Abstract

The objective of this research was to quantify the photosynthetic efficiency of Cedrela fissilis and Schinus terebinthifolius seedlings after application of salicylic acid for eight weeks. The experimental design was completely randomized, composed of four treatments, with five replicates of 20 seedlings each. The treatments consisted of increasing doses of the salicylic acid solution: 0, 100, 200, 300 mg L^-1. The solution was composed of salicylic acid, deionized water and adjuvant and applied with hand sprayer, weekly for 2 months. The parameters evaluated after the application of the acid consisted of the rate of CO₂ assimilation, leaf transpiration, stomatal conductance and internal CO₂ concentration, as well as water use efficiency, intrinsic water use efficiency and instantaneous carboxylation efficiency. In seedlings of Schinus terebinthifolius there was a reduction of the photosynthetic parameters and consequently a better use of water as the doses of the plant growth regulator were increased. In the seedlings of Cedrela fissilis the dose of 200 mg L^-1 resulted in greater CO₂ fixation per molecule of water lost and in this sense, it can be inferred that the increase in the doses of salicylic acid improved the photosynthetic efficiency, but the use of water was lower. Thus, for both species, lower doses are more recommended because there must be a balance between the fixed amount of CO₂, the plant generated from photoassimilates and the amount of water lost, in order not to generate a negative potential in the plant metabolism.

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