Na+ exclusion and proline accumulation in Urochloa spp. cultivars

Abstract

The objective of this work was to evaluate the effect of salinity on Na+ and K+ distribution and on proline content in Urochloa brizantha and Urochloa decumbens grass cultivars. Plants were grown in nutrient solution and subjected to salt stress for nine days. Shoot and root lengths and proline, total chlorophyll, K+, and Na+ contents were determined. Salt stress reduced the shoot length of cultivar Marandu but not of Xaraés and Basilisk. Total chlorophyll content was not affected by salinity in U. brizantha cultivars, but increased in cultivar Basilisk of U. decumbens. Salt-induced proline accumulation was observed in all cultivars, with a higher increase in Marandu. The K+ content in leaf blades increased in the Marandu and Basilisk cultivars under salinity conditions. 'Basilisk' showed Na+ exclusion in shoot tissues, whereas 'Marandu' and 'Piatã', followed by 'Xaraés', exhibited a higher Na+ in leaf blades. The pattern of ion distribution among cultivars was attributed mainly to differences in the ability to control the ion transport from root to shoot, since the rates of ion uptake were similarly affected by salinity. Tolerance to salt stress in grasses of the Urochloa genus is associated to Na+ exclusion and not to proline accumulation in shoot tissues.