Annona emarginata produces alkaloids of ecological and pharmacological interest and is tolerant to water and biotic stress, so it is used as rootstock for other Annonaceae fruits. There are few reports in the literature on how contrasting water stress impacts the production of specialized metabolites in Annonaceae and how primary metabolism adjusts to support such production. The objective of this investigation was to evaluate how drought and flooding stress affect alkaloid concentration and the primary metabolism of young A. emarginata plants. Three water levels (flooding, field capacity, and drought) were studied at two moments (stress and recovery). Variables analyzed were gas exchange levels, chlorophyll a fluorescence, leaf sugars, total alkaloid content, alkaloid profile, and Liriodenine concentration. The photosynthetic metabolism of A. emarginata was affected by water stress, with plants having a greater ability to adapt to drought conditions than to flooding. During the drought, a reduction in photosynthetic efficiency with subsequent recovery, higher starch and trehalose concentrations in leaves, and total alkaloids in roots (480 µg.g⁻¹) were observed. Under flooding, there was a reduction in photochemical efficiency during stress, indicating damage to the photosynthetic apparatus, without reversal during the recovery period, as well as a higher concentration of total sugars, reducing sugars, sucrose, glucose, and fructose in leaves, and Liriodenine in roots (100 µg.g⁻¹), with a lower concentration of total alkaloids (90 µg.g⁻¹). It could be concluded that there is differential tolerance of A. emarginata to water stress, inducing the modulation of alkaloid production, while drought promotes a higher concentration of total alkaloids and flooding leads to an increase in the Liriodenine concentration.

Gibberellins act to overcome dormancy and increase the germination rate of seeds of several species, including the genus Annona. Considering that Annona seeds have a high lipid content and have few sugars, the degradation of such reserves from the application of gibberellins has not been described so far. This study aimed to evaluate how the application of different gibberellic acid (GA₃) concentrations acts on the sugar and lipid degradation pattern during the germination of atemoya seeds (Annona x atemoya Mabb.). Therefore, two experiments were carried out, one to evaluate the effect of GA₃ on the germination process and another to evaluate the degradation of the reserves. To study the effect of GA₃ on germinability, four treatments with GA₃ concentrations of 0, 250, 500, and 1000 mg L⁻¹ were used. To study the degradation of reserves, the four GA₃ concentrations and five collection times were used (dry seed; seed with 1 day, 5 days, and 10 days of water acquisition; and seeds with primary root emission). Atemoya seeds showed an increase in germinability and changes in the sugar and lipid degradation pattern during the germination process in response to the treatments with GA₃. Lipid and sugar degradation was observed from 24 h after seed immersion in GA₃. The highest GA₃ concentrations (500 and 1000 mg L⁻¹) led to increases of 25% and 20%, respectively, in the germination rate, intensification of lipid degradation in seeds with primary root emission, and a decrease in sugar concentration until the 5th day.

Atemoya currently has its seeds studied in several aspects, from the technological and physiological point of view. However, for the performance of the germination test, there is no standardization in relation to the number of seeds and replicates. Thus, this work aims to determine the optimal sample size for germination tests with atemoya seeds. A germination test was carried out with 5 treatments, considering 10, 20, 30 40 and 50 seeds per sampling unit with 50 replicates of each. Data were analyzed using logistic regression, non-linear Gompertz regression models, bootstrap simulation and graphs in the form of contour lines in order to be able to infer the best binomial of the number of seeds per sampling unit and the number of replicates. The expected germination percentage, maximum germination speed and times for the beginning of the germination process, maximum germination speed and interruption of the germination process were determined. The treatment of 20 seeds per sampling unit statistically differs from that of 40 seeds by the Tukey-Kramer test with 5% significance. It could be concluded that for germination tests with atemoya seeds to have statistical validity, the smallest sample size is 10 seeds per unit, regardless of number of replicates.

