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.

Eucalyptus ESTs associated with resistance to herbicide inhibitors of aromatic and branched-chain amino acid synthesis

Herbicides inhibit enzymatic systems of plants. Acetolactate synthase (ALS, EC = 4.1.3.18) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, EC 2.5.1.19) are key enzymes for herbicide action. Hundreds of compounds inhibit ALS. This enzyme is highly variable, enabling the selective control of weeds in a number of crops. Glyphosate, the only commercial herbicide inhibiting EPSPS is widely used for non-selective control of weeds in many crops. Recently, transgenic crops resistant to glyphosate were developed and have been used by farmers. The aim of this study was the data mining of eucalypt expressed sequence tags (ESTs) in the FORESTs Genome Project database (https://forests.esalq.usp.br) related to these enzymes. Representative amino acid sequences from the NCBI database associated with ALS and EPSPS were blasted with ESTs from the FORESTs database using the tBLASTx option of the blast tool. The best blasting reads and clusters from FORESTs, represented as nucleotide sequences, were blasted back with the NCBI database to evaluate the level of similarity with available sequences from different species. One and seven clusters were identified as showing high similarity with EPSPS and ALS sequences from the literature, respectively. The alignment of EPSPS sequences allowed the identification of conserved regions that can be used to design specific primers for additional sequencings

Eucalyptus ESTs corresponding to the enzyme glutamine synthetase and the protein D1, sites of action of herbicides that cause oxidative stress

This work was aimed at locating Eucalyptus ESTs corresponding to the GS enzyme (Glutamine Synthetase, EC = 6.3.1.2) and to the D1 protein, which are directly related to resistance to herbicides that promote oxidative stress. Glutamine Synthetase corresponds to the site of action of the herbicide glufosinate. Herbicides that belong to groups such as ureas, uracils, triazines and triazinones act on the D1-Qb complex (receptor of electrons from the Photosystem II) by inactivating it. The clusters EGEQRT3302E01.g, EGEQRT3001F12.b; EGEZLV1203B04.g; EGBGFB1211H06.g and EGEZLV1205F09.g enclosed complete sequences (with 356 amino acids) of the Glutamine Synthetase enzyme. The cluster EGEQSL1054G06.g is a consensus of four reads and enclosed a complete sequence of D1 Protein (with 353 amino acids). The comparison of the sequences of Protein D1 from different species showed that the substitutions of serine (S) by glycine (G) or serine (S) by threonine (T) at the position 264 could produce plants resistant to herbicides that act on electron flow on Photosystem II. The sequence of amino acids corresponding to the cluster EGEQSL1054G06.g had a serine in position 264 indicating sensitivity of the Eucalyptus plants to herbicides that act on this site

Eucalyptus ESTs corresponding to the protoporphyrinogen IX oxidase enzyme related to the synthesis of heme, chlorophyll, and to the action of herbicides

This work was aimed at locating Eucalyptus ESTs corresponding to the PROTOX or PPO enzyme (Protoporphyrinogen IX oxidase, E.C. 1.3.3.4) directly related to resistance to herbicides that promote oxidative stress, changing the functionality of this enzyme. PROTOX, which is the site of action of diphenyl-ether (oxyfluorfen, lactofen, fomesafen), oxadiazole (oxadiazon and oxadiargyl), and aryl triazolinone (sulfentrazone and carfentrazone) herbicides, acts on the synthesis route of porphyrins which is associated with the production of chlorophyll a, catalases, and peroxidases. One cluster and one single read were located, with e-values better than e-70, associated to PROTOX. The alignment results between amino acid sequences indicated that this enzyme is adequately represented in the ESTs database of the FORESTs project

Eucalyptus ESTs related to genes for oxidative stress.

Oxidative stress generating active oxygen species has been proved to be one of the underlying agents causing tissue injury after the exposure of Eucalyptus (Eucalyptus spp.) plants to a wide variety of stress conditions. The objective of this study was to perform data mining to identify favorable genes and alleles associated with the enzyme systems superoxide dismutase, catalase, peroxidases, and glutathione S-transferase that are related to tolerance for environmental stresses and damage caused by pests, diseases, herbicides, and by weeds themselves. This was undertaken by using the eucalyptus expressed-sequence database (https//forests.esalq.usp.br). The alignment results between amino acid and nucleotide sequences indicated that the studied enzymes were adequately represented in the ESTs database of the FORESTs project.

