Leaf Appearance Research Articles

Influence of Ascorbic Acid, Gibberellic Acid and Moringa oleifera Extract for Alleviating Salinity Stress by Enhancing Antioxidant Enzymatic Activity and Some Physiological Studies on Two Tomato Cultivars

This study aimed to explain the influence of Ascorbic acid (ASA), Gibberellic Acid (GA3) and Moringa oleifera Leaf Extract (MLE) for alleviating salinity stress by enhancing antioxidant enzymatic activity as follow: Super Oxide Dismutase (SOD), Catalase (CAT), Ascorbate Peroxidase (APX), and Glutathione Reductase (GR); nitrogenous components (proline and total amino acids) and some inorganic mineral nutrient elements in two tomato cultivars, cv. Cobra (resistant) and cv. Newton (sensitive) under salinity stress. Germination tomato seeds after soaking in ASA (0.75 mM); GA3 (0.05 mM) and MLE (5%), transplanted to plastic containers containing a mixture of sand/peat-moss (1:2). The tomato seeds for both cultivars watering using distilled water until the true leaf appearance then irrigated with NaCl salinity concentrations (0.0, 50, 100, 150, 200 mM) alternative with Hoagland nutrient solution. The experiment was carried out under greenhouse conditions with temperature 18oC±1oC (night) & 22oC±2°C (day) and relative humidity varied between 60 - 70%. Overall, the results indicated that the organic and inorganic components in tomato plants for both cultivars increased significantly in the present of ASA, GA3 and MLE under salinity stress respectively compared with control, there by reduces the harmful effects of salinity and increases resistance to salinity stress more than in the absent of ASA, GA3 and MLE. The data provide strong support to the hypothesis that exogenous application of ASA, GA3 and MLE reduced the harmful effects of NaCl concentrations and increases resistance to salinity in cv. Cobra and cv. Newton respectively. The evident recorded a significantly increased the antioxidant enzymes activity, proline, total amino acids and inorganic macro-mineral nutrient elements (N+3, P+3, K+, Ca+2 & Mg+2) and micro-nutrient mineral elements (Mn+2, Fe+3 & B+2) but after soaked the seeds in ASA, GA3 and MLE, these components tended to increase more compared with the control. Whereas, the tomato seeds soaked before planting in ASA, GA3 and MLE which leads to remarkably increasing more for all antioxidant enzymatic activity, nitrogenous components and inorganic mineral nutrient elements contents respectively. The relationship between compatible solutes (osmolytes) here are the strategies that plants have developed to tolerate salt stress and produced new strains adapted to salinity stress.

Ecophysiology of Andropogon grass subjected to different cutting frequencies and intensities

ABSTRACT The objective of this study was to evaluate the morphogenic and structural characteristics, and demographic patterns of Andropogon gayanus subjected to different cutting frequencies and intensities. A completely randomized design was adopted in a 3 × 2 factorial arrangement, corresponding to three cutting heights (50, 70, and 90 cm), and two cutting intensities (50 and 70%) with four repetitions, totaling 24 plots of 7.50 × 6.25 m. For morphogenesis, there was no interaction effect (P ≤ 0.05) of treatments on stem elongation rate, leaf appearance rate, and phyllochron rate. The highest rate of leaf elongation was observed at a height of 90 cm and cut intensity of 50%, with 1.69 and 0.84 cm tiller-1 d-1 of leaf elongation at heights of 50 and 70 cm, respectively. For forage production, there was no interaction (p > 0.05) between cutting intensity and cutting height. When the pasture was managed to a cutting height of 90 cm, there was a greater increase in dry leaf mass, stalk dry mass, dead forage dry mass, and total dry forage mass, which was 50.89% and 53.29% higher than pasture heights of 50 and 70 cm, respectively. There was no interaction between factors on demographic characteristics (p > 0.05). A cutting height of 70 cm with a cutting intensity of 50% is recommended when handling this grass.

