” since 2000. The findings of the present survey call for an urgent elaboration of large-scale strategies to ensure the survival of aquatic plants, stressing on multiple functions played by aquatic plants in supporting national economy and human well-being. In this context, Italy can play a fundamental role guaranteeing temporary refuge for projected or expected species migrations along latitude and longitude gradients. Besides, in hyper-exploited landscapes man-made water bodies can further enhance the achievement of minimum conservation targets.

A spatially explicit analysis of Paysandisia archon attack on the endemic Mediterranean dwarf palm

Autochthonous plant species are heavily threatened by the increasing spread of invasive insects. The spatial distribution of invasive species’ hosts is likely to play a pivotal role in the establishment and further expansion of the invading species; more specifically, distance and density dependent (DDD) processes linked to plant spatial arrangement are crucial in determining susceptibility to attack, but they have usually been overlooked in invasive research. We take a spatially explicit approach to evaluate potential DDD processes in the interaction between Paysandisia archon, a tropical lepidopteran recently introduced in Spain, and the endemic Mediterranean dwarf palm (Chamaerops humilis) in Mallorca (Balearic Islands). Specifically, we used spatial marked point pattern analyses, which allowed testing whether DDD processes affect attack probability and intensity on three dwarf palm populations corresponding to three different invasion phases (i.e., infestation core, early expansion, and expansion front). Our approach also allowed evaluation of whether and how intrinsic palm traits (size, sex) alter the proneness to P. archon attack over a range of spatial scales. The occurrence and nature of DDD effects on C. humilis performance varied largely among localities. At the infestation core, our analyses revealed positive density dependence, i.e., reduced damage at high densities or proximity to conspecific neighbors. By contrast, the early expansion locality showed negative density dependence of C. humilis performance, whereas at the expansion front, there was no evidence of DDD effects. Larger palms were consistently more prone to P. archon attack than small ones up to scales of 50 m. We found no evidence that palm sex altered the probability of attack by P. archon. Our results highlight the importance of spatially explicit analyses for assessing invasive events and point to the need of early interventions and prioritizing management efforts on larger palms in order to guarantee the conservation of autochthonous dwarf palm populations.

Simulation-based modeling of wild blueberry pollination

The high variability of wild (lowbush) blueberry plants in spatial and genetic structure, in combination with bee foraging behavior varying between species, and the complexity of these factors interacting over time and space, are major obstacles to understanding of pollination dynamics subject to environmental change. The bottom-up modeling paradigm provides an ideal approach to bridging the gap between known mechanisms of individual organisms and unknown spatial–temporal dynamics of pollination at the field scale. By linking empirical data to stochastically-based ecological process modeling, we present a spatially-explicit agent-based simulation model that enables exploration of how various factors, including plant spatial arrangements, outcrossing and self-pollination, bee species compositions and weather conditions, in isolation and combination, affect pollination efficiency throughout a blueberry bloom season. The firmly validated open-source model is a useful tool for hypothesis testing and theory development for wild blueberry pollination researches. Sensitivity analysis suggested that fruit set and resulting measures of productivity such as fruit mass and viable seeds per fruit were sensitive to parameterization of blueberry genotype or clone size and the amount of blueberry plant cover in a field. Fruit set due to pollen compatibility was sensitive to ovule number per flower and foraging bee density. Simulation experiments allowed us to compare bee pollination efficiencies at the bee taxon population level (honey bees, bumble bees, and native solitary bees), the effect of foraging distance from bee nest or colony site on fruit set, and test whether the mechanism of gametophytic self-incompatibility (pre- vs. post-zygotic decision making by the plant) in wild blueberry pollination at the field level matters in estimating yield.

Role of tolerance to resource demand - supply mismatch in a model of annual plants

We propose and discuss a simulation model of annual plants competing for a single resource. Plants are characterised by their tolerance to a surplus of this resource and the maximum number of seeds a plant can produce in a year. Interaction among plants is reduced to blocking a part of the resource by the plant’s nearest neighbours. Spatial and temporal conditions are homogeneous. There are no trade-off mechanisms nor immigrants. Plants may suffer from both a lack and too much of the resource. We consider two systems - plants of one type (target plants) and a mixture of two types, where the second type differs from the target ones only by the tolerance to surplus of the resource. We show how the life cycle of a plant depends on its tolerance, on supply of the resource and on how it is affected by the presence of the second type of annuals. We demonstrate that even in such a simple system coexistence of the two species is possible, and we determine the conditions for this. We present also a mean field type approach to the problem, showing that the results from simulations and mean field are quite similar. However the mean field approach cannot answer questions concerning spatial arrangement of plants, like possible formation of niches for different types of plant.

