Germination,osmotic adjustment,and antioxidant enzyme activities of gibberellin-pretreated <Emphasis Type="Italic">Picea asperata</Emphasis> seeds under water stress

Germination of dragon spruce (Picea asperata Mast.) seeds pretreated with gibberellin (GA) in response to water stress and changes in the levels of osmotic adjustments as well as in activities of antioxidant enzymes were investigated. With decreasing water potential caused by increasing concentrations of PEG 6000, germination percentage and germination index decreased gradually; the decrease was especially prominent under the serious water stress from PEG −0.6 MPa. In contrast, osmotic regulation substances (free proline and soluble sugar contents), lipid peroxidation (MDA), and activities of antioxidant enzyme (ascorbate peroxidase, catalase, and peroxidase) increased markedly with decreased water potential. Similarly, the values in all parameters under −0.6 MPa PEG treatment were markedly higher than the control and −0.2 MPa PEG treatment. These results suggested that P. asperata seed germination was insensitive to water stress. In addition, seeds pretreated with GA had increased tolerance to water stress as measured by germination percentage and germination index, osmotic regulation substance, and antioxidant enzyme activities.     

Effects of drought stresses induced by polyethylene glycol on germination of Pinus sylvestris var. mongolica seeds from natural and plantation forests on sandy land

Effects of drought stresses induced by polyethylene glycol (PEG) (0.0%, 10%, 15%, 20%, 25%, and 30%, with four replicates) on germination of Mongolian pine (Pinus sylvestris var. mongolica) seeds produced in plantations (southern Keerqin sandy land) and natural forests (Hulunbeier sandy plain) were observed. The results indicated that the seeds from both provenances did not germinate when PEG concentration was more than 25%. The time of initial germination and that of its completion of stressed seeds from both provenances were delayed when compared with the unstressed seeds. The germination capacity and germination rate of natural seeds were significantly higher than those of plantation seeds for all treatment levels (P < 0.05). The mean growth rates of radicle and hypocotyl from natural seeds were significantly higher than those from plantation seeds at all treatment levels below 20% PEG treatment (P < 0.05). The ratios of radicle to hypocotyl of 20% PEG treatment were significant higher than those of the corresponding controls for both provenances (P < 0.05). These results suggested that Mongolian pine seeds/seedlings had stronger resistance to PEG drought stresses; 10% PGE stress did not significantly influence germination. Natural seeds exhibited more resistance to PEG stress than plantation seeds. It was concluded that drought stress on seed germination might be one cause of obstructed natural regeneration of Mongolian pine plantations on sandy land. It is recommended that natural seeds be used for afforestation, and light drought stress (e.g., 10% PEG stress) may be useful in improving seed germination and the growth of radicles and hypocotyls.     

