Desempenho fisiológico e bioquímico de sementes de pepino nos diferentes estádios de maturação

Abstract

PHYSIOLOGICAL AND BIOCHEMICAL PERFORMANCE OF CUCUMBER SEEDS AT DIFFERENT MATURATION STAGESABSTRACT -The objective iN this study was to evaluate the physiological and biochemical performance of cucumber seeds during the maturation process. The cucumber seeds of the hybrid "Ômega" were used and the fruits were harvested at 30, 35, 40, 45, 50 and 55 days after anthesis. The seed quality was assessed after processing and drying, by measuring fruit mass, water content, seed dry mass and mass of thousand seeds. The seed physiological quality was evaluated from the tests of germination, first counting, electrical conductivity, speed emergence index, and final stand. X-ray and electrophoresis analyses of the iso-enzymes superoxide dismutase, catalase, esterase, lipoxigenase, isocitrate liase and LEA proteins were made. An improved physiological quality of hybrid Omega cucumber seeds is obtained at 45 and 50 days after anthesis, when the fruits are greenish-white. This is supported by analysis of superoxide dismutase, catalase, lipoxygenase, isocitrate lyase and LEA proteins, as well as the X-ray test, which confirmed the results of the physiological tests.

Physiological analysis and heat-resistant protein (LEA) activity in squash hybrid seeds during development

“…This result coincides with those obtained in the germination and first count tests (Figures 5 and 6) when it was possible to observe better seed physiological quality with the advance of the maturation process. Similar results were observed in cucumber by Nakada et al (2011), who found a higher expression of LEA proteins in seeds that had higher physiological maturity. The band electrophoretic pattern analysis of these proteins may facilitate the timely detection of physiological maturation.…”

Physiological changes in osmo and hydroprimed cucumber seeds germinated in biosaline water

“…Priming, by imposing a moderate osmotic stress to seeds, induces the concentration of osmolites, such as sugars, to keep the cell´s osmotic potential compatible with maintenance of stability of cell proteins, minimizing the loss of enzymatic activity or membrane integrity which occurs when there is water or saline stress (Gonçalves et al, 2007). Catalase (CAT) prevents formation of reactive compounds, converting hydrogen peroxide into water and oxygen, which are non-reactive oxygen species (Nakada et al, 2011).The activity of CAT in the hypocotyl-root axis of 2 DAS seedlings was not affected by either methods of priming imposed on cucumber seeds (Table 7). This means these seeds showed no changes in oxidative stress, and therefore respiratory capacity, energy supply (ATP) and assimilates for seed germination may not be affected (Demirkaya et al, 2010).…”

Methods for the assessment of isoenzymes activity in sunflower seeds

“…Enzymes such as superoxide dismutase (SOD) and catalase (CAT) act as detoxification mechanisms, removing free radicals from the cells (Rosa et al, 2005). SOD transforms superoxide into hydrogen peroxide (H 2 O 2 ), acting as the first line of defense against reactive oxygen species (Nakada et al, 2011).…”

“…SOD transforms superoxide into hydrogen peroxide (H 2 O 2 ), acting as the first line of defense against reactive oxygen species (Nakada et al, 2011).…”

“…CAT activity converts hydrogen peroxide into water and oxygen (Nakada et al, 2011), functioning as a second line of defense in the cell. The decrease in CAT activity is associated with reduced seed physiological quality, since free radicals cause oxidation of unsaturated fatty acids, causing damage to membranes (Rosa et al, 2005).…”