Initial Growth of Eucalyptus with Different Spatial Arrangements in Agrosilvopastoral Systems

Success of integrating livestock farming with forestry systems or SAF′s (Agroforestry Systems) highly depends on correct chose of the tree component and the best spatial arrangement of plants, for which eucalyptus has proven as an excellent option. Therefore, the objective of this study was to evaluate eucalyptus wood yield under different spatial arrangements in agrosilvipastoral system. The arrangements were: single rows 10 × 2 m, double rows (2 × 3) + 15 m and (2 × 3) + 20 m and triple rows (3 × 2 × 3) +20 m. Silvicultural evaluations (DBH, tree height, tree volume and volume per hectare) were done eighteen months after experiment installation. The experimental design was randomized blocks with six repetitions and two trees per plot. Trees were arbitrarily identified in each spatial arrangement, numbered from 1 to 5, totaling 30 plots in each system. The DBH increased as the alleys became closer to each other, being higher in the10 × 2 m and (2 × 3) + 15 m systems; tree height increased in denser spacing—10 × 2 m, (2 × 3) + 15 m and (3 × 2 × 3) + 20 m; the volume of wood per plant and per hectare showed higher values in the 10 × 2 m and (2 × 3) + 15 m systems. The lowest yield was found in the system with the least amount of trees, i.e. (2 × 3) + 20 m (576 trees/ha).

SPATIAL ARRANGEMENTS FOR SUPER-EARLY GENOTYPES FOR COMMON BEAN PRODUCTION

The super-early genotypes (SEG) of common bean (Phaseolus vulgaris), developed by Embrapa Rice and Beans in Brazil, have a shorter life cycle (65-75 days) when compared with the full-season traditional cultivars (95-105 days). Spatial arrangements of plants for SEG should be evaluated to allow fully exploit their genetic potential. The aim of this study was to determine the effects of plant population and row spacing on grain yield and its components in super-early genotypes of common bean. The experimental design was a randomized block in a 2 x 2 x 5 factorial, with six replications, in two growing seasons (2014/2015 and 2015). The treatments consisted of the combination of two super-early genotypes of common bean (CNFC 15874 and CNFC 15875), two row spacings (0.35 and 0.45 m) and five plant densities (6, 10, 14, 18 and 22 seeds m-1). We also included a control treatment, IPR Colibri cultivar (65-75 days of life cycle) with 10 seeds m-1 density. The increase in plant density decreased yield components per plant but increased grain yield of super-early genotypes of common bean per unit area (from 1653 to 4614 kg ha-1 in 2014/2015 and from 2239 to 2537 kg ha-1 in 2015). The spatial arrangement of sowing density of 22 seeds per meter and 0.45 m row spacing allowed the highest grain yield in super-early genotypes of common bean.

Size, chlorophyll retention and protein and oil contents of grains from soybean plants grown in different spatial arrangements

The spatial arrangement of soybean plants, determined by row spacing and seeding rate, affects the intraspecific competition for water, light, and nutrients, as well as plant architecture and grain development, quality, and chemical composition. The aims of this study were to evaluate the effect of row spacing and seeding rate on the grain size produced, and the influence of these three factors on chlorophyll retention and protein and oil content in grain. Two experiments were conducted in the 2013/14 and 2014/15 growing seasons, using a 4 × 3 factorial randomized block design with three replications. Four different row spacings [20 cm (narrow row), 50 cm (conventional), 20/80 cm (twin rows) and crossed lines (50 cm)] and three seeding rates (150, 300, and 450 thousand viable seeds ha-1) were evaluated. The grains were classified by size using oblong sieves and then the effects of spatial arrangements and size of grain on the percentage of green grains and protein and oil contents were evaluated. Higher plant densities were associated with larger grain size, whereas the effects of spacing between the rows on the grain size varied between growing seasons. The arrangement in cross-rows and high plant density produced a higher percentage of green grains under weather conditions favorable to the development of this attribute. The effects of plant spatial arrangements on the contents of protein and oil in grains were variable, and it was not possible to determine whether the spatial arrangement of plants had an effect on the levels of protein and oil in grains. Larger grains had higher protein content, but oil contents were not affected by grain size.

