Methods of topographical tetrazolium testing for seed viability of Nitraria tangutorum Bobr. and N. sibirica Pall.
ABSTRACT Seeds used in this study were collected from N. tangutorum and N. sibirica growing in the desert region of northwest China. The effects of two approaches (embryos allowed to remain in the upper part of cut drupes and embryos that were squeezed out of cut drupes) to expose tissues for staining in tetrazolium solution for evaluation of seed viability were examined by comparing viable seed percentages with actual germination percentages. For embryos remaining in the upper part of the cut drupes treatment, the radicle required 52 h of staining for N. tangutorum, and 48 h for N. sibirica; however, by this time, the staining of the cotyledons was too intense to allow accurate evaluation to viability. For embryos that were squeezed out of cut drupes, the staining of the whole embryos was comparatively uniform, and appropriate for evaluating viability after 12-16 h for N. sibirica, and 16-18 h for N. tangutorum, when stained at 30°C in the dark. The tetrazolium test results for the two seed lots overestimated the actual germination recorded by about 5%. Therefore, staining of extracted embryos is a suitable method for determining viability in these two species.
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ABSTRACT: A greenhouse experiment was conducted to test the effects of sand burial depth and seed mass on seedling emergence and growth of Nitraria sphaerocarpa. Seeds of Nitraria sphaerocarpa were sorted into three size-classes (large, medium, small) and artificially buried at 0, 1, 2, 3, 4, 5 and 6cm depths in plastic pots filled with unsterilized sand. In the seven treatments, the percent emergence, seedling mass and seedling height, significantly affected by both burial depth and seed size, were highest at the optimal burial depth of 2cm burial depth, and decreased with increasing burial depth in each seed size-class. Although seedling mass was usually greatest for large seeds and least for small seeds at each burial depth, little difference was observed in seedling height at shallow burial depths of 0–3cm. In each seed size-class, with increasing burial depth, both root-mass ratio and aboveground stem-mass ratio decreased, while belowground stem-mass ratio increased. In each burial depth, with decreasing seed size, belowground stem-mass ratio increased, while root-mass ratio decreased.Plant Ecology 01/2006; 185(2):191-198. · 1.53 Impact Factor
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ABSTRACT: This study addresses the adaptation of Nitraria sphaerocarpa to blown sand at the edge of a desert oasis with regard to the aspects of soil seed banks, seedlings, and population. Horizontally, the total number of seeds per unit area decreased from the shrub canopy center to intershrub areas, and most seeds were found under shrub canopies. Vertically, the highest proportion of seeds was found at depths of 5-10 cm. The emergence percentage, seedling mass, and seedling height, which were significantly affected by both burial depth and seed size, were highest at the optimal burial depth of 2 cm, and decreased with increasing burial depth in each seed size-class. Although seedling mass was usually greatest for large seeds and least for small seeds at each burial depth, little difference was observed in seedling height at shallow burial depths of 0-3 cm. The population shows a patchy and discontinuous distribution pattern. Population height increases with increasing sand depth. Also the density increases with increasing depth of sand in the desert; however, there is a steady decrease when the depth of sand is more than 100 cm. This result indicates that the depth of sand that is most suitable for the growth of Nitraria sphaerocarpa is 100 cm. The size of the population is significantly correlated with the sand depth, which increases with increasing depth in the desert.Journal of Environmental Sciences 02/2007; 19(4):482-7. · 1.77 Impact Factor