HOW FOLIAR-APPLIED NUTRIENTS AFFECT STRESSES IN PERENNIAL FRUIT PLANTS

Both biotic and abiotic stresses disrupt metabolism and cause physiological damage to perennial fruit plants. Foliar-applied nutrients have seen limited use in protecting these plants against stress, in part because little is known about the physiological relationship between nutrients and stress resistance mechanisms in plants. Where foliar-applied nutrients have been used on perennial fruit plants, it has been to enhance acclimation to specific stresses or repair mechanisms after damage has occurred. Foliar-applied calcium, boron, copper, and zinc, used alone or in combination, have been shown to enhance acclimation or repair of stress-injured tissues. Recently, the effects of water, salinity, herbivory, nutrient, and other stresses on mineral nutrient levels in perennial fruit plants have been studied. These studies have not, however, addressed the role that the affected nutrients have on stress resistance mechanisms in these plants. An understanding of this role, such as to oxidative stress, may offer new approaches for the use of foliar-applied nutrients on perennial fruit plants.