The shoot maturation phase is important for growing mango tree because it precedes the floral induction, when plants are under stress caused by high temperatures and low water availability, that could be reduced by using plant biostimulant. Thus, the current study aimed to use a plant biostimulant containing yeast extract and amino acids to alleviate abiotic stress in mango plants, cv. Tommy Atkins, grown in semiarid environment. The experimental design consisted of randomized blocks with five treatments, five repetitions and five plants per plot. Treatments consisted of: T1) two foliar sprays with [biostimulant + KCl] + two foliar sprays with K2SO4; T2) No biostimulant and four foliar sprays with K2SO4; T3) three individual foliar sprays with biostimulant and one foliar spray with K2SO4; T4) two foliar sprays with biostimulant and two foliar sprays with K2SO4; and T5) two foliar sprays with [biostimulant + K2SO4] + one foliar spray with K2SO4. The variables evaluated were: i) leaf concentrations of soluble carbohydrates, starch, amino acids and proline; and ii) enzymatic activity of catalase and ascorbate peroxidase. The foliar spray with biostimulant during the branch maturation phase of mango trees grown in tropical semiarid environment alleviated plant abiotic stress. Three foliar biostimulant sprays and one K2SO4spray are recommended to alleviate mango plant abiotic stress in semiarid environment.

Water stress should be adequately managed during shoot maturation to improve the floral induction of mango grown in semi-arid regions. In this scenario, proline association with algal extracts has a potential stress-mitigating effect. However, even though this practice has been reported separately for some crops, its effects on mango are still unknown. From this perspective, this study investigated the role of proline and algal extract in mitigation of water deficit effects during shoot maturation of the mango variety ‘Tommy Atkins’ grown in the tropical semi-arid region. The study consisted of five consecutive individual experiments (five foliar application treatments) in a randomized block design and a 4 x 2 factorial corresponding to i) four proline concentrations (Pro): 0.0% (without proline), 0.287, 0.575, and 1.150%, and ii) the presence of algal extract (AE) (presence and absence). The following parameters were evaluated: photosynthetic pigments, soluble carbohydrates, photochemical and non-photochemical efficiency, and flowering and production uniformity. Carotenoids were interactively affected by the factors evaluated. On the other hand, as additive effects, proline provided the highest values of gas exchange and total soluble carbohydrates, with a higher internal CO2 concentration and greater flowering uniformity. The application of proline and the algal extract of A. nodosum promoted different responses in mango physiology and can be used during shoot maturation.

In guava plants, production pruning can be performed twice a year, and the return of growth is dependent on the physiological responses that are altered by the different cultivation environments and adopted management. From this perspective, this study aimed to characterize the photosynthetic dynamics of guava plants influenced by different pruning and fruit thinning intensities during two growing seasons in the region of Currais, Piauí, Brazil. The plants were distributed in a randomized block design with a factorial arrangement (3 × 3 × 2) consisting of three pruning intensities (short, medium, and long) and three fruit thinning intensities (0, 10, and 20%) during two growing seasons. The data were subjected to a cluster analysis and canonical discriminant analysis to discriminate treatment groups based on the variables. Through a cluster analysis for the evaluated treatments, it was possible to split the two pruning seasons into five different groups clustered for the first pruning season and the second pruning season. The highest assimilation values were observed in the first pruning season and especially in plants that received short pruning with 0% fruit thinning, medium pruning with 10% and 20% fruit thinning, and long pruning with 10% fruit thinning. Through the graphic representation of the canonical discriminant analysis, the first two variables explained 93.40% of the total variance contained in the nine original variables. The highest means of ambient PAR, transpiration, leaf temperature, internal carbon, and ambient temperature were observed in the second pruning season and in plants that received short pruning with 10% and 20% fruit thinning, medium pruning with 0% and 20% fruit thinning, and long pruning with 0%, 10%, and 20% fruit thinning favors a higher photosynthetic accumulation in guava plants. We observed a multiplicity of responses; however, short pruning with 10% thinning should be considered for both seasons.