Crescimento de mudas de Erythrina velutina Willd. sob fertilização potássica na fase de rustificação e restrição hídrica

Abstract

Water is a vital resource for the development of all living beings, especially plants, and is essential for physiological processes such as photosynthesis and nutrient absorption. Currently, low water availability is a common problem worldwide, and this situation has worsened with climate change, limiting the establishment of forest species. Applications of potassium fertilizer can reduce the impact of water deficit on the initial growth of seedlings, increasing their efficiency in water use. In this context, the objective of this study was to evaluate whether the application of potassium fertilizer during the rust phase reduces the stress caused by water deficit in Erythrina velutina Willd. seedlings. The experiment was conducted in a greenhouse at the Forest Nursery of the Federal Rural University of Pernambuco (UFRPE). The experiment was carried out in a completely randomized design (CRD), in a 4 x 3 factorial (4 K rates: 0, 100, 200 and 300 mg dm-³) and 3 types of daily irrigation (ID - daily application, I7 - application every 7 days and I14 - application every 14 days). Sowing was carried out in 288 cm³ tubes, and after 15 and 30 days after sowing, topdressing fertilization with macro and micronutrients was performed. When the seedlings reached 15 cm in height, a rust fertilization was performed with K rates, divided into 3 applications, every 7 days. After 15 days of the last potassium fertilization of rust, the seedlings were transplanted to 5 L pots. At 111 days after sowing (DAS), another potassium fertilization was performed divided into 3 applications, every 7 days. After 15 days of the last application, changes were imposed on the water conditions according to the safety treatments. The following morphological variables were verified: height increase (IP), stem diameter increase (IDC), number of leaflets, dry matter mass of the aerial part (MSPA), root (MSR) and total (MST), main root length (CRP), leaf area (AF), dry matter ratio of the aerial part/root (MSPA/MSR), Dickson quality index (IQD) and stomatal density; physiological results: chlorophyll indices, relative water content (TRA) and damage to cell membranes; and biochemical variables: chlorophyll and carotenoid content, hydrogen peroxide (H2O2) concentration, malondialdehyde and K content in the leaves. The data obtained were subjected to analysis of variance (ANOVA), test of means, regression analysis at 5% significance, and principal component analysis (PCA). The ideal transparency for the growth of changes is daily productivity, since there was a reduction in growth and dry matter production when water was limited. Potassium fertilization did not influence height growth, but increased root length, leaf area, chlorophyll content, cell damage and hydrogen peroxide content. The application of a dose of 200 mg dm-³ of potassium is indicated to improve photosynthetic capacity, carotenoid content, reduction of oxidative stress and greater leaf area, which may influence greater tolerance to water stress in E. velutina seedlings.