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Drought stress during wheat (Triticum aestivum L.) grain filling can affect the grain yield and its quality; effects that in some regions can be increased by the event La Niña, the cold phase of the climatic phenomenon El Niño Southern Oscillation. The aim was to evaluate if the evolution of relative water content (RWC) and stomatal conductance (gs) can be related to grain yield and its quality. Four spring wheat cultivars grown in the southern cone of South America were subjected to two levels of irrigation applied after anthesis, a well-watered treatment (Control), and another with 50 % of the Control (Stress). RWC and gs were determined weekly during the stress period and agronomic traits at harvest. With a mean grain yield decrease of 14.8 % (P

ABSTRACT: Intensification of drought in Mediterranean–type climates has limited seedling establishment. The knowledge of the ecology of selected species and its intraspecific variation to water stress at the seedling stage should be considered in order to overcome limitations. We investigated variations in growth, survival, and leaf–level physiology in four provenances of the endemic Cryptocarya alba (Mol.) during water stress and after re–watering. Seedlings were cultured in the nursery during 23 months and then subjected to two watering treatments based on soil water content (well–watered and water restriction, 0.38 and 0.17 cm3 cm−3, respectively) for 45 days. At the end of the watering treatments, seedling growth, above– and belowground biomass, survival, and leaf gas exchange were measured. Right after the watering treatments, the surviving seedlings were submitted to a recovery period of 21 days, in which all seedlings were re–watered at 0.38 cm3 cm−3 of soil water content and measured for leaf gas exchange. Provenances differed in growth and biomass allocation. Unlike growth and biomass, interaction between provenance and watering treatments was found for photosynthesis, stomatal conductance, transpiration, and water use efficiency of northern provenances, exhibiting the highest performance under water restriction. However, most variations observed occurred before the re–watering period and only a few occurred after this period. The four provenances under study exhibited similar photosynthesis and stomatal conductance after re–watering. Our study demonstrated phenotypic variation of C. alba and the capability of the species to withstand and recover from water stress.

ABSTRACT: Stress caused by extreme temperatures is one of the main elements that limit the geographical distribution and the seasonal growth of several plants, causing a severe delay in their development, reducing the photosynthetic rate and signaling the synthesis of defense compounds. Considering the current environmental changes and the damages that these changes can cause in plant physiology and growth, the objective of this work was to understand the interactions between temperature, physiology and growth, and to characterize the impact of temperature changes on the initial development of Vernonia ferruginea Less. Seedlings of this species were conditioned in germination chambers at previously adjusted constant temperatures (10, 20, 25, 30, and 35 oC) for sixty days, in order to evaluate physiological and growth parameters. The optimum temperature range for the initial growth of V. ferruginea is between 25 and 30 oC. The stress caused by sub-optimal and over-optimal temperatures affected cell homeostasis and caused a delay in the growth and development of seedlings. In stressful situations, growth inhibition and the activation of response mechanisms were observed for the adaptation and maintenance of cellular homeostasis through the accumulation of the proline osmoprotectant and soluble carbohydrates. Additionally, plants presented a normal development within a wide temperature range, despite the development delay, the change in gas exchanges and the synthesis of substances related to the defense system.

ABSTRACT: The repetitive use of glyphosate in the control of weeds in eucalyptus plantations has selected tolerant species such as Commelina benghalensis. Therefore, the use of herbicides of other mechanisms of action, such as saflufenacil, in rotation or combination with glyphosate, is necessary to reduce damages caused by C. benghalensis, whose sensitivity to herbicides can be influenced by the shading caused by the eucalyptus crop. This study aimed to assess the efficiency of saflufenacil in the management of C. benghalensis at different shading levels. Three experiments were carried out regarding a certain shading level (cultivation environment with 0, 40, and 55% shade). The experimental design was a randomized block design with five herbicide doses (0, 24.5, 49, 73.5, and 98 g ha-1 of saflufenacil) and four replications. At 28 days after herbicide application, the percentage of control and shoot dry matter were assessed, as well as the biomass allocation to leaves, stems, and roots of C. benghalensis. Plants cultivated at 0% shade presented a higher dry matter accumulation and a better distribution of biomass in leaves, stem, and roots, contributing with the increased tolerance to saflufenacil and not being controlled with effectiveness under the assessed doses. As shading was increased, plants of C. benghalensis allocated most of their biomass to the shoot, especially leaves, reducing their reserve structures and increasing the contact area with the herbicide, making them more susceptible to saflufenacil.

