Fenologia de Tabebuia caraiba (Mart.) Bureau, Caracterização morfofisiológica e conservação de suas sementes

Abstract

Tabebuia caraiba (Mart.) Bureau, a plant species belonging to the Bignoniaceae botanical family, has a high adaptability capacity, making it suitable for the recovery of degraded areas and for use in the pharmaceutical industry. Studies that relate its physiology and reproductive cycle to environmental conditions will contribute to ensuring the conservation of the species. Thus, the objective of this study was to study the ecophysiology of T. caraiba, evaluating its phenology and seed production, involving the characterization of physical, physiological and biochemical changes during maturation and storage. The variability between different T. caraíba matrices was also evaluated. In the field, the studies were carried out in the cities of São João do Cariri and Sumé, state of Paraíba, Brazil, with 30 matrices each. In the ecophysiological evaluation, each matrix was evaluated biweekly for the presence and intensity of the phenophases of budding, flowering, fruiting and leaf senescence, relating these to the precipitation pulses. Thus, it was found that T. caraiba has an annual reproductive cycle, with budding, flowering and fruiting concentrated in the dry season. Leaf senescence, which is less severe, occurred in several months and had a greater negative correlation with rainfall. Regarding seed formation and maturation, fruits were harvested from 14 to 49 days after anthesis and classified according to color. Under laboratory conditions, moisture content, germination, vigor, chemical composition and enzymatic activity of the seeds were determined. It was found that physiological maturity of the seeds occurred 42 days after anthesis, with fruits of a grayish-green color and the beginning of the opening of the slit. The increase in the concentration of proteins, lipids, starch and reducing sugars occurred until the final stage of maturation. The reduction in the activity of the enzymes superoxide dismutase and catalase can be a marker for determining seed maturity. Based on these results, fruit harvests were performed at 35, 42 and 49 days after anthesis. The seeds were packed in Kraft paper bags and stored in the refrigerator for 360 days. The water content, germination, vigor and enzymatic activity of the seeds were determined every 90 days. The seeds remained highly viable during storage, while seeds from fruits harvested 42 days after anthesis maintained high vigor. The activity of the enzymes superoxide dismutase and catalase is not linked to the seed deterioration process during storage. To study the genetic variability between and within the populations, seeds from 20 matrices were collected and analyzed for physical and physiological characteristics. Estimates of heritability, genetic variance and the relationship between genetic and environmental coefficients of variation were calculated. Principal component analysis and quantification of genetic divergence using the Mahalanobis distance were also performed. There is variability among the hues regarding the physical and physiological characteristics of seeds. The matrices SJC P03, SJC P04, SJC P11, SJC P16, SJC P17, SJC P20, Sumé P01, Sume P04, Sume P08, Sume P11 and Sume P18 are indicated as superior genotypes. The population of São João do Cariri has a greater number of matrices that generate vigorous seeds.