Browsing by Author "Contreras, S."

Now showing 1 - 12 of 12
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    Acquisition of germination capacity, photosensitivity, and desiccation tolerance in lettuce seeds
    (ISTA-INT SEED TESTING ASSOC, 2008) Contreras, S.; Rabara, R.; Bennett, M. A.; Tay, D.; McDonald, M.
    Germination capacity, photosensilivity, and desiccation tolerance are important attributes that seeds acquire during their development. Exploring the timing of the acquisition of these characteristics is important to better understand how different environmental conditions affecting the mother plant influence seed quality. Lettuce (Lactuca sativa L. cv. 'Tango') seeds were produced in die greenhouse. Seed germination under light and darkness was evaluated in fresh and desiccated seeds at 3, 5, 7, 9. 11, 13, 15. 17, 19, 21, 25, and 31 days after flowering (DAF). Seeds were desiccated approximate to 1 hour after harvest by placing them at 25 degrees C and 57% RK Seeds achieved maximum dry weight (physiological maturity, PM) at 13 DAF. In fresh seeds, 100% germination was observed 7 DAF. Onset of desiccation tolerance occurred 9 DAF, shortly after seed abscisic acid (ABA) concentration was at its highest level and coincident with the presence of abundant oil bodies in cotyledonary cells. Dark germination of fresh seeds increased from 0% at 11 DAF to 86% at 17 DAF and then decreased to less than 20% at 21 DAF. In general, desiccated seeds had lower dark germination percentages than fresh seeds. Onset of lettuce seed photosensitivity during the maturation desiccation phase was coincident with it sharp loss of seed water content from 37 to 11% between 17 and 19 DAF. These results Support the involvement of ABA in storage reserve deposition and acquisition of desiccation tolerance during lettuce seed development and suggest that Changes in seed water content during the maturation desiccation phase are associated with the onset of light requirement for lettuce seed germination.
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    Managing lettuce seed quality through nitrogen nutrition in soilless production
    (2019) Albornoz G., Francisco; Vilches, I.; Contreras, S.
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    Methacholine challenge test by wheezing and oxygen saturation in preschool children with asthma
    (2015) Caussade Larraín, Marie Solange; Castro Rodríguez, José Antonio; Contreras, S.; Bugueño, R.; Ramírez, R.; Padilla, O.; Einisman, H.; Holmgren, N.; Caussade Larraín, Marie Solange; Castro Rodríguez, José Antonio; Contreras, S.; Bugueño, R.; Ramírez, R.; Padilla, O.; Einisman, H.; Holmgren, N.
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    On the Prospect of Using the Maximum Circular Velocity of Halos to Encapsulate Assembly Bias in the Galaxy-Halo Connection
    (2019) Zehavi, I.; Kerby, S.E.; Contreras, S.; Jimenez, E.; Padilla, Nelson; Baugh, C.M.
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    Stochastic angular momentum slews and flips and their effect on discs in galaxy formation models
    (2014) Padilla, Nelson; Salazar Albornoz, S.; Contreras, S.; Cora, S.; Ruiz, A.
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    Syntheses, characterization and electrical properties of several poly(seleno-p-arylenediamines)
    (1995) Díaz Alzamora, Fernando Raúl; Tagle Domínguez, Luis Hernán; Godoy, A.; Contreras, S.
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    Temperature during seed development affects weight, germinability and storability of lettuce seeds
    (ISTA-INT SEED TESTING ASSOC, 2009) Contreras, S.; Bennett, M. A.; Tay, D.
    Seed germinability and storability are important aspects of lettuce seed quality determined by the genotype and environment of seed development. The objective of this study was to determine how temperature of the mother plant environment affects lettuce seed quality. Seeds of cv. Tango were produced in growth chambers under one of two treatments: i) high temperature (HT), with day/night temperatures of 30/20 degrees C, respectively, and ii) low temperature (LT), with temperatures of 20/10 degrees C. Seeds produced at LT were 37% heavier than seed from HT, however germination at optimal conditions (20 degrees C-light) was similar for both treatments. Seeds from HT presented higher dark germination at 18, 24 and 29 degrees C. Germinability (% and rates) under light at temperatures between 20 and 30 degrees C was similar for seeds from both treatments, however at temperatures between 30 and 40 degrees C seeds from HT performed better than those from LT. When germinated at exogenous abscisic acid concentrations or negative osmotic potentials, germinability of seed from HT was less affected than LT. After accelerated aging (41 degrees C, similar to 100%RH, 72 h), germination of normal seedlings was higher for seeds from HT. Germination after I and 2 months of storage at 30 degrees C and 74% RH was better for seeds from HT. The critical moment for temperature effects was also studied. Seed weight, dark germination at 30 degrees C and germination at low osmotic potential were shown to be determined earlier during seed development (before 5 and 4 d after flowering for seeds from LT and HT, respectively). On the other hand, seed storability was determined at the end of seed development, after physiological maturity (approximate to 16 and 11 d after flowering for LT and HT seeds, respectively). In conclusion, higher 'Tango' lettuce seed germinability and storability results were attained when seeds were produced at higher temperatures.
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    The better half - asymmetric star formation due to ram pressure in the EAGLE simulations
    (2020) Troncoso Iribarren, P.; Padilla, Nelson; Santander, C.; Lagos, C. D. P.; García Lambas, D.; Rodríguez, S.; Contreras, S.
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    The effect of assembly bias on redshift-space distortions
    (2019) Padilla, Nelson; Contreras, S.; Zehavi, I.; Baugh, C. M.; Norberg, P.
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    The evolution of assembly bias
    (2019) Contreras, S.; Zehavi, I.; Padilla, Nelson; Baugh, C. M.; Jiménez, E.; Lacerna Zambrano, Iván Andrés
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    The galaxy-dark matter halo connection : which galaxy properties are correlated with the host halo mass?
    (2015) Contreras, S.; Baugh, C. M.; Norberg, P.; Padilla, Nelson