Towards better risk assessment for conservation of flowering stones: Plant density, spatial pattern and habitat preference of Lithops pseudotruncatella in Namibia

To provide a better understanding of spatial pattern and habitat preferences for a cryptic xerophyte, a number of variables were investigated in a 10,000m2 (1ha) study area in a population of L. pseudotruncatella; plant density, spatial arrangement of plants, and habitat specificity. Two censuses, carried out in dry season and in rainy season, revealed a total of 448 and 860 plants, respectively, with a severely clumped distribution. Five out of seven plant density estimation methods, applied in dry season, produced data that vastly over-or under-estimated plant number while Adaptive Cluster Sampling and the Belt Transect method were more accurate, with 557 and 540 plants, respectively. Plant number in 10×10m test plots within the study area was positively associated with a high percentage cover of gravel and pebbles as opposed to sand or stones, and with a gentle rise as opposed to a slope in the topography of the plots. A significant association was found between the occurrence of Lithops and Avonia albissima in the test plots suggesting that the latter, which is more visible, can be used as an indicator of Lithops in the field.

Exploring the interaction of avian frugivory and plant spatial heterogeneity and its effect on seed dispersal kernels using a simulation model

Seed dispersal by avian frugivores is one of the key processes influencing plant spatial patterns, but may fail if there is disruption of plant–frugivore mutualisms, such as decline in abundance of dispersers, fragmentation of habitat, or isolation of individual trees. We used simulation model experiments to examine the interaction between frugivore density and behaviour and the spatial arrangement of fruiting plants and its effect on seed dispersal kernels. We focussed on two New Zealand canopy tree species that produce large fruits and are dispersed predominantly by one avian frugivore (Hemiphaga novaeseelandiae). Although the mean seed dispersal distance decreased when trees became more aggregated, there were more frugivore flights between tree clusters, consequently stretching the tails of the dispersal kernels. Conversely, when trees were less aggregated in the landscape, mean dispersal distances increased because seeds were deposited over larger areas, but the kernels had shorter tails. While there were no statistically meaningful changes in kernel parameters when frugivore density changed, decreases in density did cause a proportional reduction in the total number of dispersed seeds. However, birds were forced to move further when fruit availability and fruit ripening were low. Sensitivity analysis showed that dispersal kernels were primarily influenced by the model parameters relating to disperser behaviour, especially those determining attractiveness based on distance to candidate fruiting trees. Our results suggest that the spatial arrangement of plants plays an important role in seed dispersal processes – although tree aggregation curbed the mean seed dispersal distance, it was accompanied by occasional long distance events, and tree dispersion caused an increase in mean dispersal distance, both potentially increasing the probability of seeds finding suitable habitats for germination and growth. Even though low frugivore densities did not cause dispersal failure, there were negative effects on the quantity of seed dispersal because fewer seeds were dispersed.

Methodology to design agroecological orchards: Learnings from on-station and on-farm experiences

Abstract Agricultural research has to tackle complex questions such as the design of sustainable cropping systems. System experiments are innovative approaches to address this challenge and a framework to iteratively design annual cropping systems has been proposed by Debaeke et al. (2009). However, specificities of some other cropping systems are not considered. Orchards are complex perennial agroecosystems formed of grass and tree layers aiming at the production of fresh fruit that require specific design and management over space and time. To identify orchard specificities and adapt the design framework to such perennial systems, we used two case studies of orchards aiming at decreasing pesticide use in temperate (apple, system experiment) and tropical (citrus, on-farm network) fruit productions. Specificities to take into account in the design framework are: (1) the spatial heterogeneity of the orchard with grass and tree layers, and tree rows and alleys; (2) the succession and interrelations among a young unproductive and then a productive stage; (3) the permanency of the fruit-tree crop constraining the management of soil fertility, (4) ground cover and (5) pest control, especially for pests that complete their lifecycle in the orchard and can build up important populations or inoculum across years. This is especially true in tropical areas where there is no dormant season. (6) Conversely, the permanency of the orchard habitats facilitates the sowing, planting or conservation of plant assemblages (e.g., ground covers, lining hedgerows) to enhance conservation biocontrol and/or compete weeds, provided non-disruptive practices are applied. Because of their longevity, orchards contribute to foster both plant-mediated (e.g., bottom-up) and natural enemy-mediated (e.g., top-down) processes in the foodweb to avoid direct measures against pests. Interactions among the orchard life stages, spatial and functional dimensions and practices need to be explicitly considered to optimize the efficiency of the system as a whole. Using the generic framework proposed by Debaeke et al. (2009) to design annual cropping systems, our framework includes adaptations to account for orchard specificities: (i) Agronomic objectives have to be fixed for each orchard stage; (ii) The cultivar choice and the composition and spatial arrangement of plants within the orchard are key elements to provide the expected services in the long term. This entails to include an additional step of perennial spatial design; (iii) Within-time and −space interactions have to be considered in the decisional system; (iv) Evaluation has to consider all the orchard stages in the global impact or performance, to account for carry-over effects and possible ‘paybacks’ of a given stage or period to the orchard whole lifetime. Last, to handle such complex interactions, design needs knowledge from many stakeholders in the food system (growers, advisors, scientists etc.) and requires more and renewed interactions among those stakeholders in a co-design process.

