Selectivity of the plant growth regulators trinexapac-ethyl and sulfometuron-methyl to cultivated species

The aerial spraying of plant ripeners on sugar cane (Saccharum officinarum L.) crops causes often the contamination of neighboring areas, which subsidizes formal complaints from the neighbors. These contaminations are due to spraying taking place during inadequate environmental conditions or from technical mistakes during the application. One of the most important causes of this contamination is the susceptibility of the species being cultivated surrounding sugar cane. In order to evaluate the effects of sugar cane plant ripeners trinexapac-ethyl and sulfometuron-methyl on peanuts, cotton, potato, coffee, citrus, beans, sunflower, cassava, rubber, soybean, and grapes, eleven experiments - one for each species - were carried out from May 2009 to Jan. 2010. The field experiment was set according to a completely random design with five treatments and four replications. Just before or during flowering, a single treatment of trinexapac-ethyl at 100 or 200 g ha-1 and sulfometuron-methyl at 7.5 or 15 g ha-1 was applied to plants. A control treatment (plants not treated) for each species was part of each experiment. Trinexapac, at the doses of 100 and 200 g ha-1, showed selectivity to peanuts, cotton, potato, coffee, citrus, sunflower, cassava, rubber, soybean, and grape. At the lowest dose (100 g ha-1), it was selective for bean. Sulfometuron, at the dose of 7.5 g ha-1, was selective for peanuts and, at the two studied doses (7.5 and 15 g ha-1), it was selective for coffee, citrus, cassava, and rubber.

Application of plant growth regulators at pre-harvest for fruit development of 'PÊRA' oranges

O trabalho objetivou avaliar os efeitos de auxinas e giberelinas, combinados e aplicados em pré-colheita no desenvolvimento e na taxa de queda natural de frutos de laranjeira 'Pêra'. Foram utilizadas árvores de laranjeira (Citrus sinensis Osbeck) cultivar Pêra com 5 anos de idade. Os tratamentos foram: GA3 + 2,4-D 12,5mg L-1 de cada; GA3 + 2,4-D 25mg L-1; GA3 + 2,4-D 37,5mg L-1; GA3 + NAA 12,5mg L-1; GA3 + NAA 25mg L-1; GA3 + NAA 37,5mg L-1; NAA + 2,4-D 12,5mg L-1; NAA + 2,4-D 25mg L-1; NAA + 2,4-D 37,5mg L-1 e testemunha (água). Durante todo o período experimental foram realizadas três aplicações a intervalos de 45 dias. As variáveis avaliadas foram: Taxa de queda natural dos frutos (%), comprimento (mm), diâmetro (mm) e massa fresca dos frutos (g). Nenhum dos tratamentos proporcionaram alterações no desenvolvimento final dos frutos, mas reduziram a taxa de queda natural em comparação com a testemunha em até 78,05%, inibindo a abscisão dos frutos em até três meses.

Glyphosate applied at low doses can stimulate plant growth

BACKGROUND: Glyphosate blocks the shikimic acid pathway, inhibiting the production of aromatic amino acids and several secondary compounds derived from these amino acids. Non-target plants can be exposed to low doses of glyphosate by herbicide drift of spray droplets and contact with treated weeds. Previous studies have reported that low doses of glyphosate stimulate growth, although these data are very limited. The objective of this study was to determine the effects of low glyphosate doses on growth of a range of plant species.RESULTS: Growth of maize, conventional soybean, Eucalyptus grandis Hill ex Maiden, Pinus caribea L. and Commelia benghalensis L. was enhanced by 1.8-36 g glyphosate ha(-1). Growth of glyphosate-resistant soybean was unaffected by any glyphosate dose from 1.8 to 720 g AE ha(-1). The optimum doses for growth stimulation were distinct for plant species and tissue evaluated. The greatest stimulation of growth was observed for C. benghalensis and P. caribea. Shikimic acid levels in tissues of glyphosate-treated soybean and maize were measured and found to be elevated at growth-stimulating doses.CONCLUSION: Subtoxic doses of glyphosate stimulate the growth of a range of plant species, as measured in several plant organs. This hormesis effect is likely to be related to the molecular target of glyphosate, since the effect was not seen in glyphosate-resistant plants, and shikimate levels were enhanced in plants with stimulated growth. (c) 2008 Society of Chemical Industry.

