Mecanismos fisiológicos e bioquímicos associados à germinação e conservação de sementes de Syagrus romanzoffiana (Cham.) Glassman (Arecaceae)

Abstract

Syagrus romanzoffiana is a palm species widely distributed in Brazil and recognized for its ecological, economic, and landscaping importance. Despite its high potential for the restoration of degraded areas and ornamental use, the species exhibits low germination rate and speed, which limits seed propagation and hinders seedling production. Therefore, this study was structured into three articles with the aim of understanding the physiological and biochemical mechanisms involved in seed germination and conservation. In the first article, the presence of germination-inhibiting substances in extracts from seeds and endocarps of the species was investigated. Bioassays were conducted using lettuce (Lactuca sativa) seeds subjected to aqueous and hydroalcoholic extracts at different concentrations, along with the quantification of phenolic compounds present in endocarp and endosperm extracts. The results indicated that aqueous extracts did not significantly affect germination but reduced root growth, evidencing allelopathic activity. In contrast, hydroalcoholic extracts completely inhibited germination at all tested concentrations, suggesting the presence of alcohol-soluble inhibitory compounds. The detection of phenolic compounds in these tissues reinforces the hypothesis that these substances act as inhibitory agents, and further identification of other compounds involved is recommended. In the second article, the role of germination-promoting and inhibiting growth regulators was evaluated in seeds subjected or not to storage. The seeds were treated with gibberellic acid (GA₃), fluridone, and their combination. Part of the seeds was subjected to germination tests after treatment, while another portion was stored for 90 days in a freezer and subsequently evaluated for germination and viability using the tetrazolium test. The results demonstrated that storage severely compromised seed viability and that treatments with GA₃, alone or in combination, did not promote significant improvements in germination performance. The high number of abnormal seedlings and the low germination speed highlight the limitations of using stored seeds. In the third article, the influence of storage under different conditions on the physiological quality of the seeds was evaluated. Pyrenes were collected and stored under controlled room conditions, in a cold chamber, and in a freezer, considering both freshly harvested seeds and seeds dried to 5% moisture content. Germination parameters and enzymatic activity (SOD, CAT, POX, and EST) were analyzed. The interaction between moisture content and storage environment proved to be decisive for conservation. The cold chamber stood out as the most efficient condition for both moisture levels, preserving germination and vigor, while inadequate conditions resulted in loss of germination capacity. Enzymatic analyses indicated maintenance of antioxidant activity of SOD and CAT, with reductions in POX and EST in some treatments, suggesting moderate oxidative stress. It is concluded that the low germination of Syagrus romanzoffiana is associated with the presence of inhibitory compounds, limited responsiveness to growth regulators, and sensitivity to storage. Therefore, the use of freshly collected seeds is recommended, along with the development of more efficient strategies to overcome dormancy and improve seed conservation.