Rita de Cássia Félix Alvarez

Doses de fósforo e crescimento radicular de cultivares de arroz de terras altas

Very little is known of phosphorus availability for upland rice. The objective of this work was to evaluate root growth of upland rice cultivars in different conditions of phosphorus availability. The experiment was carried out in greenhouse, in a completely randomized design, as a 4 x 4 factorial, with four doses of P (0, 50, 100 and 200 mg dm-3) and four cultivars: Maravilha (modern group), IAC 201, IAC 202 and Carajas (middle group). The Carajas root system grew more in low availability of P than other cultivars. In low availability of P the cultivars IAC 201 and IAC 202 priorized root system growth to aerial growth . The Maravilha cultivar needs high Plevels to reach maximum growth. In low availability of P the upland rice cultivars decreased root diameter.

Uso do regulador de crescimento etil-trinexapac em arroz de terras altas

O trabalho foi desenvolvido com o objetivo de avaliar o uso de doses de etil-trinexapac (0; 75; 150; 225 e 300 g ha-1 de i.a.) e epocas de aplicacao (perfilhamento ativo, entre o perfilhamento ativo e a diferenciacao floral e na diferenciacao floral) no desenvolvimento e na produtividade da cultura do arroz de terras altas. O experimento foi desenvolvido no municipio de Selviria (MS), durante o ano agricola de 2006/2007. Concluiu-se que a aplicacao de 150 g ha-1 de etil-trinexapac na fase da diferenciacao floral do arroz cultivar Primavera reduz a altura de plantas, em media 0,40 m, em relacao a aplicacao nas fases do perfilhamento ativo e, entre o perfilhamento ativo e a diferenciacao floral, com ausencia de acamamento; o etil-trinexapac, em doses acima 150 g ha-1, promove maior numero de graos chochos, reduzindo a produtividade de graos, quando aplicado na fase da diferenciacao floral e, a dose de 150 g ha-1 de etil-trinexapac em qualquer epoca de aplicacao nao interfere na produtividade da cultura.

Gas exchange rates, plant height, yield components, and productivity of upland rice as affected by plant regulators

The objective of this work was to evaluate gas exchange rates, plant height, yield components, and productivity of upland rice, as affected by type and application time of plant growth regulators. A randomized block design, in a 4x2 factorial arrangement, with four replicates was used. Treatments consisted of three growth regulators (mepiquat chloride, trinexapac-ethyl, and paclobutrazol), besides a control treatment applied at two different phenological stages: early tillering or panicle primordial differentiation. The experiment was performed under sprinkler‑irrigated field conditions. Net CO 2 assimilation, stomatal conductance, plant transpiration, and water‑use efficiency were measured four times in Primavera upland rice cultivar, between booting and milky grain phenophases. Gas exchange rates were neither influenced by growth regulators nor by application time. There was, however, interaction between these factors on the other variables. Application of trinexapac-ethyl at both tillering and differentiation stages reduced plant height and negatively affected yield components and rice productivity. However, paclobutrazol and mepiquat chloride applied at tillering, reduced plant height without affecting rice yield. Mepiquat chloride acted as a growth stimulator when applied at the differentiation stage, and significantly increased plant height, panicle number, and grain yield of upland rice. Index terms: Oryza sativa, net photosynthesis, stomatal conductance, transpiration, water‑use efficiency. Taxas de trocas gasosas, altura de planta, componentes de producao e produtividade de arroz de terras altas afetados por reguladores vegetais Resumo - O objetivo deste trabalho foi avaliar taxas de trocas gasosas, altura de plantas, componentes de producao e produtividade do arroz de terras altas, influenciados pelo tipo e pela epoca de aplicacao de reguladores de crescimento vegetal. O delineamento experimental foi utilizado em blocos ao acaso, em arranjo fatorial 4x2, com quatro repeticoes. Os tratamentos consistiram de tres reguladores vegetais (cloreto de mepiquat, trinexapac‑etil e paclobutrazol), alem de um tratamento controle, aplicados em dois estadios fenologicos: inicio do perfilhamento ou primordio da diferenciacao da panicula. O experimento foi conduzido em campo com irrigacao por aspersao. A assimilacao liquida de CO2, a condutância estomatica, a transpiracao e a eficiencia do uso da agua foram avaliadas na cultivar de sequeiro Primavera, por quatro vezes, entre os estagios de emborrachamento e de grao leitoso. As trocas gasosas nao foram influenciadas nem pelos reguladores, nem pelas epocas de aplicacao. Houve interacao entre os efeitos dos fatores sobre as demais variaveis. A aplicacao de trinexapac‑etil, tanto no perfilhamento como na diferenciacao, reduziu a altura de plantas e afetou negativamente os componentes de producao e a produtividade do arroz. No entanto, o paclobutrazol e o cloreto de mepiquat, aplicados no estagio de perfilhamento, reduziram a altura das plantas sem afetar a producao. O cloreto de mepiquat atuou como promotor de crescimento quando aplicado no estagio de diferenciacao de paniculas, e aumentou significativamente a altura das plantas, o numero de paniculas e a produtividade de graos. Termos para indexacao: Oryza sativa, fotossintese liquida, condutância estomatica, transpiracao, eficiencia de uso da agua.