ABSTRACT E. indica is one of the most problematic weeds in the world because it is present in almost every continent, and there are reports of multiple resistance to herbicides by some biotypes. The objective of this paper was to analyze the growth, the development and the production of this plant's seeds, in order to generate information about its biology that can be useful for management. The experiment was carried out in a greenhouse from May to September 2015. Sixteen samples were taken during the development cycle of the plant: 3, 10, 17, 24, 31, 38, 45, 52, 59, 66, 73, 80, 87, 94, 101 and 108 days after emergence (DAE). The response variables were based on a leaf area and dry matter of each one of the parts of the plant and the number of seeds produced per plant. At 12 DAE, 80% of the seedlings of E. indica had emerged, and each plant produced more than 120 thousand seeds, closing their cycle at 120 DAE. Between 38 and 43 DAE, the plant had fast emission of new tillers, exponential accumulation of the total dry matter and substantial increase of the absolute growth rate. Due to the data observed here, we concluded that the management of E. indica must be done preferably before 38 DAE due to the exponential growth after this period, preventing the plant from producing seeds and spreading to other places.

Este trabalho teve por objetivo avaliar o crescimento de plantas jovens de nim-indiano (Azadirachta indica A. Juss.) submetidas a diferentes regimes hídricos. O delineamento experimental foi inteiramente casualizado, com sete tratamentos (100, 80, 60, 40 e 20% da capacidade de pote, suspensão de rega e reirrigado). Avaliaram-se, semanalmente, a altura, número de folhas e diâmetro do caule. Ao final do experimento, as plantas tiveram seus órgãos separados e levados à estufa para obtenção da matéria seca das folhas, caule, raízes e total e, ainda, alocação de biomassa nas folhas, caule e raízes. Também foram calculadas a área foliar, a razão de área foliar e a área foliar específica. O déficit hídrico diminuiu a altura, número de folhas e diâmetro do caule das plantas nos tratamentos mais severos. Os efeitos do estresse também foram observados na redução da matéria seca das folhas, caule, raízes e total e na alocação de biomassa para as folhas. A área foliar também apresentou reduções, mas a razão de área foliar e a área foliar específica não diferiram entre os tratamentos. As plantas reirrigadas mostraram recuperação, principalmente evidenciada pela emissão de novas folhas. Desse modo, sugere-se que para máximo crescimento o nim deve ser cultivado, na fase inicial de desenvolvimento, com 80% da capacidade de pote.This work was performed aiming to evaluate the growth of neem seedlings (Azadirachta indica A. Juss.) under water deficit. The experimental design was entirely randomized, with seven treatments (100, 80, 60, 40 and 20% of field capacity, without water and re-watering). The height, number of leaves and stem diameter were analyzed weekly. At the end of the experiment, dry matter of the leaves, shoots, roots, root to shoot ratio and biomass allocation in leaf, stem and roots were determined. Leaf area, leaf area ratio and specific leaf area were also calculated. Water stress reduced the height, number of leaves and shoot diameter in the plants of the several treatments. Water stress reduced leaf, stem and root dry matter. Only the biomass allocation to leaves was reduced. Leaf area was also reduced; however, there were not significant differences for leaf area ratio and specific leaf area. The recovery of the re-watering plants was evident by emitting new leaves. The results suggest that neem seedlings must be cultivated, in the initial phase of development, under 80% of field capacity, with maximum production.

