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Potassium (K) is an essential macronutrient for plant growth and development. Plant growth and development can be seriously affected by K deficiency. However, plants with different K efficiencies behave differently. It is still not fully understood how plants with higher K efficiency could maintain better growth in a low K environment and what is the relationship between K recycling and photosynthesis metabolism. The aim of this study was to investigate whether the difference in K re-translocation and photosynthesis transportation can explain genotype differences in K efficiency between K-efficient genotype 103 and K-inefficient genotype 122. Results of this study showed that the dry matter accumulation of genotype 122 decreased much more than that of genotype 103 affected by K deficiency environment. Root growth of the two genotypes was inhibited by K deficiency, but genotype 122 was affected more than genotype 103. Using the K utilization index as an evaluation factor for K efficiency, it was found that genotype 103 was significantly higher than genotype 122. Potassium affected the K distribution in plants for both the genotypes. Potassium was distributed more to the stem and leafstalk in a normal K environment whereas it was more to the leaf and root in a low K environment, especially for genotype 103. Potassium also affected photosynthetic products’ distribution. The leaf of genotype 122 accumulated most of its photosynthetic product while genotype 103 had better ability to transport it into the root to maintain better growth under a K-deficient environment. Results of this study indicated that more K recycling into the root and more efficient transport of the photosynthetic product into the root contribute to better root growth and therefore increased tolerance to K deficiency. [ABSTRACT FROM AUTHOR]

As a macroelement to plant, potassium (K) absorption mechanism has been widely studied. However, as for cotton genotypes with different K efficiency, how they related to the absorption patterns under K starvation is not fully understood. In this hydroponic experiment, plants were grown at different K levels: low (K1, 2 mg/L) and adequate K level (K2, 20 mg/L) for 2 weeks. K+absorption kinetic parameters were got by Michaelis–Menten equation. By applying K channel-blocking agent, tetraethylammonium and protein modifying reagent N-ethylmaleimide, we evaluated the differences in K absorption mechanisms for two typical cotton genotypes (K-efficient genotype 103 and K-inefficient genotype 122). Results showed that higher affinity to K+and better root formation of genotype 103 resulting in better adaptation in low-K+condition, whether grown in low or adequate K+environment. Further study with K+absorption inhibitors suggested the two genotypes grown in low-K+environment absorbed K+mainly by high-affinity K+absorption systems, and for seedlings grown in adequate K condition, genotype 103 absorbed K+with both K channels and high-affinity proton and mainly by high-affinity K channels, while genotype 122 absorbed K+by K channels. These results indicated that the low-K condition could induce higher affinity to absorb K+, and the two cottons with different K efficiency mainly due to different low-K adaptation and absorb K+with different patterns. This could provide a possible theory for the selection of K-efficient varieties. [ABSTRACT FROM AUTHOR]