Morphogenic and structural characteristics of Panicum cultivars during the establishment period in the Brazilian Northeast

This study aimed to evaluate the morphogenic and structural characteristics of six Panicum maximum cultivars during the establishment period. A completely randomized block design with four replicates and six treatments (Tamani, Mombaça, Massai, Tanzania, Aruana and Zuri cultivars) was used. Morphogenic (leaf appearance rate, leaf elongation rate e stem elongation rate), structural (final leaf length, tiller population density e number of leaves per tiller) and productive (forage mass, leaf blade mass, stem mass, senescent material mass and leaf:stem ratio) characteristics were evaluated. There was no difference (p > 0.05) between the cultivars in terms of the number of live leaves per tiller (2.95 leaves/tiller). Mombaça cultivar had (p < 0.05) higher canopy height (50.64 cm) compared with other cultivars. The highest (p < 0.05) tiller population density was observed in Tamani (235.90 tillers m-2) and Massai (201.60 tillers m-2) cultivars. Leaf lifespan (54.18 days), phyllochron (17.40 days/leaf) and leaf senescence rate (0.87 cm tiller day-1) were not different (p > 0.05) between cultivars. However, leaf appearance rate was higher (p < 0.05) in Tanzania (0.07 leaves tiller day-1) than in Aruana cultivar (0.05 leaves tiller day-1). Leaf blade mass was higher (p < 0.05) in Mombaça cultivar (1518.31 kg DM ha-1), whereas Massai showed higher (p < 0.05) leaf:stem ratio (9.25). Panicum cultivars Tamani, Tanzania and Massai establishment after 75 days, while the other cultivars establish at 105 days of sowing in the Brazilian Northeast.

Modeling Directional Brightness Temperature (DBT) over Crop Canopy with Effects of Intra-Row Heterogeneity

In order to improve the simulation accuracy of directional brightness temperature (DBT) and the retrieval accuracy of component temperature, a model considering intra-row heterogeneity to simulate the DBT angular distribution over crop canopy is proposed. At individual scale, the probability of leaf appearance is inversely proportional to the distance from central stem. On the basis of this assumption, we formulated leaf area volume density (LAVD) spatial distribution at three hierarchical scales: individual scale, row scale, and scene scale. The equations for directional gap probability and bi-directional gap probability were modified to adapt the heterogeneity of row structure. Afterwards, a straightforward radiative transfer model was built based on the gap probabilities. A set of simulated data was generated by the thermal radiosity-graphics combined model (TRGM) as the benchmark to evaluate both forward simulation and inversion ability of the new model; we compared the new DBT model against an existing model assuming row as homogeneous box. With the growth of crops, the canopy structure of row crops will gradually change from row structure to continuous canopy. The new DBT model agreed with the TRGM model much better than the homogeneous row model at the middle stage of the crop growth season. The new model and the homogeneous row model achieve similar accuracy at early stage and end stage. At the middle growth stage, the new model can improve the accuracy of soil temperature retrieval. We recommend the new DBT model as an option to improve the DBT simulation and component temperature retrieval for row-planted crop canopy. In particular, the more accurate component temperatures during the middle growth stage are fundamentally important in characterizing crop water status, evapotranspiration, and soil moisture, which are subsequently critical for predicting crop productivity.

Morphogenetic and structural characteristics of gamba grass subjected to nitrogen fertilization and different defoliation intensities

This study aimed to evaluate the morphogenetic, structural, and productive characteristics of Andropogon gayanus cv. ‘Planaltina’ subjected to different nitrogen fertilization levels and defoliation intensities. The experiment was done in a completely randomized design with a factorial arrangement of six nitrogen doses (0, 100, 200, 300, 400, and 500 kg N ha-1) and two defoliation intensities (15 and 30 cm). The production and structure data were grouped into rainy and dry periods, while morphogenesis data were compared only among different fertilization and defoliation intensities. The total dry forage biomass (TDFB), dry mass of leaves (DML), dry mass of stems (DMS), and dead forage dry mass (DFDM) were then determined. In addition to these variables, the morphogenetic characteristics of the plants and the numbers of tillers alive and dead were evaluated. There was no interaction (P>0.05) between the effects of nitrogen fertilization doses and the intensity of defoliation on TDFB, DML, DMS, and DFDM in both of the evaluated phases (rainy and dry). It was also observed that the rates of leaf elongation, leaf appearance, and leaf blade elongation increased with nitrogen fertilization. On the other hand, the culm elongation rate and phyllochron decreased as the dose applied increased. The defoliation intensity did not influence (P>0.05) the morphogenetic characteristics examined, nor did it affect the senescence rate of nitrogen in leaves and number of live leaves per tiller. The number of dead tillers increased linearly during the rainy period. Based on these results, to improve the efficiency of production of gamba grass it is recommended that it be managed with a defoliation intensity of 30 cm and nitrogen fertilization of 286.52 kg N ha-1 year-1.

