[en] Phalaris brachystachys and Phalaris minor are common and troublesome weeds in winter cereals in Mediterranean countries. Different distribution and soil preferences have been found for each species in Andalusia (southern Spain). In irrigated fields P. minor is more frequent while P. brachystachys has extended its range to semiarid provinces with low rainfall. This different adaptation to irrigation conditions is difficult to explain considering aspects of their biology, herbicide tolerance, or cultivation practices. The objective of this study was to assess the influence of different soil water availabilities over growth and reproductive aspects to explain the differences found in ecology and distribution of P. brachystachys and P. minor. The experiment was conducted under greenhouse controlled conditions using five levels of water availability: field capacity, light drought, moderate drought, severe drought and extreme drought. Differences between species and among treatments were found in plant height, biomass, tiller number, and reproductive traits. Field capacity and light drought treatments favoured biomass, tiller number, and panicle number in P. minor. In contrast, P. brachystachys had a positive response only in moderate drought and increased the percentage of mature panicle with increasing drought levels. These results could explain the wider distribution of P. brachystachys in fields without supplemental irrigation in semiarid areas, due to its adaptation to moderate drought conditions. It may also clarify the greater frequency of P. minor in irrigated fields and in areas with higher rainfall.

[es] Phalaris brachystachysy Phalaris minor son malas hierbas frecuentes y problem&aacute;ticas en los cereales de invierno a lo largo de la cuenca mediterr&aacute;nea. En Andaluc&iacute;a (sur de Espa&ntilde;a) se han encontrado diferencias entre especies en relaci&oacute;n a su distribuci&oacute;n y preferencias ed&aacute;ficas. En suelos regados P. minor es m&aacute;s frecuente mientras que P. brachystachys se extiende a las provincias semi&aacute;ridas con baja precipitaci&oacute;n. Esta diferente adaptaci&oacute;n a las condiciones de riego no se puede explicar por aspectos relacionados con su biolog&iacute;a, tolerancia a herbicidas o pr&aacute;cticas de cultivo. El objetivo de este estudio es evaluar la influencia de diferentes niveles de agua en el suelo sobre el crecimiento y los caracteres reproductivos de P. brachystachys y P. minor, para explicar las diferencias encontradas en la ecolog&iacute;a y distribuci&oacute;n de ambas especies. El experimento se realiz&oacute; en invernadero y se evaluaron cinco niveles de disponibilidad de agua: capacidad de campo, ligera sequ&iacute;a, sequ&iacute;a moderada, sequ&iacute;a severa y sequ&iacute;a extrema. Se encontraron diferencias entre especies en altura de planta, biomasa, n&uacute;mero de brotes y en los caracteres reproductivos. Los tratamientos a capacidad de campo y con ligera sequ&iacute;a favorecieron la biomasa, el n&uacute;mero de brotes y n&uacute;mero de pan&iacute;culas en P. minor. P. brachystachys tuvo una respuesta positiva s&oacute;lo en el tratamiento de sequ&iacute;a moderada, incrementando el porcentaje de pan&iacute;culas maduras con el incremento de los niveles de sequ&iacute;a. Estos resultados podr&iacute;an explicar una m&aacute;s amplia distribuci&oacute;n de P. brachystachys en secano y en zonas semi&aacute;ridas debido a su adaptaci&oacute;n a las condiciones de moderada sequ&iacute;a y una mayor frecuencia de P. minor en regad&iacute;o y en zonas con mayor precipitaci&oacute;n.