L.D. Tuffi Santos

Growth analysis of Digitaria insularis

Digitaria insularis is a perennial species that reproduces from seeds and rhizomes, being difficult to control after its first flowering. In order to define integrated management techniques to this species, its growth was evaluated under greenhouse conditions, using a pot filled with 0.003 m3 of soil. Height, leaf area and dry matter evaluations were carried out between 14 and 112 days after emergence (DAE), every 7 days, at 15 different times. The experiment was arranged in a completely randomized block design, with four replications. The plant was fragmented into root+rhizome, stem and leaf. After drying at 70 oC, leaf area and dry matter were determined. Highest leaf area and dry matter values were verified at 98 and 105 DAE, respectively. Leaves showed higher participation in dry matter total accumulation followed by roots+rhizome, up to 105 DAE. Dry matter accumulation of Digitaria insularis slowed down up to 45 DAE, increasing due to rhizome formation. Relative growth rate values decreased along time due to higher photo assimilate accumulation. Digitaria insularis showed slow growth up to 45 DAE, increasing from 45 to 105 DAE, suggesting the possibility of good cultural control by crops that have fast initial growth and large leaf area, covering the soil rapidly.

Levantamento fitossociológico em pastagens degradadas sob condições de várzea

An assessment was carried out of two contingently flooded low land areas, located at the Experimental Farm of Leopoldina, owned by Empresa de Pesquisa Agropecuaria de Minas Gerais (EPAMIG)-Brazil-MG. Area 1 (3 ha) was cultivated with Angola-grass (Brachiaria mutica) pasture, not well managed and without any weed control for more than 10 years. Area 2 (5 ha) was occupied by Setaria grass (Setaria anceps cv. Kazungula) pasture which had been established in the previous rainy season, with forage being affected by the slow growth of the plants. For the phyto-sociological study, the inventory square method was applied through a square of 1,0 m2, randomly placed 19 times in area 1 and 41 times in area 2. The species found were identified and recorded. In the Angola-grass pasture, 27 species were identified, distributed in 11 families; in the Setaria grass pasture, 34 species were identified, distributed in 13 families. The most representative families in number of species were: Poaceae (11); Asteraceae (6); Papilionoideae (5); Malvaceae and Euphorbiaceae (4). The most frequent species were: Cynodon dactylon, Sida rhombifolia, Cyperus esculentus, Mimosa pudica, Senna occidentalis, Setaria anceps cv. Kazungula and Paspalum urvillei. In general, both areas were infested with weeds, including toxic, spinescent and rather unpalatable plants, reducing the animal support capacity of the pastures and preventing adequate utilization of the areas by the cattle.

Efeito do glyphosate sobre a morfoanatomia das folhas e do caule de Commelina diffusa e C. benghalensis

The purpose of this work was to evaluate the effect of glyphosate in the anatomical and morphologic structures of leaves and stems of two species of Commelina, and to investigate the involvement of the starch reservation in larger tolerance to glyphosate of C. diffusa in relation to C. benghalensis. From 10 pots for each species, 9 were applied with 1440 g ha-1 of glyphosate and one was used as check. Fragments of stems and leaves were collected and fixed at time zero (before the application of glyphosate), 15, 30, and 50 days after the application (DAA). The histological slides were obtained according to the usual methodology, with emphasis to the application of the lugol reagent to check starch. Grades from 1 to 5 were given according to the growing intensity of the reaction. In leaves, the epidermal cells and the vascular tissues are just a little bit affected. How seer the mesophyll is completely disorganized, resulting in cell death. Injures are more obvious stems and leaves of C. benghalensis. Morphologically, clorotic regions and deceased spots all over the leaf surface lead to leaf fall after 15° DAA in C. benghalensis. In C. diffusa, the leaf abscission is delayed, despite the injuries are almost the same. Both species presented higher quantities of starch in the node region than the internode. C. benghalensis has few and small starch grains, compared to many and big grains in C. diffusa. In response to glyphosate application , there was a variation in the number of starch grains in the stem to the time after the application. C. diffusa will always have larger possibilities to recover after glyphosate application because of its larger reservation of starch.