PEG模拟干旱对毛竹种子萌发及生长生理特性的影响

[目的]通过比较不同程度干旱胁迫对毛竹种子萌发及生长生理的影响,探究毛竹种子萌发期对水分胁迫的耐受机理,为毛竹的水分管理提供科学依据。[方法]以毛竹种子为试验材料,采用培养皿滤纸萌发的方法研究不同浓度(0%、5%、10%、15%、20%、25%) PEG-6000溶液对其种子萌发、生长、渗透调节物质、抗氧化酶活性的影响。并对种子萌发率、胚根和胚芽的生长量与PEG胁迫浓度间进行回归分析。[结果](1)对照组(CK)和5%处理组在第4天开始发芽,其余各处理组的发芽起始时间随处理浓度的升高逐渐延迟,25%处理组不发芽。(2)最终发芽率、发芽势、发芽指数、活力指数、胚根长度、胚芽长度随PEG浓度的升高呈现先增大后减小的趋势,且均在5%浓度达到最大值。干旱胁迫下毛竹种子发芽率日变化曲线中对照组和5%处理组间存在唯一交叉点。毛竹种子在PEG胁迫下发芽率的临界值和极限值分别为14. 49%和19. 27%。(3)胚根和胚芽最终长度均在5%浓度时达到最大值,其后随着浓度的升高而减小,处理间差异显著(P 0. 05)。对照组和5%处理组的胚根平均长度日变化曲线存在交叉点。PEG胁迫下胚根生长的临界值和极限值分别为20. 43和23. 01%。(4)胚根中SOD、POD、CAT的活性均随PEG浓度的升高呈先上升后下降的趋势,且分别在5%、10%、10%浓度时达到最大值。(5) MDA和可溶性蛋白含量随PEG浓度的升高而持续升高,但低浓度(0%10%)时MDA含量差异不显著。[结论]低浓度干旱胁迫抑制发芽前期毛竹种子萌发以及胚根的形成,但显著提高毛竹种子的最终发芽率并且促进胚根后期的生长;而高浓度PEG干旱胁迫延迟毛竹发芽,抑制整个发芽时期的发芽率以及胚根、胚芽的生长; PEG浓度高于15%的干旱胁迫使毛竹的抗氧化酶系统发生紊乱,并对组织膜系统造成显著伤害。     

干旱胁迫下沙地赤松等松科植物种子萌发特性

[目的]以北方干旱区常用的3种松科植物沙地赤松、樟子松和青海云杉为研究对象,分析其种子萌发特性及对干旱胁迫的响应。沙地赤松为辽宁省固沙研究所于2014年筛选审定的新品种,目前在辽宁省生长状况良好,尚未有过其抗旱能力的相关研究。青海共和是高寒沙区,将沙地赤松与青海省常见的两种松科植物青海云杉和樟子松进行对比,以期为沙地赤松在青海引种试种提供参考。[方法]采用不同浓度PEG-6000溶液模拟干旱胁迫的方法进行种子萌发试验,利用模糊隶属函数对干旱胁迫下3种松科植物的种子相对发芽率、相对胚根长、相对胚芽长、萌发胁迫指数、萌发抗旱指数和萌发活力指数等6项指标进行综合评价。[结果]低浓度的PEG-6000溶液对3种松科植物种子萌发和胚根生长发育均有促进作用;随着干旱胁迫程度的加剧,3种松科植物的发芽率、幼苗鲜质量、活力指数、萌发胁迫指数、萌发抗旱指数均呈先上升后下降的趋势;种子萌发期耐水分胁迫能力为沙地赤松樟子松青海云杉。[结论]沙地赤松比樟子松和青海云杉的抗旱性强,适宜在青海引种试种。     

Promotion of germination of coniferous seeds by snow stratification combined with dehydration-rehydration treatment

Five chemical and four non-chemical presowing treatments were tested on seeds of three conifers (Larix principis-rupprechtii Mayr, Pinus sylvestris L. var. mongolica Litv, and Pinus tabulaeformis Carr.). By itself, cold stratification with snow for 60 days did not significantly improve the germination percentage over that of soaking the seed in warm water (45 °C) for 12 hours. However, including either one or two dehydration-rehydration cycles after the cold stratification did improve both the percentage and speed of germination of seed from all three species. Soaking seed for 12 hours in various chemicals (KNO₃, CaCl₂, CuSO₄, KMnO₄ and GA₃) before germination was less effective than the snow stratification followed by double dehydration-rehydration treatments (Chang and Lin, 1989).     