Some morphophysiological responses of Brachiaria brizantha cv. Marandu, cv. Piatã, cv. Arapoty, B163, B166 and B. ruziziensis R124 were compared in plants grown in pots, under flooded and well-drained conditions. Flooding reduced leaf elongation rate in all accessions. Leaf dry mass production was lower under flooding than in the control plants in all the studied accessions, except in cv. Piatã. Root dry mass production was reduced by flooding in cv. Marandu and in R124, while the proportion of biomass allocated to roots was reduced by flooding only in R124. It was not possible to detect significant differences between water regimes in the percentage of biomass allocated to culms and leaves for all accessions. Flooding decreased the number of tillers in cv. Marandu, in B163, B166 and in R124. Relative growth rate was decreased by flooding in cv. Marandu, in B163 and in R124. Flooding reduced gas exchange parameters in all accessions, but cv. Arapoty. The accessions tested differ in their relative tolerance to flooding. B. brizantha cv. Arapoty is considered the most tolerant. B. ruziziensis R124 is the most sensitive, followed by B. brizantha cv. Marandu. B. brizantha cv. Piatã, B163 and B166 are intermediate in flooding tolerance.Respostas morfofisiológicas de Brachiaria brizantha, cultivares Marandu, Piatã, Arapoty, B163, B166 e B. ruziziensis (R124), foram comparadas em plantas cultivadas em vasos, sob alagamento ou em solo bem drenado. O alagamento do solo reduziu a taxa de alongamento foliar de todos os acessos. Sob alagamento, houve queda na produção de biomassa de folhas em todos os acessos, com exceção do cultivar Piatã. A produção de raízes reduziu com o alagamento do solo no cv. Marandu e em R124, enquanto o percentual de biomassa alocado para as raízes diminuiu apenas no acesso R124. Não foi possível detectar diferenças entre regimes de água na alocação de biomassa para colmos e folhas em nenhum dos acessos. O alagamento diminuiu o número de perfilhos nos cultivares Marandu, B163, B166 e R124. Com o alagamento do solo, a taxa de crescimento relativo diminuiu nos cultivares Marandu, B163 e R124. Com exceção do cultivar Arapoty, o alagamento reduziu as trocas gasosas de todos os acessos estudados. Os acessos avaliados diferiram quanto à tolerância relacionada ao alagamento do solo: o cv. Arapoty é relativamente mais tolerante, enquanto o B. ruziziensis (R124) é menos tolerante, seguido pelo Marandu, e os cultivares Piatã, B163 e B166 têm tolerância intermediária.

Some physiological and morphological responses of five Brachiaria brizantha accessions (BRA000591 cultivar Marandu, BRA003441, BRA002844, BRA004308 and BRA004391) were compared for plants grown in pots under flooding and well-drained conditions for 14 days. Flooding caused a significant reduction in leaf dry mass production in all accessions, but, for root biomass, no differences between treatments could be detected in BRA003441 and BRA004391. No adventitious root production was observed in flooded BRA003441; all other accessions produced adventitious roots when flooded. Relative growth rate was reduced by flooding only in BRA000591 and BRA004308. Leaf elongation rate was reduced by flooding in all accessions, however, more severely in BRA003441. Net photosynthesis was reduced by flooding in all accessions, but with less intensity in BRA004391. For all accessions, there was a close relationship between net photosynthesis and stomatal conductance under flooding. The five accessions tested differed in tolerance to flooding. BRA004391 was the most tolerant. Accession BRA003441 was the most sensitive, followed by BRA000591 cultivar Marandu. Accessions BRA002844 and BRA004308 were classified as intermediate in flooding tolerance.Algumas respostas morfológicas e fisiológicas de cinco acessos de Brachiaria brizantha (BRA000591 cultivar Marandu, BRA003441, BRA002844, BRA004308 e BRA004391) foram comparadas em plantas cultivadas em vasos, sob condições de solo alagado e bem drenado, durante 14 dias. O alagamento reduziu significativamente a produção de massa seca foliar em todos os acessos, mas para a massa seca radicular, não foi possível encontrar diferenças entre tratamentos em BRA003441 e BRA004391. Somente BRA003441 não produziu raízes adventícias sob alagamento. A taxa de crescimento relativo foi reduzida pelo alagamento somente em BRA000591 e BRA004308. A taxa de elongação foliar foi reduzida pelo alagamento do solo em todos os acessos, porém, com maior severidade em BRA003441. O alagamento reduziu a fotossíntese líquida em todos os acessos, porém, menos intensamente em BRA004391. Em todos os acessos encontrouse uma estreita relação entre as taxas de fotossíntese líquida e a condutância estomática sob alagamento. Os cinco acessos testados diferiram na sua tolerância relativa ao alagamento do solo. BRA004391 foi o mais tolerante. O acesso BRA003441 foi o menos tolerante, seguido por BRA000591 cultivar Marandu. Os acessos BRA002844 e BRA004308 foram considerados como intermediários em tolerância ao alagamento do solo.

