power in the fruit. However, the main physiological and molecular mechanism of
inducing tolerance to low-temperature stress caused by melatonin remains unclear.
As a positive regulator of the anti-ROS process, the data show that melatonin can not
only directly purify some ROS but also modulates antioxidant enzymes and
improves cellular antioxidant protection. Melatonin increases peach tolerance to
cooling after harvest. Compared to control peaches, melatonin treatment slows
down and reduces cooling injuries in fruit during storage in refrigeration chambers.
Melatonin increases the expression of the genes involved in the antioxidant protective system, and also causes an increase in ascorbate and regulating genes involved
in the ascorbate-glutathione cycle. AsA and GSH can directly detoxify ROS and thus
contribute to the nonenzymatic ROS removal [39].
The role of phytohormones, alleviating the adverse effects of abiotic and biotic
stress in plants, is widely described in the literature. Among the plant hormones,
salicylic acid (SA) acts as a signaling and regulatory molecule in plant responses to
environmental stresses by SA-mediated control of metabolic and molecular processes [61, 62].
There are different pathways for salicylic acid biosynthesis. One of them is found
in peaches and its precursor is mandelonitrile (MD) [90]. In this pathway, MD acts as
an intermediate molecule between the cyanogenic glycosidic cycle and SA biosynthesis [91]. The contribution of the different pathways to the total amount of SA
varies according to plant species, their physiological status, and their rate of development [92–96]. For example, although it is generally accepted that the contribution
of phenylalanine (Phe) ammonium lyase (PAL) pathway to the total amount of SA is
small, this pathway becomes important during the interactions between the plant
organism and the pathogen [62]. Furthermore, it has been found that treatment with
MD increases the SA content and provides partial protection against the Plum pox
virus (PPV) infection in peach plants [91].
The cyanoglucoside pathway (CNglcs) is involved, at least in part, in the biosynthesis of SA in peach plants, and MD acts as an intermediate molecule between SA
biosynthesis and the CNglcs cycle [91]. It is known that SA is a signaling molecule
in the plant protection response that can cause tolerance to various abiotic and biotic
loads [61, 97]. Various authors have shown that SA can alleviate NaCl-induced
injuries. This response, however, is somewhat controversial, and the results depend
on plant species and their developmental phase in addition to the concentration of
SA and the mode of administration [61, 98, 99]. In terms of biotic stress, peach
plants GF305 are commonly used for plant–pathogen interaction studies with PPV,
and it has been reported that PPV infection can cause oxidative stress at the
subcellular level in these plants [92]. At least 10% of the total SA content in
micropropagated peach trees was found to be due to the cycles of CNglcs by MD
[91]. Under salt stress conditions, the increase observed in the concentration of SA in
untreated (control) and Phe- treated micropropagated peaches correlated with elevated levels of SA precursor MD, whereas in PPV-infested shoots this correlation
was observed only in control plants. Taken together, these results suggest that under
stress conditions the major part of SA should come from isochorismate (IC) and PAL
pathways [93, 94].
16 Deranged Physiology of Peach
395
inducing tolerance to low-temperature stress caused by melatonin remains unclear.
As a positive regulator of the anti-ROS process, the data show that melatonin can not
only directly purify some ROS but also modulates antioxidant enzymes and
improves cellular antioxidant protection. Melatonin increases peach tolerance to
cooling after harvest. Compared to control peaches, melatonin treatment slows
down and reduces cooling injuries in fruit during storage in refrigeration chambers.
Melatonin increases the expression of the genes involved in the antioxidant protective system, and also causes an increase in ascorbate and regulating genes involved
in the ascorbate-glutathione cycle. AsA and GSH can directly detoxify ROS and thus
contribute to the nonenzymatic ROS removal [39].
The role of phytohormones, alleviating the adverse effects of abiotic and biotic
stress in plants, is widely described in the literature. Among the plant hormones,
salicylic acid (SA) acts as a signaling and regulatory molecule in plant responses to
environmental stresses by SA-mediated control of metabolic and molecular processes [61, 62].
There are different pathways for salicylic acid biosynthesis. One of them is found
in peaches and its precursor is mandelonitrile (MD) [90]. In this pathway, MD acts as
an intermediate molecule between the cyanogenic glycosidic cycle and SA biosynthesis [91]. The contribution of the different pathways to the total amount of SA
varies according to plant species, their physiological status, and their rate of development [92–96]. For example, although it is generally accepted that the contribution
of phenylalanine (Phe) ammonium lyase (PAL) pathway to the total amount of SA is
small, this pathway becomes important during the interactions between the plant
organism and the pathogen [62]. Furthermore, it has been found that treatment with
MD increases the SA content and provides partial protection against the Plum pox
virus (PPV) infection in peach plants [91].
The cyanoglucoside pathway (CNglcs) is involved, at least in part, in the biosynthesis of SA in peach plants, and MD acts as an intermediate molecule between SA
biosynthesis and the CNglcs cycle [91]. It is known that SA is a signaling molecule
in the plant protection response that can cause tolerance to various abiotic and biotic
loads [61, 97]. Various authors have shown that SA can alleviate NaCl-induced
injuries. This response, however, is somewhat controversial, and the results depend
on plant species and their developmental phase in addition to the concentration of
SA and the mode of administration [61, 98, 99]. In terms of biotic stress, peach
plants GF305 are commonly used for plant–pathogen interaction studies with PPV,
and it has been reported that PPV infection can cause oxidative stress at the
subcellular level in these plants [92]. At least 10% of the total SA content in
micropropagated peach trees was found to be due to the cycles of CNglcs by MD
[91]. Under salt stress conditions, the increase observed in the concentration of SA in
untreated (control) and Phe- treated micropropagated peaches correlated with elevated levels of SA precursor MD, whereas in PPV-infested shoots this correlation
was observed only in control plants. Taken together, these results suggest that under
stress conditions the major part of SA should come from isochorismate (IC) and PAL
pathways [93, 94].
16 Deranged Physiology of Peach
395