Boron rates for triticale and wheat crops

No reports are registered on responses to boron fertilization nutrient deficiency and toxicity in triticale crops. The aim of this study was to evaluate triticale response to different rates of boron in comparison to wheat in an hapludox with initial boron level at 0.08 mg dm-3 4 FONT FACE=Symbol>´ /FONT> 4 factorial design trial completely randomized blocks design (n = 4). Boron rates were 0; 0.62; 1.24 and 1.86 mg dm-3; triticale cultivars were IAC 3, BR 4 and BR 53 and IAPAR 38 wheat crop was used for comparison. The wheat (IAPAR 38) crop presented the highest boron absorption level of all. Among triticale cultivars, the most responsive was IAC 53, presenting similar characteristics to wheat, followed by BR 4; these two crops are considered tolerant to higher boron rates in soil. Regarding to BR 53, no absorption effect was observed, and the cultivars was sensitive to boron toxicity. Absorption responses differed for each genotype. That makes it possible to choose and use the best-adapted plants to soils with different boron rates.

No Brasil não existem registros de respostas de adubação com boro para a cultura do triticale, sendo a ação deste nutriente uma incógnita, tanto em relação a deficiência quanto a toxidez, causas que levam a redução de produtividade. O objetivo deste trabalho foi avaliar a resposta do triticale a diferentes níveis de boro em comparação com o trigo (Triticum aestivum). Utilizou-se um Latossolo Vermelho distrófico com teor inicial de boro de 0,08 mg dm-3. O delineamento foi um fatorial 4 FONT FACE=Symbol>´ /FONT> 4, distribuído em blocos casualizados, com quatro repetições, quatro níveis de boro: 0; 0,62; 1,24 e 1,86 mg dm-3 de B e três cultivares de triticale, IAC 3, BR 4 e BR 53, mais um cultivar de trigo, IAPAR 38, para comparação. Cada cultivar respondeu de forma diferente com relação às variáveis estudadas em função da aplicação de diferentes níveis de boro. O trigo (IAPAR 38) apresenta maior eficiência na absorção de boro. A cultivar de triticale mais responsiva quanto à absorção foi a IAC 3, que apresentou característica semelhante ao trigo, seguida da cultivar BR 4, demonstrando serem cultivares tolerantes a maiores níveis de boro no solo. Para a BR 53, não ocorreu efeito para absorção, com a cultivar apresentando sensibilidade à toxidez de boro. A eficiência de absorção é diferenciada para cada genótipo possibilitando a escolha e utilização de plantas que possuam maior adaptação ao meio.

Boron rates for triticale and wheat crops

No reports are registered on responses to boron fertilization nutrient deficiency and toxicity in triticale crops. The aim of this study was to evaluate triticale response to different rates of boron in comparison to wheat in an hapludox with initial boron level at 0.08 mg dm-3 4 FONT FACE=Symbol>´ /FONT> 4 factorial design trial completely randomized blocks design (n = 4). Boron rates were 0; 0.62; 1.24 and 1.86 mg dm-3; triticale cultivars were IAC 3, BR 4 and BR 53 and IAPAR 38 wheat crop was used for comparison. The wheat (IAPAR 38) crop presented the highest boron absorption level of all. Among triticale cultivars, the most responsive was IAC 53, presenting similar characteristics to wheat, followed by BR 4; these two crops are considered tolerant to higher boron rates in soil. Regarding to BR 53, no absorption effect was observed, and the cultivars was sensitive to boron toxicity. Absorption responses differed for each genotype. That makes it possible to choose and use the best-adapted plants to soils with different boron rates.

