Correlations between carbon isotope discrimination and leaf conductance to water vapor in common beans

Se midio la discriminacion de isotopos de carbono (delta) en el campo, en 10 cv. de frijol. Se registro una variacion sustancial (mas de 2 por ciento) en los valores delta de las hojas y se mantuvieron estas diferencias entre las etapas de desarrollo vegetativo y reproductivo. Estas lineas de frijol tambien presentaron diferencias sustanciales en conductancia foliar con respecto al vapor de agua, y nuevamente estas diferencias se mantuvieron a traves de las etapas de desarrollo. Las diferencias en conductancia foliar se correlacionaron positivamente con los valores delta, sea que la conductancia se midiera como conductancia foliar total o como conductancia individual del haz o del enves. Se observaron diferencias en densidad estomatica, y diferencias leves entre lineas de frijol en cuanto a contenido foliar de N de Kjeldahl, lo cual se interpreta como indicador de la similitud en capacidad fotosintetica entre lineas de frijol. Por lo tanto, ya que los valores delta y la conductancia foliar se correlacionaron positivamente, estos datos sugirieron que pudieron haber diferencias entre lineas de frijol en el grado al cual los estomas limitaron las tasas de intercambio fotosintetico de gases. (RA-CIAT) spa

Carbon isotope discrimination (delta) was measured in the field on 10 cultivars of common bean (Phaseolus vulgaris L.). There was substantial variation (more than 2 percent) in leaf delta values and these differences were maintained between vegetative and reproductive developmental stages. These bean lines also exhibited substantial differences in leaf conductance to water vapor, and again these differences were maintained across developmental stages. The differences in leaf conductance were positively correlated with delta values, whether conductance was measured as total leaf conductance or as the individual conductances of either upper or lower leaf surfaces. The observed differences in stomatal density. There were small differences among bean lines in their leaf Kjeldahl nitrogen contents, which is interpreted as indicating that photosynthetic capacity among bean lines was similar. Thus, because delta values and leaf conductance were positively correlated, these data suggested that there may have been differences among bean lines in the extent to which stomata limited photosynthetic gas exchange rates. (AS) eng