The Influence of Potassium on the Transpiration Rate and Stomatal Opening in Triticum aestivum andPisum sativum

Abstract

The investigation concerns the influence of potassium on the transpiration rate of Triticum aestivum and Pisum sativum grown in nutrient solutions. Plants with high amounts of potassium were found to have the lowest transpiration rates. Shoot/root ratio, stomatal frequency, and stomatal aperture were correlated with the potassium concentration in the leaves. In Triticum no correlations with leaf concentration of Na were evident.Short term experiments were carried out in order to investigate the effects on the transpiration rate of a sudden increase in potassium concentration in the nutrient solution. An addition of potassium chloride to potassium deficient wheat plants resulted in a decrease in the transpiration rate of up to 50 "/o within two hours. Comparative tests with sodium chloride resulted in a decrease in transpiration rate of the same magnitude, indicating that the short-time reaction is not specific to potassium.The experiments show that the transpiration rate can be regulated by varied potassium and sodium concentrations. The observed effect is supposed to be due to changes in the stomatal aperture.

K+ starvation inhibits water-stress-induced stomatal closure

“…Our results showed that, in olive and sunflower grown in similar controlled conditions, moderate potassium starvation inhibited water-stress-induced stomatal closure. Similar findings have been reported by other authors for sugar cane (Sudama et al, 1998), wheat and pea (Brag, 1972) and, more recently, the 'Chemlali de Sfax' olive cultivar Figure 6. Effect of water availability in the growth medium (irrigation vs. drought) and K + concentration in irrigation water (low K vs. normal K) on stomatal conductance in sunflower leaves.…”

“…However, in some of these studies, the potassium deficiency was extreme (Hsiao and Läuchli, 1986). In contrast, other authors suggest that potassium deficiency favours stomatal opening and transpiration in wheat and peas (Brag, 1972), sugar cane (Sudama et al, 1998) and, more recently, in the olive cultivar 'Chemlali de Sfax' (Arquero et al, 2006). It is not yet clear why potassium-deficient plants are more susceptible to dehydration.…”

Effects of Potassium Deficiency on the Photosynthesis and Respiration of Leaves of Sugar Beet

“…During the 1st week the Na concentration increased 5- shown to effect changes in stomatal aperture (3,32) and may have substituted for K directly as the cation taken up by the guard cells. It could also have acted by conserving the supply of leaf K: the addition of Na to K-limited plants might have caused K+ ions to move from the vascular tissue into the mesophyll cells through a cation exchange mechanism, thus releasing K+ ions for specific functions such as stomatal opening.…”

Effect of potassium on the tolerance to PEG-induced water stress of two white clover varieties (Trifolium repens L.)

“…In alfalfa, a severe K deficiency generally brings on an increase in the stomatal closure (People and Koch, 1979). A low potassium concentration in the nutrient solution produced plants with a high transpiration rate (Brag, 1972). In our work we have used a hydroponic system to study the response of white clover to a stress induced by an osmotic agent.…”