Abstract

Potassium (K⁺) is an essential nutrient and the most abundant cation in plant cells. Plants have a wide variety of transport systems for K⁺ acquisition that catalyze K⁺uptake across a wide spectrum of external K⁺ concentrations and mediate K⁺movement within the plant, as well as its release into the environment. The KUP/HAK/KT transporter family plays a key role in K⁺ homeostasis in plant cells. The present study demonstrates that habanero pepper plantlets have a clear pattern of K⁺ uptake when re-supplemented with K⁺ after K⁺ starvation. Habanero pepper plantlets, re-supplemented with a solution containing low concentrations of K⁺ after 72, 96 or 120 h of K⁺ starvation were able to decrease the amount of K⁺ inthe solution at different time points. To study the effect of NH₄⁺, we added different concentrations of NH₄NO₃ to the medium solution and demonstrated that NH₄⁺inhibited K⁺ uptake in a dose-dependent manner. When the plantlets weresubjected to K⁺ starvation for 72 h and then re-supplemented with 50 or 100 µM K⁺,exposure to K⁺ channel blockers (10 mM CsCl and 20 mM TEA) decreased their K⁺uptake compared with the control treatment. A model demonstrating the process ofK⁺ uptake through an NH₄⁺-insensitive component was proposed.

Key words: Potassium, high affinity transporters, channel blockers, ammonium.

Abbreviation

CsCl, Cesium chloride; HAK, high-affinity potassium transporters;TEA, tetraethylammonium; HATS, high-affinity potassium system.