Stem Dry Mass Research Articles

Trait‐based community assembly of aquatic macrophytes along a water depth gradient in a freshwater lake

Summary Trait‐based approaches provide a framework for integrating the distribution of functional traits associated with ecological strategies into the responses of plant community dynamics along environmental gradients. We used a trait‐based approach to unravel the processes governing macrophyte community assembly along a water depth gradient. We sampled 42 plots and 1513 individual plants and measured 12 functional traits and abundance of 17 macrophyte species. The results showed significant evidences of habitat filtering (i.e. a significant reduction in the range and variance of trait values) and of niche differentiation (i.e. trait values distributed more evenly than expected), both of which affected the functional responses of macrophyte communities associated with different sets of traits in significant different patterns along the gradient. Habitat filtering effects increased significantly for specific leaf area and leaf carbon content along the gradient. Niche differentiation effects increased significantly for leaf dry mass content, but decreased for ramet size, shoot height and leaf carbon content with increasing water depth, implying that the relative strength of biotic competition in a specific functional niche would vary with water depth. Intraspecific trait variability promoted significantly the detection of habitat filtering effects on stem diameter, lamina thickness and stem dry mass content, and niche differentiation effects on specific leaf area, leaf dry mass content, shoot height, stem diameter, stem dry mass content and ramet size. Community assembly processes shape the functional trait distribution within communities along environmental gradients through hierarchical effects of habitat filtering and niche differentiation. Our study highlights that niche differentiation plays a structuring role in macrophyte community assembly and that intraspecific trait variability is an important factor influencing macrophyte community dynamics.

Functional traits composition predict macrophytes community productivity along a water depth gradient in a freshwater lake.

Functional trait composition of plant communities has been proposed as a helpful key for understanding the mechanisms of biodiversity effects on ecosystem functioning. In this study, we applied a step-wise modeling procedure to test the relative effects of taxonomic diversity, functional identity, and functional diversity on macrophytes community productivity along water depth gradient. We sampled 42 plots and 1513 individual plants and measured 16 functional traits and abundance of 17 macrophyte species. Results showed that there was a significant decrease in taxonomic diversity, functional identity (i.e., stem dry mass content, leaf [C] and leaf [N]), and functional diversity (i.e., floating leaf, mean Julian flowering date and rooting depth) with increasing water depth. For the multiple-trait functional diversity (FD) indices, functional richness decreased, while functional divergence increased with water depth gradient. Macrophyte community productivity was strongly determined by functional trait composition within community, but not significantly affected by taxonomic diversity. Community-weighted means (CWM) showed a two times higher explanatory power relative to FD indices in determining variations in community productivity. For nine of sixteen traits, CWM and FD showed significant correlations with community productivity, although the strength and direction of those relations depended on selected trait. Furthermore, functional composition in a community affected productivity through either additive or opposite effects of CWM and FD, depending on the particular traits being considered. Our results suggested both mechanisms of mass ratio and niche complementarity can operate simultaneously on variations in community productivity, and considering both CWM and FD would lead to a more profound understanding of traits–productivity relationships.

Growth and dry mass partitioning in plant parts of lentil

The experiment was carried out under sub-tropical condition (24°75´ N latitude and 90°50´ E longitude) to investigate the growth, dry mass production and its partitioning into plant parts of three lentil varieties viz. BINA masur1, BINA masur2 and BINA masur3. The leaf area and total dry mass plant−1 were superior in BINA masur3 over its growth period followed by BINA masur2 with same statistical rank. In contrast, BINA masur1 performed inferiority in leaf area and total dry mass plant−1. Dry mass partitioning into seed (HI) was significantly greater in BINA masur2 and BINA masur3 with being the highest in BINA masur2 but total economic yield and its related traits were greater in BINA masur3 than in BINA masur2. Results indicated that percent contribution of dry mass partitioning into different plant parts had no significant influence on seed yield but leaf and stem dry mass production had influence on seed yield in lentil. BINA masur3 produced the highest in leaf and stem dry mass and also showed the highest seed yield followed by BINA masur2. In contrast, BINA masur1 showed the lowest seed yield for contributed lower leaf dry mass.

