Metabolomic and transcriptomic analysis of Lycium chinese and L. ruthenicum under salinity stress.

BACKGROUND: High soil salinity often adversely affects plant physiology and agricultural productivity of almost all crops worldwide, such as the crude drug known as wolfberry. However, the mechanism of this action in wolfberry is not fully understood yet. RESULTS: Here in this study, we studied different mechanisms potentially in Chinese wolfberry (Lycium chinese, LC) and black wolfberry (L. ruthenicum, LR) under salinity stress, by analyzing their transcriptome, metabolome, and hormone changes. The hormone detection analysis revealed that the ABA content was significantly lower in LR than LC under normal condition, and increased sharply under salinity stress in LR but not in LC. The transcriptome analysis showed that the salinity-responsive genes in wolfberry were mainly enriched in MAPK signaling, amino sugar and nucleotide sugar metabolism, carbon metabolism, and plant hormone signal transduction pathways in LC, while mainly related to carbon metabolism and protein processing in endoplasmic reticulum in LR. Metabolome results indicated that LR harbored higher flavone and flavonoid contents than LC under normal condition. However, the flavone and flavonoid contents were hardly changed in LR, but increased substantially in LC when exposed to salinity stress. CONCLUSIONS: Our results adds ABA and flavone to mechanism understanding of salinity tolerance in wolfberry. In addition, flavone plays a positive role in resistance to salinity stress in wolfberry.

Comparative transcriptome analysis of two contrasting wolfberry genotypes during fruit development and ripening and characterization of the LrMYB1 transcription factor that regulates flavonoid biosynthesis.

BACKGROUND: Lycium barbarum and L. ruthenicum have been used as traditional medicinal plants in China and other Asian counties for centuries. However, the molecular mechanisms underlying fruit development and ripening, as well as the associated production of medicinal and nutritional components, have been little explored in these two species. RESULTS: A competitive transcriptome analysis was performed to identify the regulators and pathways involved in the fruit ripening of red wolfberry (L. barbarum) and black wolfberry (L. ruthenicum) using an Illumina sequencing platform. In total, 155,606 genes and 194,385 genes were detected in red wolfberry (RF) and black wolfberry (BF), respectively. Of them, 20,335, 24,469, and 21,056 genes were differentially expressed at three different developmental stages in BF and RF. Functional categorization of the differentially expressed genes revealed that phenylpropanoid biosynthesis, flavonoid biosynthesis, anthocyanin biosynthesis, and sugar metabolism were the most differentially regulated processes during fruit development and ripening in the RF and BF. Furthermore, we also identified 38 MYB transcription factor-encoding genes that were differentially expressed during black wolfberry fruit development. Overexpression of LrMYB1 resulted in the activation of structural genes for flavonoid biosynthesis and led to an increase in flavonoid content, suggesting that the candidate genes identified in this RNA-seq analysis are credible and might offer important utility. CONCLUSION: This study provides novel insights into the molecular mechanism of Lycium fruit development and ripening and will be of value to novel gene discovery and functional genomic studies.

Physiological responses of Goji berry (Lycium barbarum L.) to saline-alkaline soil from Qinghai region, China.

Recently, Goji berry (Lycium barbarum L.) has been extensively cultivated to improve the fragile ecological environment and increase the income of residents in Qinghai Province, northwestern China. However, few studies have focused on the physiological responses of Goji berry under salt stress and alkali stress. Gas exchange, photosynthetic pigments, and chlorophyll fluorescence were evaluated in response to neutral (NaCl) and alkali (NaHCO3) salt stresses. Nine irrigation treatments were applied over 30 days and included 0(Control group), 50, 100, 200, and 300 mM NaCl and NaHCO3. The results showed that salt and alkali stress reduced all the indicators and that alkali stress was more harmful to Goji berry than salt stress under the same solution concentrations. The salt tolerance and alkali resistance thresholds were identified when the index value exceeded the 50% standard of the control group, and threshold values of 246.3 ± 2.9 mM and 108.4.7 ± 2.1 mM, respectively, were determined by regression analysis. These results were used to identify the optimal water content for Goji berry. The minimum soil water content to cultivate Goji berry should be 16.22% and 23.37% under mild and moderate salt stress soils, respectively, and 29.10% and 42.68% under mild and moderate alkali stress soil, respectively.