The effect of two natural light-growing conditions (understory versus light gaps) and the interaction with nutrient availability (through fertilization) was studied in the understory herb Begonia decandra, in the Luquillo Experimental Forest in Puerto Rico. Sixteen potted plants obtained from cuttings were randomly chosen and distributed in each of eighth forest environments (four light gaps and four understories), for a total of 128 plants. Fertilizer was applied to half of the plants in each site. After seven months in the two given microenvironments, increased light and fertilization resulted in greater growth and some changes in the biomass allocation patterns. All measured variables responded similarly to reported changes for tree seedlings and saplings from other tropical and subtropical regions. Total growth parameters (height, biomass and leaf area) were very sensitive to increases in the main resource (light). The addition of nutrients treatments were less important in producing changes in the allocation variables (root to shoot ratio, leaf area ratio, and specific leaf mass) under conditions of high light availability. Changes due to nutrient levels were relatively greater on plants grown under understory conditions. Also, small light differences among sites can cause significant changes in the variables related to total growth. Lastly, plant mortality in the nutrient treatments was found to be independent of mortality in two forest light environments. Some hypotheses about resource acquisition and plant growth are not supported by this data.Se estudia el efecto de dos regímenes de luz natural (claros del bosque y el sotobosque) y su interacción con la disponibilidad de nutrimentos sobre el crecimiento y la repartición de biomasa de Begonia decandra, una hierba del sotobosque en el Bosque Experimental de Luquillo, Puerto Rico. Dieciseis plantas en macetas obtenidas por estacas se asignaron aleatoriamente a cada uno de los ocho sitios del bosque (cuatro en claros y cuatro en el sotobosque), para un total de 128 plantas. Se aplicó fertilizante completo a la mitad de las plantas de cada sitio. Después de siete meses en los ambientes estudiados, la adición de nutrimentos afectó positivamente el crecimiento total y produjo algunos cambios en los patrones de repartición de biomasa. La respuesta general en las variables estudiadas fue similar a las respuestas obtenidas en plántulas y brinzales de árboles de otras regiones tropicales. La biomasa y el área foliar fueron muy sensibles al incremento del recurso principal (luz). La fertilización afectó menos los patrones de asignación de biomasa (relación raíz/vástago, masa foliar específica y cociente de área foliar) cuando las plantas están en los claros, y estos cambios fueron más pronunciados cuando el recurso principal es limitante (en el sotobosque). Las diferencias lumínicas debidas al sitio pueden causar diferencias importantes en las variables relacionadas al crecimiento total. La mortalidad de plantas en los tratamientos con nutrientes fue independiente de la mortalidad en los tratamientos lumínicos. Algunas hipótesis sobre adquisición de recursos y crecimiento vegetal no son sustentadas por este estudio.