Influence of nutrient and water additions on functional traits of Salsola nitraria in desert grassland

Aims Our objective was to better understand the response of plant functional traits of Salsola nitraria to environmental change, such as global climate change and nutrient addition, in desert grassland. Methods We conducted field experiments of moisture and nutrient additions for three years(2009–2011) in a desert grassland of northwest Xinjiang in China. We investigated plant functional traits of S. nitraria and in the fourth year(2012) measured plant height, stem fresh mass, stem dry mass, leaf fresh mass, leaf dry mass, etc. under different treatments of nutrient and water additions. Important findings The combination of fertilizer and moisture had a significant influence on stem fresh mass, leaf fresh mass, leaf area, specific leaf area, leaf saturated water content, and leaf dry matter content(two-way ANOVA, p 0.05), while the effect of either fertilizer or moisture alone was not significant. None of the treatment effects on plant height were significant. The maximum values of plant height, stem fresh weight, stem dry weight, leaf saturated fresh weight, leaf dry weight, leaf area, and specific leaf area appeared in the snow and fertilizer additions(N1 W2), and the second highest was in the control(N0 W0). Maximum leaf saturated water content was observed in the control(N0 W0), and the second highest appeared in the snow and fertilizer additions(N1 W2). The fertilizer addition(N1 W0) could significantly decrease the level of leaf saturated water content. In all of the treatments, leaf dry matter content was higher than that under the control, and among them, the rain addition(N0 W2) significantly increased leaf dry matter content. In the control, there were many significant negative correlations between leaf dry matter content and other functional traits and many significant positive correlations between different functional traits. After the fertilizer and/or moisture addition, the correlation coefficient was reduced. In desert grassland of the Junggar Basin, the different performance of S. nitraria under different treatments was the result of plant adaptations to environmental changes.

