12.6: Potassium- An overlooked limiting element?

Nitrogen \((\mathrm{N})\) is one of the most abundant elements on the earth and plays an important role in modern agriculture (Chen et al., 2018). N has an irreplaceable role in organ construction, material metabolism, fruit yield, and the quality formation of fruit trees (Warner et al., 2004; Liu et al., 2010; Bai et al., 2016). Sufficient \(\mathrm{N}\) application not only improves the photosynthetic efficiency of the leaves but also promotes flower bud differentiation (Li et al., 2012; Wei et al., 2016; Liu et al., 2018), enhances fruit setting rate, and increases yield (Raese et al., 2007). Due to the one-sided pursuit of high yield and large fruits by fruit farmers, the excessive application of \(\mathrm{N}\) fertilizer in apple orchards has become common in China. The applied \(\mathrm{N}\) fertilizer dose is are more above the demand of the tree (Ge et al., 2018). Furthermore, the over application of \(\mathrm{N}\) increases the input cost of farmers, decreases fruit yield and quality (Chen et al., 2017), and directly leads to a decreased \(\mathrm{N}\) utilization rate. Excessive \(\mathrm{N}\) also indirectly results in adverse ecological effects, including the increased \(\mathrm{N}\) deposition, the intensification of the greenhouse effect, soil acidification, and the eutrophication of water bodies (Liu et al., 2013; Zhu and Zhang, 2017). Therefore, it is a main issue for Chinese apple production to promote the efficient utilization of \(\mathrm{N}\) to improve the quality and yield of apple.

Potassium \((K)\) is the most abundant inorganic cation, and it is important for ensuring optimal plant growth (White and Karley, 2010). K is an activator of dozens of important enzymes, such as protein synthesis, sugar transport, \(\mathrm{N}\) and \(\mathrm{C}\) metabolism, and photosynthesis. It plays an important role in the formation of yield and quality improvement (Marschner, 2012; Oosterhuis et al., 2014). K is also very important for cell growth, which is an important process for the function and development of plants (Hepler et al., 2001). In terms of the growth-promoting mechanism of \(K\), it is generally agreed that \(K\) stimulates and controls ATPase in the plasma membrane to generate acid stimulation, which then triggers cell wall loosening and hydrolase activation (Oosterhuis et al., 2014), thus promoting cell growth. \(\mathrm{K}\) has strong mobility in plants and plays an important role in regulating cell osmotic pressure and balancing the cations and anions in the cytoplasm (Kaiser, 1982; Hu et al., 2016a). Through these processes, \(\mathrm{K}\) is involved in the regulation of stomatal opening and closing, cell elongation, and other important physiological processes. There are many studies on the effect of \(K\) level on plant growth. Jin et al. (2007) found that the highest yield and fruit quality were obtained in Red Fuji apple under treatment with \(600 \mathrm{~kg} / \mathrm{ha}\) K; Wang et al. (2017) determined that \(6 \mathrm{mMK}\) treatment promoted pear growth and improved photosynthetic efficiency; and Lu et al. (2001) also reported increased production with better fruit quality parameters in navel orange supplied under \(500 \mathrm{~kg} / \mathrm{ha} \mathrm{K}\). There is an interaction between \(\mathrm{K}\) and other nutrient ions. High \(\mathrm{K}\) concentrations in the soil solution inhibit Mg uptake and may induce Mg deficiency in plants (Tränkner et al., 2018). However, \(\mathrm{K}\) deficiency could promote the absorption of \(\mathrm{Na}^{+}\)and \(\mathrm{Ca}^{2+}\) in maize (Du et al., 2017), and could inhibit \(\mathrm{N}\) absorption in cotton and significantly reduce the content of \(\mathrm{NO}_3^{-}\)in the leaves (Hu et al., 2017). It is evident that \(K\) affects significantly the absorption and utilization of other nutrients by plants, and the appropriate \(K\) level differs in different crops.

Among the interactions between \(\mathrm{K}\) and other nutrients, the interaction with \(\mathrm{N}\) is the most important. Some studies evaluated the relationship between \(\mathrm{K}\) and \(\mathrm{N}\) metabolism. In contrast to the antagonistic relationship between \(\mathrm{K}^{+}\)and \(\mathrm{NH}_4{ }^{+}\)nutrition, the acquisition rates of \(\mathrm{K}^{+}\)and \(\mathrm{NO}_3{ }^{-}\)are often found to be positively correlated (Rufty et al., 1981; Coskun et al., 2016), and sufficient K supply can promote \(\mathrm{N}\) metabolism and enhance the synthesis of amino acids and proteins (Ruan et al., 1998; Ruiz and Romero, 2002). Hu et al. (2016b) found that K deficiency could reduce Nitrate reductase (NR), Glutamine synthetase (GS), and Glutamate synthase (GOGAT) activities and inhibit nitrate absorption in cotton, whereas Armengaud et al. (2009) found that K deficiency could up-regulate the activities of GS and Glu dehydrogenase (GDH) in Arabidopsis. Metabolism of \(\mathrm{N}\) affected by \(\mathrm{K}\) appears to vary in different types of plants. Meanwhile, the level of \(\mathrm{K}\) has a significant impact on \(\mathrm{C}\) metabolism, and also a strong interaction exists between \(\mathrm{C}\) metabolism and \(\mathrm{N}\) metabolism in the metabolic process and energy level (Hu et al., 2017).

