WEED CONTROL

Author: MEDJDOUB FRAIHAT RATIBA.
Year: 2003.
University: LLEIDA [www.udl.es].
Place of defense: INGENIEROS AGRONOMOS.
Place of preparation: ESTACIÓN EXPERIMENTAL DEL AULA DEI (CSIC).

Summary: There is a delicate balance between growth and productivity of the fruit trees. The disruption of this balance leads to excessive vegetative growth, conversely realcionado with fruit quality, pest control and / or diseases, and trade performance. To cope with this problem was introduced the use of plant growth regulators. The increasingly restrictive conditions regarding the use of inhibitors of growth in fruit growing and the recent appearance on the market of a new product have led this study. During three years of experimentation, 1999, 2000, 2001, have been carried out 8 trials with adult trees of the variety "Golden Smoothee" Red Gala 'Royal Gala' and "Fuji" in the conditions of the Ebro Valley. The ninth experiment was conducted on young trees in pots in the experimental station of Aula Dei. The study of the effect of prohexadiones-Ca was approached from the point of view of evolution, considering the continuity of parameters with methods of statistical analysis of data repeated over time. Through experimentation ealizada has shown that the prohexadiones-Ca inhibits the growth of the apple tree in condicones Valley Ebro without inducing changes in the yield and quality of fruit, provided that the mode of implementation is the correct one. An application with a single concentration 100-500 mg L-1 in full bloom effectively inhibits growth. However, in certain cases, the emergence of a second recrecimiento in the middle of the season forced to make two applications, one in full bloom with a dose 100-250, and another between 60 and 65 days after full bloom with a dose equal or lower. The inhibicón the length of outbreaks was accompanied by a decrease in the length of internodes, as well as a decrease in fresh and dry weights, and the leaf area index (LAI). On the contrary, it increases the photosynthetically active radiation (PAR), the net photosynthetic activity, the amount of chlorophylls per unit area fliar, thickness, and water retention in buds and leaves, leaf also increases the concentration of CO2 and stomatal conductance indeplendientemente of chlorophyll. According to the merger, the date of treatment and the number of applications, such changes may be reversible or stable over the period of vegetative growth. Applying prohexadiones-Ca induced an increase in the concentration of calcium, magnesium, manganesco, copper and zinc leaf; effect was stable throughout the season. Also, the prohexadione-Ca increased the flow of export leaf nitrogen into other organs. Depending on the variety and experimental conditions, there have been increases in soluble carbohydrates such as sorbitol in leaves, shoots and fruits. Finally, the red varieties studied, prohexadione-CA increased the surface of the colored variety "Fuji" while increasing saturation and intensity of red color on both sides of the apple, shaded and exposed to the sun.

Author: RUIZ SANTAELLA MORENO JUAN PEDRO.
Year: 2004.
University: CÓRDOBA [www.uco.es].
Place of defense: FACULTAD DE MEDICINA.
Place of preparation: FACULTAD DE MEDICINA.

Summary: Cihalofop-butil (CS), acid-2-[4 - (4-ciano-2fluorofenoxi) phenoxy] propionic butil ester (R), is a herbicide belonging to the family of acid ariloxifenoxipropanoatos, inhibitors of the enzyme acetyl coenzyme A carboxylase (ACCasa). During tests conducted prospecting rice Spain (Seville, Valencia and Sadajoz) and American (Valley in California) first appeared biotypes of Echinochloa beyond the control field. Tests confirmed dose this point, getting resistance factors (FR) near 27. The studies of the mechanisms respqnsables of resistance (electron microscopy) showed a differential absorption due to the different distribution and density waxes epicuticulares. No differences were obtained with respect to the translocation of CS staying almost 95% in the leaf treated. In vitro tests of the ACCasa ruled mutation as a mechanism for gaining resistance values 150en all biotypes near 2 J.lM. Trials of in vivo metabolism gave us the foundation of the mechanisms of resistance. With respect to rice (O. sativa L.) was an inactivation function esterase sharply reducing the formation of cihalofop acid, which was the real herbicide. In addition, increased metabolism non-toxic metabolites formed by oxidation reactions. In the case of Echinochloa differences were observed between the metabolism of CS between biotypes SyR latter forming a much larger amount of non-toxic metabolites (diácido, amide and conjugated). Essays In vitro metabolism through isolation system containing monooxygenase P450 suggested the non-involvement of this enzyme system in the metabolism of CS, not being inhibited by proadifen, ketoconazole or KCN, specific inhibitors of protein group with hemo. In vivo studies with glutatión-S-transferasas could suggest the involvement of the latter or of any system mono-oxigenasa not have a group hemo within. The morphological and molecular studies (RAPDs) biotypes characterized as Echinochloa oryzoides.