Nutrient stress signals: Elucidating morphological, physiological, and molecular responses of fruit trees to macronutrients deficiency and their management strategies

Essential macronutrients, including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), significantly contribute to plant growth and developmental processes. The occurrence of nutritional stress, particularly the inadequate application of essential macronutrients, leads to the manifestation of numerous deficiency symptoms because of suboptimal nutrients supply. The utilization of visual deficiency symptoms has been widely employed in the field of plant nutrition for the purpose of assessing the nutritional status and optimizing the efficacy of fertilizer application. Hence, it is imperative to comprehend the morphological, physiological, and molecular changes exhibited by fruit trees in response to nutrient stress. This review discussed to establish a comprehensive connection between the visual phenotypic deficiency symptoms and the underlying molecular and physiological responses correlated with macronutrient dynamics in fruit trees. we proposed a range of nutrient management strategies, including integrated nutrient management and the principles of the 4 R's (right source, right rate, right time, and right place) that can be supportive for better plant growth and optimized production under nutrients stress environment. We also explored the significant contribution of advanced molecular tools such as omics tools (genomics, transcriptomics, proteomics, metabolomics, and ionomics) and automatized technologies (imaging technology, remote sensing, and in-field sensors). These advancements are integral to integrated nutrient management, as these can be harnessed for improving fruit tree nutrition and promoting sustainability in orchard systems. These recent advancements underlying plant responses to nutrients deficiencies offer an invaluable opportunity for a deeper understanding of macronutrients functionality in fruit trees.