Effects of aluminum on plant growth and nutrient uptake in young physic nut plants

Aluminum (Al3+) toxicity is a major limiting factor to crop productivity in acid soils. The effects of aluminum on root and shoot growth of physic nut (Jatropha curcas L.) young plants and, the uptake and distribution of phosphorus, calcium, magnesium and aluminum in the roots and shoots were investigated in the present study. Plants were grown in 2.5L pots in a greenhouse. After fourteen days of adaptation to nutrient solution, plants were exposed to Al concentrations of 0, 370, 740, 1,100 and 1,480 mu mol L-1, corresponding to an active Al3+ solution of 13.3, 35.3, 90.0, 153.3 and 220.7 mu mol L-1, respectively. The dry matter partitioning between roots, stems and leaves, and the concentrations of P, Ca, Mg and Al in plant tissue, were measured after 75 days exposure to Al. The increasing level of Al3+ activity in solution progressively decreased the growth of the shoot and root of physic nut plants, and at the two highest active Al3+ levels, plants showed morphological abnormalities typical of the toxicity caused by this metal. Higher Al3+ activity reduced P concentrations in leaves and Ca and Mg in leaves and roots of physic nut, demonstrating the effect of Al on the uptake, transport and use of these nutrients by plants. The Al accumulated preferentially in the roots of physic nut, whereas only a small amount was transported to shoots.

Yield and Composition of the Essential Oil of Basil on Plant Growth Regulators Application

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Endophytic microorganisms from coffee tissues as plant growth promoters and biocontrol agents of coffee leaf rust

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Potential of the insect growth regulator, fluazuron, in the control of Rhipicephalus sanguineus nymphs (Latreille, 1806) (Acari: Ixodidae): Determination of the LD95 and LD50

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of plant growth regulators in the rooting of Pinus cuttings

O trabalho avaliou o enraizamento de estacas de Pinus caribaea var. hondurensis Morelet sob a ação de diferentes níveis de reguladores vegetais. As estacas foram feitas de brotações de 4 a 6cm de comprimento de mudas de P. caribaea var. hondurensis Morelet com corte bisel na base sendo as acículas basais eliminadas. A base das estacas foram submetidas aos tratamentos por 2 segundos com os seguintes tratamentos: 1- NAA 2000mg L-1; 2- NAA 4000mg L-1; 3- NAA 6000mg L-1; 4- NAA 2000mg L-1 + PBZ 100mg L-1; 5- NAA 4000mg L-1 + PBZ; 6- NAA 6000mg L-1 + PBZ; 7- IBA 2000mg L-1; 8- IBA 4000mg L-1; 9- IBA 6000mg L-1; 10-IBA 2000mg L-1 + PBZ; 11- IBA 4000mg L-1 + PBZ; 12- IBA 6000mg L-1 + PBZ e testemunha. Após os tratamentos as estacas foram plantadas em tubetes contendo 50% de palha de arroz carbonizada e 50% de vermiculita. As avaliações realizadas aos 60 dias após o plantio mostraram que estacas de P. caribaea tratadas com IBA levaram a maior porcentagem de estacas enraizadas que aquelas tratadas com NAA, sendo o mais efetivo, IBA a 4000mg L-1 em conjunto com 100mg L-1 de paclobutrazol.

Dimorphic cypsela germination and plant growth in Synedrella nodiflora (L.) Gaertn. (Asteraceae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Gibberellin and cytokinin effects on soybean growth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stem anatomy of Lycopersicon esculentum Mill. treated with different plant growth regulators

The effects of plant growth regulators GA(3) 50 mg. L-1, NAA 100 mg. L-1, CCC 1500 mg.L-1 and SADH 3000 mg.L-1 on stem anatomy of Lycopersicon esculentum Mill cv. Angela Gigante were studied. Two sets of experiments were carried out in greenhouse during two separte periods. Anatomical studies,revealed that growth promoters induced increased xylem thickness and increased the number of tracheary elements while the growth retardants decreased xylem thickness and induced fiber formation.

Effect of the insect growth regulator diflubenzuron on the predator Podisus nigrispinus (Heteroptera: Pentatomidae)

Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is a common natural predator of defoliating caterpillars in agricultural and forest systems. Insecticides acting as growth regulators of insect pests can indirectly affect their predators through consumption of contaminated prey. We examined the reproductive performance of P. nigrispinus fed on caterpillars of Anticarsia gemmatalis Hubner (Lepidoptera: Noctuidae) reared on soybean leaves exposed to the chitin synthesis inhibitor, diflubenzuron. Caterpillars of A. gemmatalis were fed for 12 h with treated soybean leaves and offered to adults of the predator P. nigrispinus over five consecutive days. The fertility of P. nigrispinus was reduced when feeding on diflubenzuron treated caterpillars, especially at the beginning of the reproductive period, but recovered 3 weeks later. The effects of diflubenzuron ingestion on the life table parameters of P. nigrispinus included an increase in the period taken to double the population size, and reductions in the intrinsic rate of population increase, generation duration, and net reproductive rate. Diflubenzuron therefore had an indirect negative effect on the reproduction and the population dynamics of the non-target predator P. nigrispinus. Clearly, its use in integrated pest management requires further evaluation.