Colonization, Baker's law, and the evolution of gynodioecy in Hawaii: implications from a study of Lycium carolinianum.

PREMISE: As Baker's law suggests, the successful colonization of oceanic islands is often associated with uniparental reproduction (self-fertility), but the high incidence of dimorphism (dioecy, gynodioecy) on islands complicates this idea. Lycium carolinianum is widespread, occurring on the North American mainland and the Hawaiian Islands. We examined Baker's ideas for mainland and island populations of L. carolinianum and examined inbreeding depression as a possible contributor to the evolution of gynodioecy on Maui. METHODS: Controlled crosses were conducted in two mainland populations and two populations in Hawaii. Treatments included self and cross pollination, unmanipulated controls, and autogamy/agamospermy. Alleles from the self-incompatibility S-RNase gene were isolated and compared between mainland and island populations. Given self-compatibility in Hawaii, we germinated seeds from self- and cross- treatments and estimated inbreeding depression using seven traits and a measure of cumulative fitness. RESULTS: Mainland populations of Lycium carolinianum are predominately self-incompatible with some polymorphism for self-fertility, whereas Hawaiian populations are self-compatible. Concordantly, S-RNase allelic diversity is reduced in Hawaii compared to the mainland. Hawaiian populations also exhibit significant inbreeding depression. CONCLUSIONS: Self-compatibility in Hawaii and individual variation in self-fertility in mainland populations suggests that a colonization filter promoting uniparental reproduction may be acting in this system. Comparison of S-RNase variation suggests a collapse of allelic diversity and heterozygosity at the S-RNase locus in Hawaii, which likely contributed to mate limitation upon arrival to the Pacific. Inbreeding depression coupled with autonomous self-fertilization may have led to the evolution of gynodioecy on Maui.

[Study on membrane type leaf water evaporation inhibitors for improving effect of preventing diseases and pest controlling of Lycium barbarum].

Through indoor and field comparative experiments, the properties of membrane type leaf evaporation inhibitors and its effects on photosynthesis of Lycium barbarum and compatibility and synergistic of pesticide were studied. The evaporation inhibitors and L. barbarum were chosen to investigate the suppression of water evaporation and the compatibility with pesticides. The effect of evaporation inhibitors on photosynthesis of L. barbarum leaves was determined by the chlorophyll fluorescence imaging system. The results showed that water evaporation of L. barbarum leaves of different leaf age were evidently suppressed after treated with evaporation inhibitor. The inhibitor was well compatible with pesticide and effectively improved the pesticide efficacy，and had no significant effect on chlorophyll fluorescence parameters. It is concluded that the evaporation inhibitor has good compatibility with the pesticide, and has remarkable effect of restraining moisture evaporation, which make it can be used for reducing the dosage and improving the efficacy of the pesticide in the field of L. barbarum.

Isolation and characterization of a salt stress-responsive betaine aldehyde dehydrogenase in Lycium ruthenicum Murr.

As compatible solute, glycine betaine (GB) plays a significant role in salinity tolerance in GB accumulating plants. Solanaceous crops such as tomato (Solanum lycopersicum) and tobacco (Nicotiana tabacum) are salt sensitive and naturally GB non-accumulators. In Solanaceae, only the Lycium genus has been recorded as halophytes in China, and several Lycium species have been reported as GB accumulators. The last biosynthetic step of GB is catalyzed by aminoaldehyde dehydrogenase (AMADH) with betaine aldehyde dehydrogenase (BADH) activities. Failure of GB synthesis in tomato and tobacco was attributed to lack of BADH activity. Here, by comparing the BADH functional residues of AMADHs between the Lycium genus and solanaceous crops, we predict that all studied AMADH1s have low BADH activities while only LbAMADH2 from L. barbarum has high BADH activity. For two AMADHs in L. ruthenicum, results from substrate enzyme assays confirmed low BADH activity of LrAMADH1 and no BADH activity of LrAMADH2. Despite the very low GB contents in L. ruthenicum seedlings (< 0.5 µmol g-1 fresh weight), GB contents in fruits are up to 150 µmol g-1 FW, inferring fruits of L. ruthenicum as good GB sources. In NaCl treated seedlings, accompanied by elevated GB accumulation, expression of LrAMADH1 was up-regulated, indicating response of LrAMADH1 to salt stress in L. ruthenicum. Virus-induced silence of LrAMADH1 leads to less GB accumulation than control, revealing that LrAMADH1 participates in GB synthesis in planta. Collectively, our results show that LrAMADH1 is the bona fide BADH, which responds to salt stress in L. ruthenicum.