Crescimento do eucalipto sob efeito da deriva de glyphosate

The possible negative effects of glyphosate drift on eucalyptus plants throughout their cycle are one of the many issues faced in forestry. Thus, 120 plants presenting variable degrees of intoxication were randomly selected at day 30 after application of 1.440 g ha-1 glyphosate, aiming to control the weeds in an area of Eucalyptus grandis x E. urophylla (urograndis hybrid) at 120 days after transplantation. The treatments were constituted by the following intervals: 0-5; 6-10; 11-20; 21-30; 31-40 and 41-50% of plant intoxication with 0-5% being considered the control treatment. Height and diameter were evaluated after plant selection, up to 360 days after application (DAA) and the intoxication symptoms were evaluated during this period. At 360 DAA wood volume (m3) was estimated and height and diameter gains were calculated. Plants with initial intoxication above 31% presented lesser height and diameter at 270 DAA Height gains were lesser in plants with initial intoxication above 41%. Lesser diameter was observed from 21% intoxication, with the plants with 41-50% intoxication displaying the lesser values for diameter growth. The damage caused by the drift affected wood production at 270 DAA, with the plants with 21-30, 31-40 and 41-50% intoxication being the ones presenting reduced wood volume of 18, 26 and 48%, respectively, in relation to the control treatment. The results confirmed the damage caused by glyphosate drift to eucalyptus plants. However, new evaluations should be performed to monitor the growth and development of the plants until the end of their cycle so as to elucidate the drift effects on the final production.

Intoxicação de eucalipto submetido à deriva simulada de diferentes herbicidas

Besides glyphosate, which is widely utilized, other herbicides such as triclopyr and carfentrazone-ethyl, have a potential use in eucalypt plantations. However, the non-selective nature of these herbicides may lead to plant intoxication due to leaf contact during application. This work aims to evaluate the effects of some herbicides drift on Eucalyptus urophylla, simulated by applying the following subdoses: 0, 43.2, 86.4 and 172.8 g ha-1 of glyphosate; 14.4, 28.8 and 57.6 g ha-1 of triclopyr; 0.84, 1.68 and 3.36 g ha-1 of carfentrazone-ethyl; and the following mixtures: 43.2 g ha-1 of glyphosate + 14.4 g ha-1 of triclopyr; 86.4 g ha-1 of glyphosate + 28.6 g ha1 of triclopyr; 43.2 g ha-1 of glyphosate + 1.68 g ha-1 of carfentrazone-ethyl; and 86.4 g ha1 of glyphosate + 3.36 g ha-1 of carfentrazone-ethyl. The seedlings, about 50 cm high, were applied the herbicides in such a way that their superior third was not reached 45 days after transference. Glyphosate drift caused the most damage to the plant, followed by carfentrazone-ethyl and triclopyr, respectively. Eucalypt plants exposed to a subdose of 172.8 g ha-1 of glyphosate and to glyphosate + carfentrazone-ethyl mixtures, had the highest percentage of intoxication and the lowest growth during the evaluation periods. The plants exposed to triclopyr drift presenting 56.25 and 15.10% of intoxication at 15 and 30 days after application, respectively, were recovered, indicating a lesser triclopyr drift risk, compared with the other herbicides and mixtures studied.

Movimento do herbicida imazapyr no perfil de solos tropicais

The experiment was carried out in columns filled with three different tropical soils, (very clayey soil, sand loam soil and sand clay loam soil) to evaluate ascending and descending movement of imazapyr. After applying 1 kg ha-1 of the herbicide on each column surface, columns were submitted to three conditions: 1) 14 min/35 min rainfall simulation followed by 48 hours rest; 2) 14 min/35 min rainfall simulation followed by 30 days rest; and column inversion after applying imazapyr on the surface, under sub irrigation during 20 days, followed by 10 days rest. After this stage, columns were sectioned every 5 cm of depth. Sorghum bicolor was sowed as bioindicator on each portion and after 20 days of sowing, dry matter of the above ground tissue was evaluated. The higher herbicide descending movement observed was in sandy loam soil, followed by sandy clay loam and clay soil. The ascending movement of this herbicide occurred together with water, causing herbicide distribution in all the column area in sandy clay loam and sandy loam soils, while clay soil showed a smaller ascending movement. Imazapyr presents high mobility on all three soils, together with water movement in the soil profile, both in ascending and descending motions. Such high mobility may cause ground water contamination, and also cycles of permanence of this product in the superficial layers of the soil, depending on humidity availability.

