Effects of ammonium nitrate, cesium chloride and tetraethylammonium on high-affinity potassium uptake in habanero pepper plantlets (Capsicum chinense Jacq.)
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 resupplemented 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+ in the 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 were subjected to K+ starvation for 72 h and then resupplemented 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 of K+ uptake through an NH4+-insensitive component was proposed.
Key words: Potassium, high affinity transporters, channel blockers, ammonium.