Climate change causes increasingly longer periods of drought, often causing the death of plants, especially when they are in the early stages of development. Studying the benefits provided by arbuscular mycorrhizal (AM) fungi to plants in different water regimes is an efficient and sustainable strategy to face climate change. Thus, this study investigated the influence of AM fungi on Handroanthus serratifolius seedlings under different water regimes, based on biochemical, and nutritional growth parameters. The experiment was carried out in H. serratifolius seedlings cultivated with mycorrhizas (+AMF) and without mycorrhizas (-AMF) in three water regimes; a severe water deficit (SD), a moderate water deficit (MD), and a well-watered (WW) condition. AM fungi provided greater osmoregulation under water deficit conditions through the accumulation of soluble sugars, total free amino acids, and proline, as well as by reducing sugar. The increase in the absorption of phosphorus and nitrate was observed only in the presence of fungi in the well-watered regimen. A higher percentage of colonization was found in plants submitted to the well-watered regimen. Ultimately, AM fungi promoted biochemical, nutritional, and growth benefits for H. serratifolius seedlings under the water deficit and well-hydrated conditions, proving that AMF can be used to increase the tolerance of H. serratifolius plants, and help them to survive climate change.

Studies on the relationship between Handroanthus serratifolius and arbuscular mycorrhizal fungi (AMF) are limited in the literature. The influence of AMF spore density on plant development is fundamental information to determining the degree of benefits in this relationship. Therefore, the objective of this study was to investigate the effects of different AMF spore densities on thirty‐day‐old H. serratifolius seedlings, focusing on growth and biochemical parameters using a completely randomized experimental design with three different spore densities and control. The spore densities were classified as low, medium, and high, with 1.54, 3.08, and 12.35 spores g⁻¹, respectively. Plant growth analysis, mycorrhizal colonization, nitrogen compound concentration, and carbohydrate analysis were performed. The medium spore density treatment showed the greatest increases in biomass, height, leaf area, and root volume. Furthermore, greater absorption of phosphorus and better dynamics in nitrogen metabolism were observed in mycorrhizal plants compared to the control since the ammonium and nitrate compounds were rapidly incorporated into protein and chlorophyll compounds. The carbohydrate analysis revealed the influence of source‐sink dynamics on sugar concentration in different plant parts. These findings support the importance of determining the appropriate spore density for assessing the symbiotic relationship between forest species and AMF.

O milho (Zea mays L.) é uma cultura de importância socioeconômica no mundo devido ao uso na alimentação humana e animal. No entanto, assim como outros vegetais, o déficit hídrico afeta seu rendimento, problema que pode ser minimizado com a inoculação de Fungos Micorrízicos Arbusculares (FMA). Portanto, objetivou-se avaliar a influência dos FMA, oriundos da Savana de Alter-do-Chão, no crescimento e parâmetros bioquímicos das plantas de milho submetidos a dois regimes de irrigação. Para isso, as mudas de milho foram submetidas a dois tratamentos, um contendo 200 g de inóculo (CI) e outro na ausência do inóculo (SI). As análises de crescimento ocorreram em dois períodos, no primeiro, entre os dias 16 e 32 as plantas estavam sob condições de irrigação adequada, no segundo, entre os dias 32 e 40, a irrigação foi suspensa no trigésimo segundo dia. O delineamento experimental foi inteiramente casualizado, conduzido em casa de vegetação localizada na Universidade Federal do Oeste do Pará, Santarém, PA – Brasil e observados por 40 dias. Foram analisadas as Taxas de Crescimento Absoluto (TCA) e Taxas de crescimento Relativo (TCR) em dois regimes hídricos. Parâmetros bioquímicos foram analisados a partir da leitura dos pigmentos foliares e quantificação dos teores de Açúcar Solúvel Total (AST) e Açúcar Não redutor (ANR). A TCR foi superior nas plantas com FMA, cerca de 150% e 33% para o primeiro e segundo período de análise, já a TCA foi cerca de 2X maior nas plantas com FMA, ademais o índice do balanço de nitrogênio, clorofila, flavonoides e antocianinas foi em média 20% superior nas plantas com FMA em relação às plantas sem FMA. Além disso, os teores de AST e ANR foram influenciados nas folhas, onde os maiores níveis foram identificados principalmente durante o crescimento inicial das plantas sob irrigação.