Cytokinin-Regulated Physiological Parameters Affected by an Exogenous Dopamine Spray in Brussels Sprout (Brassica oleracea var. gemmifera)

Root restriction on the first stage of seedling growth decreases post-transplant biomass accumulation. Several studies in different vegetables and ornamental plants have suggested that this restriction would be overcome by means of a single 6-benzylaminopurine (BAP) spray. Based on this, the aim of this work was to evaluate the effects of both pre-transplant single BAP and dopamine (a cytokinin antagonist) sprays on the growth of Brussels sprout (Brassica oleracea var. gemmifera) plants grown in 200 plug cells tray-1, during different times of the annual cropping period. The responses of dopamine-sprayed plants were not completely similar to those previously reported. The different physiological processes studied in dopamine-sprayed plants through some growth parameters showed that dopamine affected mainly the rate of leaf appearance, which in turn positively affected both individual and total leaf area expansion. Dopamine-sprayed plants showed a higher leaf source, which allowed them to accumulate a higher biomass on both a fresh and dry weight basis during the initial vegetative growth stages. The effects of both BAP and dopamine were partially related to the environmental conditions during the experiments.

A pH-neutral electrolyzed oxidizing water significantly reduces microbial contamination of fresh spinach leaves

There are growing demands globally to use safe, efficacious and environmentally friendly sanitizers for post-harvest treatment of fresh produce to reduce or eliminate spoilage and foodborne pathogens. Here, we compared the efficacy of a pH-neutral electrolyzed oxidizing water (Ecas4 Anolyte; ECAS) with that of an approved peroxyacetic acid-based sanitizer (Ecolab Tsunami® 100) in reducing the total microbial load and inoculated Escherichia coli, Salmonella Enteritidis and Listeria innocua populations on post-harvest baby spinach leaves over 10 days. The impact of both sanitizers on the overall quality of the spinach leaves during storage was also assessed by shelf life and vitamin C content measurements. ECAS at 50 ppm and 85 ppm significantly reduced the bacterial load compared to tap water-treated or untreated (control) leaves, and at similar levels (approx. 10-fold reduction) to those achieved using 50 ppm of Ecolab Tsunami® 100. While there were no obvious deleterious effects of treatment with 50 ppm Tsunami® 100 or ECAS at 50 ppm and 85 ppm on plant leaf appearance, tap water-treated and untreated leaves showed some yellowing, bruising and sliming. Given its safety, efficacy and environmentally-friendly characteristics, ECAS could be a viable alternative to chemical-based sanitizers for post-harvest treatment of fresh produce.

Neutral electrolyzed oxidizing water is effective for pre-harvest decontamination of fresh produce

Pre-harvest sanitization of irrigation water has potential for reducing pathogen contamination of fresh produce. We compared the sanitizing effects of irrigation water containing neutral electrolyzed oxidizing water (EOW) or sodium hypochlorite (NaClO) on pre-harvest lettuce and baby spinach leaves artificially contaminated with a mixture of Escherichia coli, Salmonella Enteritidis and Listeria innocua (~1 × 108 colony-forming units/mL each resuspended in water containing 100 mg/L dissolved organic carbon, simulating a splash-back scenario from contaminated soil/manure). The microbial load and leaf quality were assessed over 7 days, and post-harvest shelf life evaluated for 10 days. Irrigation with water containing EOW or NaClO at 50 mg/L free chlorine significantly reduced the inoculated bacterial load by ≥ 1.5 log10, whereas tap water irrigation reduced the inoculated bacterial load by an average of 0.5 log10, when compared with untreated leaves. There were no visual effects of EOW or tap water irrigation on baby spinach or lettuce leaf surfaces pre- or post-harvest, whereas there were obvious negative effects of NaClO irrigation on leaf appearance for both plants, including severe necrotic zones and yellowing/browning of leaves. Therefore, EOW could serve as a viable alternative to chemical-based sanitizers for pre-harvest disinfection of minimally processed vegetables.