References

Armengaud, P., Sulpice, R., Miller, A. J., Stitt, M., Amtmann, A., and Gibon, Y. (2009). Multilevel analysis of primary metabolism provides new insights into the role of potassium nutrition for glycolysis and nitrogen assimilation in Arabidopsis roots. Plant Physiol. 150, 772–785. doi: 10.1104/pp.108.133629.

Bai, L. Q., Deng, H. H., Zhang, X. C., Yu, X. C., and Li, Y. S. (2016). Gibberellin is involved in inhibition of Cucumber growth and nitrogen uptake at Suboptimal root-Zone temperatures. PLoS One 11:e0156188. doi: 10.1371/journal.pone.0156188.

Chen, Q., Ding, N., Peng, L., Ge, S. F., and Jiang, Y. M. (2017). Effects of different nitrogen application rates on ¹⁵ N-urea absorption, utilization, loss and fruit yield and quality of dwarf apple. Chin. J. Appl. Ecol. 28, 2247–2253..

Chen, G. D., Wang, L., Fabrice, M. R., Tian, Y. N., Qi, K. J., Tao, S. T., et al. (2018). Physiological and nutritional responses of pear seedlings to nitrate concentrations. Front. Plant Sci. 9:1679. doi: 10.3389/fpls.2018.01679.

Coskun, D., Britto, D. T., and Kronzucker, H. J. (2016). The nitrogen–potassium intersection: membranes, metabolism, and mechanism. Plant Cell Environ. 10, 2029–2041. doi: 10.1111/pce.12671.

Du, Q., Zhao, X. H., Jiang, C. J., Wang, X. G., Han, Y., Wang, J., et al. (2017). Effect of potassium deficiency on root growth and nutrient uptake in maize (Zea mays L.). Agric. Sci. 8, 1263–1277. doi: 10.4236/as.2017.811091.

Ge, S. F., Zhu, Z. L., Peng, L., Chen, Q., and Jiang, Y. M. (2018). Soil nutrient status and leaf nutrient diagnosis in the main apple producing regions in China. Hortic. Plant J. 4, 89–93. doi: 10.1016/j.hpj.2018.03.009.

Hepler, P. K., Vidali, L., and Cheung, A. Y. (2001). Polarized cell growth in higher plants. Annu.Rev. Cell. Dev. Biol. 17, 159–187. doi: 10.1146/annurev.cellbio.17.1.159.

Hu, W., Jiang, N., Yang, J., Meng, Y., Wang, Y., Chen, B., et al. (2016a). Potassium (K) supply affects K accumulation and photosynthetic physiology in two cotton (Gossypium hirsutum L.) cultivars with different K sensitivities. Field Crop. Res. 196, 51–63. doi: 10.1016/j.fcr.2016.06.005.

Hu, W., Zhao, W., Yang, J., Oosterhuis, D. M., Loka, D. A., and Zhou, Z. (2016b). Relationship between potassium fertilization and nitrogen metabolism in the leaf subtending the cotton (Gossypium hirsutum L.) boll during the boll development stage. Plant Physiol. Biochem. 101, 113–123. doi: 10.1016/j.plaphy.2016.01.019.

Hu, W., Coomer, T. D., Loka, D. A., Oosterhuis, D. M., and Zhou, Z. (2017). Potassium deficiency affects the carbon-nitrogen balance in cotton leaves. Plant Physiol. Biochem. 115, 408–417. doi: 10.1016/j.plaphy.2017.04.005.

Jin, H. C., Zhang, L. S., Li, B. Z., Han, M. Y., and Liu, X. G. (2007). Effect of potassium on the leaf nutrition and quality of Red Fuji apple. Acta Agric. Bor Occid. Sin. 16, 100–104. doi: 10.3969/j.issn.1004-1389.2007.03.026.

Kaiser, W. M. (1982). Correlation between changes in photosynthetic activity and changes in total protoplast volume in leaf tissue from hygro-, meso-and xerophytes under osmotic stress. Planta 154, 538–545. doi: 10.1007/BF00402997.

