No difference in activity of Sod-1 genotypes of Poa annua to short-term treatment of ambient gaseous organic pollution

Our previous studies indicated that genotypes at locus Sod-1 of Poa annua changed clinally along a gradient of gaseous organic pollution. In the present study, we aimed to know whether there were differential responses of activities of different superoxide dismutase （SOD） genotypes to short-term treatment of ambient gaseous organic pollution. Significant bias from Hardy-Weinberg equibrium was observed on locus Sod-1, and no genotype Sod- l-BB was found. Significantly increased activities were observed in most treatments for genotype Sod-1-AA and in one treatment for genotype Sod-1-AB. However, no significant difference in SOD activities was found between the two genotypes. It was interpreted that fitness difference between the two genotypes was small and treatment duration was too short or extent of ambient organic pollution was too low to lead to differential responses. Other environmental factor effects on activities of superoxide dismutases can also explain the results.

Effects of water depth on clonal characteristics and biomass allocation of Halophila ovalis (Hydrocharitaceae)

Halophila ovalis is a dioecious seagrass with a wide geographical and water depth range.The objective of this study was to understand its plasticity in clonal characteristics and biomass and also its allocation between above-and belowground in seagrass beds at different water depths.Methods Four monospecific H.ovalis beds,Shabei,Xialongwei,Beimu and Yingluo,which have different water depths at maximum tide level(MTL)but otherwise similar environmental conditions,were studied.We measured main clonal characteristics,i.e.horizontal internodal length,branching angle,shoot height,leaf length and width,and rhizome diameter.Above-and belowground biomasses of H.ovalis were also estimated using a harvest method.Important Findings We found no significant differences in coverage,leaf pair density or number of stem nodes per square meter between the four study sites.However,horizontal internodal length,leaf length,width,rhizome diameter and shoot height all increased significantly with the increases in water depth from 2-to 9-m MTL and decreased when the water depths were greater than 9-m MTL.No significant difference in above-or belowground biomass between the seagrass beds was found.However,the ratio of above-to belowground biomass was significantly higher in the shallowest site compared to the other three seagrass beds,indicating that more biomass was stored belowground in deeper water.The results demonstrated plastic responses in clonal characteristics and biomass allocation in H.ovalis across the water depth gradient.

Demographic Genetic Structure of Cryptomeria japonica var. sinensis in Tianmushan Nature Reserve, China

Genetic changes over space and time provide insights into the relative roles of evolutionary factors in shaping genetic patterns within plant populations. However, compared with spatial genetic structure, few studies have been conducted on genetic changes over time. In this study, we used six polymorphic microsatellite loci to assess genetic variation of six size-classes of the population of Liushan, Cryptomeriajaponica var. sinensis, in the Tianmushan National Nature Reserve, whose origin was debatable. The mean number of alleles per locus and expected heterozygosity were 4.583 and 0.5999 respectively, lower than other conifers with the same life history characteristics. FST was 0.0024-0.003, and the pairwise test revealed no significant differentiation in any pair of size classes. Significant heterozygosity excesses were detected in five size classes except the oldest one, indicating bottleneck event（s）. The above results support the hypothesis that Tianmushan population was introduced and followed by natural regeneration.