Deep learning-based detection of seedling development

BackgroundMonitoring the timing of seedling emergence and early development via high-throughput phenotyping with computer vision is a challenging topic of high interest in plant science. While most studies focus on the measurements of leaf area index or detection of specific events such as emergence, little attention has been put on the identification of kinetics of events of early seedling development on a seed to seed basis.ResultImaging systems screened the whole seedling growth process from the top view. Precise annotation of emergence out of the soil, cotyledon opening, and appearance of first leaf was conducted. This annotated data set served to train deep neural networks. Various strategies to incorporate in neural networks, the prior knowledge of the order of the developmental stages were investigated. Best results were obtained with a deep neural network followed with a long short term memory cell, which achieves more than 90% accuracy of correct detection.ConclusionThis work provides a full pipeline of image processing and machine learning to classify three stages of plant growth plus soil on the different accessions of two species of red clover and alfalfa but which could easily be extended to other crops and other stages of development.

Forage yield and morphogenesis of Megathyrsus maximus cultivars in Roraimas’s savannas

In order to evaluate the forage productivity and the morphogenic and structural characteristics of Megathyrsus maximus cultivars (Massai, Mombasa, Kenya, Tamani, Tanzania and Zuri), an experiment was conduct under natural environmental conditions in the savannahs of Roraima. The highest yields of green dry matter (GDM) were found with cultivars Zuri (4,317 kg ha-1) and Mombasa (4,115 kg ha-1), followed by Kenya (3,868 kg ha-1) and Tamani (3,755 kg ha-1), while Massai (3,341 kg ha-1) and Tanzania (3,225 kg ha-1) were the least productive. GDM yield was directly correlated with LAI and inversely proportional to tiller population density (TPD). The cultivars Tanzania and Kenya had the highest number of tiller leaves and leaf appearance rates, while the highest leaf expansion rates were estimate in cultivars Zuri and Kenya. The highest average length of tiller leaves was estimate in the cultivars Zuri and Mombasa. Leaf senescence rates were inversely proportional to TPD and the highest recorded with the cultivars Mombasa and Tamani. The six cultivars of M. maximus showed satisfactory forage yields and can be recommend for cultivation in the edaphoclimatic conditions of the of Roraima’s savannas. The determination of morphogenic and structural characteristics can contribute to the establishment of appropriate and specific management practices for each cultivar, aiming to optimize its productivity and reduce losses due to leaf senescence.

Climatic determinants of lowland rice development

AbstractAccurate modelling of plant development is the basis for any assessment of climate change impact on crop yields. Most rice models simulate development (phenology) based on temperature and photoperiod, but often the reliability of these models is reduced beyond the environment they were calibrated for. In our study, we tested the effects of relative air humidity and solar radiation on leaf appearance rate in greenhouse experiments and analysed data sets from field studies conducted in two extremely different rice‐growing environments in Nepal and Senegal. We also analysed environmental effects on duration to flowering of one popular IRRI material (IR64) for eight different sites covering the entire temperature range where rice is widely cultivated. Both low relative air humidity and low solar radiation significantly decreased leaf appearance rate. Mean air temperature explained 81% of the variation in duration to flowering across sites, which was furthermore significantly influenced by relative air humidity. Across all sites, a simple linear regression approach including mean air temperature and mean relative humidity in the calculation of duration to flowering led to a root mean square error (RMSE) of 10 days, which was slightly lower than the RMSE of 11 days achieved with an automated calibration tool for parameter optimization of cardinal temperatures and photoperiod sensitivity. Parameter optimization for individual sites led to a much smaller prediction error, but also to large differences in cardinal temperatures between sites, mainly lower optimum temperatures for the cooler sites. To increase the predictive power of phenological models outside their calibration range and especially in climate change scenarios, a more mechanistic modelling approach is needed. A starting point could be including relative air humidity and radiation in the simulation procedure of crop development, and presumably, a closer link between growth and development procedures could help to increase the robustness of phenological models.

Artropodofauna associada à cagaiteira (<i>Eugenia dysenterica</i> DC., Myrtaceae) em coleção de germoplasma ex situ em Goiás, Brasil