不同分枝数对桑树幼苗生长发育的影响

以我国常见经济林木桑树（<em>Morus alba</em>）为试验材料，从气体交换、形态变化和地上生物量方面研究5种分枝模式（1、2、3、4和5枝）对幼苗生长发育的影响。结果显示：（1）分枝数为1的植株的净光合速率（<em>P</em>_n）最高，达到8.6 μmol·m^-2·s^-1。随着分枝数增加，<em>P</em>_n显著下降，直至分枝数达到3枝及其以上时，净光合速率保持相对稳定，为4.3 μmol·m^-2·s^-1。而气孔导度（<em>g</em>_s）、胞间CO₂浓度（<em>C</em>_i）和蒸腾速率（<em>E</em>）则不受分枝数的影响。（2）随着分枝数增加，总叶片数量、总叶面积和总枝长都显著增加，最终分别达到114.3，10481.1 cm²和457.1 cm，而平均单枝叶片数、平均单枝基径、平均单叶面积和比叶面积则显著减少。（3）随着分枝数的增加，植株的总叶生物量和总枝生物量无显著变化，但平均每枝叶干重、平均每枝枝干重和平均每枝总生物量随分枝数的增加而逐渐减少。研究结果表明了分枝数增加可能导致叶片间对光资源的竞争强度增大，引起净光合速率下降，叶片面积变小，单枝长度和生物量减小。另一方面，植株则通过生长出更多的叶片数量，以及更大的总叶片面积来尽可能地消除竞争带来的不利影响，提高对光环境资源的利用。;<em>Morus alba</em> L. is a valuable multipurpose species and is widely distributed in central, northern and southwestern China. This species is one of the most economically important cultivated tree species in China and also provides basic raw materials supporting vigorous development of China's sericulture and textile industries. Most previous studies related to <em>M. alba </em>have primarily focused on cultivation techniques, pest control, quality improvement and development of resources. Previous studies have not yet provided data related to the photosynthetic capacity of this species or leaf growth patterns, and in particular, no studies have addressed the change of biomass in plants with a different number of branches. In this study, 3-year-old mulberry seedlings were transplanted from the garden of the Sichuan Academy of Agricultural Sciences to investigate the effects of branch number on plant growth. Five branch number models were used; that is, one, two, three, four, or five branches were left on the stem of saplings for experimental purposes, and the saplings were allowed to grow for 6 months. We investigated differences in various gas exchange factors, including net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration and transpiration rate for plants using the five branch models during the growing season. From the aspect of plant morphological growth, we measured the growth rates based on leaf number, branch length and basal diameter for the five branch models, once every ten days. After the growing season, we measured the differences of leaf biomass, above ground stem biomass and total biomass among plants used for the five branch model experiments. We also analyzed biomass allocation in<em> M. alba</em> with the different branch models. The results show that the single-branch saplings had the highest net photosynthetic rate (<em>P</em>_n) (8.6 μmol·m^-2·s^-1). As the number of branches on a plant increased, the<em> P</em>_n was observed to decrease significantly and remained relative stable (4.3 μmol·m^-2·s^-1) when the number of branches was three or more. In contrast, stomatal conductance (<em>g</em>_s), intercellular CO₂ concentration, (<em>C</em>_i) and transpiration rate (<em>E</em>) showed no significant changes in all <em>M. alba</em> saplings. Also, total leaf number (<em>TLN</em>), total leaf area (<em>TLA</em>), and total stem lengths (<em>TSL</em>) of saplings increased significantly as the number of branches increased to a maximum of 114.3 leaves, 10481.1 cm², and 457.1 cm, respectively. However, the number of leaves per branch (<em>LN/B</em>), basal diameter per branch (<em>BD/B</em>), mean surface area per leaf (<em>LA/L</em>) and specific leaf area (<em>SLA</em>) obviously decreased in multiple-branch saplings and to 22.9 leaves, 7.57 mm, 87.3 cm² and 48.91 cm²/g, respectively. Moreover, branch number had no effect on the total dry biomass accumulation and allocation, but mean leaf dry mass per branch (<em>LM/B</em>), mean stem dry mass per branch (<em>SM/B</em>), and mean dry mass per branch (<em>DM/B</em>) gradually decreased with the increase in branch number, with values of 8.61 g, 9.51 g and 18.12 g, respectively. The results suggest that an increase in branch number may result in more intense competition for light resources between leaves, resulting in a lower net photosynthetic rate, smaller leaf area, and shorter stem length per branch as leaves compete for light and resources used to produce biomass. To eliminate the negative effects of such competition as much as possible, saplings can grow additional leaves as well as enlarge their total leaf area to make better use of limited light resources.

Uso de Bioestimulantes no Crescimento de Plantas de Zea mays L.

The objective of the present study was to evaluate the effect of commercial products, biostimulants, on the initial development of maize seedlings of the cultivar BRS 1055, regarding the indicators of the phenological cycle quality.. A completely randomized blocks experimental design in a factorial scheme was used with three biostimulants and five sampling periods, with four replications. The indicators of the phenological cycle quality assessed were plant height, stem diameter, leaf area, leaf dry mass, stem dry mass and root dry weight. The treatment T6 (BU-RG + BU-VG) showed the highest growth rate for plant height (1.84 cm day -1 ). The treatments T5 (BU-EC + BU-VG) and T6 (BU-RG + BU-VG) showed the highest growth rate of stem diameter (0.25 cm day -1 ) and leaf area (45.76 cm 2 day -1 ), respectively. The treatment T2 (BU-RG) presented the highest growth rate for leaf dry mass (0.15 g day -1 ). The treatments T2 (BU-RG), T4 (BU-VG) and T6 (BU-RG + BU-VG) showed greater stem dry mass (0.10 g day -1 ); and T4 (BU-VG) and T6 (BU-RG + BU-VG) superior root dry weight (0.17 g day -1 ). The biostimulants

