Symbiotic nitrogen fixation in black locust (Robinia pseudoacacia L.) seedlings from four seed sources

We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified ^15N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight （50.6-80.1 g）, total N （1.31-2.16 g） and proportion of nitrogen derived from the atmosphere （ 0-51%）. A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.

Influences of Seed Source, Pre-chilling, Light and Temperature on the Germination of South African Pelargonium sidoides

Pelargonium sidoides DC is used in herbal medicine for the treatment of various infections. The roots are being indiscriminately harvested for local and export trade and the collection rate is becoming unsustainable. Seed germination dynamics of this species was studied with the aim to reveal factors that influence its survival in the wild in order to adopt the appropriate germination conditions for use in ex-situ propagation and conservation program. Germination was affected by age of seeds, temperature and pre-chilling conditions. Temperature higher than 25 oC reduced germination by 60%. When seeds of P. sidoides were subjected to pre-chilling treatment for seven days, there was a significant drop in final germination by 29% compared to the other treatments. Although, final germination was not affected by different light treatments, continuous light significantly promoted germination velocity Seeds harvested from the plants grown in the green house performed better in germination than those collected from the field. The ecological implications of these observations on the propagation and conservation ofP. sidoides are discussed.

Genetic evaluation of twenty seed sources of Asparagus racemosus

A field trial of 20 seed sources of Asparagus racemosus was conducted at the Forest Research Institute, Dehradun, Uttarakhand, India to evaluate their performance of different economic traits. Genotypic variance, phenotypic variance, genotypic coefficient of variance （GCV） and phenotypic coefficient of variance （PCV） for number of shoots, shoot height, shoot weight, number of roots, root length, root diameter and root weight were calculated. Maximum genotypic and phenotypic variance was observed in shoot height among the shoot - related traits and root length among the root - related traits. For the shoot height, genotypic variance, phenotypic variance, genotypic coefficient of variance, phenotypic coefficient of variance were 231.80, 3924.80, 61.26 and 1037.32, respectively, where those of the root length were 9.55, 16.80, 23.46 and 41.27, respectively. The maximum genetic advance and genetic gain were obtained for shoot height among the shoot-related traits and root length among the root-related traits. Index values were developed for all the seed sources based on the four most important traits, and Panthnagar （Uttrakhand）, Jodhpur （Rajasthan）, Dehradun （Uttarakhand）, Chandigarh （Punjab）, Jammu （Jammu and Kashmir） and Solan （Himachal Pradesh）, were promising seed sources for root production.

Dynamics of Phaeocystis globosa bloom and implications for its seed sources in the Beibu Gulf,China

Algal blooms of haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf,South China Sea(SCS)since 2011.Recent evidence suggests that TypeⅠand TypeⅣare the two dominant genotypes of P.globosa coexisting in this area,and their marker pigment profiles,colony sizes,and genetic information differ.Two genotype-specific quantitative polymerase chain reaction(qPCR)assays were used to clarify the distribution and dynamics of P.globosa bloom in the Beibu Gulffrom November 2018 to February 2019.Results show that the patterns of spatial-temporal distribution of TypeⅠand TypeⅣwere similar,the abundance of TypeⅣwas higher than that of TypeⅠduring the algal bloom,and thus TypeⅣcells dominated the P.globosa bloom in winter 2018.The relationships between environmental factors and P.globosa abundance indicated that temperature and nitrate were critical to the distribution and dynamics of P.globosa blooms in this area.The distribution of P.globosa cells in different water masses before the bloom revealed that the westward water via the Qiongzhou Strait,the SCS bottom water,and the current in the northwestern waters of Hainan Island could transport P.globosa cells into the Beibu Gulf serving as the seed sources triggering the intense blooms in the Beibu Gulf.

Variation in cone and seed characters in blue pine (Pinus wallichiana) across natural distribution in western Himalayas

We analyzed 17 seed sources （seed stands） ofPinus wallichiana for variations present in cone and seed characters, scattered over natural distribution in north-west Himalayan states （Uttarakhand and Himachal Pradesh） of India. The significant variations were observed in cone weight, cone length, cone width, seed length, seed width, seed weight, seed germination, radicle length, and plumule length among different seed sources of the species. Significant positive correlation between seed weight, cone weight and cone width showed that seed weight in the species depend more on the cone size. Seed germination was also positively correlated with seed weight, cone weight and radicle length in the study. The estimates of variability with regard to genetic parameters for seed weight, seed germination, cone length, cone width, cone weight showed wide range of variation in the study. Seed weight showed high heritability values coupled with maximum genetic gain. Traits with such values indicate presence of good amount of heritable additive components and are under strong genetic control. The findings of the study revealed that seed sources expressed both phenotypic and genotypic differences in the seed and cone traits which might be due to the differences in genetic make up of various seed sources and environmental factors i,e. genotypic and environmental interaction, The study suggests that the seed weight should be given the top priority for the further improvement of this species.