Floral size and shape evolution following the transition to gender dimorphism.

PREMISE OF THE STUDY: Floral morphology is expected to evolve following the transition from cosexuality to gender dimorphism in plants, as selection through male and female function becomes dissociated. Specifically, male-biased dimorphism in flower size can arise through selection for larger flowers through male function, selection for smaller flowers through female function, or both. The evolutionary pathway to floral dimorphism can be most effectively reconstructed in species with intraspecific variation in sexual system. We examined the evolution of flower size and shape in Lycium californicum, whose populations are either gender dimorphic with male and female plants, or cosexual with hermaphroditic plants. METHODS: Floral morphology was characterized in populations spanning the species' complete range. For a subset of the range where cosexual and dimorphic populations are in close proximity, we compared the size and shape of flowers from female and male plants in dimorphic populations to hermaphrodites in cosexual populations, accounting for variation associated with abiotic environmental conditions. KEY RESULTS: The magnitude of flower size dimorphism varied across dimorphic populations. After controlling for environmental variation across cosexual and dimorphic populations, flowers on males were larger than flowers on females and hermaphrodites, whereas flower size did not differ between females and hermaphrodites. Flower shape differences were associated with mating type, sexual system, and environmental variation. CONCLUSIONS: While abiotic environmental gradients shape both overall flower size and shape, male-biased flower size dimorphism in L. californicum appears to arise through selection for larger flowers in males but not smaller flowers in females.

Influence of Rhizoglomus irregulare on nutraceutical quality and regeneration of Lycium barbarum leaves under salt stress.

Whether arbuscular mycorrhizal fungi augment the nutraceutical quality of crops under salt stress is critical as a potential agronomic practice in salinized farmland. To evaluate the effect of Rhizoglomus irregulare on the nutraceutical quality of Lycium barbarum leaves under salt stress, we analyzed growth parameters and the rutin, polysaccharide, acidic polysaccharide, and amino acids contents of 2 harvests. Inoculation of R. irregulare significantly increased the regenerated bud number (partial eta squared (PES) = 0.577, P < 0.0001) and rutin concentration (PES = 0.544, P < 0.001) of L. barbarum leaves, with and without salt stress. The biomass of the 2nd harvest (PES = 0.355, P = 0.0091) and acidic polysaccharide (PES = 0.518, P = 0.001) of L. barbarum leaves were notably enhanced by R. irregulare under 200 mmol/L salt level. Rhizoglomus irregulare had insignificant effect on polysaccharide (PES = 0.092, P = 0.221) and amino acids levels (PES = 0.263, P = 0.130) in the leaves of L. barbarum. However, inoculation by R. irregulare decreased proline level (PES = 0.761, P = 0.001) in the leaves of L. barbarum when subjected to salt stress. Taken together, these results indicate that R. irregulare significantly improved the nutraceutical quality and facilitated the sustainable production of L. barbarum leaves exposed to salt stress.

Arbuscular mycorrhizas influence Lycium barbarum tolerance of water stress in a hot environment.

Arbuscular mycorrhizal (AM) fungi can assist their hosts to cope with water stress and other abiotic stresses in different ways. In order to test whether AM plants have a greater capacity than control plants to cope with water stress, we investigated the water status and photosynthetic capacity of Lycium barbarum colonized or not by the AM fungus Rhizophagus irregularis under three water conditions during a hot summer. Sugar levels and transcriptional responses of both plant and AM fungus aquaporin genes in roots were analyzed. Compared with control plants, AM plants increased transpiration rate and stomatal conductance but decreased leaf relative water content under moderate water stress. Severe water stress, however, did not inhibit the quantum yield of PSII photochemistry in AM plants versus control plants. AM plants had higher expression levels of plasma membrane intrinsic proteins or tonoplast intrinsic proteins and Rir-AQP2 and lower leaf temperature than control plants under dry-hot stress. Additionally, AM plant sugar levels under normal water conditions were similar to those of control plants under moderate water stress, but sugar levels of AM plants especially increased with severe water stress. When these aspects of performance of AM and control plants under different water conditions are compared overall, AM plants displayed an obvious superiority over control plants at coping with moderate water stress in the hot environment; AM plants maintained normal photochemical processes under severe water stress, while sugar levels were affected strongly.

