Estudos fisiológicos e bioquímicos em plantas de Amaranthus cruentus L. (Amaranthaceae) submetidas à elicitação com metil jasmonato e ácido salicílico

Abstract

Amaranth plants have numerous bioactive compounds which are widely used in various industrial sectors. However, as they are produced in small quantities by vegetables, they become insufficient to attend commercial demand. In this context, elicitation emerges as the most effective method to increase the synthesis of these substances.Thus, the present study aimed to characterize the physiological and biochemical responses of amaranth plants in presence of the growth regulators methyl jasmonate (MeJa) and salicylic acid (AS), at a concentration of 100 μM, after 24, 48, 72 and 96 hours of application, in different cultivation methods: in vitro and hydroponic. Thus, four studies were conducted, the first being responsible for developing the protocol of multiplication and establishment in vitro of Amaranthus cruentus L. BRS Alegria, to obtain plants with adequate phytosanitary conditions for possible exploration of their bioactive compounds. Results showed the effect of reducing the concentration of salts and sucrose of the MS medium on morphogenic variables in micropropagated plants, also enabling the reduction of production costs. In the second study, the main objective was to analyze the ability of MeJa and AS to increase the production of bioactive metabolites and osmotic adjustment in plants grown in vitro. For this, the micropropagation of the specie occurred as described, which was subsequently submitted to the elicitors MeJa and AS, added to the culture medium, at a concentration of 100 µM, in addition to the control treatment, exempt from them. The collection of plant material for analysis occurred after 24, 48, 72 and 96 hours. The presence of growth regulators promoted the accumulation of flavonoids and amarantine and MeJa induced the performance of osmotic adjustment, overcoming the imposed stress condition. The same treatments previously mentioned were also tested in the hydroponic cultivation system, generating two other studies. In one of them, the objective was to evaluate the osmotic adjustment, the increase in the production of bioactive metabolites as well as the antioxidant capacity of A. cruentus plants. The observed results showed that the growth regulators promoted the performance of the osmotic adjustment in hydroponic conditions, presenting expressive increases in the contents of compounds such as betalains and flavonoids, also increasing the antioxidant capacity. Finally, the last study aimed to evaluate the photosynthetic pigment index, osmotic adjustment and antioxidant capacities, as well as the carbohydrate content in A. cruentus plants. The answers obtained showed that the elicitation promoted an increase in the levels of chlorophyll and nitrogen, mainly 48 hours after application. AS stimulated the synthesis of proline, unlike MeJa, which promoted osmotic adjustment possibly through other osmolytes. The presence of elicitors also changed the redox homeostasis of the plants, with H2O2 generated as a possible inducer of secondary metabolites. And finally, it was observed that MeJa and AS are able to increase the carbohydrate content, probably due to the improvement of photosynthetic processes.