Eugenia dysenterica é uma espécie nativa do Cerrado com potencial para exploração econômica em função do seu uso na alimentação. No entanto, estudos são necessários para possibilitar a domesticação da espécie em plantio comercial. Atualmente, os frutos são obtidos a partir do extrativismo em áreas do Bioma Cerrado. A artropodofauna associada à Eugenia dysenterica é praticamente desconhecida. Assim, o presente estudo teve como objetivo avaliar a artropodofauna associada às folhas de Eugenia dysenterica. Avaliamos quinzenalmente a artropodofauna em plantas de Eugenia dysenterica na coleção de germoplasma ex situ da Escola de Agronomia, UFG. Para tanto, três ramos do terço médio foram amostrados em 16 plantas. Posteriormente, sete folhas/ramo foram selecionadas e analisadas sob microscópio estereoscópio. As cochonilhas foram os artrópodes mais abundantes em Eugenia dysenterica. A presença de folhas novas no mês de outubro coincidiu com a eclosão das ninfas da cochonilha Ceroplastes acutus e com o aparecimento de galhas foliares causadas por dípteros. A superfamília Coccoidea e a família Aleyrodidae foram classificadas como superabundantes e superfrequentes. Duas famílias de Thysanoptera foram encontradas: Thripidae e Phlaeothripidae. Com relação aos ácaros, as espécies fitófagas foram as mais abundantes, seguidas pelos ácaros predadores. As famílias Phytoseiidae e Tenuipalpidae foram as mais representativas nas amostras. Aleirodídeos, dípteros e a cochonilha Ceroplastes acutus estão associados à emissão de novas folhas da cagaiteira. Este é o primeiro relato de ocorrência de espécies de ácaros, tripes e da cochonilha Ceroplastes acutus em Eugenia dysenterica.

Differential growth response of green and variegated Ficus benjamina to exogenous cytokinin and shade

Abstract Benjamin fig (Ficus benjamina) is an important foliage and landscape crop species comprising green and variegated genotypes. The latter develop leaves with yellow and white leaf areas which may impose lower photosynthetic activity, thus resulting in slower growth than green genotypes. In many species, the exogenous supply of cytokinin to pot-grown plants promotes growth, mainly due to enhanced carbon fixation. In this work, we analyze the effect of spraying the cytokinin 6-benzylaminopurine (BAP) on growth and development of green and variegated Ficus benjamina genotypes. Two experiments were carried out in a greenhouse, in which either different number of BAP applications (Experiment 1) or different BAP concentrations (Experiment 2) were tested. In Experiment 2, plants were grown under three different light intensities. BAP sprays promoted rate of leaf appearance, leaf expansion and whole-plant growth, and the effect was stronger in variegated than in green plants. The relative growth rate promotion by BAP was associated with increased net assimilation rate rather than with variation in the leaf area ratio. On the other hand, shading had a more negative impact on growth and development of variegated plants than in green ones. Variegated plants, unlike green ones, developed leaves with high specific leaf area under the lowest light intensity. This led to high leaf area ratio values, which helped to maintain relative growth rates close to those of plants under moderate shading.

Assessing the role of ageing and light availability in leaf mortality in the mango tree

Mango is a tropical crop characterized by the heterogeneity in size and quality of its fruits at harvest. Source-sink relationships have been identified as a key factor on these traits. Consequently, it is of main importance to characterize foliage distribution of the mango tree over time to assess its ability to produce fruits. Mango tree is an evergreen tree and its leaves last for several years. While leaf appearance has been well characterized, leaf mortality has been poorly studied for now. The goal of this work was to characterize leaf mortality in the mango tree, and in particular the influence of age and light availability on this phenomenon. We digitized the 3D architecture of a 13-year-old mango tree with foliage information. Using this 3D mockup, we characterized the number of leaves per growth units at different depths in the structure and related growth units depth with their age. Using a model of light interception, we then estimated the amount of light intercepted by the different growth units of the tree and tested its influence on their number of leaves. Leaves were present up to the fifth growth unit from the axis end. Leaf mortality drastically increased with growth unit depth. For each level of depth, light environment had a significant influence on the number of leaves remaining on the growth unit. Leaves in unfavourable light conditions had a 2-time higher probability to fall compared to the leaves in the most favourable light conditions. The resulting leaf mortality probability will be included into a functional-structural plant model (FSPM) to simulate faithfully foliage distribution within the tree. Using this FSPM that simulates fruit growth, it will be possible to study the impact of the foliage distribution on the heterogeneity of fruit production and quality.