Emergência e qualidade de mudas de Enterolobium contortisiliquum (Vell.) Morong (Fabaceae) em diferentes substratos

Este trabalho objetivou avaliar diferentes substratos na emergência e crescimento de mudas de Enterolobium contortisiliquum. Foram avaliadas composições a partir dos materiais vermiculita, moinha de carvão vegetal, subsolo, composto orgânico e serragem de madeira, totalizando 16 tratamentos. Durante 120 dias, avaliaram-se a emergência, o índice de velocidade e o tempo médio de emergência, a altura total da planta, o comprimento da raiz, o comprimento da parte aérea, o diâmetro do colo, o número de nódulos, a massa seca da raiz, a massa seca da parte aérea e o volume de raiz, além do índice de qualidade de Dickson. A maioria dos substratos apresentou resultados satisfatórios, destacando-se os tratamentos com 50% de vermiculita e 50% de composto orgânico e o tratamento com 33% de vermiculita, 33% de moinha de carvão vegetal e 33% de composto orgânico.

Impact of the timing and duration of weed control on the establishment of a rubber tree plantation

Rubber tree production is reduced by weeds that compete for environmental resources; therefore, the timing and duration of weed control influences weed interference. The objectives of this study were to evaluate the growth of rubber tree (Hevea brasiliensis) plants, to determine the critical period for weed control, and to evaluate the growth recovery of rubber trees that coexisted with weeds for different periods of time after planting. Two groups of treatments were established under field conditions in the first year of the investigation: one group contained crescent periods of weed infestation, while the other contained crescent periods of weed control, also including a weed-free check and a total weedy check. In the second year of the investigation, the weeds were totally controlled. Urochloa decumbens was the dominant weed (over 90% groundcover). Crop growth was greatly reduced due to the weed interference. Plant height decreased more rapidly than did any other characteristic. Plant height, leaf dry mass, and leaf area decreased by 99%, 97% and 96%, respectively, and were the most reduced characteristics. Plant height also recovered more rapidly than did any characteristic when the period of weed control was lengthened. However, stem dry mass increased by 750%, making it the most recovered characteristic. The critical period for weed control was between 4 and 9½ months after planting in the first year; however, the rubber trees showed an expressive growth recovery when the weeds were controlled throughout the second year.

Amazon palm biomass and allometry

Palms (family Arecaceae) are abundant in Amazonian forests, but the allometry of these monocotyledonous plants remains poorly quantified. Woody palm biomass is most commonly estimated with dicotyledonous tree models, which leaves substantial uncertainty as to their true biomass and productivity. We developed the first extensive dataset of directly-measured arborescent palm biomass: 136 individuals from nine species in terra firme and wetland forests — Astrocaryum murumuru, Attalea phalerata, Bactris gasipaes, Euterpe precatoria, Iriartea deltoidea, Mauritia flexuosa, Mauritiella aculeata, Oenocarpus bataua, and Socratea exorrhiza. We created single species (n=8–21) and family-level (n=97–106) allometric equations, using diameter, stem height, total height, and stem dry mass fraction, to estimate (i) total aboveground biomass for all species, (ii) belowground biomass for the two wetland species (Mauritia and Mauritiella), and (iii) leaf mass for all species. These new palm models were then applied to nine 1-ha plots in the southwestern Amazon (Tambopata) to calculate the impact on forest biomass estimates once palm mass is estimated with palm-specific models, rather than from models created for dicot trees. We found that stem height was the best predictor variable for arborescent palm biomass, but the relationship between stem height and biomass differed among species. Most species showed weak biomass–diameter relationships, but a significant relationship could be identified across all species. The new palm models were better estimators of palm mass than existing dicot models. Using our species-level models increased estimates of palm biomass at our study site by 14–27%, compared to using recently published pantropical biomass models for trees. In other forests, the effect of using these palm equations on biomass estimates will depend on palm sizes, abundance, and species composition.