Ensaios de competição intra-específica foram conduzidos sobre Amaranthus viridis L. e A. hybridus L., a última espécie com dois biótipos distintos, tipo verde e tipo roxo. Os três ensaios, conduzidos separadamente, utilizaram cinco densidades de sementes por vaso. Em termos gerais, as sementes germinadas prontamente foram a razão do surgimento da próxima geração, visto que estabeleceram plântulas rapidamente e estas venceram em competição. A partir de certo número de sementes semeadas (20 por vaso), o número de plantas adultas obtidas revelou-se independente do número de sementes semeadas, o que indica que a capacidade de suporte do ambiente, ao invés do tamanho do banco de sementes no solo, é a razão da regulação do tamanho populacional; a mesma observação aplica-se à produção de matéria seca. Sob condições de competição, as espécies A. hybridus - tipo verde e A. viridis produziram maior quantidade de biomassa para reprodução (22% a 34%) do que A. hybridus - tipo roxo (15% a 18%). As primeiras, portanto, revelaram-se mais estrategistas-r que a última.Intraspecific competition trials were carried out for Amaranthus viridis L. and A. hybridus L., the latter species with two distinct biotypes, a green and a purple type. Three independent trials were made, with five different seed densities per pot for each species or biotype. In general terms, seeds that germinated promptly were responsible for the formation of the next generation, these early seedlings being more competitive. The carrying capacity was reached with 20 seeds per pot, no increase in the number of adult plants observed by increasing the seed density. This shows that the environmental suporting capacity, not the size of the seed bank in the soil, regulates the population size. A similar conclusion holds true for dry matter yield. Under competition, the species A. hybridus - green biotype and A. viridis produced larger biomass for reproductive structures (22% to 34%) than A. hybridus - purple biotype (15% to 18%), the former species being therefore better r-strategists than the latter.

O objetivo deste trabalho foi estudar a interferência interespecífica entre duas espécies de Amaranthus -- A. viridis e A. hybridus ¾, esta última com dois biótipos distintos (verde e roxo); ambas ocorriam associadas em dois locais. Nas populações de cada local foram feitos ensaios de substituição independentes, em vasos, nos quais observou-se que as populações que germinam mais prontamente são as que vencem em competição, ou seja, se estabelecem e produzem maior número de sementes. Houve tendência de A. hybridus (tipo verde) dominar tanto A. hybridus (tipo roxo) como A. viridis, e de A. hybridus (tipo roxo) dominar A. viridis. Em cultivo misto, houve casos em que as espécies estavam competindo pelos mesmos recursos, ou explorando recursos diferentes do ambiente, ou mesmo com antagonismo mútuo.The objective of this paper was to study the interspecific interference between two Amaranthus species -- A. viridis and A. hybridus --, the latter with two distinct biotypes (green and purple); both species ocurred in two localities. In the populations of each of the locations, some independent substitution trials were made in pots, and it could be concluded that the populations that germinate more readily are those which are superior in competition i.e., those that establish themselves and produce the largest number of seeds. There was a tendency for A. hybridus (green biotype) to dominate both A. hybridus (purple biotype) and A. viridis, and for A. hybridus (purple biotype) to dominate A. viridis. In mixed stands, there were cases where the species were competing for the same resources, cases where they were exploiting different environmental resources, and even cases of mutual antagonism.

