Cation selectivity in cotton (Gossypium hirsutum L.) grown on calcareous soil as affected by potassium fertilization, cultivar and growth stage

Background and aims: Selective uptake of K over Na has been proposed as a mechanism employed by plants to tackle high soil salinity. However, the impact of other dominant soil cations such as Ca and Mg and essentiality of higher K/Ca and K/Mg selectivity for plant performance under adverse growing conditions have been studied much less. We addressed this topic by looking at cation selectivity in cotton grown on calcareous soil supplemented by K. Methods: Cation selectivity in leaves was determined as a ratio of two cations to the respective ratio in the soil over two growth seasons, three growth stages, and two cotton cultivars. Concurrently, instantaneous and long-term leaf traits related to CO₂ assimilation, N and water use efficiency were assessed. Results: Potassium addition did not affect on cation selectivity; growth stages and their interaction with years were allotted with the most of the variation found for cation selectivity and many of the physiological traits. Cultivar Carmen compared to Elina had higher K selectivity, was water conservative and had higher fiber quality. Elina took up Na selectively over Mg in an effort to sustain stomata open. Conclusions: The reported results indicated an importance of improved cation selectivity to optimize K⁺ nutrition in plants grown on calcareous soils. Under conditions of low K⁺ availability, cotton cultivars took up selectively Na and Mg over Ca, to optimize its water relations and photosynthetic performance. Cation selectivity was largely affected by growth stages and was correlated with stomata functioning.