TAMANHO ÓTIMO DE PARCELA PARA A CULTURA DE GIRASSOL EM TRÊS ARRANJOS ESPACIAIS DE PLANTAS

RESUMO: O objetivo deste estudo foi avaliar o tamanho ótimo de parcela de três híbridos de girassol em três arranjos espaciais de plantas. O teste de uniformidade foi instalado no campo experimental da Universidade Federal do Recôncavo da Bahia, em Cruz das Almas, Brasil, em 2012. As parcelas foram compostas por seis linhas de 36 m, sendo dispostos três arranjos espaciais de plantas, quais sejam: A1 (0,45 mx 0,49 m); A2 (0,70 mx 0,32 m); e A3 (0,90 mx 0,25 m). Foram distribuidos em cada arranjo três híbridos de girassol: Hélio 250; Hélio 253; e Aguara 3. Para a avaliação do tamanho ótimo de parcela , aos 110 dias após a semeadura, foi colhida uma amostra de 180 unidades básicas (plantas) por parcela, no qual foram avaliadas a altura final de planta, o diâmetro final da haste e o diâmetro do capítulo. Foram simulados 31 tamanhos de parcela dos três híbridos e para cada variável analisada em cada planta considerada como uma unidade básica. A estimativa do tamanho de parcela para a cultura de girassol foi calculada pelo método de máxima curvatura modificada. O uso combinado do híbrido H253, instalado no arranjo de 0,45 mx 0,49 m, promoveu a obtenção do maior valor da máxima curvatura, estimando-se o tamanho ótimo de parcela de seis plantas.

Quality indicators of soybean conventional and cross-seeding

The studies on the spatial arrangement of plants in cross-seeding soybean system are scarce, and then needed to check if this seeding system has higher quality compared to conventional. In this context, the aimed of this study was to evaluate the quality of cross-seeding soybeans compared to conventional, through statisti­cal process control. The experiment was conducted in the agricultural area of Jaboticabal - SP, using a mecha­nized set tractor-seeder precision with spacing of sowing row set to 0.45 m, and the experimental design com­pletely randomized with 30 repetitions for treatment in conventional sowing and soybean cross. The variables or assessed quality indicators consisted of longitudinal distribution of seeds (normal spacing, defective and double) and final seedling stand. Soybean crop quality indicators are essential to carry out the monitoring of variability and factors that influence the operation. The normal spacing feature is outside the control limits, both for conventional sowing, and for cross-seeding in the main line. Additional keywords: control charts; Glycine max ; variability.

Short-term browsing by roe deer has little effect on survival and growth of sessile oak seedlings

We studied the effect of roe deer (Capreolus capreolus) browsing on the growth and mortality of sessile oak (Quercus petraea) seedlings. First, we measured the height and basal diameter, and counted the number of shoots of the 849 seedlings of an experimental plantation, 60 of which were individually protected by fencing. We then introduced two tame roe deer females every day for three weeks from late May to mid-June. Measurements and counts were repeated after roe deer removal, then once again the following winter. We found no significant effect of browsing on mortality, total height, or basal diameter of the seedlings. However, the browsed seedlings exhibited a lower number of shoots despite regrowth observed after roe deer removal. We propose to use the tolerance of oak to deer browsing to promote natural and inexpensive methods, to protect oak during regeneration, such as the spatial arrangement of plants or the use of slash or surrounding vegetation in favourable environments.

Physiological basis of yield variation in response to row spacing and plant density of mungbean grown in subtropical environments

In this study, we investigated the extent and physiological bases of yield variation due to row spacing and plant density configuration in the mungbean [Vigna radiata (L.) Wilczek] variety “Crystal” grown in different subtropical environments. Field trials were conducted in six production environments; one rain-fed and one irrigated trial each at Biloela and Emerald, and one rain-fed trial each at Hermitage and Kingaroy sites in Queensland, Australia. In each trial, six combinations of spatial arrangement of plants, achieved through two inter-row spacings of 1m or 0.9m (wide row), 0.5m or 0.3m (narrow row), with three plant densities, 20, 30 and 40 plants/m2, were compared. The narrow row spacing resulted in 22% higher shoot dry matter and 14% more yield compared to the wide rows. The yield advantage of narrow rows ranged from 10% to 36% in the two irrigated and three rain-fed trials. However, yield loss of up to 10% was also recorded from narrow rows at Emerald where the crop suffered severe drought. Neither the effects of plant density, nor the interaction between plant density and row spacing, however, were significant in any trial. The yield advantage of narrow rows was related to 22% more intercepted radiation. In addition, simulations by the Agricultural Production Systems Simulator model, using site-specific agronomy, soil and weather information, suggested that narrow rows had proportionately greater use of soil water through transpiration, compared to evaporation resulting in higher yield per mm of soil water. The long-term simulation of yield probabilities over 123 years for the two row configurations showed that the mungbean crop planted in narrow rows could produce up to 30% higher grain yield compared to wide rows in 95% of the seasons.

