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 08/2006; 185(2):191-198. DOI:10.1007/s11258-005-9094-z · 1.64 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. DOI:10.1016/S1001-0742(07)60081-3 · 1.92 Impact Factor
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ABSTRACT: Nitraria sphaerocarpa Maxim. (Zygophyllaceae) is a desert shrub, emerged seedlings may easily be covered by sand, thus the influence of sand burial on seedling survival and growth was studied. The experiment was conducted under controlled greenhouse conditions. Seeds were sorted into three size-classes and buried at 2cm depths in plastic pots filled with sand. Two weeks after seedling emergence, seedlings were buried in sand to various depths of 0, 33, 67, 100 and 133% of their mean height. Seedling survivorship, height, mass, relative height growth rate, absolute height growth rate, biomass allocation to root, biomass allocation to belowground stem and biomass allocation to aboveground stem were significantly affected by burial depth, however, seedling survivorship, mass, relative height growth rate were not significantly affected by seed size. In the unburied and partial burial treatments, individual seedlings exhibited high survivorship of approximately 85–100% for all size-classes seeds. However, only about 60, 39 and 43% seedlings survived when the burial depth reached 100% of their height, for large, medium and small sized seeds, respectively. When the burial depth increased to 133% of seedling height, no seedlings survived. Seedling height, mass and absolute height growth rate in partial burial treatments, were higher than those of the unburied and completely buried treatments. In each seed size class, with increasing burial depth, or in each burial depth, with decreasing seed size, there was a tendency that both biomass allocation to root and biomass allocation to belowground stem increased, while biomass allocation to aboveground stem decreased. The burial experiment of N. sphaerocarpa showed that partial burial at depth of 33 and 67% of seedling height increased seedling vigor, however, when burial depth reached the whole height of seedlings, it reduced the seedling vigor, and the burial at depth of 133% of their height, led to death of all seedlings.Plant and Soil 06/2007; 295(1):95-102. DOI:10.1007/s11104-007-9265-x · 3.24 Impact Factor