聚乙二醇模拟干旱对三种木麻黄种子萌发的影响

为研究木麻黄Casuarinaceae.种子苗困难地造林,以木麻黄为试验材料,用不同渗透势浓度的聚乙二醇(PEG-6000)模拟干旱胁迫,探讨干旱胁迫对木麻黄种子发芽率、发芽势、胚轴和胚根长度及发芽指数、活力指数的影响。结果表明,不同浓度PEG胁迫处理均降低了种子的发芽率,延缓了木麻黄种子萌发进程;种子的发芽率、发芽指数和活力指数均随胁迫强度的增加呈明显下降趋势。当-1.20 MPa的PEG胁迫处理的种子在试验结束时仍未能萌发,表明-1.20 MPa是木麻黄种子萌发的临界水势。当PEG浓度为150 g/L时,三种木麻黄幼苗的胚根最长,且当PEG浓度为100 g/L时,三种木麻黄胚根长度长于对照组,但差异不显著,说明高于-0.40 MPa的水势有利于木麻黄种子胚根的生长。木麻黄幼苗苗高生长则是随着PEG浓度的升高而逐渐减缓。通过比较得知木麻黄种子抗旱性较强。     

果翅、盐分及干旱胁迫对白梭梭种子萌发的影响

从生态学角度研究了果翅、温度、盐分和干旱胁迫等因素对白梭梭种子萌发的影响,结果表明:去除种翅能显著促进种子萌发,无翅种子比有翅种子萌发速率快(P<0.05),提早1 d达最高萌发率。变温条件有利于种子萌发。白梭梭种了萌发率随着NaCl浓度增加而降低,但在0.9 mol.L-1的浓度中仍有2%的种子萌发;将未萌发的种子移至蒸馏水中后,部分种子可以萌发,在较低浓度盐溶液(0.05～0.6 mol.L-1)中培养的种子其萌发恢复率低,而高浓度(0.7～1.0 mol.L-1)中培养的种子其萌发恢复率高。在较低程度的干旱胁迫下,白梭梭种子迅速萌发,而较高程度的干旱胁迫下种子萌发受抑制,在PEG浓度50%时不萌发;同等干旱胁迫程度下,无翅种子比有翅种子萌发率高。     

Effect of Azospirillum lipoferum and Azotobacter chroococcum on germination and early growth of hopbush shrub (Dodonaea viscosa L.) under salinity stress

Reduced physiological efficiency as well as low and irregular germination rate under environmental stress conditions (e.g., salinity) are among the major factors affecting the propagation of numerous plants, in particular medicinal ones. A factorial experiment using a completely randomized design was employed to evaluate the effect of plant growth-promoting rhizobacteria (PGPR) on hopbush seed germination and seedling growth under salinity stress. After the seeds were inoculated with the Azospirillum lipoferum, Azotobacter chroococcum, and Azospirillum + Azotobacter and exposed to salinity stress at six levels, they were placed into a germinator at 20°C temperature and 65% relative humidity with a photoperiodic regime of 16 h light/8 h dark at 1,000 lux fluorescent light. The seeds inoculated with the bacterial strains could tolerate salinity levels of up to 50 dS/m and germinate. The combined treatment of Azospirillum + Azotobacter increased germination percentage at 20 and 50 dS/m levels by 21.67 and 10%, respectively. Also, A. chroococcum at 15 and 20 dS/m and Azospirillum + Azotobacter at 50 dS/m stress levels increased germination rate by 88, 316, and 155%, respectively, compared with the control. Furthermore, plant growth parameters—e.g., root and stem length, root and stem dry and fresh weights, as well as the ratios of root length and weight to the stem counterparts—were considerably enhanced by Azotobacter chroococcum treatment under elevated salinity stress (15 and 20 dS/m), relative to the control. Inoculation with A. chroococcum more favorably affected on and was also more compatible with Dodonaea viscosa seedlings leading to considerably improved seedlings growth parameters as well as seed germination under salinity stress.     

