Effect of high hydrostatic pressure on seeds Carica papaya
The breaking of seed dormancy induced by stress [1] is extremely important with regard to the acceleration of germination process [1,2]. Abiotic stress processes, just like high hydrostatic pressure (HHP), are applied in several biotechnological studies, mainly because HHP induces changes in physiological and biochemical processes [3]. Pretreatment with a stress induction tool can be lethal or induce the synthesis of protective factors. When the stress does not kill the organism, it is called sublethal stress, and it can even increase the resistance to other stresses. High hydrostatic pressure is an important model in stress response study, for it has the ability to change the plasma membrane fluidity so as to keep the organism alive, which allows studies on the metabolic changes. Water is used as the medium of fluid pressure transmission since it has lower compressibility and greater compatibility, resulting in less risk of contamination. In our experiment, Carica Papaya seeds were put into a polyethylene tube containing water, the system is then closed in a capsule of high resistance steel, and suffers pressures between 10 and 400 MPa. The seeds were set to germinate in vitro, while the pressure transfer fluid present in the capsule was used to analyze abscisic acid per HPLC. The HHP generated positive effects due the seed hydration, which reflected in the percentage and speed of germination [4]. The begin of the seeds germination subjected to HHP was anticipated to 70 hours due to greater water retention, characterized by the increasing of weight (about 2.8 times greater when compared to dry weight), followed by germination values between 70-90%, while the seeds subjected to ambient pressure (control group) showed hydration of about 2.4 times and germination around 55-65%. The ambient pressure (0.1 MPa) showed lower water retention, resulting in lower mean percentage and germination speed when compared to HHP treatments. The abscisic acid (ABA) is closely related to tolerance to stress conditions (HHP) and its relation to gibberellin (GA) is crucial in the process of germination. The pressure transfer fluid has proven useful for the detection of abscisic acid, characterized by the presence of chromatograph peak with retention time equals to analyses of samples fortified with industrial ABA. The analyses of the HPLC chromatograms demonstrate changes in the composition of the water used as medium of pressure transfer. The seeds undergoing HHP pressure showed through gas chromatogram, differences between the concentrations of protein, peptides and phenol, when compared to the seeds subjected to hydrostatic control group. The balance between the concentrations of abscisic acid and gibberelin is related to germination. The presence of ABA in fluid of pressure transfer indicates a factor of germination capacity of seeds subjected to HHP stress. HHP stress is an effective biotechnological tool in the search for new mechanisms of stimulation of Carica Papaya seeds in order to provide improved germination and breaking of dormancy. Some data obtained in this experiment were omitted because due to patent submission.
Resposta fisiológica de sementes de feijão caupi ao estresse salino
This work aimed to evoluate physiological response of cowpea (Vigna unguiculata L. Walp) seeds submitted to salt stress. Seeds of cultivars 'Epace-10'; 'Canapu' and 'Pitiuba' of cowpea, were submitted to germination test in germinator at 250C, in "germitest" papers imbibed in distilled water or in 0, 10, 50, 100 and 200mol m-3 NaCl solutions. At the first and second counting of the germination test, normal seedlings were accounted, weighted and dried, obtaining data for vigor, total germination, fresh matter weight and dry matter weight. The seedlings hypocotyls, root and total length were measured total proteins content in cotyledons were obtained from germinating seeds. The presence of salt at concentrations higher than 50mol m-3 NaCl affect the germination, seedlings growth and cotyledons total protein synthesis of all cowpea cultivars. The seeds of cultivar pitiuba were is more tolerant to salinity, than the cultivars Canapu and Epace-10.
Xylem sap analysis reveals new facts of salt tolerance in rice genotypes
Danos por salinidade em arroz e em outras especies sensiveis ao estresse salino sao devidos ao transporte excessivo de NaCl, desde o sistema radicular ate as folhas; assim, baixo transporte de sais para os ramos pode ser uma caracteristica importante na determinacao da resistencia salina. Uma vez que a absorcao rapida dos ions sodio e uma parte crucial da resposta do arroz a salinidade, conduziram-se experimentos para comparar-se o fluxo (apoplastico) pelo desvio (bypass flow) de dois genotipos de arroz (IR4630 e IR15324) diferindo na tolerância salina, visto ser esse fluxo uma das principais rotas pelas quais o Na+ entra nas raizes de arroz. Experimentos com as folhas mais jovens completamente expandidas (terceira a partir do apice), usando-se o PTS (um corante fluorescente como um tracador apoplastico para a corrente transpiratoria) e o inseto Philaenus spumarius para amostragens da seiva do xilema, nao demonstraram qualquer diferenca aparente no chamado fluxo pelo desvio entre os dois genotipos. A similaridade da concentracao de Na+ na seiva do xilema de ambos genotipos foi respaldada pelos resultados de medicoes de PTS. Apesar dessa similaridade, a concentracao de Na+ nos tecidos da terceira folha, como um todo, em IR15324 (linhagem sensivel) foi cerca de duas vezes maior que em IR4630 (linhagem tolerante). As taxas de transpiracao ao longo 8 d de salinizacao foram similares entre os dois genotipos, evidenciando que o maior acumulo de NaCl nas plantas de IR15324 nao foi, provavelmente, devido a diferencas de suprimento de sal as folhas, via uma rota apoplastica. Os resultados deste trabalho sugerem que a diferenca na tolerância salina pode ser uma consequencia de danos as folhas 1 e 2 em IR15234, que permitiram maior vazamento de Na+ no floema - e consequentemente transporte de Na+ para a folha 3.