Melatonin Counteracts Drought Induced Oxidative Damage and Stimulates Growth, Productivity and Fruit Quality Properties of Tomato Plants

Abstract

Melatonin “N-Acetyl-5-methoxytryptamine” (MT) has recently been considered as a new plant growth regulator with multiple physiological functions. Although many previous studies have confirmed that exogenous applied-MT can alleviate the deleterious effects of drought stress in many plant species, most of these studies were exclusive on seeds, seedlings, and young plants for a short period of their life cycles. Therefore, the knowledge of using MT as a potential promising agricultural foliar application to improve crop productivity and quality is still insufficient under adverse open field conditions. In this study, we investigated the effect of MT as a foliar application at 0, 20, and 40 ppm on tomato plants that were grown in the open field under the long term of optimal and deficit irrigation conditions. The results indicated that exogenous MT significantly enhanced plant growth, chlorophyll and activities of antioxidant enzymes, including ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POX). This improvement was associated with a marked reduction in proline and soluble sugars. In addition, applied-MT worked as a protective agent against oxidative damage by reducing the cellular content of toxic substances such as H2O2 and malondialdehyde (MDA). Similarly, MT-treated plants showed greater total fruit yield with improving its quality attributes like total soluble solids (TSS), ascorbic acid, and lycopene. Generally, the highest significant fruit yield either under well-watered (13.7%) or water deficit (37.4%) conditions was achieved by the treatment of 20 ppm MT. These results indicate that exogenous MT played an essential role in enhancing tomato tolerance to deficit irrigation and could be recommended as a promising agricultural treatment under such conditions.

Melatonin Treatment to Pomegranate Trees Enhances Fruit Bioactive Compounds and Quality Traits at Harvest and during Postharvest Storage

“…In addition, we recently found that 0.1 mM melatonin preharvest treatment increased crop yield of pomegranate trees [ 54 ], as well as in tomato plants under acid rain [ 40 ] or water-deficit stress conditions [ 57 ], with these effects being attributed to the ability of melatonin treatment on boosting the stress tolerance of tomato plants, throughout an increase in leaf chlorophyll content and photosynthetic rate. Thus, given the semi-arid climate conditions of Southern Spain, the melatonin treatment could have an additional effect, increasing tree net photosynthesis rate and productivity throughout enhancement of tree tolerance to heat and drought stresses [ 23 , 58 ], and in turn, leading to enhanced economic profit for growers.…”

Mechanisms of Plant Antioxidants Action

“…I have received many excellent manuscripts that try to shed some light on the potential mechanism of action of antioxidants and also described the identification of new compounds, bringing to the collection nine articles [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ] and two reviews [ 16 , 17 ].…”

“…Three works (two articles and one review) focused on the properties of melatonin. Melatonin is an interesting molecule with complex functions and potentiality [ 10 , 15 , 16 ]. Khan et al [ 16 ] have analyzed the mechanism of exogenous melatonin in various crops that can improve plant growth and development in response to various abiotic and biotic stresses by regulating antioxidant machinery in plants (both the enzymatic and non-enzymatic antioxidant defense systems), with a concomitant decrease in lipid peroxidation and plasma membrane damage.…”

“…Ibrahim et al [ 15 ], starting from the recent observation that melatonin can be considered a growth regulator with multiple physiological functions in plants and its exogenous application can decrease the deleterious effects of drought stress, have analyzed foliar application of melatonin to tomatoes under long-term optimal and deficient irrigation conditions to improve crop productivity and quality. In the range of 0–40 ppm, melatonin increases plant growth, total fruit yield, quality attributes (soluble solids, ascorbic acid, and lycopene content), chlorophyll content, and antioxidant enzyme activities (such as ascorbate peroxidase, catalase, and peroxidase), with a concomitant reduction of the amino acid proline, soluble sugars, H 2 O 2 , and dangerous substances (such as malondialdehyde) derived from oxidative injuries to cellular components, suggesting the possible utilization of melatonin under specific conditions and in enhancing tomato tolerance to deficient irrigation.…”

“…In the range of 0–40 ppm, melatonin increases plant growth, total fruit yield, quality attributes (soluble solids, ascorbic acid, and lycopene content), chlorophyll content, and antioxidant enzyme activities (such as ascorbate peroxidase, catalase, and peroxidase), with a concomitant reduction of the amino acid proline, soluble sugars, H 2 O 2 , and dangerous substances (such as malondialdehyde) derived from oxidative injuries to cellular components, suggesting the possible utilization of melatonin under specific conditions and in enhancing tomato tolerance to deficient irrigation. The stress tolerance topic has also been analyzed by Buttar et al [ 15 ]. The authors have analyzed the protection mechanism of melatonin on wheat seedlings treated with heat stress.…”