Effects of NaCl stress on seed germination, leaf gas exchange and seedling growth of Pteroceltis tatarinowii

Effects of NaCl on seed germination, leaf gas exchange and seedling growth were investigated. The germination of P. tatarinowii seeds was delayed in the presence of NaCl, and was significantly inhibited when NaCl concentration exceeded 17 mM (1.0 g·L⁻¹). NaCl treatments induced reductions of transpiration rate, stomatal conductance and net photosynthetic rate and their reductions were significant with the increasing of NaCl concentration. However, intercellular CO₂ concentration in seedling leaves under salt stress was significantly higher than that of controls. There was a significant reduction in survival, basal diameter increment and height increment with increasing NaCl concentration 50 days after NaCl treatment, and a significant reduction in the dry weight increment of roots, stems, and leaves was also observed in the NaCl treatments. The deleterious effect on the biomass increment was more evident in the case of stems and leaves. Results from this study suggest that P. tatarinowii is sensitive to salinity stress and the salinity threshold for seedling growth might be less 34 mM (2.0 g·L⁻¹). Biography: FANG Sheng-zuo (1963–), male, Professor, College of Forest Resources and Environment, Nanjing Forestry University, Nanjing 210037, P. R. China.     

Chemical composition,phytotoxic and antifungal activities of <Emphasis Type="Italic">Pinus pinea</Emphasis> essential oil

The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of Tunisian Pinus pinea Linn. was analyzed by GC and GC/MS. Sixty-six compounds were identified, representing 98.5% of total oil, which was found to be rich in monoterpene hydrocarbons (73.1%) particularly limonene (54.1%), α-pinene (7.7%), and β-pinene (3.4%). The yield and the physico-chemical properties were determined. Results of the antifungal activity study by in vitro contact assay showed that P. pinea oil significantly inhibited the growth of ten plant pathogenic fungi. Moreover, herbicidal properties of the oil, tested on Sinapis arvensis L., Lolium rigidum Gaud., and Raphanus raphanistrum L., indicated that the oil completely inhibited the seed germination at a high concentration, while at low doses the oil acted by decreasing and delaying the germination and inhibiting the seedling growth of all tested weeds unlike the commercial herbicide. Our results showed that P. pinea essential oil could be valorized as bioproduct for biocontrol of weeds and fungal plant diseases.     

Responses of germination and radicle growth of two Populus species to water potential and salinity

The effects of water potential, NaCl and Na2SO4 on germination and radicle growth of two riparian tree species, Populus euphratica Oliv. and P. pruinosa Schrenk (Salicaceae), were tested. Growth chamber studies revealed an optimum temperature range for seed germination of both species between 15-35℃. The final germination percentage of both species decreases with decreasing water potential in all types of solution applied in the experiments. P. pruinosa was less tolerant to low ψw stress than P. euphratica, especially in salt solutions. Germination percentages fell below 20% for P. pruinosa at -0.6 MPa (NaCl) or -0.4 MPa (Na2SO4) and for P. euphratica at -1.2 MPa (NaCl) or-0.6 MPa (Na2SO4). Radicle growth of both species was inhibited by high concentrations of PEQ NaCl and Na2SO4. However, growth was enhanced at -0.13 and -0.29 MPa in PEG or at -0.13 MPa in NaCl solutions compared to distilled water. Radicle growth of P. euphratica was higher than that of P. pruinosa. Germination and radicle growth of both species exhibited ion toxicity. Na2SO4 was more toxic than iso-osmotic solutions of NaCl. Radicle growth proved to be more sensitive than seed germination. Thus, flooding does not only yield the necessary soil moisture for germination but also favors seedling establishment of both species through leaching of salts from the soil surface. The different sensitivity of the species during their early growth stages might, moreover, contribute to the observed differences in their distribution in the Talim Basin (northwest China).     

