Silício no crescimento, status hídrico e osmoproteção de mudas de mamoeiro cultivado sob supressão hídrica

Abstract

Papaya (Carica papaya L.) is one of the main fruits grown in Brazil, being a culture of tropical and subtropical climate. The country stands out as the second largest producer and exporter of this fruit, with great emphasis on production in the Northeast region. One of the main factors limiting the productivity of this crop in the Region is the irregular rainfall. It is essential, therefore, to make possible alternative means of minimizing damage or inducing tolerance to water deficit, such as through stress-reducing compounds such as silicon (Si). Among the many benefits of this micronutrient in relation to the induction of resistance to water stress, we highlight the stimuli to osmoregulatory mechanisms, which are promoted by increasing the content of compatible osmolytes in the cytosol, in addition to increasing water status and growth. To verify the effectiveness of Si in promoting resistance to water stress in papaya, the present study aimed to evaluate the effect of this element as an attenuator by evaluating seedling growth, water status and osmoregulation. The work was carried out at Campus IV of the State University of Paraíba (UEPB), located in the municipality of Catolé do Rocha. Five concentrations of silicon dioxide (0; 2; 3; 4 mmol L^-1 ) and three levels of soil water availability (40, 60 and 80% of the field capacity applied in pots) were tested, with 5 replicates, making 120 experimental units. The seedlings were subjected to 30 days of stress, starting from 45 days after emergence. At 75 days after emergence, the variables of growth and water status were measured, as well as the collection of material for the evaluation of osmolytes. The doses of Si positively influenced the height of the seedlings, stem diameter and root volume of papaya. Si also promoted improvements in leaf water status, in the leaf concentration of total soluble sugars and total free amino acids, but it did not influence the biochemical characteristics of the papaya seedling root. 4 mmol L^-1 of Si was the dose that promoted the best performance of papaya seedlings submitted to water deficit. The increase in leaf water status, in the concentration of total soluble sugars and total free leaf amino acids promoted greater growth of papaya plants.