Danos visuais e anatômicos causados pelo glyphosate em folhas de Eucalyptus grandis

Symptomatology is one of the most important criteria used to determine the damages caused by biotic and abiotic factors in plants. However, microscopic aspects are needed to elucidate intoxication mechanisms and early injury diagnosis. This work aimed to evaluate the effects of four commercial glyphosate formulations under simulated spray drift (Scout®, Roundup NA®, Roundup transorb® and Zapp QI®) on the morphoanatomy of six Eucalyptus grandis clones (UFV01, UFV02, UFV03, UFV04, UFV05 and UFV06). Following glyphosate application (129.6 g ha-1), symptoms were monitored daily and, at 14 days, leaf samples from the regions without visible symptoms were collected for microscopic analysis. All clones presented chlorosis and necrosis at the fourth day of glyphosate exposure, regardless of the formulation used. The UFV04 clone did not show any anatomical damage. The other clones suffered plasmolysis, cellular collapse, hypertrophy and formation of cicatrisation tissue. However, changes in leaf blade thickness were not observed. Plants exposed to Roundup transorb® presented the greatest visible intoxication percentage. Anatomically, plants exposed to Roundup NA® showed a higher number of damages. Analysis considering both anatomic and visible damages showed that UFV06 clone was the most susceptible to the formulations tested. The results confirmed the diagnostic and prognostic value of visual and anatomical analysis, respectively, and showed that these parameters are essential to evaluate clone susceptibility and the the phytotoxic potential of herbicides.

Características da epiderme foliar de eucalipto e seu envolvimento com a tolerância ao glyphosate

In reforestation areas, glyphosate drift causes injuries in Eucalyptus plants. Preliminary research work and field observations point out a differential tolerance to glyphosate among cultivated genotypes. Within this context, the anatomical structures of leaf epidermis of five species of eucalypt, correlated to glyphosate tolerance under simulated drift were studied. The factorial design was used, with the species (Eucalyptus urophylla, E. grandis, E. pellita, E. resinifera and E. saligna) and 05 subdoses (0, 43.2, 86.4, 172.8 and 345.6 g e.a. ha-1 of glyphosate) simulating a drift. Immediately before herbicide application, totally expanded leaves were collected for anatomical analysis of epidermal surface through dissociation methodology. Among the studied species, E. resinifera was found to be the most tolerant to glyphosate drift, presenting the lowest values for intoxication percentage 45 days post-application, with no difference among the others. The five species present glabrous, amphistomatic leaves with anomocytic type stomata and prominent cuticle. Despite being present on both faces, stomata are rare on the adaxial face, exhibiting low index and stomatic density. The highest values for TUFFI SANTOS, L.D. et al. Planta Daninha, Vicosa-MG, v. 24, n. 3, p. 513-520, 2006 514 stomatic index were observed on E. resinifera, while E. saligna presented the highest stomatic density. Subepidermic cavities evidenced on the surface by the overlying cells are present in the five species, with the highest density on E. pellita. A high correlation was found between intoxication percentage and number of epidermic cells on the adaxial surface, indicating the involvement of this characteristic with differential tolerance to the herbicide. Studies on absorption, translocation and metabolism of glyphosate in eucalypt must be undertaken to elucidate the differential behaviour of genotypes concerning glyphosate drift.Em areas de reflorestamento, a deriva do glyphosate causa injurias nas plantas de eucalipto. Trabalhos preliminares de pesquisa e observacoes de campo apontam para uma tolerância diferencial ao glyphosate entre os genotipos cultivados. Nesse contexto, objetivou-se estudar as estruturas anatomicas da epiderme foliar de cinco especies de eucalipto, correlacionando com a tolerância ao glyphosate em deriva simulada. Utilizou-se o esquema fatorial, sendo cinco especies (Eucalyptus urophylla, E. grandis, E. pellita, E. resinifera e E. saligna) e cinco subdoses (0; 43,2; 86,4; 172,8 e 345,6 g e.a. ha-1 de glyphosate), simulando uma deriva. Imediatamente antes da aplicacao do herbicida, coletaram-se folhas, totalmente expandidas, para analise anatomica da superficie epidermica segundo metodologia de dissociacao. Entre as especies estudadas, E. resinifera mostrou-se mais tolerante a deriva de glyphosate, apresentando os menores valores de porcentagem de intoxicacao aos 45 dias apos aplicacao, nao sendo encontrada diferenca entre as demais especies. As cinco especies apresentam folhas glabras, anfiestomaticas, com estomatos do tipo anomocitico e cuticula proeminente. Apesar de presentes em ambas as faces, os estomatos sao raros na face adaxial, apresentando baixo indice e densidade estomatica. Os maiores valores para indice estomatico foram observados em E. resinifera, enquanto E. saligna apresentou a maior densidade estomatica. Cavidades subepidermicas evidenciadas na superficie pelas celulas de cobertura estao presentes nas cinco especies, com maior densidade em E. pellita. Houve alta correlacao entre a porcentagem de intoxicacao por glyphosate e o numero de celulas epidermicas da superficie adaxial, indicando envolvimento desta caracteristica com a tolerância diferencial ao herbicida. Estudos sobre absorcao, translocacao e metabolismo do glyphosate em eucalipto devem ser realizados para elucidar o comportamento diferencial de genotipos diante da deriva de glyphosate.