Interference of Grasses on the Growth of Eucalyptus Clones

This experiment aimed to study the interference of Urochloa decumbens, Brachiaria plantaginea, Brachiaria ruziziensis and Panicum maximum (100 plants m-2 density), on the initial growth of clones of eucalyptus (Eucalyptus urograndis) clones 1, 2, 3, 4 and 5. Each pot had one plant of eucalyptus and five weed plants. The experimental design was completely randomized with four replications, constituting a 5x5 factorial design. The height and the diameter of eucalyptus plants were evaluated at 0, 15, 28, 41 and 50 days after weeds transplanting (DAT). At 50 DAT was measured the foliar area of eucalyptus plants, as well as the dry mass of eucalyptus plants (leaves and stem) and the dry mass of weeds. The five clones suffered negative interference during the coexistence with weeds. The clones showed different behaviors through the interaction with weeds. For the more susceptible characteristics to interference – leaves and stem dry mass – eucalyptus clones 3, 4 and 5 were more sensitive to the presence of weeds.

Effects of water replacement levels and nitrogen fertilization on growth and production of gladiolus in a greenhouse

The gladiolus is a cut flower used for interior decoration. It is a short cycle, easy driving crop with low implantation costs and fast payback. These factors allow for its cultivation in small areas in which commercial production of bulbs for domestic and foreign markets is also possible. Furthermore, it has high economic value because it is among the most important cut flowers grown in Brazil and is the third in product volume. This study aimed to evaluate the effect of different water replacement levels in the soil (50%, 75%, 100%, 125%, 150% of field capacity water volume) and nitrogen doses (0, 30, 60, 90, 120mgdm−3) on crop growth and production in a greenhouse. The species studied was the Gladiolus x grandiflorus L., White Friendship variety. The experimental design consisted of randomized blocks in a 5×5 factorial scheme with four replications. The growth and yield of gladiolus were characterized by the following variables: number of leaves, total plant height, floral spike and stem length, number and diameter of flowers, floral dry mass stem and number of days to bolting and flowering. Using the statistical software Sisvar, data were subjected to an analysis of variance at the 5% level of significance using the F test and to polynomial regressions. For nitrogen fertilization, there was a significant response only to the variable of floral stem dry mass. For the water replacement levels, responses were significant for all of the variables analyzed. The management of water irrigation at replacement levels above 75% of field capacity allowed for the length of the floral stems to be classified for commercial purposes, and for the number of flowers, water replacement levels above 100% provided a better commercial classification.

Stem biomass, C and N partitioning and growth efficiency of mature pedigreed black spruce on both a wet and a dry site

Worldwide, efforts to manage atmospheric CO2 are being explored both by reducing emissions and by sequestering more carbon (C). Stem biomass, C, and nitrogen (N) parameters were measured in plots of first-generation (F1), 32-year-old black spruce (Picea mariana (Mill.) B.S.P.) from four full-sib families studied previously for drought tolerance and differential productivity on both a dry and a wet site in central Ontario, Canada. The wet site had greater stem wood N and bark N concentrations than the dry site. Site differences in N were most likely driven by soil moisture stress impairing N uptake, as soil N was equal at both sites. Drought-tolerant (faster growing) families had lower wood density than drought-intolerant families on the wet site but there were no wood density differences between families on the dry site. Allometric analysis showed greater total stem dry mass per unit total belowground dry mass for drought-tolerant than intolerant families and for wet than dry sites, indicating a differential allocation of photosynthate dependent on both genotype and environment. Allometric analysis also showed greater total stem dry mass per unit total needle dry mass (growth efficiency) for drought-tolerant than intolerant families and for the wet than the dry site. This indicates greater productivity is a result of greater growth efficiency caused by greater net photosynthesis (shown previously) and greater partitioning of biomass to stem relative to total roots. The variation in physiological processes documented in our previous investigations and the biomass allocation variation shown here most probably underlie the increase in stem productivity from both black spruce tree improvement programs and increased water availability.

