Anatomical and Physiological Performance of Jojoba Treated with Proline under Salinity Stress Condition

Abstract

A field trial study was conducted for two consecutive seasons 2020 and 2021 in approximately 8-month-old jojoba plants to evaluate the physiological responses following salt treatment and the role of proline as a foliar application to enhance jojoba tolerance to salinity stress. Jojoba plants were irrigated once a week for four months with diluted seawater in concentrations of 5000, 10,000, and 15,000 ppm and tap water (control). Anti-stress proline was applied four times throughout the experiment, the first at the beginning of the experiment and another three times at 30-day intervals, at concentrations of 0, 300, and 450 ppm. The effect of proline treatments on jojoba plant behavior includes growth vegetative characteristics, namely plant height increase percentage (PHIP), shoot number increase percentage (NSIP), stem diameter increase percentage (SDIP), number of leaves, leaf thickness, leaf area, and fresh and dry weights of leaves, and chemical characteristics, namely chlorophyll a and b, total chlorophyll, carotenoids, leaf mineral contents (N, P, K, Na, and Cl), total phenolic content (TPC), and proline concentration. Moreover, the impacts of proline on hydrogen peroxide (H2O2), superoxide anion (O2•−), malondialdehyde (MDA), and ion leakage (IL) under salinity stress were investigated. Briefly, proline at 450 ppm enhanced all studied growth and physiological characteristics and promoted the antioxidant system of jojoba plants compared with the control and other treatments. The anatomical structure of leaves was also examined, and favorable variations in the anatomical structure were detected in the stressed and proline-treated plants. Exogenous application of proline enhanced most of this anatomical characteristic of jojoba leaf under saline stress. In conclusion, proline as a foliar application at 450 ppm under salinity stress of 10,000 ppm enhances jojoba tolerance to salinity stress by modifying the physicochemical and morphological characteristics of jojoba plants.

Exogenous Proline Improves Salt Tolerance of Alfalfa through Modulation of Antioxidant Capacity, Ion Homeostasis, and Proline Metabolism

“…Proline accumulation is particularly associated with adaptation to salt stress in many plant species [ 19 , 25 , 26 ]. It has been suggested that proline is involved in the osmotic potential of leaves, and consequently, in osmotic adjustment, plants benefit from a greater proline content under salt stress [ 44 ]. Proline accumulated during a stress episode is degraded to provide a supply of energy to drive growth once the stress is relieved.…”

Horticultural Plants Facing Stressful Conditions—Ways of Stress Mitigation

“…Aboryia et al [4] evaluated the effect of foliar-applied proline on the enhancement of jojoba tolerance to salt stress. The physiological responses to proline treatment were manifested by an increase in the content of chlorophylls, carotenoids, minerals (N, P, K, Na, and Cl), and phenols in leaves, as well as the promotion of the antioxidant system compared with the control plants.…”

“…The presented research studies were conducted at the morphological, anatomical, physiological, and molecular levels. The authors described the impact of stress caused by salinity [1][2][3][4][5][6][7], high temperature [8,9], drought [9], spring frosts [10], copper [11], asbestos [12], and biotic stress [13]. Different plant species were studied, i.e., sunflower, zinnia, orchid, buttercup, tomato, snap bean, lettuce, jojoba, grapevine, strawberry, and apple.…”