No abstract

Background: Agricultural soils are affected by secondary salinization due to the fragile ecological environment and lack of scientific management. It is of interest to utilize the germplasm resources of salt-tolerant plants and improve their salinity stress resistance. Seed germination of the medicinal halophyte Glycyrrhiza glabra is affected by soil salt content and temperature during seeding. This study determined the favourable soil temperature for G. glabra seed germination in salinised soil. Methods: Four sodium chloride concentration gradients (control, hyposaline, medium-saline and hypersaline) and 3 temperatures (low- medium- and high temperature) were used for a total of 12 treatments; 30 seeds were utilised in each treatment and each treatment was repeated 3 times. Result: G. glabra seed germination indexes significantly decreased with increased salt concentration. Interestingly, higher temperature could improve the salt tolerance of seeds. Seed germination percentages of hyposaline, medium-saline and hypersaline treatments were higher at elevated temperature than those at low temperature by 33.53%, 127.1% and 41.7%, respectively and were higher than those at medium temperature by 14.1%, 121.6% and 54.6% respectively. Therefore, G. glabra seeds growing in saline habitats should be sown in summer. This study provided a scientific basis for medicinal plant cultivation in salinised soil.

The alien weed Xanthium italicum (Italian cocklebur) severely decreases the Helianthus annuus (oil sunflower) seed yield; however, its mechanisms remain unknown. To explore the relative intensity of competition between the two plants and to test the hypothesis that interspecific competitive pressure from Italian cocklebur causes a reduction in the yield and quality of oil sunflower seeds, a replacement experiment using the two species was performed under simulated common water-supply conditions of sunflower farmlands, and differences in growth parameters, seed yield, and seed quality of oil sunflower between monoculture and interplanting conditions were compared. The results showed that compared with those under monoculture conditions, the seed yield (biomass), oil content, and 1000-seed weight of oil sunflower interplanted with Italian cocklebur decreased by 7.75%, 23.48%, and 13.86%, respectively, under low water supply. Moreover, these parameters were reduced by 19.85%, 24.36%, and 16.19%, respectively, under high water supply. The interspecific competitive intensity of X. italicum was significantly higher than that of oil sunflower under both water-supply conditions. Given the competitive inhibition from the exotic plant, the vegetative and reproductive growth of the native crop was significantly impaired, and its seed yield and oil content were significantly reduced.

Ammopiptanthus nanus (M. Pop.) Cheng f. is a very important resource plant that integrates soil and water conservation, afforestation of barren mountains, and ornamental, medicinal, and scientific research functions and is also a critically endangered plant in China, remaining in only six small fragmented populations in the wild. These populations have been suffering from severe anthropomorphic disturbances, causing further losses in genetic diversity. However, its genetic diversity level and genetic differentiation degree among the fragmented populations are still unclear. Inthis study, DNA was extracted from fresh leaves from the remnant populations of A. nanus, and the inter-simple-sequence repeat (ISSR) molecular marker system was used to assess its level of genetic diversity and differentiation. The result was that its genetic diversity is low at both species and population levels, with only 51.70% and 26.84% polymorphic loci, respectively. The Akeqi population had the highest genetic diversity, whereas the Ohsalur and Xiaoerbulak populations had the lowest. There was significant genetic differentiation among the populations, and the value of the genetic differentiation coefficient (Gst) was as high as 0.73, while the gene flow value was as low as 0.19 owing to spatial fragmentation and a serious genetic exchange barrier among the populations. It is suggested that a nature reserve and germplasm banks should be established as soon as possible for elimination of the anthropomorphic disturbances, and mutual introductions between the populations and introduced patches of the species, such as with habitat corridors or stepping stones, should be performed simultaneously to improve the genetic diversity of the isolated populations for the conservation of this plant.

