Photosynthetic Assimilation of the Guava (Psidium guajava) cv. Paluma under Different Pruning and Fruit Thinning Intensities

Abstract

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.