Common reed absorbs K<sup>+</sup> more selectively than rice against high Na<sup>+</sup>/K<sup>+</sup> ratio in nutrient solution

2017-10-11T14:23:01Z (GMT) by Kyoko Higuchi Kumiko Hara
<p>The introduction of an active Na<sup>+</sup> excretion system from salt-tolerant plants in salt-sensitive crop plants might necessitate enhancement of the robustness of K<sup>+</sup> homeostasis and lead to improved plant growth under salt stress. To address this issue, we compared the acquisition and retention of K<sup>+</sup> under excess Na<sup>+</sup> concentrations in the common reed, which possesses excellent Na<sup>+</sup> excretion ability, and low-Na<sup>+</sup> excreting rice. Under excess Na<sup>+</sup> concentrations, common reed maintained constant K<sup>+</sup> content in all plant parts, whereas K<sup>+</sup> content in rice decreased with increasing Na<sup>+</sup> concentration. Preferential uptake of K<sup>+</sup> against high Na<sup>+</sup>/K<sup>+</sup> ratio in nutrient solution was approximately 10 times higher in common reed than in rice. The impact of excess Na<sup>+</sup> on net K<sup>+</sup> absorption rate of common reed was small. On the other hand, the net K<sup>+</sup> absorption rate of rice was decreased by excess Na<sup>+</sup> concentration. However, after the Na<sup>+</sup> concentration in the nutrient solution was decreased from 50 to 1 mM, K<sup>+</sup> absorption in rice recovered immediately. Thus, selectivity of K<sup>+</sup> transporters or channels for K<sup>+</sup> over Na<sup>+</sup> in roots could be involved in the differences in K<sup>+</sup> accumulation in rice and common reed.</p>