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Objective: To characterize morphological and reproductive aspects of Chascolytrum subaristatum (Lam.) Desv., in the Entre Ríos province, Argentina. Materials and Methods: A comparative analysis was carried out of two observation periods, in which the inflorescences and seeds of Ch. Subaristatum were attended. In March, 2016, caryopses collected the previous year were planted. At the beginning of spring, 10 plants were evaluated during 2016 and 2017. he beginning of flowering, maturity and harvest moment, number of inflorescences, nodes and paracladia, and number of spikelets, were recorded. In addition, the weight, moisture and germination of anthecia with caryopses, were determined. The results between harvests, relative to the number of nodes and anthecia, were compared through the mean difference test for independent samples. The chi square test was applied for the homogeneity of proportions. Results: The structural morphology of the inflorescence in both years showed low variability. The percentage of inflorescences increased 37 % in the second year with regards to the first. The results of weight, moisture and germination of the caryopses showed significant differences between the harvest years (p ≤ 0,05). Non-deep physiological dormancy was observed, which was overcome after dry storage. Conclusions: Regarding the relation of the inflorescence with the productive aspects, harvest and seed quality, to manage the grassland appropriately, and to avoid grazing at the moment of development of the reproductive tillers, is suggested. In the Entre Ríos region, seed production is possible, and varies according to the conformation of the inflorescence, plant age and harvest year. [ABSTRACT FROM AUTHOR]

In order to detect and to quantify the damage caused by natural aging of the initial stages of maize germination and the initial growth of plants, the Laboratory of Biotechnology, Instituto Politécnico Nacional, Ticomán, México, in 2005, performed a physical and physiological analysis of seeds of two ages, 6 and 19 years old, of two single crosses of the maize hybrids H28 and H30, and their inbred parental lines. The seeds were stored without control of temperature and humidity. Our study had a total of 12 treatments. A randomly blocked design with two replications of 10 seeds each was used. Variables evaluated were: content of humidity, pericap integrity, solute lixiviation, seed viability and radical protrusion. The results indicated that the physical variables (humidity content and pericarp integrity) remained unchanged during the seed storage period; however, the physiological variables (radicle protrusion and viability) were affected (p ≤ 0.05) by aging. Solute lixiviation was significantly (p ≤ 0.05) profuse in 19 year old seeds. Correlations between viability and radical protrusion (0.98 **), viability and leaching out solutes ( - 0.66 *), as well as between leaching out solutes and radical protrusion ( - 0.66 *), were significant. [ABSTRACT FROM AUTHOR]

The objective of this work was to determine the effects of different temperatures on the germination process of Ziziphus mistol Grisebach seeds, and if they had a light requirement to germinate. Under controlled conditions the seeds were incubated in trays and placed in germination chambers regulated at constant temperatures of 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45° and alternated temperature of 20°/30 °C (16/8 h) and conduced under continuous darkness or under daily photoperiod of 8 h light. The evaluated parameters in photoperiod conditions were: the germination velocity or First count (% of normal seedlings at 8 days from incubation) and the germination percentage or Final count (% or normal seedlings at 12 days from incubation). The evaluated parameter in continuous dark conditions was the percentage of germinated seeds (% of seeds at least with radicule emission at 12 days from incubation). The seeds of this specie showed an optimal range of germination temperatures between constant 25° and 35°C as well as alternant temperatures of 20°/30°C. The extremes cardinal temperatures were registered at 15° and 40°C. It was not observed light requirements for germination. [ABSTRACT FROM AUTHOR]

The viability of seeds of mistol (Ziziphus mistol Grisebach) during the storage was determined. Seeds with 7% moisture content were stored in hermetic containers at ambient (30 ± 10°C) and low (4± 3°C) temperatures during 2 years. Percentage and velocity of germination were monitored every three months. Seeds retained viability either under 4°C and ambient temperature conditions during 21 months. Under this last condition, germination percentage start to decline at 24 months. The velocity of germination diminished from 9 months on, under both storage conditions being move accentuated under ambient temperature. [ABSTRACT FROM AUTHOR]