Produtividade de arroz de terras altas em função de reguladores de crescimento

Upland rice yield as a function of growth regulators The use of sprinkler-irrigation and/or high levels of fertilization in upland rice can increase plant height and hence plant lodging. Lodging can be controlled by using growth regulators, in order to reduce plant height. The objective of this study was to evaluate the efficiency of plant growth regulators applied at the stage of panicle primordium differentiation on the reduction of plant height and the impact on grain yield and its components of upland rice cultivar Primavera, under sprinkler irrigation. The experiment was arranged in a 3x4 factorial randomized blocks design with four replications. Treatments consisted of: mepiquat chloride and trinexapac-ethil applied at doses 9, 50, 100, and 200 mg a.i. ha-1, and paclobutrazol at doses of 0, 25, 50, and 100 mg a.i. ha-1. Plant growth regulators reduced rice plant height; increasing doses of regulators reduced upland rice grain yield and its components; trinexapac-ethyl was the most harmful to rice grain yield.In this study , it was not identified the dose of growth regulator that allied reduction in plant height and did not cause decrease in rice yield.

Rooting of healthy and CVC-affected 'Valência' sweet orange stem cuttings, through the use of plant regulators

Citrus variegated chlorosis (CVC) is a disease caused by Xylella fastidiosa. Using different concentrations of plant regulators, such as auxins (indole-3-butyric acid) and gibberellic acid biosynthesis-inhibitor (paclobutrazol), physiological rooting capacity of healthy and CVC-affected stem cuttings were evaluated in order to investigate the importance of plant hormone imbalance and xylem occlusion in plants with CVC. The percentages of dead, alive and rooted cuttings, cuttings with callus and mean number of roots per cuttings did not show statistical differences in response to the distinct concentrations of synthetic plant regulators. There were differences only between healthy and CVC-affected cuttings. This showed the importance of xylem occlusion and diffusive disturbances in diseased plants, in relation to root initiation capacity and hormonal translocation in the plant tissue.

Adaptabilidade e estabilidade de genótipos de feijão caupi ereto via REML/BLUP e GGE Biplot

The objective of this study was to investigate the association between the GGE Biplot and REML/BLUP methods and select cowpea genotypes that meet simultaneously high grain yield, adaptability and stability in the Mato Grosso do Sul environments. The experiments were carried out from February to July 2010, 2011 and 2012 in the municipalities of Dourados, Aquidauana and Chapadao do Sul. The experiments in Chapadao do Sul were conducted only in the years of 2010 and 2011, totaling eight environments. After detecting significant genotypes × environments (GE) interaction, the adaptability and the phenotypic stability of cowpea genotypes were analyzed by GGE Biplot and REML/BLUP methods. These methods were concordant in the identification of the best cowpea genotypes for the State of Mato Grosso do Sul. The BRS- Tumucumaque and BRS-Guariba cultivars are the closest to the ideal in terms of high grain yield and phenotypic stability, being suitable for cultivation in the State.

Leaf gas exchange and yield of three upland rice cultivars

Studies of physiological parameters associated with crop performance and growth in different groups of upland rice (Oryza sativa L.) may support plant breeding programs. We evaluated the role of gas exchange rates and dry matter accumulation (DMA) as traits responsible for yields in a traditional (cv. ‘Caiapo’), intermediate (cv. ‘Primavera’) and modern (cv. ‘Maravilha’) upland rice cultivars. Leaf gas exchange rates, DMA, leaf area index (LAI), harvest indexes (HI) and yield components were measured on these genotypes in the field, under sprinkler irrigation. Panicles per m2 and DMA at flowering (FL) and heading, as well as CO2 assimilation rates (A) were similar across these cultivars. The highest yield was found in ‘Primavera’, which may be explained by (i) a two-fold higher HI compared to the other cultivars, (ii) greater rates of DMA during spikelet formation and grain-filling, as well as (iii) a slow natural decrease of A in this cultivar, at the end of the season (between FL and maturation).