Characterization of six PHT1 members in Lycium barbarum and their response to arbuscular mycorrhiza and water stress.

Phosphorus (P) is vitally important for most plant processes. However, the P available to plants is present in the soil in the form of inorganic phosphate (Pi), and is often present in only limited amounts. Water stress further reduces Pi availability. Previous studies have highlighted the important roles of members of the PHOSPHATE TRANSPORTER 1 (PHT1) family and arbuscular mycorrhizal (AM) associations for Pi acquisition by plants growing in various environments. In order to understand the Pi uptake of Lycium barbarumL., a drought-tolerant ligneous species belonging to the Solanaceae family, we cloned and characterized six L. barbarum genes encoding transporter proteins belonging to the PHT1 family, and investigated their transcriptional response to AM associations and water stress. The six cloned PHT1 genes of L. barbarum had a similar evolutionary history to that of PHT1 genes found in other Solanaceae species. Three of these genes (LbPT3, LbPT4 and LbPT5) were AM-induced; the other three genes (LbPT1, LbPT2 and LbPT7) played distinct roles in Pi acquisition, translocation and remobilization in roots and leaves. AM-induced PHT1 genes maintained their function under water stress, while moderate and severe water stress upregulated non-AM-induced PHT1 genes in roots and leaves, respectively. Moreover, although LbPT1 was upregulated in AM roots under water stress, LbPT2 and LbPT7 were inhibited in AM roots, which suggested that an AM association satisfied the demand for Pi in roots under water stress and that LbPT1 may play a role in translocating Pi from roots to shoots in this situation.

A Key Role of Xanthophylls That Are Not Embedded in Proteins in Regulation of the Photosynthetic Antenna Function in Plants, Revealed by Monomolecular Layer Studies.

The main physiological function of LHCII (light-harvesting pigment-protein complex of photosystem II), the largest photosynthetic antenna complex of plants, is absorption of light quanta and transfer of excitation energy toward the reaction centers, to drive photosynthesis. However, under strong illumination, the photosynthetic apparatus faces the danger of photodegradation and therefore excitations in LHCII have to be down-regulated, e.g., via thermal energy dissipation. One of the elements of the regulatory system, operating in the photosynthetic apparatus under light stress conditions, is a conversion of violaxanthin, the xanthophyll present under low light, to zeaxanthin, accumulated under strong light. In the present study, an effect of violaxanthin and zeaxanthin on the molecular organization and the photophysical properties of LHCII was studied in a monomolecular layer system with application of molecular imaging (atomic force microscopy, fluorescence lifetime imaging microscopy) and spectroscopy (UV-Vis absorption, FTIR, fluorescence spectroscopy) techniques. The results of the experiments show that violaxanthin promotes the formation of supramolecular LHCII structures preventing dissipative excitation quenching while zeaxanthin is involved in the formation of excitonic energy states able to quench chlorophyll excitations in both the higher (B states) and lower (Q states) energy levels. The results point to a strategic role of xanthophylls that are not embedded in a protein environment, in regulation of the photosynthetic light harvesting activity in plants.

Phenolic compounds as indicators of drought resistance in shrubs from Patagonian shrublands (Argentina).