不同钠盐对班克松种子萌发的影响

采用不同浓度的NaCl、Na2SO4和Na2CO3溶液处理班克松种子,测定发芽率、发芽势和发芽指数,研究钠盐胁迫对班克松种子发芽的影响。结果表明:低浓度(10、20 mmol·L-1)的NaCl、Na2SO4可以促进种子萌发,随着浓度增加,抑制作用加强,250 mmol·L-1的各项指标降到最低。Na2CO3溶液对种子萌发有较强的抑制作用,浓度相同时,Na2CO3胁迫下的各指标值均小于NaCl、Na2SO4。250 mmol·L-1时各项指标为0。由此可以得出,班克松种子具有耐盐性,但对不同钠盐的敏感性不同,对NaCl、Na2SO4的耐受性要高于Na2CO3。     

PEG 模拟水分胁迫对思茅松种子萌发的影响

采用PEG-6000（聚乙二醇）不同浓度溶液,研究模拟水分胁迫对思茅松种子萌发的影响。结果表明,随着PEG-6000浓度的增加,思茅松种子的发芽率、发芽势、日均发芽率、峰值和发芽值先上升后下降,各处理间无显著差异。适宜质量浓度（5％）的PEG-6000处理能促进种子萌发,思茅松种子表现出一定耐旱能力。     

Somatic embryogenesis in sawara cypress (<Emphasis Type="Italic">Chamaecyparis pisifera</Emphasis> Sieb. et Zucc.) for stable and efficient plant regeneration,propagation and protoplast culture

Somatic embryogenesis inChamaecyparis pisifera was initiated from immature seeds collected from the end of June to early July. We obtained initiation frequencies ranging from 12.5 to 33.3% using whole seed explants in liquid media. Embryogenic cultures were maintained and proliferated for more than a year in solid and liquid media. High maturation frequencies of ‘high quality’ embryos were obtained on maturation media containing abscisic acid (ABA), activated charcoal (AC), and polyethylene glycol (PEG) as osmotic agent. More than one thousand cotyledonary embryos on average per 100 mg initial fresh weight of embryogenic cells were attained on medium containing 100μM ABA, 2 gL⁻¹ AC, and 150 gL⁻¹ PEG. About 97% germination frequencies and 92% plant conversion rates were achieved without any pretreatment. Growing of plants regenerated from somatic embryos has been monitored in the field. Furthermore, a procedure for culture of protoplasts isolated from embryonal masses was also described. This work was supported in part by the Japan Science and Technology Corporation and in part by a Grant for Research for the Future Program from the Japan Society for Promotion of Science.     

Fire resistance of European pines

Pine resistance to low- to moderate-intensity fire arises from traits (namely related to tissue insulation from heat) that enable tree survival. Predictive models of the likelihood of tree mortality after fire are quite valuable to assist decision-making after wildfire and to plan prescribed burning. Data and models pertaining to the survival of European pines following fire are reviewed. The type and quality of the current information on fire resistance of the various European species is quite variable. Data from low-intensity fire experiments or regimes is comparatively abundant for Pinus pinaster and Pinus sylvestris, while tree survival after wildfire has been modelled for Pinus pinea and Pinus halepensis. P. pinaster and P. pinea, and Pinus canariensis in special, are better equipped to survive fire, but low-intensity fire is tolerated even by species often referred to as fire-sensitive (P. halepensis and Pinus radiata). The relative fire resistance of European pine species is assessed on the basis of (i) morphological and experimental data, and (ii) mortality modelling that considers fire behaviour. Limitations of these approaches to rate fire resistance are discussed, and the current knowledge gaps are indicated.     

Effect of priming on the germination of<Emphasis Type="Italic">Peltophorum dubium</Emphasis> seeds under water stress

Peltophorum dubium seeds provided by Anhembi, SP were scarified in 98% H2SO4 for 15 rain to overcome mechanical dormancy. Seeds were primed in solutions of 0.2% Captan at 10℃ and 27℃, PEG 6000 -1.0 MPa at 10℃ and 27℃, 0.5 mol KNO3, 0.75 Mol KNO3, 1.0 Mol KNO3. Eight treatments including the primed seeds and nonprimed seeds, five replicates with 100 seeds for each treatment, were set to 15-cm-Petri dish with double filter paper moistened with testing solution PEG in refrigerator at 27℃. For the experiments of all the groups, osmotic potential were 0.0, -0.2, -0.4, -0.6, -0.8, -1.0, -1.2, and -1.4 MPa. P. dubium seeds were also set to water stress experiment in rolled paper with PEG solutions from 0.0 to -1.0 MPa.Germination percentage decreased with the increase of PEG concentration. Control group had a better germination percentage than other groups. Germination hardly occurred in PEG -1.4 MPa.     