Rentabilidade na semeadura cruzada da cultura da soja

O plantio cruzado da soja consiste em semear a área em duas passadas de modo que a segunda fique perpendicular à primeira, formando um tabuleiro de xadrez. Desta forma, o objetivo do trabalho foi avaliar a produtividade e os custos de produção da cultura da soja quando semeada em diferentes arranjos de semeadura cruzada. O experimento foi realizado nas safras 2011/2012 e 2012/2013, em área cultivada em sistema de plantio direto. O delineamento experimental foi em blocos casualizados com 5 tratamentos e 8 repetições. Os tratamentos foram: semeadura em linhas paralelas com adubação e população de plantas recomendada; semeadura cruzada com população e adubo em dobro; semeadura cruzada com população recomendada e adubo em dobro; semeadura cruzada com população em dobro e adubação recomendada; semeadura cruzada com população de plantas e adubo recomendado. Os resultados mostraram maior produtividade para o tratamento de semeadura cruzada com população de plantas em dobro e adubo recomendado; apesar disto, a semeadura convencional em linhas paralelas apresenta maior receita líquida do que a semeadura cruzada da soja sendo, então, mais rentável para o produtor.

English

The increase in maize yield is directly related to management practices, especially the manipulation of spatial arrangement of plants. This work aimed, evaluated the effect of conventional and twin-row spacing in different plant densities for maize, in the crop year 2011/2012. The treatments consisted of combinations between two rows spacing (twin-row spacing (0.2 x 0.7 m) and conventional spacing (0.7 m)) and five plant populations (50,000; 65,000; 80,000; 95,000 and 110,000 plants ha-1). It was evaluated the plant height, insertion height of the first ear, stem diameter, number of rows, number of kernels per ear, weight of 1,000 kernels, ear weight and yield. The use of twin row spacing provided better results for stem diameter, number of rows, number of kernels per ear, weight of 1,000 kernels, ear weight and the average maize yield. The stem diameter, number of kernels per ear, weight of 1,000 kernels and ear weight responded negatively to increased plant density. Key words: Plant arrangement, yield, agronomic characteristics.

English

The aim of this study was to evaluate the effect of the weed competition with different spacings in the culture of flaxseed (Linum usitatissimum L.). The experiment was conducted at the Campus of Unioeste - Cascavel, Paraná State, using the split-plot design in which the plots consisted of presence and absence of weeds and subplots consisted of row spacings (0.15, 0.30, and 0.45 m) with six replications. Plant height, number of capsules, stems and seeds per plant and yield (kg.ha-1) were determined. The increase of spacings between rows and the coexistence with the weed community were detrimental to production components of flaxseed. Key words: Linunm usitatissimu L., competition, spatial arrangement of plants.

Efeito dos arranjos espaciais de plantas na sanidade de híbridos de milho

SAP: 6335 Data do envio: 02/04/2012 Data do aceite: 10/12/2012 The correct density of plant population is a factor considered by farmers to increase yield. However, the plant arrangement provides a specific microclimate that could favor the development of phytopathogens and physiological abnormalities, affecting the crop development. This study aimed to examine the effects of plant arrangement on the sanity of five corn hybrids (XB 6010, XB 6012, XB 7253, XB 9003 and AG 9010), in two spacings (0.45 and 0.90 m between lines) and five plant populations (50,000, 60,000, 70,000, 80,000 and 90,000 plants ha-1). The experiment was conducted in 2009, in Selviria (Mato Grosso do Sul, Brazil), and the following traits were measured: presence of multiple ears, maize bushy stunt phytoplasma, tropical rust and leaf blight. The results were submitted to statistical analysis; the effects of hybrids and spacings were compared through Tukey’s test, and the effects of population, through regression analysis. The results indicated that the spatial arrangement of plants influence the sanity of the hybrids differently. Presence of multiple ears and tropical rust decreased linearly as the population increased, and maize bushy stunt phytoplasma was not influenced. As for leaf blight, only the hybrid XB 6012 was affected by the population, with the occurrence of the highest manifestation of symptoms in a population of 72,594 plants ha-1.