Acúmulo de forragem e características morfogênicas e estruturais de Megathyrsus maximus cv. Tamani sob intensidades de desfolhação

Abstract. The effects of defoliation intensity (10, 20, 30 and 40 cm above soil level) on green dry matter (GDM) yield and morphogenetic and structural characteristics of Megathyrsus maximus cv. Tamani were evaluated under field conditions in Roraima´s savannas. The effects of defoliation intensity on the GDM yields, leaf area index and leaf elongation rates was adjusted to the quadratic regression model and maximum values recorded with cutting at 28.2; 33.3 and 21.6 cm above soil level, respectively. The population tiller density, number of leaves tiller-1 and leaf appearance rate was inversely proportional to the defoliation intensity, while the opposite occurred for to average leaf length and leaf senescence rate. Apical meristem removing percentage was higher with increasing defoliation intensity. Regrowth vigor showed close negative correlation with defoliation intensity. Pastures of M. maximus cv. Tamani managed under 25 to 30 cm residue provides higher forage productivity, larger efficiency of forage utilization, greater tissue renewal and canopy structure more favorable to grazing.Keywords: Green dry matter, leaves, tillering, senescence

Examination of drought stress of two genotype maize hybrids with different fertilization

In the growing season of 2019, we analysed stress resulting from climatic factors on maize hybrids of different genotypes, with the aim of gaining a better understanding of the physiological responses of each hybrid, which might support the elaboration of a cost-effective irrigation plan.
 Our experiments were carried out at the Látókép Experimental Station of the University of Debrecen on calcareous chernozem soil in a small-plot long-term field trial with strip plot design. In the scope of the experiment, N-fertilizer doses were applied as basic fertilizer and top-dressing in addition to the non-fertilized (control) treatment. The 60 and 120 kg N/ha doses applied as basic fertilizers in the spring were followed by top-dressing in the V6 phenophase with a +30 kg N/ha dose. Measurements were carried out with the involvement of the Renfor early (FAO 320) and Fornad (FAO 420) late maturity hybrids-
 The stomata of the plants became more and more closed with the progression of the phenological phases; their stomatal conductance decreased. However, the hybrids responded differently to environmental stress. In the case of the Renfor hybrid, the highest conductance (669 mmol/m2-s) was recorded in the V12 phenophase with the 150 kg N/ha treatment. The stomata were more open due to the high turgor pressure, allowing plants to evaporate properly. The plant was in its worst physiological condition on 2nd July, at the time of the appearance of the last leaf in the case of the 120 kg N dose (224 mmol/m2-s). The value measured in the V12 phenophase has already shown that the stomata were closing due to the self-regulating system of the plant. It would have been necessary to dispense irrigation water following the measurement. This confirms the finding that water stress can be prevented by measuring stomatal conductance.
 In the case of the Fornad hybrid, stomatal conductance was the highest on 12th June (630 mmol/m2-s) in the 90 kg N/ha treatment and it was the lowest (183 mmol/m2-s) in VT (emergence of the last leaf) phenophase in the 60 kg N/ha treatment. In this case, the appropriate time for applying irrigation water would have been early July, when the conditions for the plants were still adequate. Subsequently, the stomata began to close due to a reduction of the water resources available to them.
 There was a significant correlation between soil moisture and stomatal conductance, as well as between temperature and stomatal conductance.

Thermal Time as a Parameter to Determine Optimal Defoliation Frequency of Perennial Ryegrass (Lolium perenne L.) and Pasture Brome (Bromus valdivianus Phil.)

The herbage mass and nutritional value of harvested forage are fundamental determinants of the production potential of pastoral systems. The objective of this study was to evaluate the growth dynamics and accumulated herbage mass expressed in dry matter (DM) of perennial ryegrass (Lolium perenne L.) and pasture brome (Bromus valdivianus Phil.) pastures, using thermal time (TT) as a defoliation criterion. Thirty plots (15 of L. perenne and 15 of B. valdivianus) were distributed in three field blocks and subjected to five defoliation frequencies (DF) determined by TT, expressed as the accumulated growing degree-days (AGDD; DF1 = 90, DF2 = 180, DF3 = 270, DF4 = 360, and DF5 = 450 AGDD) for one year (2016), at the Austral Agricultural Experimental Station of the Universidad Austral de Chile. Every three days, the total leaf length (TLL) was measured, and the leaf elongation rate (LER, cm L−1), leaf growth rate (LGR, cm L−1), leaf appearance rate (LAR, d L−1), phyllochron (AGDD L−1), and accumulated herbage mass per hectare (kg DM ha−1) were calculated. Defoliations were scheduled according to AGDD, and a sample was taken from each cutting to determine (dry matter ‘DM’, crude protein ‘CP’, neutral detergent fiber ‘NDF’, acid detergent fiber ‘ADF’, water-soluble carbohydrates ‘WSC’ and metabolizable energy ‘ME’). The pastures that were allocated to DF5 presented higher DM yields (12,600 kg DM ha−1 year−1), TLL (54.6 cm), and LER (0.63 cm d−1) compared to pastures with high DF (90 and 180 ADGG). B. valdivianus presented a lower phyllochron than L. perenne (74.4 vs 87.9 AGDD L−1, respectively). Concentrations of CP and ME decreased from the shortest DF (90 AGDD) to the largest DF (450 AGDD), dropping from 221 to 138 g kg−1 CP and from 2.6 to 2.4 Mcal kg−1 DM of ME. All variables were affected by the season (Ssn) (p < 0.001). The AGDD can be used as a defoliation criterion and a tool to balance yield with nutritive value according to the farmer’s needs.