Loblolly pine seed dormancy: constraints to germination.

Stratification by moist chilling is often used to break seed dormancy in loblolly pine (Pinus taeda L.). The role that moist chilling plays at the cellular level in preparing the embryo for germination and early seedling growth was investigated. Moist chilling did not affect the embryo's ability to mobilize seed storage proteins, which is a biochemical marker of early seedling growth. Analysis of in vivo protein synthesis profiles indicated that moist chilling has only a subtle effect on gene expression in the embryo or germinant. The means by which moist chilling affects interactions between the seed coat and the living tissues of the seed also was studied. Although the seed coat is mainly a mechanical barrier to germination, seed coat replacement studies showed that moist chilling alleviates some factor(s) in the seed coat that significantly inhibit germination.     

Influence of osmotic pressure on somatic embryo maturation in Pinus densiflora

The effect of an osmoticum, polyethylene glycol (PEG), on somatic embryo production was examined using embryogenic cells of Pinus densiflora. In the basal medium containing 30 μM abscisic acid and 6% maltose, the quality of the embryos formed was poor even though somatic embryos were produced. The addition of PEG with molecular weight of 4000 or 8000 significantly enhanced the development of both the quality and quantity of somatic embryos. Furthermore, higher levels of a constant osmotic pressure with PEG 8000 in a range from about 300 to 450 mmol/kg could remarkably enhance the morphogenesis of somatic embryos and their number of embryos produced. A higher stable osmotic pressure with an appropriate molecular weight of PEG is a key factor for the production of good quality somatic embryos in P. densiflora.     

不同引发处理对了哥王种子萌发的影响

以了哥王种子为材料,通过比较不同浓度的GA3、PEG、NaCl、复合盐KNO3·KH2PO4预浸种处理后种子发芽率、发芽势、发芽指数、活力指数等指标,研究不同引发剂对了哥王种子萌发的影响,结果表明：4种引发剂浸种处理均显著促进了哥王种子的萌发及幼苗生长,各指标提高效果均以GA3处理最好,PEG次之,再之为复合盐KNO3·KH2PO4, NaCl引发效果较差,并且随着引发剂浓度的升高呈先升高后降低的趋势。     

Sources of Diplodia pinea endophytic infections in Pinus patula and P. radiata seedlings in South Africa

Diplodia pinea, an opportunistic and latent pathogen, can significantly affect Pinus productivity worldwide. Despite being studied in South Africa for almost 100 years, the source of D. pinea inoculum responsible for seedling infection is unknown. The aim of this study was to determine the role of seed in vertical transmission of D. pinea and to investigate sources of inoculum leading to horizontal transmission to pine seedlings. Surface‐disinfected seeds were inoculated with spore and mycelium suspensions of D. pinea to determine its effect on germination. In addition, isolation of the fungus was performed from surface‐disinfected seeds, asymptomatic seedlings collected from nurseries, plantations where pines naturally regenerate and recently established fields, to assess transmission and incidence of endophytic D. pinea infections. Inoculation of seeds with D. pinea spore suspensions affected speed and rate of germination. The fungus was isolated from surface‐disinfected seeds in only a few instances (2–3%) and was not found in healthy seedlings collected from greenhouses and nurseries, suggesting that vertical transmission of the fungus does not occur or is rare. In contrast, D. pinea was isolated from 40% of seedlings obtained from the understory of mature P. patula trees showing that horizontal transmission from mature to young trees sustains the D. pinea inoculum in South African pine plantations.