UNLABELLED: Plants exposed to drought stress, as usually occurs in Patagonian shrublands, have developed different strategies to avoid or tolerate the lack of water during their development. Production of phenolic compounds (or polyphenols) is one of the strategies used by some native species of adverse environments to avoid the oxidative damage caused by drought. In the present study the relationship between phenolic compounds content, water availability and oxidative damage were evaluated in two native shrubs: Larrea divaricata (evergreen) and Lycium chilense (deciduous) of Patagonian shrublands by their means and/or by multivariate analysis. Samples of both species were collected during the 4 seasons for the term of 1 year. Soil water content, relative water content, total phenols, flavonoids, flavonols, tartaric acid esters, flavan-3-ols, proanthocyanidins, antioxidant capacity and lipid peroxidation were measured. According to statistical univariate analysis, L. divaricata showed high production of polyphenols along the year, with a phenolic compound synthesis enhanced during autumn (season of greatest drought), while L. chilense has lower production of these compounds without variation between seasons. The variation in total phenols along the seasons is proportional to the antioxidant capacity and inversely proportional to lipid peroxidation. Multivariate analysis showed that, regardless their mechanism to face drought (avoidance or tolerance), both shrubs are well adapted to semi-arid regions and the phenolic compounds production is a strategy used by these species living in extreme environments. The identification of polyphenol compounds showed that L. divaricata produces different types of flavonoids, particularly bond with sugars, while L. chilense produces high amount of non-flavonoids compounds. SYNTHESIS: These results suggest that flavonoid production and accumulation could be a useful indicator of drought tolerance in native species.

Correlated polymorphism in cytotype and sexual system within a monophyletic species, Lycium californicum.

BACKGROUND AND AIMS: Polyploidy has important effects on reproductive systems in plants and has been implicated in the evolution of dimorphic sexual systems. In particular, higher ploidy is associated with gender dimorphism across Lycium species (Solanaceae) and across populations within the species Lycium californicum. Previous research on the association of cytotype and sexual system within L. californicum sampled a limited portion of the species range, and did not investigate evolutionary transitions between sexual systems. Lycium californicum occurs in arid regions on offshore islands and mainland regions in the south-western United States and Mexico, motivating a more comprehensive analysis of intraspecific variation in sexual system and cytotype across the full range of this species. METHODS: Sexual system (dimorphic vs. cosexual) was determined for 34 populations across the geographical range of L. californicum using field observations of pollen production, and was confirmed using morphological measurements and among-plant correlations of primary sexual traits. Ploidy was inferred using flow cytometry in 28 populations. DNA sequence data from four plastid and two nuclear regions were used to reconstruct relationships among populations and to map transitions in sexual system and ploidy. KEY RESULTS: Lycium californicum is monophyletic, ancestrally diploid and cosexual, and the association of gender dimorphism and polyploidy appears to have two evolutionary origins in this species. Compared with cosexual populations, dimorphic populations had bimodal anther size distributions, negative correlations between male and female floral traits, and larger coefficients of variation for primary sexual traits. Flow cytometry confirmed tetraploidy in dimorphic populations, whereas cosexual populations were diploid. CONCLUSIONS: Tetraploidy and gender dimorphism are perfectly correlated in L. californicum, and the distribution of tetraploid-dimorphic populations is restricted to populations in Arizona and the Baja California peninsula. The analysis suggests that tetraploidy and dimorphism likely established in Baja California and may have evolved multiple times.

Molecular cloning and identification of a flavanone 3-hydroxylase gene from Lycium chinense, and its overexpression enhances drought stress in tobacco.

Flavonoids, as plant secondary metabolites, are widespread throughout the plant kingdom and involved in many physiological and biochemical processes. Drought resistance is attributed to flavonoids with respect to protective functions in the cell wall and membranes. The flavanone 3-hydroxylase (F3H) gene which encodes flavanone 3-hydroxylase, is essential in flavonoids biosynthetic pathway. Lycium chinense (L. chinense) is a deciduous woody perennial halophyte that grows under a large variety of environmental conditions and survives under extreme drought stress. A novel cDNA sequence coding a F3H gene in Lycium chinense (LcF3H, GenBank: KJ636468.1) was isolated. The open reading frame of LcF3H comprised 1101 bp encoding a polypeptide of 366 amino acids with a molecular weight of about 42 kDa and an isoelectric point of 5.32. The deduced LcF3H protein showed high identities with other plant F3Hs, and the conserved motifs were found in LcF3H at similar positions like other F3Hs. The recombinant protein converted naringen into dihydrokaempferol in vitro. Since studies have shown that amongst flavonoids, flavan-3-ols (catechin and epicatechin) have direct free radical scavenging activity to maintain the normal physiological function of cells in vivo, these data support the possible relationship between the oxidative damage and the regulation of LcF3H gene expression in L. chinense under drought stress. In order to better understand the biotechnological potential of LcF3H, gene overexpression was conducted in tobacco. The content of flavan-3-ols and the tolerance to drought stress were increased in LcF3H overexpressing tobacco. Analysis of transgenic tobacco lines also showed that antioxidant enzyme activities were increased meanwhile the malondialdehyde (MDA) content and the content of H2O2 were reduced comparing to nontransformed tobacco plants. Furthermore, the photosynthesis rate was less decreased in the transgenetic plants. These results suggest that LcF3H plays a role in enhancing drought tolerance in L. chinense, and its overexpression increases tolerance to drought stress by improving the antioxidant system in tobacco.

