Name: Camila Reis dos Santos
Type: PhD thesis
Publication date: 09/07/2020
Advisor:

Name	Role
Viviana Borges Corte	Advisor *

Examining board:

Name	Role
Camilla Rozindo Dias Milanez	Internal Alternate *
Hildegardo Seibert França	Internal Examiner *
IAN DRUMOND DUARTE	External Alternate *
LEONARDO VALANDRO ZANETTI	External Examiner *
Pedro Corrêa Damasceno Junior	Internal Examiner *
VITOR DE LAIA NASCIMENTO	External Examiner *
Viviana Borges Corte	Advisor *

Summary: Abiotic stress leads to a series of physiological, biochemical and molecular
changes that negatively affect plant growth and productivity. Drought and
salinization, usually manifested as osmotic stress, are threats to agriculture in
many cultures, especially in arid and semi-arid regions. The mechanisms of
tolerance of plants to abiotic changes involve the action of signaling agents, so
that stress is perceived and transmitted to cellular machinery. Sodium
nitroprusside (SNP) has been identified as a bioactive molecule that plays
multifunctional roles in the growth and productivity of plants under normal or
stress conditions. In this sense, the objective of the present study was to
investigate the effect of SNP in seeds of Lactuca sativa L. submitted to water
and salt stress. The treatments were classified according to the substances
used in the initial germination phase. To analyze the effect of water stress, the
treatments carried out were: water (Control); PEG (Recovery Effect); PEG +
SNP100 and PEG + SNP200 (Association Effect PEG / SNP); SNP100 and
SNP200 (Protection Effect). For saline stress: water (Control); NaCl (Recovery
Effect); NaCl + SNP100 and NaCl + SNP200 (Association Effect NaCl / SNP);
SNP100 and SNP200 (Protection Effect). The following attributes were
evaluated: germination rate, germination speed index, fresh and dry mass of
shoot and root, shoot and root length, and superoxide dismutase (SOD),
catalase (CAT) and peroxidase (POX) activity. A completely randomized design
was adopted for the experiment. The potential of -0.6 Mpa for saline and water
stress prevented the germination of lettuce seeds. The SNP applied after
osmotic stress recovered germination and was beneficial for gaining dry mass
in lettuce seedlings. The pre-applied SNP guaranteed the germination of lettuce
seeds exposed to salt stress. The SNP increased the activity of the antioxidant
enzymes SOD and CAT, showing an efficient ROS elimination system during
exposure to osmotic stress. With the current climate changes and considering
the relevance of studies involving physiological mechanisms of species
tolerance to abiotic stresses, the results of this work were socialized beyond the academic pairs and walls, through the practice of pedagogical intervention
carried out in a public High School bringing out the commitment of giving back
to society about the benefits of science.

Keywords: Water scarcity • salinity • tolerance • seeds • Lactuca sativa •
popularization of science.