Supplementation with NPK Prior to Water Restriction Confers Different Biochemical and Growth Modulations in a Native and Exotic Species Present in a Brazilian Semi-arid Region

Drought and altered nutrient dynamics are aggravated by anthropic actions, especially in semiarid environments, such as Brazilian Seasonally Dry Tropical Forests (Caatinga). However, it is not known how nutrient levels affect growth and biochemical responses in plants present in the Caatinga under drought. The aim of this study was to evaluate morphological and biochemical responses in Pavonia varians (native species with medicinal potential) and Megathyrsus maximus (invasive exotic species used in cattle feeding) present in the Caatinga with the application of nitrogen, phosphorus and potassium (NPK) under water restriction and rehydration. The experiment was conducted in a greenhouse with seedlings collected from the Catimbau National Park (Pernambuco, Brazil) in a factorial design with NPK application and water regimes. Plants were harvested after water restriction and after rehydration. NPK application improved the responses of P. varians to water restriction, increasing the leaf dry weight, total N, total K, and proline content. Additionally, MDA and H₂O₂ levels decreased in P. varians under water restriction with NPK application. In contrast, M. maximus without NPK application under water restriction increased SOD and CAT enzyme activities and decreased MDA levels. After rehydration, both species exhibited growth recovery. NPK application in P. varians increased the total K and total soluble carbohydrate contents, while M. maximus increased the number of leaves and root dry weight. Species have different mechanisms for combating drought stress, especially non-enzymatically through proline. Nutritional treatment with pre-stress NPK was an effective alternative against oxidative damage, especially for the native species P. varians.