Intraspecific variation in gender strategies in Lycium (Solanaceae): associations with ploidy and changes in floral form following the evolution of gender dimorphism.

UNLABELLED: • PREMISE OF THE STUDY: An association between polyploidy and gender dimorphism has been noted in several plant lineages. Whereas the majority of Lycium species are diploid and have hermaphroditic flowers in cosexual populations, gender dimorphism (gynodioecy, dioecy) has been shown to be uniformly associated with polyploidy in previous studies. Preliminary field observations suggested that some populations of Lycium carolinianum were dimorphic, providing a test of this association.• METHODS: We assessed sexual systems and cytotype variation (to infer ploidy) across 17 populations of L. carolinianum. Comparison of flowers in cosexual and dimorphic populations were used to infer changes in reproductive morphology associated with the evolution of gynodioecy.• KEY RESULTS: The majority of populations were cosexual in gender expression, but dimorphism was present in the Yucatán and in some populations in Hawaii. Populations varied in ploidy and were either diploid or tetraploid. Floral sexual dimorphism was present in all gynodioecious populations, though the magnitude differed and was cryptic in some cases. Our results are consistent with the hypothesis that following the evolution of gynodioecy, flowers on hermaphrodites increased in size.• CONCLUSIONS: Dimorphic sexual systems have likely evolved convergently in L. carolinianum. In contrast to previous studies, dimorphism is not perfectly associated with polyploidy. Although our sample from the Yucatán was both tetraploid and dimorphic, all populations in Hawaii were diploid regardless of sexual system. Ongoing phylogeographic and mating system studies will contribute to our understanding of reproductive evolution in this widespread, polymorphic species.

Identification and validation of reference genes for quantitative real-time PCR normalization and its applications in lycium.

Lycium barbarum and L. ruthenicum are extensively used as traditional Chinese medicinal plants. Next generation sequencing technology provides a powerful tool for analyzing transcriptomic profiles of gene expression in non-model species. Such gene expression can then be confirmed with quantitative real-time polymerase chain reaction (qRT-PCR). Therefore, use of systematically identified suitable reference genes is a prerequisite for obtaining reliable gene expression data. Here, we calculated the expression stability of 18 candidate reference genes across samples from different tissues and grown under salt stress using geNorm and NormFinder procedures. The geNorm-determined rank of reference genes was similar to those defined by NormFinder with some differences. Both procedures confirmed that the single most stable reference gene was ACNTIN1 for L. barbarum fruits, H2B1 for L. barbarum roots, and EF1α for L. ruthenicum fruits. PGK3, H2B2, and PGK3 were identified as the best stable reference genes for salt-treated L. ruthenicum leaves, roots, and stems, respectively. H2B1 and GAPDH1+PGK1 for L. ruthenicum and SAMDC2+H2B1 for L. barbarum were the best single and/or combined reference genes across all samples. Finally, expression of salt-responsive gene NAC, fruit ripening candidate gene LrPG, and anthocyanin genes were investigated to confirm the validity of the selected reference genes. Suitable reference genes identified in this study provide a foundation for accurately assessing gene expression and further better understanding of novel gene function to elucidate molecular mechanisms behind particular biological/physiological processes in Lycium.

[Effect of exogenous calcium on seed germination and seedling physiological characteristics of Lycium ruthenium].