Desiccation tolerance in seeds of Annona emarginata (Schldtl.) H. Rainer and action of plant growth regulators on germination

Annona emarginata (Schldtl.) H. Rainer (araticum-de-terra-fria) is used as a rootstock for several species of Annonaceae. It is suggested that these seeds should be sown immediately after extraction and, therefore, they could be intolerant to desiccation. There are several mechanisms involved with desiccation tolerance. Soluble sugars, for example, can accumulate and act as osmoprotectants for the membrane system during desiccation. The aim of this study is to assess desiccation tolerance in A. emarginata seeds. In addition, we examined the soluble sugars involved in desiccation tolerance. Finally, we determined the effect of gibberellic acid (GA4+7) and N-(phenylmethyl)-aminopurine in promoting the germination of seeds with different water contents. The experiment consisted of a randomized 4×5 factorial design (desiccation levels × concentration of growth regulators). After drying, seeds containing 31 (control), 19, 12 and 5% water were incubated in different concentrations of GA4+7 N-(phenylmethyl)-aminopurine (0, 250, 500, 750 and 1000 mg L-1) for 60 hours. The experiment was conducted in a germination chamber with alternating temperature and photoperiod of 20oC for 18 hours of darkness and 30oC for 6 hours of light. We analyzed electrical conductivity, germination rate, mean germination time, germination speed, frequency and uniformity of germination, percentage of dormant seeds and soluble sugar profile in intact seeds through high-performance liquid chromatography (HPLC). The data were subjected to analysis of variance, and the means were compared using Tukey's test at a threshold of p<0.05. The results showed that seeds of A. emarginata appears to be desiccation tolerant and, also, that sucrose increases when seed water content is reduced to values as low as 12%, exogenous GA4+7+N-(phenylmethyl)-aminopurine improves its germinability.

Phosphorus solubilizing and iaa production activities in plant growth promoting rhizobacteria from brazilian soils under sugarcane cultivation

Plant Growth Promoting Rhizobacteria (PGPR) has been used as a biofertilizer, bringing benefits to agriculture as Phosphorus Solubilizing Bacteria (PSB), indole-acetic acid (IAA) producers, and with other activites. The goal of this report was the identification of PGPR from soils under sugarcane crops by 16S rRNA sequencing, and the evaluation of the ability of phosphorus solubilizing and IAA production by biological assays. The isolates of this work were obtained from three areas of sugarcane crop from São Paulo State, Brazil. All isolates came from rhizosphere soil, and in a total of 60 isolates just 10 have showed high ability in phosphorus solubilizing. The selection of PSB may be done by phenotypic and/or genotypic characterization. Among ten isolates Enterobacter sp. (FJ890899), Entrobacter homaechei subsp. verschuerennii (FJ890998), Burkholderia sp. (FJ890895), and Labrys portucalensis (FJ890891) were able to IAA production. © 2006-2012 Asian Research Publishing Network (ARPN).

Action of the insect growth regulator fluazuron, the active ingredient of the acaricide Acatak®, in Rhipicephalus sanguineus nymphs (Latreille, 1806) (Acari: Ixodidae)

The present study evaluated the efficacy of fluazuron (active ingredient of the acaricide Acatak®) and its effects on Rhipicephalus sanguineus nymphs fed on rabbits exposed to different doses of this insect growth regulator. Three different doses of fluazuron (20 mg/kg, 40 mg/kg, and 80 mg/kg) were applied on the back of hosts (via pour on), while distilled water was applied to the Control group. On the first day of treatment with fluazuron (24 h), hosts were artificially infested with R. sanguineus nymphs. Once fully engorged, nymphs were removed and placed in identified Petri dishes in Biochemical Oxygen Demand (BOD) incubator for 7 days. After this period, engorged nymphs were processed for ultramorphological analysis. The results revealed alterations in the ultramorphology of many chitinous structures (smaller hypostome and chelicerae, less sclerotized scutum, fewer sensilla, fewer pores, absence of grooves, marginal and cervical strips and festoons in the body, even the anal plaque was damaged) that play essential roles for the survivor of ticks and that can compromise the total or partial development of nymphs and emergence of adults after periodic molting. Our findings confirm the efficacy of fluazuron, a more specific and less aggressive chemical to the environment and human health, and that does not induce resistance, in nymphs of the tick R. sanguineus in artificially infested rabbits treated with this arthropod growth regulator (AGR), indicating that it could be used in the control of this stage of the biological cycle of the tick R. sanguineus. © 2013 Wiley Periodicals, Inc.