Ação do ácido salicílico nas características morfofisiológicas e bioquímicas em mudas de Schinus terebinthifolius Raddi. E Cedrela fissilis VELL.

Abstract

The study aimed to evaluate the morphological and physiological changes in seedlings of Schinus terebinthifolius and Cedrela fissilis in response to the use of salicylic acid. In addition, biochemical responses were determined when seedlings were submitted to water deficiency, after the application of the regulator. The research was performed in two stages, initially, doses of salicylic acid (0, 100, 200 and 300 mg L-1) were applied in cedar and aroeira seedlings, weekly for 2 months. The parameters evaluated after the application of the acid consisted of the increases in height, diameter, dry mass of roots and shoot, leaf area of the seedlings, loss of electrolytes, lignin content in roots and stem, phenolic compounds, chlorophyll pigments and gas exchange. After this period, the 7-month-old seedlings previously in tubes were transplanted into 5-liter pots, filled with a mixture of local soil and humus in the proportion of 3: 1 and submitted to water suspension. The experimental design was arranged in subdivided plots and consisted of 4 doses of salicylic acid (0, 100, 200 e 300 mg L-1), 4 times of stress (0, 4, 8 e 12 days) and 3 replicates. The evaluations were the contents of nitrate and free ammonium content, total soluble amino acids, proteins, proline, glycine betaine, starch, total soluble carbohydrates, sucrose, relative water content and chlorophyll pigment content. Nitrogen and carbon metabolism were altered as a function of days of stress and salicylic acid application, in addition, it was observed that CRA was the major influent of the variation in compatible solutes, based on the fact that, due to the imbalance the osmotically adjusts the cellular content. In Schinus terebinthifolius seedlings the 300 mg L-1 dose resulted in a higher balance between shoot and root system. For the first part of the experiment, the height, dry matter mass of shoot and root and leaf area reduced, the diameter and the lignin content, however, increased as the doses of salicylic acid evolved. Cedrela fissilis plants, smaller doses were able to alter quality characteristics of interest, because they are more intensely reduced in the middle and, therefore, higher doses intensify the effect of stress. The dose of 300 mg L-1 of salicylic acid increased the contents of phenolic compounds, loss of electrolytes and lignin and therefore would not be recommended as it may generate imbalance in cellular content. In the Cedrela fissilis seedlings the 200 mg L-1 dose resulted in higher CO2 fixation per molecule of water lost and in this sense, the increase in salicylic acid doses improved the photosynthetic efficiency, but the water use was lower. Therefore, for both species, lower doses are more recommended because there must be a balance between the fixed amount of CO2, that is, the plant generated photoassimilates and the amount of water lost, in order not to generate a negative potential in the plant metabolism. The nitrogen and carbon metabolism were modified when stress days intensified and salicylic acid was applied, but the CRA was the major influence of the variation in compatible solutes, since the strategy is to balance the water content in function of the osmotic component of the cells.