QUALIDADE DE SEMENTES DE Copaifera langsdorffii Desf. SOB EFEITOS DE TRATAMENTOS PRÉ-GERMINATIVOS

Abstract

Copaiba (Copaifera langsdorffii Desf.) is a tree species with a wide distribution in Brazil and great genetic variability. Its seeds are black in color, ovoid, and have integumentary dormancy because they have structures that prevent the diffusion of water and gases into the embryonic tissue, requiring pre-germination treatments to overcome dormancy, which provides rapid and uniform germination. Considering that the species presents wide genetic variability and its seeds present tegumentary dormancy, it is needed to investigate the physical, physiological, biochemical, and histochemical characteristics in the seeds of different batches collected in different matrices, as well as in the seeds submitted to treatments to overcome dormancy relating them to the seed physiological quality. This study aimed to evaluate the physiological, physical, biochemical, and histochemical characteristics of seed batches of Copaifera langsdorffii Desf. from different matrices and in seeds under effects of pre-germination treatments to overcome tegumentary dormancy. Thus, two experiments were carried out using C. langsdorffii seeds collected daily in the Cerrado biome (Brazilian Savannah) after the recent fruit dispersion from five matrices; In the first experiment, seeds from a single matrix (neutralizing genetic interference) were subjected to seventeen pre-germination treatments, comprising: (a) mechanical scarification of the embryo opposite side, soaking in distilled water for 6 h, 12 h, 18 h, s and 24 h; (b) mechanical scarification and soaking in distilled water for 6 h, 12 h, 18 h, and 24 h; (c) chemical scarification with sulfuric acid for 45 min and 90 min; (d) thermal scarification with distilled water at 90 ºC for 1 min and 3 min; (e) thermal shock for 1 min in distilled water at 90 ºC and subsequent immersion in distilled water at 0 ºC for 1 min; (f) immersion in 70% ethyl alcohol for 10 min, 20 min, and 30 min plus the control (without pre-germination treatment). In the second experiment, seeds collected from five matrices formed the seed batch treatments. Both experiments were submitted to physical, physiological, biochemical, and histochemical quality evaluations. The seed dormancy of C. langsdorffii is successfully overcome with mechanical scarification of the embryo opposite side. The pre-germination treatment with chemical scarification with sulfuric acid for 90 min produced deleterious cellular changes to the seeds, lower activity of α-amylase and β-amylase enzymes, which are associated with germination quality and with increased stress due to the high detection of enzymes of the antioxidant system superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX), and polyphenol oxidase (PPO), in addition to high levels of the malondialdehyde enzyme (MDA) detected in seeds in deterioration process due to lipid peroxidation. The batch 2 originating from matrix 2 showed inferior physiological, physical, biochemical, and histochemical quality compared to batches from other matrices, considering the analysis of radiographic images, germination, germination speed index, low levels of α-amylase and β-amylase enzymes, high detection of SOD, CAT, APX, POX, and PPO enzymes, and high detection of the MDA content.