Pre-harvest potassium foliar application improves yield, vase life and overall postharvest quality of cut gladiolus inflorescences

Abstract

Gladiolus (Gladiolus grandiflorus L.) is a commercial ornamental plant cultivated for its inflorescences. Improving quality and vase life (VL) of gladiolus inflorescences is an important research topic for both the growers and the sellers. For this reason, we studied the effects of preharvest potassium (K+) foliar application on postharvest physiological and biochemical changes. Our hypothesis was that K+ foliar application could improve preharvest physicochemical responses such as photosynthesis and stomatal conductance and also improve postharvest quality by reducing oxidative damage in cells. In series of pot experiments we studied the effects of 0 %, 1 %, 2 % and 3 % K+ on net CO2 assimilation (As), stomatal conductance (gs), transpiration (E), water use efficiency (WUE), soluble sugars (SS), total soluble proteins (TSP), VL and antioxidant activity of gladiolus cv. Manhatten. The results showed that K+ application, especially on inflorescences treated with the highest K+ concentrations, positively affected As and WUE. This resulted in higher SS and TSP by 45 % and 93 %, respectively. Potassium supplementation improved VL and reduced postharvest oxidative stress by enhancing superoxide dismutase (SOD) and catalase (CAT) enzyme activities. The 3 % K+ treatments increased SOD by up to 107 % and CAT by up to 188 %, compared to the control inflorescences. K+ treatments at 3 % significantly reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, by up to 42 % and 57 %, respectively indicating a strong reduction of oxidative stress. We suggest that, K+ supplementation strategies may improve postharvest quality of cut gladiolus inflorescences and extend VL by enhancing antioxidant activity and reduce oxidative stress.