No Brasil não existem registros de respostas de adubação com boro para a cultura do triticale, sendo a ação deste nutriente uma incógnita, tanto em relação a deficiência quanto a toxidez, causas que levam a redução de produtividade. O objetivo deste trabalho foi avaliar a resposta do triticale a diferentes níveis de boro em comparação com o trigo (Triticum aestivum). Utilizou-se um Latossolo Vermelho distrófico com teor inicial de boro de 0,08 mg dm-3. O delineamento foi um fatorial 4 FONT FACE=Symbol>´ /FONT> 4, distribuído em blocos casualizados, com quatro repetições, quatro níveis de boro: 0; 0,62; 1,24 e 1,86 mg dm-3 de B e três cultivares de triticale, IAC 3, BR 4 e BR 53, mais um cultivar de trigo, IAPAR 38, para comparação. Cada cultivar respondeu de forma diferente com relação às variáveis estudadas em função da aplicação de diferentes níveis de boro. O trigo (IAPAR 38) apresenta maior eficiência na absorção de boro. A cultivar de triticale mais responsiva quanto à absorção foi a IAC 3, que apresentou característica semelhante ao trigo, seguida da cultivar BR 4, demonstrando serem cultivares tolerantes a maiores níveis de boro no solo. Para a BR 53, não ocorreu efeito para absorção, com a cultivar apresentando sensibilidade à toxidez de boro. A eficiência de absorção é diferenciada para cada genótipo possibilitando a escolha e utilização de plantas que possuam maior adaptação ao meio.

Sementes de feijão submetidas a ciclos e períodos de hidratação-secagem

The hydration-dehydration technique may cause physiological and biochemical modifications in bean seeds, affecting their physiological quality. Seeds cv. Carioca were submitted to hydration-dehydration treatments for 6, 12 and 24 hours with three hydration cycles. The objective was evaluate the effects caused by hydration-dehydration treatments on bean seed physiological quality. The experimental design was completely randomized, with four replications, 3 x 3 factorial, with an absolute control. At the first germination count the hydration-dehydration duration and cycle treatments were superior in relation to the control. Regarding the protein fractions the treated seed globulin and prolamin concentrations increased significantly as compared to the controls. The leached cations (Ca, Mg and K) in the seed imbibition solution had a similar behaviour in relation to the electrolytic leakage.

A técnica de hidratação-secagem pode ocasionar alterações fisiológicas e bioquímicas em sementes de feijão e afetar sua qualidade fisiológica. Sementes do cultivar Carioca foram submetidas a tratamentos de hidratação-secagem por 6, 12 e 24 horas com três ciclos de hidratação, com o objetivo de avaliar os efeitos causados por períodos e ciclos de hidratação-secagem na qualidade fisiológica das sementes. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições, analisado estatisticamente em esquema fatorial 3 x 3 com uma testemunha absoluta. Para a primeira contagem da germinação, os tratamentos de períodos combinados com ciclos de hidratação-secagem, apresentaram superioridade em relação ao tratamento testemunha. Na avaliação de grupos de proteínas, as concentrações de globulinas e prolaminas nas sementes submetidas aos tratamentos, foram significativamene superiores a testemunha. Os cátions (Ca, Mg e K) lixiviados para solução de embebição das sementes tiveram comportamento semelhante à condutividade elétrica das mesmas.

Sementes de feijão submetidas a ciclos e períodos de hidratação-secagem

The hydration-dehydration technique may cause physiological and biochemical modifications in bean seeds, affecting their physiological quality. Seeds cv. Carioca were submitted to hydration-dehydration treatments for 6, 12 and 24 hours with three hydration cycles. The objective was evaluate the effects caused by hydration-dehydration treatments on bean seed physiological quality. The experimental design was completely randomized, with four replications, 3 x 3 factorial, with an absolute control. At the first germination count the hydration-dehydration duration and cycle treatments were superior in relation to the control. Regarding the protein fractions the treated seed globulin and prolamin concentrations increased significantly as compared to the controls. The leached cations (Ca, Mg and K) in the seed imbibition solution had a similar behaviour in relation to the electrolytic leakage.

A técnica de hidratação-secagem pode ocasionar alterações fisiológicas e bioquímicas em sementes de feijão e afetar sua qualidade fisiológica. Sementes do cultivar Carioca foram submetidas a tratamentos de hidratação-secagem por 6, 12 e 24 horas com três ciclos de hidratação, com o objetivo de avaliar os efeitos causados por períodos e ciclos de hidratação-secagem na qualidade fisiológica das sementes. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições, analisado estatisticamente em esquema fatorial 3 x 3 com uma testemunha absoluta. Para a primeira contagem da germinação, os tratamentos de períodos combinados com ciclos de hidratação-secagem, apresentaram superioridade em relação ao tratamento testemunha. Na avaliação de grupos de proteínas, as concentrações de globulinas e prolaminas nas sementes submetidas aos tratamentos, foram significativamene superiores a testemunha. Os cátions (Ca, Mg e K) lixiviados para solução de embebição das sementes tiveram comportamento semelhante à condutividade elétrica das mesmas.