Li, G., Zhang, Z. S., Gao, H. Y., Liu, P., Dong, S. T., Zhang, J. W., et al. (2012). Effects of nitrogen on photosynthetic characteristics of leaves from two different stay-green corn (Zea mays L.) varieties at the grain-filling stage. Can. J. Plant Sci. 92, 671–680. doi: 10.4141/cjps2012-039.

Liu, L., Peng, F., and Wang, X. (2010). Effects of bag-controlled release fertilizer on nitrogen utilization rate, growth and fruiting of the ‘Fuji’ apple. J. Plant Nutr. 33, 1904–1913. doi: 10.1080/01904167.2010.512050.

Liu, X. J., Zhang, Y., Han, W. X., Tang, A. H., Shen, J. L., Zhang, F. S., et al. (2013). Enhanced nitrogen deposition over China. Nature 494, 459–462. doi: 10.1038/nature11917

Liu, Z., Gao, J., Gao, F., Liu, P., Zhao, B., and Zhang, J. W. (2018). Photosynthetic characteristics and chloroplast ultrastructure of summer Maize response to different nitrogen supplies. Front. Plant Sci. 9:576. doi: 10.3389/fpls.2018.00576.

Lu, J. W., Chen, F., Wan, Y. F., Liu, D. B., Yu, C. B., Wang, Y. Q., et al. (2001). Effect of application of potassium on the yield and quality of Navel Orang. J. Fruit Sci. 18, 272–275..

Marschner, H. (2012). Marschner’s Mineral Nutrition of Higher Plants. Cambridge, MA: Academic press..

Oosterhuis, D., Loka, D., Kawakami, E., and Pettigrew, W. (2014). The physiology of potassium in crop production. Adv. Agron. 126, 203–234. doi: 10.1016/B978-0-12-800132-5.00003-1.

Raese, J. T., Drake, R. S., and Curry, A. E. (2007). Nitrogen fertilizer influences fruit quality, soil nutrients and cover crops, leaf color and nitrogen content, biennial bearing and cold hardiness of ‘Golden Delicious’. J. Plant Nutr. 30, 1585–1604. doi: 10.1080/01904160701615483.

Ruan, J., Wu, X., Ye, Y., and Hardter, R. (1998). Effect of potassium, magnesium and sulphur applied in different forms of fertilisers on free amino acid content in leaves of tea (Camellia sinensis L). J. Sci. Food Agric. 76, 389–396. doi: 10.1002/(SICI)1097-0010(199803)76:3<389::AID-JSFA963<3.0.CO;2-X.

Rufty, T. W., Jackson, W. A., and Raper, C. D. (1981). Nitrate reduction in roots as affected by the presence of potassium and by flux of nitrate through the roots. Plant Physiol. 68, 605–609. doi: 10.2307/4266953

Ruiz, J., and Romero, L. (2002). Relationship between potassium fertilisation and nitrate assimilation in leaves and fruits of cucumber (Cucumis sativus) plants. Ann. Appl. Biol. 140, 241–245. doi: 10.1111/j.1744-7348.2002.tb00177.x.

Tränkner, M., Tavakol, E., and Jákli, B. (2018). Functioning of potassium and magnesium in photosynthesis, photosynthate translocation and photoprotection. Physiol. Plant. 163, 414–431. doi: 10.1111/ppl.12747.

Wang, Y. Z., Zhang, H. P., Huang, X. S., Wang, J. Z., Cheng, R., Chen, G. D., et al. (2017). Effect of potassium supply on plant potassium distribution and growth and leaf photosynthetic capacity of Pyrus pyrifolia. J. Nanjing Agric. Univ. 40, 60–67. doi: 10.7685/jnau.201603054.

Wei, S. S., Wang, X. Y., Shi, D. Y., Li, Y. H., Zhang, J. W., Dong, S. T., et al. (2016). The mechanisms of low nitrogen induced weakened photosynthesis in summer maize (Zea mays L.) under field conditions. Plant Physiol. Biochem. 105, 118–128. doi: 10.1016/j.plaphy.2016.04.007.

White, P. J., and Karley, A. J. (2010). Potassium Cell Biology of Metals and Nutrients. Berlin: Springer, 199–224..

Zhu, L. X., and Zhang, W. (2017). Effects of controlled-release urea combined with conventional urea on nitrogen uptake, root yield, and quality of Platycodon grandiflorum. J. Plant Nutr. 40, 662–672. doi: 10.1080/01904167.2016.1249799

Excerpted from:

Xu, X., Du, X., Wang, F., Sha, J., Chen, Q., Tian, G., ... & Jiang, Y. (2020). Effects of potassium levels on plant growth, accumulation and distribution of carbon, and nitrate metabolism in apple dwarf rootstock seedlings. Frontiers in Plant Science, 11, 904. Accessed December 2023 at https://www.frontiersin.org/articles/10.3389/fpls.2020.00904/full. CC-BY-4.0