Role of Humic Acid on Inducing Salt Tolerance of Ivy Geranium (Pelargonium peltatum L.) Plants

Abstract

Saline water is used in floriculture as an alternative to freshwater in arid regions such as Saudi Arabia (SA). However, salt stress considerably accelerates serious physio-biochemical changes associated with a decline in plant establishment. Recently, humic acid (HA) foliar spraying has induced plant stress tolerance in the era of climate change; however, its precise roles in the floriculture industry within saline conditions are not yet well documented. A factorial pot experiment throughout the 2022/2023 season was conducted in the Nursery of Sustainability and Environmental Developmental Department, King Saud University, Riyadh, SA, to evaluate the potential effects of HA (0, 500, 1000 and 2000 mg/L) on growth, flowering and some physiological characteristics of Ivy geranium (Pelargoniumpeltatum) plants irrigated with saline water (230 “control”, 2000 and 4000 mg/L NaCl). Irrigation with saline water markedly inhibited plant growth, flowering attributes, the chlorophyll index, as well as macro and micro-nutrient levels, but increased the content of iron, sodium and proline in plant shoots relative to plants irrigated with non-salinized water. However, HA mainly at 1000 mg/L significantly improved plant growth, flowering capacity, nutrient status, proline accumulation and chlorophyll index under salinized or non-salinized irrigation water. Additionally, spraying of HA concentrations (500, 1000 and 2000 mg/L) under normal or salinity conditions significantly increased shoot sodium content relative to non-treated plants under such salinity levels. Our findings highlight the significance of HA concentrations (500, 1000 and 2000 mg/L) in improving the salt tolerance of Ivy geranium. Within the scarcity of irrigation water, it is recommended to irrigate Ivy geranium with saline water up to 4000 mg/L NaCl associated with spraying HA concentrations in special 1000 mg/L.