Cassava stems: a new resource to increase food and fuel production

AbstractGiven the growing global population, mankind must find new ways to lower competition for land between food and fuel production. Our findings for cassava suggest that this important crop can substantially increase the combined production of both food and fuel. Cassava stems have previously been overlooked in starch and energy production. These food‐crop residues contain about 30% starch (dry mass) mostly in the xylem rather than phloem tissue. Up to 15% starch of the stem dry mass can be extracted using simple water‐based techniques, potentially leading to an 87% increase in global cassava starch production. The integration of biofuel production, using residues and wastewater from starch extraction, may bring added value. The cassava roots on which biofuels and other products are based can be replaced by cassava stems without land use expansion, making root starch available as food for additional 30 million people today.

Physiological Dynamics of Maize Nitrogen Uptake and Partitioning in Response to Plant Density and N Stress Factors: I. Vegetative Phase

ABSTRACTFrom a physiological perspective, field studies that quantify the influence of plant density (PD) and N rate on biomass (BM) and N uptake are needed to build more functional partitioning models for maize (Zea mays L.). The overall goal was to quantify the effects of maize hybrid (two genotypes), PD (low = 54,000; medium = 79,000 and high = 104,000 pl ha‐1), and N rate (low = 0, medium = 112 and high = 224 kg N ha‐1) on the organ‐specific dry mass and N allocation, and on the resource capture (ratio of leaf area index [LAI] to BM), and resource use efficiency (ratio of N uptake to LAI) parameters, during the vegetative phase at four site‐years. Allometric analyses revealed that the resource capture was primarily affected by the PD, and the resource use efficiency by the N rate. The stoichiometry between leaf and stem dry mass was unaffected by the treatment factors, but no isometry was documented (greater BM to the stem than leaf). The N rate primarily modified the leaf and stem N concentrations (0N vs. 112–224N). With respect to resource use efficiency, modifications in the leaf N content per unit of LAI were joint outcomes of changes in leaf mass and %N (N concentration). In contrast, physiological changes in the stem N content per unit of LAI were more dependent on changes in the stem %N (greater N storage capacity) rather than in the stem mass. Intensifying competition with neighboring plants reduced per‐plant mass similarly in both leaf and stem structures, and improving N supply was proportionately more beneficial in maintaining plant mass and stem %N at high PD during vegetative growth.

Emergence and Performance of Two Invasive Swallowworts (Vincetoxicumspp.) in Contrasting Soil Types and Soil pH

AbstractThe alien invasive vines black and pale swallowwort are currently spreading across eastern North America, invading parklands, old fields, restored forest sites, and other natural areas. These plants spread by wind-borne seed and can form dense stands where they become established. Although their current geographic ranges overlap, there is little known overlap locally. Preliminary observations and anecdotal information have associated black swallowwort with low-pH inceptisols and pale swallowwort with high-pH alfisols. We conducted a common garden field experiment repeated over two years and a growth chamber germination experiment to assess whether seedling emergence and performance of these two swallowworts are affected by soil type and/or soil pH. Soil pH was artificially modified. In the common garden experiment, plants of both species grown on the Onondaga County soil type (an alfisol) produced a smaller root mass than on the Orange County soil (an inceptisol). Also, in one of two years more seedlings emerged and plants produced more follicles on the Onondaga County soil. Soil pH did not affect seedling emergence, although plants grown on low pH soils had a smaller root dry mass compared with plants grown on higher pH soils. Soil pH effects on stem length, stem dry mass, and follicle production were inconsistent among years. Species differences were also evident, with more pale swallowwort seedlings emerging than black swallowwort seedlings, whereas black swallowwort plants mostly had greater biomass and fecundity than pale swallowwort plants. In the growth chamber experiment, final percentage seed germination was greater on the Onondaga County soil than on the Orange County soil. The germination speed index as well as the probability to reach 50% germination for black swallowwort was higher on the Onondaga County soil than the Orange County soil, but only at lower pH levels. The germination speed index of pale swallowwort on the Orange County soil was higher than black swallowwort at low, but not high, pH levels. In contrast, black swallowwort had a higher probability of reaching 50% germination than pale swallowwort on the Orange County soil at higher pH levels. Contrary to our expectations, interactions between the two swallowwort species with their associated soil type or with their presumably preferred soil pH were weak, contradictory, or non-existent in both experiments. This suggests that these two species can colonize and grow well in a relatively wide range of soil pH conditions. From a management perspective, our results suggest that the current range and local overlap of these two species will continue to increase and that early detection rapid response (EDRR) programs should be established in susceptible regions not yet colonized by these two invasive vines.

