Respostas fisiológicas e bioquímicas de sementes de Coffea arabicaL. ao condicionamento com moléculas sinalizadoras

Abstract

One of the most cultivated species for commercial purposes is Coffea arabica L. (Rubiaceae); however, due to slow germination and low seed longevity, the time required for seedling and plant development is longer. There are also abiotic limitations that can affect the plant, with water stress being the primary factor. Thus, seeds subjected to artificial stress conditions can provide insights into the species capacity to adapt to natural stress conditions. Given the above, this study aimed to evaluate physiological priming as a strategy to improve germination, vigor, and water deficit tolerance in Coffea arabica L. seeds primed with different signaling molecules. The Catuaí Amarelo IAC-62 cultivar was used. The seeds with parchment were maintained in aerated solutions of the following reagents: 100 µM sodium nitroprusside, 0.75 µM chitosan, 50 mg L⁻¹ gibberellin, 100 µM indole-3-acetic acid (IAA), and water, and were primed for seven days. Subsequently, they were removed from priming, washed under running water, and subjected to germination tests. Both nursery experiments and laboratory tests were conducted. In the nursery, the seeds were sown, with parchment, in plastic bags. The substrate used was soil and sand in a 2:1 ratio, plus NPK fertilization. Each bag received three seeds, for a total of 12 bags per replication, with three replications per treatment. The experimental design was a split-plot randomized block design, with unprimed seeds as the control, and seeds primed in the presence of the four signaling molecules and water. The seeds were irrigated for six months after sowing, at which point irrigation for the stress treatment was suspended, and the seedlings were maintained at 40% field capacity for 30 days. After this period, seedling survival and growth capacity were measured, and material was collected for biochemical analyses. The laboratory tests were performed 0, 3, and 6 months after priming, using seeds without parchment. Germination tests were conducted with four replications of 25 seeds per plot. The seeds were placed in paper rolls moistened with 2.5 times their weight in water (non-stress) or a PEG-6000 solution at -0.6 MPa and maintained in a Mangelsdorf-type germinator at 20-30°C under constant light for 45 days. Counts were performed at 15, 30, and 45 days. For enzymatic analyses, seedlings stored at -80°C were used. The analyses were performed for catalase (CAT), superoxide dismutase (SOD), lipid peroxidation (MDA), and hydrogen peroxide (H₂O₂). The results indicated that the application of chitosan to Coffea arabica L. seeds promoted positive biochemical effects associated with the activation of the antioxidant system and the reduction of oxidative damage during storage.