Estresse luminoso e silício em Alibertia edulis: processos fotoquímicos e crescimento de mudas

Abstract

Alibertia edulis (Rich) A. Rich (marmelo-do-cerrado, Rubiaceae) is a tree and fruit species, found in the Cerrado and has several uses. However, abiotic stress due to low or high luminous availability can lead to damage to the photochemical device and seedling growth of this species. Silicon, in the form of silicates, has contributed to plant tolerance the adverse conditions. For A. edulis there are no studies associating this elemento with luminous stress. The objective of this study was to evaluate the effect of silicon on photochemical processes and A. edulis seedling growth of under diferente light availability. The experimente was carried out in plastic pots, testing four doses of silicon (potassium silicate - K2SiO3) leaf path spraying: 0.0; 2.5; 5.0; and 10.0 mL L-1 , arranged under three luminous availability based on 0% shading levels (full sun), 30% and 70%. The evaluations were performed at 60 days after transplanting. The cultivation in full sun and 70% shade were stressful for thid species. The greatest growth characteristics occurred in seedlings grown uner 30% shade. The increasing application of K2SiO3 caused damage to the reaction center through the lowest photochemical yields under full sun, and increased photochemical efficiency on photosystem II when in 30% shade. Seedlings under 70% shade are little responsive to K2SiO3 and have lower growth and biomass production. The use of K2SiO3 contributed to leaf water regulation. The application of 10.0 mL.L -1 promoted na increase in chlorophyll indexes, leaf area, biomass production, morphophysiological índices and quality of seedlings grown under 0% and 30% shade. Therefore, the use of K2SiO3 at a dose of 10.0 mL.L -1 mitigated the negative effects of luminous stress from the full sun and contributed to obtaining high quality A. edulis seedlings in environment with high and moderate light availability.