Sweet cherries (Prunus avium L.) are susceptible to cracking, a physiological disorder that leads to significant economic losses. Calcium (Ca) is known to reduce the incidence and severity of cracking in sweet cherries. Several studies have investigated the mechanisms by which Ca reduces macrocracking in sweet cherries, and the following are some of the key findings:

Cell wall strengthening: Ca plays a crucial role in strengthening the cell walls of cherry fruit. It does this by promoting the formation of calcium pectate, which is a component of the middle lamella that holds adjacent cell walls together. Stronger cell walls are less susceptible to rupture, thus reducing the risk of cracking.

Enhanced membrane stability: Ca helps stabilize the cell membranes of cherry fruit by interacting with phospholipids and proteins in the membrane. This interaction helps maintain the integrity of the cell membranes, reducing the leakage of cellular contents and preventing the collapse of cells, which can lead to cracking.

Regulation of water relations: Ca plays a role in regulating water uptake and movement within cherry fruit. It helps maintain the proper water balance by controlling the opening and closing of stomata, which are pores on the leaf surface that allow for gas exchange. By regulating water uptake and movement, Ca helps prevent excessive water accumulation in the fruit, which can contribute to cracking.

Inhibition of ethylene production: Ethylene is a plant hormone that is involved in fruit ripening and senescence. High levels of ethylene can promote cracking in sweet cherries. Ca has been found to inhibit the production of ethylene in cherry fruit, thereby reducing the risk of cracking.

Improved calcium nutrition: Adequate Ca nutrition is essential for maintaining the overall health and quality of cherry fruit. When cherry trees are deficient in Ca, the fruit is more susceptible to cracking. Proper Ca fertilization and management can help ensure that cherry trees have sufficient Ca levels, reducing the incidence of cracking.

It is important to note that while Ca plays a significant role in reducing macrocracking in sweet cherries, it is not the sole factor involved. Other factors such as weather conditions, rootstock selection, and cultural practices can also influence the occurrence of cracking. Therefore, a holistic approach that combines Ca management with other best practices is necessary to effectively control cracking and ensure high-quality cherry production.