Abstract
Seeking the development of nature-friendly agronomic techniques, the use of natural sources to promote plant growth and increase agricultural yield has gained relevance. In this context, the use of biofertilizers or biostimulants obtained from microalgae has been studied, as these microorganisms have in their composition a great diversity of bioactive molecules. This study aimed to evaluate the effect of microalga Asterarcys quadricellulare (CCAP 294/1) on organic onion production, verifying its action on metabolism, growth and yield of two cultivars. Thus, two experiments were carried out: (i) foliar applications on onion plants grown in pots in a greenhouse; (ii) foliar applications on field-grown onion under an organic system. Both experiments were undertaken using solutions with spray-dried microalga biomass at concentrations of 0.05, 0.15, 0.25 and 0.4 g L−1. Biometric variables, yield of bulbs and biochemical variables were evaluated indicating that the use of A. quadricellulare promoted plant growth and increases in bulb caliber and yield of both onion cultivars. The microalga biomass stimulated plant metabolism by increases in contents of chlorophyll, carotenoids, amino acids, and the nitrate reductase enzyme activity in leaves, also free amino acids and total sugar contents in bulbs, highlighting the biomass concentration of 0.25 g L−1.
Highlights
Organic agriculture uses methods that minimize damage to the environment, producing food sustainably [1]
Numerous species of microalgae have been studied for their plant growthpromoting effect linked to their use as biofertilizers and biostimulants [4] especially associated with several bioactive compounds present in these organisms, such as polysaccharides, glycosides, phytohormones, polyamines, lipids, and free L-amino acids [3,5–9]
The fresh mass of leaves presented increases, promoted by Asterarcys quadricellulare (AQ) 5 and AQ 15 in Alvará of 34.65 and 48.75% over the control, respectively; as well as a remarkable increase was promoted by AQ 5 and AQ 25 in Perfecta, respectively, of 151.87 and 162.73% over the control (Figure 1a)
Summary
Organic agriculture uses methods that minimize damage to the environment, producing food sustainably [1]. In this sense, the use of biofertilizers has expanded its applicability and may contribute to an increase in yield [2,3]. Numerous species of microalgae have been studied for their plant growthpromoting effect linked to their use as biofertilizers and biostimulants [4] especially associated with several bioactive compounds present in these organisms, such as polysaccharides, glycosides, phytohormones, polyamines, lipids, and free L-amino acids [3,5–9]. The use of the green microalgae (Chlorophyta) Chlorella vulgaris promoted growth in corn and wheat plants [10,11]. The bioactivity of a biomass hydrolysate from the cyanobacteria Asthrospira platensis in bioassays was identified, promoting growth and production of lettuce [6].
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