Ethylene and Gibberellin: Two Key Phytohormones for Stimulating and Alleviating the Postharvest Associated Oxidative Stress in Rosa hybrida L.

Ethylene and gibberellin are two key phytohormones in regulating the postharvest physiological mechanism of plants. The present work aimed to understand the relationship between phytohormones and physiological responses to oxidative stress in transgenic (TR) and wild type (WT) roses at the bud and half-opening stages. The cut roses were subjected to exogenous exposure to 1 µL/L ethylene gas and 80 mg/L gibberellin (GA3) at both stages for 24 h. The TR cut roses were less sensitive to ethylene as they contained the mutant etr1-1 gene. The main physiological parameters and endogenous phytohormones were measured in the outer ring of the petals by a factorial method in a completely randomized design in triplicates using GC, HPLC, and UV/VIS spectroscopy techniques. Endogenous ethylene and GA3 increased and decreased with the flower opening and senescence in both lines, respectively. Antagonistic action in metabolism was observed by endogenous production and exogenous application of two phytohormones. GA3 treatment significantly alleviated the postharvest-associated oxidative stress, so that the cut roses had the highest total protein, soluble carbohydrates, proline, and DPPH scavenging capacity, as well as the lowest MDA content and antioxidant enzyme activities at both bud and half-open stages. Both studied phytohormones can effectively control physiological responses associated with oxidative stress.