**4. Behavior of anthocyanins in soil salinity**

Anthocyanins are a type of phenolic pigment that dissolves in water. Pigments are found in glycosylated forms. The red, purple, and blue pigments found in fruits and vegetables are called anthocyanins. The anthocyanin content of berries, currants, grapes, and even some tropical fruits is quite high. Edible vegetables rich in anthocyanins have a red to purple hue and include leafy greens, cereals, roots, and tubers.

There are several different types of anthocyanin pigments, but the most common one is cyanidin-3-glucoside, which is present in a wide variety of plant species [58]. They are glycosides and acylated, while anthocyanidins are 3-hydroxy, 3-deoxy, and O-methylated. Cyanidin, delphinidin, pelargonidin, peonidin, petunidin, and malvidin are some of the most common types of anthocyanidins. Aside from the usual anthocyanins, plants have also been found to have acylated anthocyanins. Acylated anthocyanin has four subtypes: acrylated, coumaroylated, caffeoylated, and malonylated. These compounds become active under the saline stress. Some of them get induced in response to salt stress and hike the amount of synthesis of anthocyanins in the concerned plant. While anthocyanins appear red in acidic conditions, they change to a more typical blue color when the pH level is raised. Extraction, separation, and measurement of anthocyanins have all greatly benefited from the use of chromatography [59]. There have been several studies that link the production of anthocyanins to the induction of various types of stress in plants; however, very few of these studies have examined the rise in anthocyanin levels that occurs in response to salt stress [60].

Anthocyanins in soil salinity can help promote beneficial microbial activity in the soil. Anthocyanins are plant pigments that can help protect the plant against environmental stress such as soil salinity. They can also act as an antioxidant, scavenging for free radicals and reducing oxidative stress. Furthermore, they can induce the production of plant growth regulators and plant hormones, which can stimulate beneficial microbial activity in the soil. This includes bacteria and fungi that can improve soil fertility and nutrient availability. Additionally, anthocyanins can also stimulate the production of enzymes and metabolites that can help to increase the microbial activity in the soil. When plants are subjected to salinity stress, their metabolic processes undergo alterations. These changes manifest themselves first in the vegetative part of the plant (i.e., the leaves) and later in the reproductive organs of the plant (i.e., the flowers). Thus, leaves with intact polyphenols and antioxidants may indicate that the plant's response to salt stress occurred before the 10th day. Salinity may have decreased anthocyanins in flowers because metabolic activities were inhibited, other pigments accumulated, or the plant's antioxidative mechanisms had exhausted their supply [61]. Salinity affects anthocyanin accumulation differently, thus more research is needed. In salinity-exposed tomato genotypes, For instance, Borghesi et al. [62] demonstrated that the accumulation of anthocyanins in two different tomato genotypes reacted in opposing ways when they were exposed to saline. The study suggests that the production and localization of anthocyanins may help the plant acquire resistance to a variety of environmental challenges and that the adaptive advantages of anthocyanins are considerably less muddled in nonreproductive tissues [63].
