Preharvest Trehalose Application Modulates Morpho–Physiological Traits of Gladiolus ( <i>Gladiolus grandiflorus</i> L.) and Postharvest Longevity of Cut Flower by Improving Water Relations and Scavenging ROS

The short vase life (VL) of gladiolus cut flowers reduces their commercial importance. Trehalose (Tre), a phyto‐product that plays a unique role in plant functioning and environmental safety, can be used to improve VL. This work assessed a preharvest spray of Tre to mitigate postharvest (PHV) oxidative stress in “White Prosperity” gladiolus cut flowers and its physiological and PHV‐related mechanisms. The treatments were 1 g L −1 (Tre1), 2 g L −1 (Tre2), and 3 g L −1 (Tre3), and a distilled water control. Foliar applied Tre3 (3 g L −1 ) improved VL. Trehalose spray improved ornamental traits, VL, and number of opened florets. Tre reduced oxidative injury to the membrane structure, as depicted by lower accumulation of hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA), by increasing antioxidant defense system activities. Tre also influenced total soluble proteins, sugars, phenols, and proline contents as well as floral hormonal levels, including salicylic acid, abscisic acid, and ascorbic acid. Tre could improve plant health by influencing photosynthesis and increasing VL by enhancing sugars, osmoprotectants, and antioxidant capacity.