Na+ accumulation in shoot is related to water transport in K+-starved sunflower plants but not in plants with a normal K+ status.
Sunflower plants (Helianthus annuus L. cv Sun-Gro 380) grown in nutrient solutions with different K+ levels were used to study the effect of potassium status on water uptake, Na+ uptake and Na+ accumulation in the shoot. Changes in nutrient potassium levels induced evident differences in internal potassium content. When both low and normal-K+ plants were exposed to 22 degrees C and salinity conditions (25 or 50 mM NaCl) during a short time period (9h), water uptake in low-K+ plants was greater than in normal-K+ plants. In addition, K+ starvation favoured the Na+ uptake and the Na+ accumulation both in the root and in the shoot. When the plants were exposed to heat stress by a sharp increase of the temperature to 32 degrees C during the same period of time, the stimulating effect of K+ starvation on the water uptake was even greater. The high temperature increased Na+ uptake in both types of plants, but the Na+ accumulation in the shoot was only favoured in low-K+ plants. The results suggest that Na+ accumulation in the shoot is more dependent on the water uptake in low-K+ plants than in normal-K+ plants, and this effect could explain the greatest susceptibility to the salinity in K+-starved plants under high transpiration conditions, which are typical in dry climates.
Quintero
José Manuel
JM
Departamento de Ciencias Agroforestales, Escuela U. Ingeniería Técnica Agrícola, Universidad de Sevilla, Ctra. Utrera, Km. 1, E-41013 Sevilla, Spain. jqariza@us.es
Fournier
José María
JM
Benlloch
Manuel
M
D001692:Biological Transport; D006368:Helianthus / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013696:Temperature; D014867:Water / Q000378:metabolism*
D014867:Water; D012964:Sodium; D011188:Potassium