Gas Exchange of Oiticica Seedlings in Response to Potassium Fertilization and Water Turning

Aims: This objective of this work was to evaluate the effects of water deficiency on physiological aspects of oiticica plants, as well as the capacity of potassium fertilization to attenuate such effects.

Study Design: The treatments were distributed in an entirely randomized design (DIC), consisting of a 4x4 factorial, with four levels of potassium (K) and four water turning, with five repetitions.

Place and Duration of Study: The experiment was conducted in a shaded environment, with 50% light interception, in the Forest Nursery of UAEF/UFCG, between January 2020 and July 2020.

Methodology: The relative water content (RWC), transpiration (E) and photosynthesis (A) rates, stomatal conductance (gs), and internal CO2 concentration (Ci) were evaluated, and from the values of A and E, the intrinsic water use efficiency (EUAi) was calculated and, with the data of A and Ci, the carboxylation efficiency (A/Ci).

Results: There was significant interaction of treatments in the parameters RWC, E, gs, A and EUAi and isolated effect of water turning on Ci and A/Ci. Irrigation daily or every five days provided the maintenance of higher water status and better stomatal behavior, and the plants were sensitive to water stress provided by longer water turnings (every 10 and 15 days). The fertilization with 100 and 150 mg dm-3 of K kept the values of E and A high, even under low water availability.

Conclusion: Potassium fertilization proved to be effective in attenuating the negative effects caused by water deficiency on gas exchange and WUEi of the seedlings, with highlights for 100 and 150 mg dm-3 of K levels.