OBJECTIVE: In order to get the method for improving the salt resistance of Lycium ruthenium seeds and seedlings under NaCl stress, the seed germination and physiological characteristics of L. ruthenium seedlings was studied. METHOD: Several physiological indexes of L. ruthenium seeds under NaCl stress, such as the germination rate (Gr), germination vigor (Gv), germination index (Gi), vigor index (Vi), and relative salt damage rate were measured. Other indexes of the seedlings like relative water contents (RWC) , chlorophyll contents, soluble protein contents, electrolyte leakage, the contents of malondialdehyde (MDA), and peroxidase (POD) were also measured. RESULT: NaCl at lower concentration could promote the seed germination but inhibit the seed germination at higher concentration. After the treatment by CaCl2 at the different concentrations, all germination indexes were increased. With the increase of salt concentration, the relative water contents and the contents of chlorophyll were decreased, the content of MDA and electrolyte leakage were increased. The change trend of POD activity showed the first increase and then decrease with the increase of salt concentration, which was similar to that of the soluble protein. After the treatment by CaCl2, relative water contents, chlorophyll and POD activities were decreased more slowly, and also electrolyte leakage and MDA contents increased slowly. CONCLUSION: The CaCl2 could significantly alleviate the damages to the seeds and seedlings of L. ruthenium under NaCl stress, and promote the salt resistance to the seeds and seedlings of L. ruthenium.

[Comparative study of growth potential on hardwood cutting of Lycium barbarum strains].

OBJECTIVE: To lay foundation of strains selection through primary selection of 44 strains of Lycium barbarum. METHODS: Used the single plant selection. RESULTS: Screened out 22 strains of Lycium barbarum by preliminary determination of germination rates and seeding rates of hardwood cutting, the growth potential of 2009-26, 2009-21, 2009-17, 2009-29, 2009-2 were better than those of others strains. CONCLUSION: 2009-26 has better growth potential except the length of root, the result provides a basis for further screening can focus on research for 2009-26.

[Effects of covering on growth potential and chlorophyll content of hardwood cutting of Lycium barbarum].

OBJECTIVE: To study the effect of plastic film covering, straw covering, plastic film covering in greenhouse and no-covering cutting on growth and Chlorophyll content of Lycium barbarum hardwood cutting seedlings. METHODS: Single factor randomized block design method was used in this research. RESULTS: The effect of different covering treatments on germination rate, seedling rate and growth potential were all plastic film covering in greenhouse > plastic film covering > straw covering > no-covering cutting. Chlorophyll a, Chlorophyll b, Chlorophyll a + b content and Ca/Cb were significantly different with different coverings in different periods. CONCLUSION: The optimal covering on hardwood cutting of Lycium barbarum is plastic film covering in greenhouse. Both plastic film and straw covering are better than no-covering cutting.

[Effects of irrigation amount on leaf structure, photosynthetic physiology, and fruit yield of Lycium barbarum in arid area].

Lycium barbarum is an important traditional medicinal plant in China. Under controlled condition, a field experiment was conducted to study the effects of different monthly irrigation quota on the leaf structure, photosynthetic physiology, and fruit yield of L. barbarum, aimed to determine an appropriate irrigation amount for the plant. When the monthly irrigation quota was less than 900 m3 x hm(-2), the leaf area, leaf thickness, palisade tissue thickness, cell tense ratio (CTR), net photosynthetic rate (Pn), intrinsic water use efficiency (WUE), stomatal limitation value (Ls), and fruit yield of L. barbarum all increased significantly with monthly irrigation quota, while leaf stoma density and intercellular CO2 concentration (Ci) showed a reverse trend. When the irrigation quota was more than 900 m3 x hm(-2), the Ci increased with irrigation quota, the leaf area, stoma density, and fruit yield had no obvious change, whereas the other indices showed a reverse trend. The leaf transpiration rate and Gs were the highest at irrigation quota 450 m3 x hm(-2), being 8.02 and 324 mmol x m(-2) x s(-1), respectively; whereas at other irrigation quota, these two indices were lower than the control. In terms of saving water, the monthly irrigation quota 900 m3 x hm(-2) was more appropriate for Lycium barbarum.