Sorção do imazapyr em solos com diferentes texturas

Knowledge about herbicide behavior in the environment, especially in soil, allows predicting possible impacts caused by its use in agricultural systems. An experiment using Sorghum bicolor as a bio-indicator was carried out to evaluate imazapyr sorption in soil. Sorption was evaluated in washed sand and in soils of 3 different textures: very clayed, sandy clayed loam and sandy loam, respectively from Sete Lagoas, Joao Pinheiro and Rio Casca - Minas Gerais. The value of I50, which inhibits 50% of dry biomass accumulation of the test-plant, and sorption relation (SR = I50 soil - I50 sand/I50 sand) were determined. I50 values observed were 29.41, 10.20 and 7.33 mg kg-1 and SR values were 9.77, 2.73 and 1.68, respectively for very clayed, sandy clayed loam and sandy loam soils. The order of substrate sorption presented by imazapyr was very clayed > sandy clay loam > sandy loam > washed sand. In sandy soil and soil with low organic matter content, low imazapyr sorption predisposes the product to leaching, and it may contaminate the underground water.

Exsudato radicular de imazapyr aplicado sobre mudas de diferentes clones de eucalipto

In the renewal of eucalypt crops, after tree harvesting, it is necessary to eliminate the sprouts that interfere with the initial development of the new stands. This elimination can be made by applying some herbicides on the shoots. One of the herbicides used is imazapyr, which, according to preliminary works carried out at the Universidade Federal de Vicosa, is capable to exsudate through the root system. In this case, questions arise concerning the exsudate ability to interfere in the development of the new plants; whether this capacity is the same for all eucalypt clones; at which imazapyr dose this problem is more serious; and the intensity at which the herbicide exsudate will interfere with the growth of the new stands. This work evaluated whether the root systems of different clones present different imazapyr exsudation intensities and the effect of the applied doses on herbicide concentration in the soil profile and its influence in subsequent crops. A dry mater decrease was verified in the sorghum plants when compared to the checks, in both 0-15 and 15-30 cm soil layers, evidencing imazapyr exsudation through the root system of the four clones analyzed. The toxic effect of the exsudates was observed in the entire soil volume reached by the eucalypt root system. Increased imazapyr doses increased the toxicity symptoms in sorghum imazapyr exsudation by all eucalypt clones was similar at the two depths analyzed.