Does low potassium availability modulate the physiological responses of Corymbia seedlings and Eucalyptus cuttings?

Aims Eucalypt plantations in Brazil have expanded into regions with highly weathered soils and marked heat and water deficits, where potassium (K) availability becomes a major constraint due to its role in osmotic adjustment, stomatal regulation and water use efficiency. This study evaluated physiological responses to potassium fertilization of two Corymbia species ( Corymbia citriodora subsp . variegata – CCV and Corymbia henryi – CH) recently introduced into breeding programs, and two traditional Eucalyptus urophylla × E. grandis cuttings (I144 and H13). Methods The experiment followed a completely randomized 4 × 2 factorial design and was conducted in pots for six months under greenhouse conditions. Leaf water potential (Ψf), gas exchange, biomass allocation, leaf anatomy and plant nutrition were evaluated. Results During the most stressful period, Ψf was 21% more negative under potassium omission (− K). Gas exchange was not affected by fertilization but differed among genotypes. Clone I144 showed higher stomatal conductance and transpiration, resulting in 26% lower water use efficiency. Potassium omission reduced root biomass by 23%. Despite this, I144 accumulated 34% more K in total biomass than the other genotypes under − K. Under potassium fertilization (+ K), genotypes exhibited 23% higher K use efficiency. Conclusions The physiological assessments of Eucalyptus and Corymbia revealed that the response to potassium fertilization is highly dependent on the intrinsic characteristics of each genotype, independent of the genus, species or propagation method (ex. seed or cutting).