Seed germination responses for varying KNO3 and NaNO3 stress in Trifolium alexandrinum. L cultivars

Abstract: Egyptian clover (Trifolium alexandrinum L.) is a forage legume considered to be of high nutritional values and palatable as cattle feed. Germination of the seed is affected by water availability and environmental stress prevailing there in. Three cultivars of T. alexandrinum viz. Bundel Berseem 1 (BB1), Bundel Berseem 2 (BB2), and Bundel Berseem 3 (BB3) were germinated under varying NaNO3 and KNO3, concentration range of 0 mM, 25 mM, 50 mM, 75 mM, 100 mM, and 150 mM. Our experiment revealed that up to 50 mM salt concentration, the tested cultivars responded in similar way but when the concentration started to reach 100 mM and 150 mM significant differences between the germination rates of the three cultivars and their respective TI were found for radicle emergence, plumule emergence and cotyledonary leaf appearance. BB1 was found to be more susceptible to the salt stress and the other tested cultivars BB2 and BB3 were comparatively tolerant to salinity.

Revegetación de suelo arenizado con Butia lallemantii en el suroeste del estado de Rio Grande do Sul, Brasil

Butia lallemantii is endemic from sandy soils in the state of Rio Grande do Sul (RS). Sandblasted soils stand out for fragile characteristics of low fertility, water availability and intense sand displacement. However, studies on planting techniques, use of fertilizers and alternative products that may favor the establishment of plants in these soils are lacking. Therefore, the objective of the study was to evaluate the survival and leaf appearance of the B. lallemantii plants established by the revegetation method in sandy soil, with the increase of mineral fertilizer and hydroretentor polymer, as well as monitoring the movement of sand particles. The plants were collected in Alegrete / RS, classified in stipe diameter and kept in substrate (soil, animal waste and rice husk, 1:1:1) for eight months. In field plantation, the doses of NPK and hydrogel were randomly placed between five graded rules in the soil, for periodic sand displacement readings. Survival, appearance of live leaves and sand displacement were evaluated monthly, with a randomized block design (100 seedlings/block). Results showed higher survival and presence of living leaves in the plants of block one, and average displacement of sand in the spring period. Therefore, plants of larger stipe diameter class show higher potential for survival and larger number of live leaves, in addition, sand displacement mainly happens during spring.

Morphogenetic and structural characteristics of Megathyrsus maximus cv. Centenário under defoliation intensities

The effect of defoliation intensities (20, 30, 40 and 50 cm above soil level) on green dry matter (GDM) yield and morphogenetic and structural characteristics of Megathyrsus maximus cv. Centenário were evaluated under field conditions in Roraima´s savannas. The effects of defoliation intensities on the GDM yields, leaf area index and leaf elongation rates was adjusted to the quadratic regression model and maximum values recorded with cutting at 35.8; 44.9 and 30.2 cm above soil level, respectively. The tiller population density, number of leaves tiller-1 and leaf appearance rate was inversely proportional to the intensity of defoliation, while the opposite occurred for to average leaf length and leaf senescence rate. Apical meristem removal percentage was higher with increasing defoliation intensity. Vigor regrowth showed close negative correlation with defoliation intensity level. Pastures of M. maximus cv. Centenário managed under 30 to 35 cm residue provides higher forage productivity, larger efficiency of forage utilization, greater tissue renewal and canopy structure more favorable to grazing.