To explore the impact of invasive weed Xanthium italicum Moretti on the economic crop Safflower, field experiments were conducted, the growth-related characters and the relative intensity of competition between the two species was explored. The results showed that under monoculture conditions, the stem height, crown width, stem diameter and the biomass of X. italicum root, stem and leaves were 1.14, 1.96, 1.82, 4.42, 4.21 and 3.99 times as high as those of Safflower, respectively. When the two species coexisted, the growth related characters of Xanthium italiana were further significantly improved, while the growth related characters of safflower were significantly decreased. When coexisted with X. italicum, the corolla biomass, hydroxysafflor yellow A content of corolla, seed yields, 100-seed weight, and seed oil content of Safflower in the interplanted treatment 90.04%, 33.11%, 63.89%, 40.58%, and 25.61% lower than those in the monocultured treatment, respectively. Relative yield (RY) and Competitive balance index (CB) of X. italicum and Safflower showed that the interspecific competitiveness of X. italicum was significantly higher than that of Safflower. Under the competitive inhibition of X. italicum, not only the vegetative growth, but also the reproductive growth, yield, and quality of the economic organs of Safflower were significantly negatively impacted.

Italian cocklebur (Xanthium italicum Moretti) invades liquorice farmlands, but specific consequences of the invasion remain unclear. Therefore, in this study, we simulated soil fertility levels of liquorice farmlands and performed replacement experiments to compare the relative competition intensity between X. italicum and Chinese liquorice (Glycyrrhiza uralensis), and investigated the differences in the effects of planting patterns (monoculture and mixture) on the growth and reproduction of the two species. Under monoculture treatment, the growth of X. italicum was more than that of G. uralensis. Vegetative and reproductive growth of X. italicum was significantly increased under mixture culture treatment compared to that under monoculture treatment; however, growth and clonal reproduction ability of G. uralensis were significantly suppressed. The biomass and contents of secondary metabolites of G. uralensis were significantly decreased under mixed culture treatment, and rhizome development was completely inhibited after mixed planting with X. italicum. The differences in vegetative growth between the two plants became larger under mixed culture treatment. Therefore, X. italicum exhibited significantly higher competitiveness than G. uralensis when coexisting within a community, and the X. italicum exerted significantly negative effects on the growth, reproduction, nodule development, yield of medicinal materials and contents of medicinal secondary metabolites of G. uralensis.

Background: Although both the root and rhizome of Glycyrrhiza inflata have been used as medicinal material, the sales volume and price of its root are much higher than its rhizomes. Limiting the growth of liquorice rhizomes while improving the yield and quality of its root has become an important problem. Methods: Two irrigation patterns (surface drip irrigation and subsurface drip irrigation, i.e. DI and SDI) and three irrigation levels (40%-50%, 60%-70% and 80%-90% of the maximum soil water capacity) were used in this study. Result: The plant height, crown width, root length, root biomass and concentrations of the five medicinal components (glycyrrhizic acid, glycyrrhetinic acid, glycyrrhizin, liquiritigenin and isoliquiritigenin) of the SDI treatments were significantly higher than those of the DI treatments. The above parameters reached their maximum under the SDI90 treatment (SDI with 80%-90% of the maximum soil water capacity). The rhizome growth of the liquorice was promoted with an increase in irrigation amount, but the biomass of the rhizomes under SDI treatment was significantly lower than that under DI treatment. Thus, the regime of SDI with a relatively high water supply can effectively promote the yield and medicinal quality of liquorice roots, while inhibiting the development of its rhizomes.

Background: Glycyrrhiza is an important medicinal plant that has been in shortage in recent years because of high demand and exhaustive harvesting. Investigating the drought tolerance of liquorice species can inform the artificial cultivation of liquorice under different water conditions and help address the shortage. Methods: Seeds of G. uralensis, G. glabra and G. inflata were treated with different concentrations of polyethylene glycol (PEG)-6000 solutions to simulate different levels of drought stress. The germination process germination rate, germination index, vigour index, stress tolerance index and recovery germination percentage of seeds were measured. Drought tolerance was evaluated using the membership function. Result: Low concentrations of PEG promoted the seed germination of G. glabra and G. inflata, whereas high concentrations inhibited the seed germination of all three plants. The degree of inhibition increased with increasing PEG concentration. Under mild PEG stress, the drought tolerance of G. uralensis was highest and that of G. glabra was the lowest. However, under severe PEG stress, the drought tolerance of G. glabra was the highest and that of G. uralensis was the lowest. Therefore, seeds of G. uralensis should be sown in relatively moist soil and those of G. glabra in relatively arid soil.