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The use of natural bioactive sources to promote plant growth and crop yield gains, such as those obtained from algae, are in evidence as a sustainable agriculture practice. In this sense, recently the calcareous alga Lithothamnium sp. had its bioactive plant growth promoting effect related to the presence of high degree of humification humic acid with pronounced auxin-like effects, while the cyanobacterium Arthrospira platensis (Spirulina plantensis) has the plant growth promoting effect attributed to a pool of bioactive molecules, such as the free L-amino acids and polyamines. To explore the effect of algae sources combinations as plant biostimulants, the aim of this work was to evaluate the effects of foliar application of micronized Lithothamnium (Lm) associated with A. platensis (Ap) dried biomass in onion (Allium cepa) metabolism, growth and yield. For that, adopting an step by step approach three experiments were conducted: (i) foliar application to onion plants grown in pots in greenhouse comparing algae sources alone and combined, (ii) foliar application to onion plants in the field under organic system testing algae sources combinations (first season), and (iii) foliar application in the field comparing doses and frequencies of selected combinations (second season). The association of algae sources promoted growth and biochemical changes, thus pigment contents, total sugars, amino acids and nitrate reductase enzyme activity were improved, increasing the onion yield by two seasons in a nature friendly way.

The development of new natural biostimulant sources for a sustainable agriculture is a strategic issue aiming to improve the healthy food production. In this sense, the goal was to identify the biostimulant action of the calcareous alga Lithothamnium sp. (Rhodophyta) on onion in two experiments, (i) in pots and (ii) at field under organic system, both in factorial scheme with two onion cultivars and foliar sprays with micronized Lithothamnium sp. at concentration of 1.5 and 3.0 g L−1. The plant growth promotion and commercial yield improvement of two onion cultivars were achieved and related to changes on amino acid metabolism and source-to-sink flow stimuli. Better nutrient acquisition also was achieved related to the stimuli to thin roots growth, with N, Mg, Mn, Zn, and Cu content in bulbs improved at 3.0 g L−1, while 1.5 g L−1 allowed highest Ca, Mg, Mn, and Zn content in bulbs. Thus, the results presents Lithothamnium sp. as novel biostimulant source to grow onion, which effects related to the presence of bioactive humic acid that calcareous algae release by micronization.

This work is based on the hypothesis that the depositions of the calcareous alga Lithothamnium sp. at the bottom of the ocean contain bioactive humic substances which may promote plant growth. To achieve this, micronized Lithothamnium sp. powder was investigated in terms of the degree of humification using a colorimetric approach; the bioactivity in comparison with that of auxin IAA (3-indole acetic acid) using a bioassay with Vigna radiata and the effect of foliar sprays on organically grown tomatoes. Humification and formation of humic acid were identified to a high degree in micronized Lithothamnium sp., which was highly bioactive showing auxin hormone-like activity. When applied as foliar sprays, rooting, growth, and yield were improved and concentrations of amino acids, sugars, and protein of tomato plants increased. Thus, the results presented a novel use for Lithothamnium sp., whereby the calcareous algae depositions provided a highly active humic acid for use as a plant biostimulant.

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.

Made available in DSpace on 2018-12-11T16:48:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-02-01 Developing new and natural sources of plant growth promotors is essential to ensure the safe and sustainable production of vegetables for human consumption. In recent years, the potential of microalgae as plant biostimulants has been investigated. Arthrospira platensis (Spirulina platensis) biomass is a recognized protein source and its enzymatic hydrolysis contains molecules such as polyamines with potential to promote plant growth. Therefore, the aim of the present study was to investigate the biostimulant properties of hydrolyzed biomass of A. platensis. Bioassays were performed to determine auxin-like and cytokinin-like bioactivity of the hydrolysates. In addition, its effect on lettuce seedling growth was investigated and an organic system field trail performed where yield and free polyamine levels in leaves quantified. The hydrolysates had a cytokinin-like effect in the bioassay. Foliar applications promoted the growth of lettuce seedlings with the 4-h reaction hydrolysate (Sph4) being the most effective at promoting growth and increasing the spermine content by 64% in the lettuce leaves. The polyamine concentration was also compared in non-hydrolyzed A. platensis and Sph4. Hydrolysis resulted in a 34% increase in spermine content. It was concluded that Sph4 is a natural plant growth promoter that can be used as a raw material for biostimulants, and spermine could be an active compound and a metabolic indicator of Sph4 bioactivity. Universidade Federal do Paraná, Rua dos Funcionários, 1540 Széchenyi István University, Győr University of KwaZulu Natal Pietermaritzburg Universidade Estadual Paulista – UNESP Universidade Estadual Paulista – UNESP

No presente trabalho, objetivou-se avaliar os efeitos da aplicação foliar do extrato da alga Ascophyllum nodosum, do ácido L-glutâmico e do Ca+2, no crescimento e produção de plantas de feijão (Phaseolus vulgaris L.). O experimento foi conduzido em casa de vegetação com os seguintes tratamentos: testemunha; aplicações foliares de soluções contendo 60 g L-1 de ácido L-glutâmico; contendo 60 g L-1 de extrato de alga; contendo 100 g L-1 de Ca+2 na forma de CaCl2; contendo 30 g L-1 de ácido L-glutâmico e 30 g L-1 extrato de alga; contendo 30 g L-1 de ácido L-glutâmico e 100 g L-1 de Ca+2; contendo 30 g L-1 de extrato de alga e 100 g L-1 de Ca+2; contendo 15 g L-1de ácido L-glutâmico associado a 15 g L-1 de extrato de alga e 100 g L-1 de Ca+2, aos 12, 28 e 42 dias após a emergência das plantas. Para a aplicação foliar, cada solução foi diluída em água na concentração de 3 ml L-1. Ao longo do ciclo foram avaliadas variáveis biométricas e ao final quantificou-se a produção de grãos por planta. Identificou-se o efeito dos tratamentos no crescimento inicial, ao longo do ciclo das plantas e na produção de grãos, caracterizando o efeito bioestimulante da solução contendo 30 g L-1 de extrato de alga e 100 g L-1 de Ca+2, e da solução contendo 15 g L-1de ácido L-glutâmico associado a 15 g L-1 de extrato de alga e 100 g L-1 de Ca+2.