The ability of a plant to extract soil water during water deficit affects growth and grain yield crop. Experiments were conducted to evaluate the water extraction and rooting patterns of three genotypes (Arawaca, Acarigua and Piritu) of Sesame (Sesamum indicum L.) during periods of water deficit imposed at productive stage of growth, on a Fluventic Haplustolls, Maracay-Venezuela, during period of January-April of 1994 and 1995. Profiles of volumetric water content of the soil were measured with a neutron moisture meter, root, biomass and leaf area samples were taken at ending of water deficit period. There are differences in water extraction to drought, among genotypes, Arawaca showed significantly greatests water extraction (53.6 mm) at root zone of crop (0.15 -0.55 m) during the early water deficit period (CST). While the genotypes Acarigua and Piritu showed similar extractable water (40.0 y 39.1 mm respectively). The differences of soil water extraction among genotypes were related to root system patterns and canopy cover of each genotype. Piritu developed the 60% of its root system on the first O.25 m of soil profile and showed the less root length density (0.41 cm cm -3 respectively). A greater root system, with a better capacity to explore the soil, of Acarigua and Arawaca allows a greater amount of water uptake from soil profile. The minor water extraction by Arawaca during CSTR was correlated to its smaller canopy cover (0.65 M2 M2) during this period. The root characteristics of the genotypes suggest its better adaptative value in cropping areas with high risk of water deficit.

A partir de los resultados obtenidos en los ensayos previos realizados en la camara germinadora se constato la existencia de un alto grado de heterogeneidad en el plantel producido. Mediante el analisis de los diferentes elementos de control de los factores ambientales de que esta dotada la camara se pudo apreciar que la causa fundamental de la heterogeneidad del plantel era la falta de uniformidad del riego. A lo largo de un ano se han venido realizando diversos ensayos cuyo objetivo es tanto evaluar con la mayor profundidad posible cuales son las causas del mal comportamiento del sistema de riego, como buscar alternativas tecnicamente viables que doten a la camara germinadora de un sistema de riego altamente localizado lo suficientemente fiable. Se ha comprobado que, si bien el sistema de riego esta correctamente calculado, las boquillas empleadas no reunen las condiciones necesarias de uniformidad ni en el caudal que aportan, ni en la distribucion del agua que deberia ser la de cono lleno. En este momento se estan probando otros tipos de boquillas y otros sistemas de riego alternativos que permitan resolver el problema de la heterogeneidad en la distribucion del agua de riego.