Name: Nair Hildelgard Soares dos Santos
Type: PhD thesis
Publication date: 05/10/2022
Advisor:

Name	Role
Levi Pompermayer Machado	Co-advisor *
Valéria de Oliveira Fernandes	Advisor *

Examining board:

Name	Role
FERNANDA BRÊDA ALVES	External Examiner *
JEAN CARLOS VENCIONECK DUTRA	External Examiner *
Levi Pompermayer Machado	Co advisor *
Maria do Carmo Pimentel Batitucci	Internal Alternate *
SABRINA GARCIA BROETTO	External Alternate *
Stéfano Zorzal de Almeida	Internal Examiner *
Valéria de Oliveira Fernandes	Advisor *
Viviana Borges Corte	Internal Examiner *

Summary: Currently the global demographic pressure on agricultural production requires new and sustainable approaches to meet the growing demand for plant biomass for human feed, animal feed and energy production. Therefore, there has been growing interest in natural biostimulant substances in agriculture due to the challenge of balancing technological development with environmental
conservation. Microalgae have several biotechnological applications, including biostimulants. In modern agriculture, microalgae are an ecologically correct option to replace chemical fertilizers, as they can be used as biostimulants, soil modifiers and food additives. The objective of this work was to evaluate the effects of the application of microalgae extracts on the germination and growth of bean (Phaseolus vulgaris L.), corn (Zea mays L.) and papaya (Carica papaya L.) crops. It was possible to evidence that aqueous extracts obtained from microalgae presented biostimulating growth potential, considering that all seeds used in this study showed positive germ responses. It is
noteworthy that most seeds obtained higher germination values, mean time, good speed indices, and better initial performance when submitted to extracts of species of the genus Chlorella, mainly at concentrations 1.0 g/L and 1.5 g/L. For the growth experiment, Scenedesmus acuminatus extract showed efficacy in stimulating the growth of bean plants, considering that plants submitted to this extract obtained higher grain yield per plant and higher number of pods. Thus, it can be affirmed that the biostimulant, when applied by foliar, is capable of promoting the transport of photoassimilates for the seeds, which would result in greater accumulation of mass in the seeds. It is also possible to
attribute the positive effect of S. acuminatus extract on the yield and productivity of the bean crop to the availability of micronutrients present in this microalgae. It is necessary to highlight that to evaluate the action of extracts produced from algae, one should consider the agricultural crop to be tested, and concentrations. Because the seeds may present a different physiology and this influences the mechanism of action of the extracts, consequently presenting different responses from those obtained in this study. From the results it is possible to attribute the importance of microalgae in the agricultural sector, for its potential for the development of new biostimulating products of plant growth.

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