Fruit Peel Soil Supplementation Induces Physiological and Biochemical Tolerance in Schefflera arboricola L. Grown Under Heat Conditions

Schefflera plant is propagated and grown under greenhouse cultivation, and most of these greenhouses are low-cost. In the summer, the heat generated in greenhouses becomes a limiting factor for plant growth and, subsequently, limits the production of high-quality species under greenhouse conditions. The powder of banana (B), orange (O), and pomegranate (P) peels and their combinations were added as soil supplementation at rates of 8 and 16 g/pot to the pots of Schefflera plants, which were grown during the summer season under a low-cost greenhouse. The growth analysis was estimated after 150 and 180 days from planting. Heat conditions significantly inhibited the relative growth rate, crop growth rate, and absolute growth rate (AGR) of Schefflera plants, but fruit peel applications were shown to markedly mitigate its negative impact. Fruit peel applications augmented the shoot and root growth rates and leaf pigments, decreased AGR reduction, promoted relative water content, increased membrane stability index (MSI), and alternated the phenotypic plasticity index (PPI). Fruit peels significantly increased total phenol and flavonoid levels as well as the antioxidant activity (DPPH), which positively alleviated the oxidative damage (decreased H2O2 and MDA contents) that occurred in plant leaves, and induced heat-shock protein synthesis, leading to plants with greater heat tolerance. Orange peel application at the rate of 16 g/pot to the potting soil is more beneficial for root initiation and development during the early phases of Schefflera plant life, as well as more effective in increasing the aerial portions and inducing resistance to heat conditions in low-cost polyethylene greenhouses.