La biología floral, biología de polinización y sistema de apareamiento fueron estudiados en dos especies nativas y tres especies introducidas presentes en un fragmento de bosque caducifolio secundario en Venezuela. Todas las especies estudiadas presentaron corolas tubulares, largas y estrechas; predominando los colores rojos. La antesis de todas las especies fue diurna, entre las 04:00 y las 11:00. La producción de néctar fue alta, excepto para Salvia coccinea (Lamiaceae) (nativa). Nicotiana glauca (Solanaceae) (nativa) y Erythrina mitis (Fabaceae) (introducida) compartían sus polinizadores Chlorostilbon mellisugus y Amazilia tobaci (Apodiformes, Throchilidae). S. coccinea recibió visitas legítimas de Heliconius erato (Lepidóptera). Kalanchöe daigremontiana y K. pinnata (Crassulaceae) (exóticas) no recibieron ninguna visita legítima. Todas las especies fueron hermafroditas. K. daigremontiana y K. pinnata resultaron xenógamas obligadas; mientras S. coccinea, N. glauca y E. mitis resultaron parcialmente autocompatibles no autógamas. Las cinco especies mostraron una alta a-signación de biomasa total con respecto a otros sistemas de polinización. La a-signación de biomasa reproductiva fue siempre menor a las asignaciones de biomasa de atracción y de biomasa vegetativa floral. La asignación de biomasa masculina fue mayor que la femenina para N. glauca, S. coccinea y E. mitis, y menor para K. daigremontiana y K. pinnata. Las especies introducidas no parecen afectar notoriamente las eficiencias reproductivas de las especies nativas. Las eficiencias reproductivas de las especies nativas fueron superiores a las de las especies introducidas. Las eficiencias reproductivas de las especies introducidas resultaron bajas, debido a que se encuentran afectadas por la ausencia de sus polinizadores naturales.The floral biology, the pollination biology and the mating system were studied in two native and three introduced species of an arboretum in Venezuela. All the species presented thin, long, tubular corollas; predominantly red. The antheses were diurnal (between 04:00 and 11:00 hr). Nectar production was high, except for Salvia coccinea (Lamiaceae) (native). Nicotiana glauca (Solanaceae) (native) and Erythrina mitis (Fabaceae) (introduced) shared their hummingbird pollinators, Chlorostilbon mellisugus and Amazilia tobaci (Apodiformes, Throchilidae). S. coccinea was pollinated by Heliconius erato (Lepidoptera). Kalanchöe pinnata and K. daigremontiana (Crassulaceae) (exotic) did not receive any visits. All the species were hermaphrodite. K. daigremontiana and K. pinnata were obligate outcrossers, and S. coccinea N. glauca and E. mitis were partialy outcrossers and non-autogamus. The species presented high total biomass allocation, compared to other polination systems. The reproductive biomass allocation were allways smaller than the attraction and vegetative biomass allocation. The male biomass allocation were greater than the female biomass allocation in N. glauca, S. coccinea and E. mitis; and smaller in K. daigremontiana and K. pinnata. The introduced species did not seem to affect the reproductive efficiencies of the native species during our observation period. The lowest reproductive efficiencies in introduced species resulted as a consequence of the absence of their natural pollinators.

[fr] Les plantes de cinq populations de l'épicéa commun [Picea abies (L.) Karst.] provenant des différentes altitudes du massif de Snieznik Klodzki dans les Sudètes (une chaîne des montagnes en Pologne) ont été cultivées dans la serre. Leurs paramètres suivants ont été analysés: la hauteur, la longueur des racines, le poids frais et le poids sec des racines, des tiges, des aiguilles, des bourgeons et l'allocation de la biomasse. La haute corrélation a été notée entre les paramètres des plantes et l'altitude des stations des arbres ayant été les semenciers des graines. Ce résultat montre une plutôt bonne adaptation écologique de ces populations, probablement introduites dans le massif de Snieznik Klodzki. Les aspects écologiques et les conséquences de l'adaptation de l'épicéa commun aux conditions montagneuses pour la sylviculture sont discutés. [es] Plántulas de cinco poblaciones de abeto rojo [Picea abies (L.) Karst.] procedentes de diferente altitud en el macizo de Snieznik Klodzki, en los Montes Sudetes, (Polonia) se cultivaron en invernadero. Se han analizado los parámetros siguientes: altura y longitud de las raíces, pesos fresco y seco de raíces, tallos, hojas y yemas, así como la distribución de la biomasa. Como resultado se obtuvo una correlación alta entre los parámetros de las plántidas y la altitud de las estaciones donde se colectaron las semillas. Esto indica una adaptación relativamente buena de esas poblaciones, probablemente introducidas. Finalmente se discuten algunos aspectos ecológicos y de silvicultura.