Desiccation Periods of Urochloa brizantha ‘Piatã’ Before Sunflower Sowing

In no-till farming, which integrates crops and livestock, the crop that is sown is often noted for reduced productivity. The aim of this experiment was to study the influence of a desiccation period of Urochloa brizantha ‘Piatã’ on sunflower ‘Aguará 4’ development and productivity. The desiccation was carried out using glyphosate herbicide at a dose of 1.92 kg·ha-1. The treatments consisted of seven periods of U. brizantha desiccation (27, 22, 17, 10, 5, 3 and 0 days) prior to sunflower sowing (2010/11). The experimental design established randomized blocks with five replicates. The reduced period between cover desiccation and crop sowing impaired sunflower development (capitulum diameter, plant height, leaf area, and leaf and stem dry masses) over the course of the evaluations, especially for periods less than or equal to 10 days. Thus, our data suggest that sunflower producers should carry out the desiccation at least ten days prior to sowing.

English

&nbsp; &nbsp; The aim of this research was to evaluate the effect of three NaCl levels in nutrient solution on initial development and regrowth of nine&nbsp;Pennisetum&nbsp;spp. genotypes. The experiment was carried out in greenhouse conditions, using a completely randomized design, distributed in a 9 &times; 3 factorial arrangement [nine&nbsp;Pennisetum&nbsp;spp. genotypes (Cameroon, &lsquo;Mercker M&eacute;xico&rsquo;, Mott, &lsquo;Elefante B&rsquo;, Taiwan 2.37, Taiwan 227, Taiwan 2.114, IRI 381, and the interspecific hybrid HV 241) and three NaCl levels (0, 60 and 100 mM)], with four replications. Traits associated with plant growth at 30, 60 and 90 days after planting (DAP) were evaluated. The results indicate a significant effect (P&lt;0.05) of treatments on the vegetative traits in the initial stages development and regrowth, detaching decrease in tillers number, leaf and stem dry mass at 60 DAP; decrease in total mass (TM, leaf + stem) from 18.41 to 3.11 g, root mass (RM) from 6.52 to 0.38 g, and TM/RM ratio on the average of genotypes at 90 DAP. However, this reduction is lower for the Cameroon cultivar, showing to be a salt-tolerant cultivar. &nbsp; Key words:&nbsp;Electrical conductivity, interspecific hybrid,&nbsp;Pennisetum purpureum, saline stress. &nbsp;

Response of Eucalyptus (Eucalyptus urograndis) Plants at Different Doses of Glyphosate

The aim of this study was to evaluate the response of eucalyptus plants submitted to the application of glyphosate increasing rates. The doses 0.0, 3.6, 7.2, 18, 36, 72 and 180 g ha-1 of acid equivalent (ae) of glyphosate were applied on plants. At 7, 15, 22, 29, 36 and 42 days after application (DAA) was determined leaves relative chlorophyll content and quantum efficiency of photosystem II. At 22 and 42 DAA plant height and stem diameter were measured. At 42 DAA were determined the leaves dry mass, stem dry mass and foliar area. The height, diameter, leaves and stem dry masses and foliar area were converted to percentages, whereas the controls as 100%. These variables were fitted to the model described by Gauss equation. The data chlorophyll content and quantum efficiency of photosystem II were submitted to mean comparison, and when they differed, we performed the Tukey test at 5% probability. All the features presented here showed some hormetic effect promoted by reduced rates of glyphosate and the increments observed in these characteristics (when compared to control) ranged between 5.92 and 33.18% at 42 DAA. From average curve with height, diameter, leaves dry mass, stem dry mass and foliar area can be concluded that the increase averaged 12% on application of 16 g a.e. of glyphosate ha-1. For leaves chlorophyll content significant differences were observed only at 29 DAA, while for quantum efficiency of photosystem II significant differences were found only at 7 DAA.

