Effect of Acid and Alkali Stress on Seed Germination and Seedling Growth of Caragana versicolor

With seeds of Caragana versicolor in Purang County, Tibet as the materials, the seed germination and seedling growth of C. versicolor were measured under acid and alkali stress, and the soil acidity and alkalinity for normal growth and development of C. versicolor were determined, so as to provide the theoretical basis for cultivation of C. versicolor in acidified or alkaline soil. The results showed that the seed germination of C. versicolor was promoted when treated by strong acid (pH 3) and strong alkali (pH 11) solutions, and the seedling effect was good. The results also indicated that C. versicolor was a kind of plant with strong acid and alkali resistance, suitable for cultivation in acid and alkali soil areas.

Photoresponse Process and Model Comparison of Paeonia ludlowii under Saline-alkali Stress

The research aimed to analyze changes in photosynthetic characteristics of Paeonia ludlowii under saline-alkali stress, and annual seedlings of P. ludlowii were taken as the materials. Photoresponse process of P. ludlowii leaves under saline-alkali stress was simulated, and different models were used to fit photoresponse curve. The results showed that P n of P. ludlowii leaves showed the trend of first rising and then declining with PAR increased under saline-alkali stress;both G s and T r showed a rising trend with PAR increased;C i showed the trend of first declining and then rising with PAR increased. Photoresponse curve fitted by modified rectangular hyperbolic model had the best effect, and it was the optimal fitting model. P. ludlowii could adapt to saline-alkali stress in lower concentration, showing that P. ludlowii could be introduced and cultivated in saline-alkali land at a lower level.

Phenotypic Diversity of Different Populations of Paeonia ludlowii in Nyingchi of Tibet

[Objectives] To study the differences in fruit traits of different populations of Paeonia ludlowii , and to provide basic data for the identification, protection and utilization of germplasm resources of P. ludlowii .[Methods] Nine fruit traits of three different populations of P. ludlowii in Tibet were tested and analyzed.[Results] The mean values of 9 fruit traits of P. ludlowii were different in different populations;the coefficients of variation of different traits of different populations were also different;there were morphological differences of different sizes among individuals in each population;there were significant differences in 8 traits (pod length, pod width, pod thickness, pod weight, seeds per pod, seed length, seed width, and seed weight) among different populations. Among the 9 traits of the three P. ludlowii populations, the variability of the five traits was higher in the fruit pods, the variation degree of five traits including pod weight, pod thickness, seeds per pod, and seed weight was higher. It is of great significance for the screening and preservation of the germplasm resources of P. ludlowii . According to the principal component analysis (PCA), the seed weight, seed width, and seed length, i.e. the seed traits, were the main factors causing differences in fruit traits among populations. There was a certain correlation between different traits of P. ludlowii . Among the 36 Pearson- related combinations of 9 fruit traits, 11 combinations had extremely significant correlations, and 8 combinations had significant correlations, indicating that there was a certain correlation between fruit traits in the growth and development. Through cluster analysis, three populations of P. ludlowii can be divided into two categories. The BV population was a category, which is characterized by long pods, long seeds, wide seeds, thick seeds and large seed weight. Therefore, the BV population is suitable material for breeding excellent varieties.[Conclusions] This study provides basic data for the identification, protection and utilization of germplasm resources of P. ludlowii .

Floristic Study of Vascular Plants in Typical Plant Communities in the Middle and Upper Reaches of the Yarlung Zangbo River

[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed,to provide scientific basis for the estimation and protection of plant diversity,construction of ecological security shelter for the Tibetan Plateau.[Methods] In the middle and upper reaches of the Yarlung Zangbo River,quadrat (line transect) method was applied to investigate the phytocoenoses in sample plots,and relative literature was used to analyze the floristic composition and floristic element of vascular plants in the middle and upper reaches of the Yarlung Zangbo River.[Results]① There are 96 species (including subspecies and variations),69 genera of 35 vascular plant families,accounting for 16.83%,5.48%,1.66% and 11.63%,2.02%,0.31% of total vascular plant families,genera and species in Tibet and China.② There are 24 monotypic-genus families,accounting for 68.57% of the total family number in the local area;22 monotypic-species families,accounting for 62.86% of the total family number in the local area.Local flora shows the characteristics of ancient relict,such as Euphorbiaceae,Rubiaceae,Liliaceae and Ranunculaceae,they are all ancient primitive groups of the third flora and the fourth flora.③ Local vascular plant genera fall into 10 areal types and 8 variations.④ Temperate elements are much more than tropical elements,R/T is 0.19,indicating that vascular plants have typical temperate nature and residual tropical nature.There are only a few endemic genera,but more endemic species to the local area,and these species are closely related,of which there are some transitional species,indicating that local flora is too young to experience more differentiation and specialization.⑤ There are 24 Chinese endemic species,accounting for 25% of total number of species in the local area;among which there are 12 endemic species to Tibet,accounting for 50% of endemic species to China,12.5% of total number of species in the local area.Four key wild plant species are included in the second batch of national key protection.[Conclusions]① There are scarce plant groups in the local area.② Among the obvious advantages,single-genus (species) families possess the absolute advantage,and the flora has ancient origins.③ The local flora has diversified distribution types,and the complicated geographical elements.④ Temperate species possess obvious advantages,and the flora is young.⑤ Rich unique and rare species have high species diversity protection and research value.