Effect of pre-soaking and pre-chilling treatments on seed germination of Pinus roxburghii provenances from western Himalaya, India

After subjecting the seeds to GA3 and H2O2 treatments for 24 h and chilling at 2-3℃ for a period of 15 days, we conducted the seed germination tests for 21 different seed sources ofPinns roxburghii from western-central Himalaya under laboratory conditions at various temperatures viz., 20℃, 25℃ and 30℃ inside a seed germinator. The results reveal that the soaking of seeds in H2O2 （1% v/v） and GA3 （ 10 mg.L^-1） solutions manifested 82.39% and 78.19% germination, respectively whereas untreated seeds exhibited 70.79% average germination. Both GA3 and H2O2 treatments caused an appreciable shortening of the germination period by 8 days and 10 days, respectively. Moist-chilling did improve the rate and percentage of germination when germinated at 20℃ over 21 days; however total germination was not affected at temperatures 25℃ and 30℃, Although the seeds of P. roxburghii germinate well due to lack of dor- mancy, the increasing demand for large quantities of seeds of P. roxburghii for reforestation programmes make pre-sowing treatments useful in improving the rate and percentage of gemaination.

A Three-Dimensional Model of Transport and Diffusion of Seeding Agents within Stratus

It is essential to learn the temporal and spatial concentration distributions and variations of seeding agents in cloud seeding of precipitation enhancement. A three-dimensional puff trajectory model incorporating a mesoscale nonhydrostatic model has been formulated, and is applied to simulating the transporting and diffusive characteristics of multiple line sources of seeding agents within super-cooled stratus. Several important factors are taken into consideration that affect the diffusion of seeding materials such as effects of topography and vertical wind shear, temporal and spatial variation of seeding parameters and wet deposition. The particles of seeding agents are assumed to be almost inert, they have no interaction with the particles of the cloud or precipitation except that they are washed out by precipitation. The model validity is demonstrated by the analyses and comparisons of model results, and checked by the sensitivity experiments of diffusive coefficients and atmospheric stratification. The advantage of this model includes not only its exact reflection of heterogeneity and unsteadiness of background fields, but also its good simulation of transport and diffusion of multiple line sources. The horizontal diffusion rate and the horizontal transport distance have been proposed that they usually were difficult to obtain in other models. In this simulation the horizontal diffusion rate is 0.82 m s(-1) for average of one hour, and the horizontal average transport distance reaches 65 km after 1 4 which are closely related to the background Fields.

Dendroclimatic analysis of white pine (Pinus strobus L.)using long-term provenance test sites across eastern North America

Background: The main objective of this study was to examine the climatic sensitivity of the radial growth response of 13 eastern white pine(Pinus strobus L.) provenances planted at seven test sites throughout the northern part of the species’ native distribution in eastern North America.Methods: The test sites(i.e., Wabeno, Wisconsin, USA; Manistique, Michigan, USA; Pine River, Michigan, USA; Newaygo,Michigan, USA; Turkey Point, Ontario, Canada; Ganaraska, Ontario, Canada; and Orono, Maine, USA) examined in this study were part of a range-wide white pine provenance trial established in the early 1960 s in the eastern United States and Canada. Principal components analysis(PCA) was used to examine the main modes of variation [first(PC1) and second(PC2) principal component axes] in the standardized radial growth indices of the provenances at each test site.The year scores for PC1 and PC2 were examined in relation to an array of test site climate variables using multiple regression analysis to examine the commonality of growth response across all provenances to the climate of each test site. Provenance loadings on PC1 and PC2 were correlated with geographic parameters(i.e., latitude, longitude,elevation) and a suite of biophysical parameters associated with provenance origin location.Results: The amount of variation in radial growth explained by PC1 and PC2 ranged from 43.4% to 89.6%. Dendroclimatic models revealed that white pine radial growth responses to climate were complex and differed among sites. The key dendroclimatic relationships observed included sensitivity to high temperature in winter and summer, cold temperature in the spring and fal(i.e., beginning and end of the growing season), summer moisture stress, potential sensitivity to storminduced damage in spring and fal, and both positive and negative effects of higher winter snowfal. Separation of the loadings of provenances on principal component axes was mainly associated with temperature-related bioclimatic parameters of provenance origin at 5 of the 7 test sites close to the climate influence of the Great Lakes(i.e., Wabeno,Manistique, Pine River, Newaygo, and Turkey Point). In contrast, differences in radial growth response to climate at the Ganaraska test site, were driven more by precipitation-related bioclimatic parameters of the provenance origin location while radial growth at the easternmost Orono test site was independent of bioclimate at the provenance origin location.Conclusions: Study results suggest that genetic adaptation to temperature and precipitation regime may significantly influence radial growth performance of white pine populations selected for use in assisted migration programs to better adapt white pine to a future climate.