Glomus mosseae associated bacteria and their influence on stimulation of mycorrhizal colonization, sporulation, and growth promotion in guava (Psidium guajava L.) seedlings

Arbuscular mycorrhiza (AM) associated bacteria were isolated from G. mosseae spores from different guava cropping systems in southern India. Seven bacteria were isolated and evaluated for their performance in stimulation of AM fungal colonization and spore proliferation in the roots of guava seedlings. Of the seven isolates, four G. mosseae associated bacterial isolates were selected based on their efficiency in stimulation of AM root colonization and spore production. They were identified as Pseudomonas putida (HM590706), Pseudomonas aeruginosa (HM590705), Brevibacillus sp. (HM590700), and Bacillus subtilis (HM590703) by polymerase chain reaction amplification of 16S rRNA. Ability of the four isolates to produce indole acetic acid and GA3 was analysed by high performance liquid chromatography and their P and Zn solubilization potential was assessed in vitro. Of these isolates, P. putida was selected for further studies for growth promotion attributes and ability to stimulate AM fungal colonization and spore proliferation in guava seedlings. Further evaluation indicated that application of G. mosseae along with P. putida produced significantly higher leaf, stem, shoot, and root dry masses, total biomass, and total leaf area than other treatments followed by G. mosseae and P. putida alone. Application of G. mosseae with P. putida significantly increased the contents of leaf chlorophyll, phenol, and total glomalin, acid and alkaline phosphatase activities, AM fungal colonization, and spore population in the rhizosphere of guava seedlings compared with either G. mosseae or P. putida alone. The results obtained show that combined inoculation of G. mosseae with its associated bacterium, P. putida, significantly improved AM fungal colonization and spore proliferation in addition to enhancement of the growth promotion in guava seedlings. These findings have a significant impact for the raising of guava seedling root stocks for commercial multiplication.

Interação entre manejo de plantas daninhas e adubação de cobertura no crescimento inicial de Eucalyptus grandis x E. urophylla

Diante da crescente necessidade de realização de boas técnicas de manejo florestal, foi conduzido um experimento de campo com o objetivo de avaliar a possível interação entre o manejo de plantas daninhas e a adubação de cobertura no desenvolvimento de plantas de eucalipto. Os tratamentos foram dispostos em blocos ao acaso, em esquema fatorial 5x3, constituído de cinco situações de controle das plantas daninhas (testemunha "no mato"; testemunha "limpa"; isoxaflutole; glyphosate; isoxaflutole+glyphosate - em pré e pós- emergência, respectivamente) e três doses de adubação de cobertura (0,5 x; x; e 1,5 x, em que x corresponde à dose recomendada para adubação da cultura). No tricentésimo dia após o plantio do eucalipto, a massa de matéria seca de folhas e a massa de matéria seca de caule foram as características mais sensíveis à interferência das plantas daninhas. Quando em convivência com essas plantas, as doses de adubação de cobertura não promoveram grandes alterações nas variáveis supracitadas, indicando a competição da cultura com as plantas daninhas pelo recurso oferecido. Já nos tratamentos que ficaram livres da convivência com as plantas daninhas por todo o período avaliado (testemunha "limpa") ou por grande parte dele (isoxaflutole + glyphosate), a maior dose de adubação de cobertura foi responsável pelos maiores valores de massa de matéria seca de folhas e caule.