Annona emarginata is a native Brazilian species capable of producing at least ten alkaloids of ecological, agronomic, and pharmacological importance. Some studies have explored the effect of external phytoregulators on the production of alkaloids, including the effect of auxins, which, like alkaloids, derive from the shikimic acid pathway. Thus, this study aimed to evaluate how indole acetic acid (IAA) and its inhibitor 2,3,5-triiodobenzoic acid (TIBA) impact the production of alkaloids and the primary metabolism of A. emarginata, which brings advances in the understanding of the mechanisms of alkaloid synthesis and can aid in the bioprospection of molecules of interest in Annonaceae. The design was completely randomized, with three treatments (control, IAA [10⁻⁶ M] and TIBA [10⁻⁶ M]) and five collection times (12, 36, 84, 156, and 324 h). The following variables were analyzed: total alkaloids, alkaloid profile, nitrate reductase activity, gas exchange in photosynthesis, chlorophyll a fluorescence, sugars, starch, and antioxidant activity. Of the twelve alkaloids analyzed, discretine and xylopine were not detected in the control plants; however, both were detected when IAA was applied (in roots and leaves) and xylopine (in roots) when the inhibitor was applied. The alkaloid asimilobine was not detected with the use of TIBA. Variations in alkaloid concentrations occurred in a punctual manner, without significant variations in photosynthesis and nitrate reductase activity, but with variations in the antioxidant system and sugar concentrations, mainly at 156 h, when the highest alkaloid concentrations were observed with the use of TIBA. It could be concluded that IAA is capable of selectively modulating the production of alkaloids in A. emarginata, either due to an external source or by the application of its inhibitor (TIBA).

Plant regulators, such as auxins, modulate the synthesis of specialized metabolites and aid in the bioprospection of molecules. Annona emarginata is known to produce antifungal alkaloids and serves as a rootstock for Annona atemoya. This study evaluated the effects of indoleacetic acid (IAA), indolebutyric acid (IBA), and naphthaleneacetic acid (NAA) applications on the accumulation of alkaloids in ungrafted A. emarginata and grafted with A. atemoya. Total alkaloids were analyzed by spectrophotometry, and alkaloid profiles were analyzed by DI-MS at 8, 14, and 20 days after treatments (DAT). The results indicated that IAA and NAA had the strongest effects on increasing the synthesis of alkaloids in the roots of ungrafted seedlings. In grafted plants, IBA had a more pronounced effect on roots; however, at final evaluation, all three auxins had an impact on both roots and leaves. Chemometric analysis revealed that auxins also altered the alkaloid composition in both seedling types. Nineteen alkaloids were identified regardless of treatment and harvest time. Eight alkaloids were identified for the first time in A. emarginata and nine were identified in A. atemoya. The main alkaloids found in ungrafted seedlings treated with IAA, IBA, and NAA were liriodenine and lanuginosine. In grafted seedlings, liriodenine and reticuline were the primary alkaloids found in roots, whereas liriodenine, lanuginosine, and reticuline were significantly present in leaves. The use of auxins to enhance alkaloid biosynthesis demonstrates their potential for bioprospection and the development of crops tolerant to biotic stress.

Vaccinium corymbosum L. ‘Biloxi’ is a cultivated blueberry variety valued for its rich content of phenolic compounds, which contribute to its strong antioxidant activity and recognized health benefits. There is little information on the effects of GA₃ and BA on blueberry, especially when used in combination. This study aimed to evaluate whether GA₃ and BA alter the yield and quality of V. corymbosum ‘Biloxi’ fruits. The experiment included 12 treatments consisting of GA₃ (25, 50 and 100 mg L⁻¹) and BA concentrations (50 and 100 mg L⁻¹) alone and combined and a control. The following parameters were analyzed: yield (g) and number of fruits per plant, mass, diameter, pH, soluble solids (SS), titratable acidity (TA), soluble sugars, total phenols, flavonoids, anthocyanins and antioxidant activity. The results indicate that foliar GA₃ and BA application improved the antioxidant capacity and biochemical composition of fruits, without negatively affecting production traits such as yield, fruit size or maturation period. The increases in antioxidant activity, phenol metabolites (total phenols, anthocyanins and flavonoids), soluble sugars, SS and SS/TA ratio were higher with the combination of GA₃ and BA at 100 mg L⁻¹. These results suggest that the combination of GA₃ and BA is a promising approach to sustainably improve fruit quality in commercial blueberry cultivation, providing both economic and nutritional benefits.