盐碱胁迫对牛叠肚幼苗渗透调节物质及叶绿素含量的影响

为了探讨牛叠肚幼苗对盐碱胁迫的生理适应性,以盆栽牛叠肚组培苗为试材,就不同浓度的NaCl、Na2SO4、NaHCO3和Na2CO3胁迫处理对其叶片中的叶绿素含量和部分有机渗透调节物质的影响进行了试验。结果表明:在中性盐(NaCl、Na2SO4)和碱性盐(NaHCO3、Na2CO3)的胁迫处理下,牛叠肚叶片叶绿素的合成中均出现了"低促高抑"的现象,而游离脯氨酸的积累对叶绿素的合成并未起到直接作用。在单价盐碱(NaCl、NaHCO3)的胁迫处理下,牛叠肚幼苗主要通过可溶性糖、游离脯氨酸、可溶性蛋白的交替积累来发挥其渗透调节功能;在二价盐碱(Na2CO3、Na2SO4)的胁迫处理下,可溶性糖、游离脯氨酸和可溶性蛋白的积累趋势各异,其中,在Na2CO3胁迫条件下三者同步积累,共同发挥其渗透调节功能,而在Na2SO4的胁迫处理下,牛叠肚幼苗主要通过可溶性糖和可溶性蛋白的彼此协同作用来降低盐碱伤害,并且二者的积累有利于叶绿素的合成。     

盐胁迫对紫丁香种子萌发及复萌的影响

为了探究紫丁香的耐盐性,用不同浓度盐溶液(浓度分别为0、50、100、150mmol/L的NaCl溶液和Na2SO4溶液)处理紫丁香种子,研究盐胁迫条件对紫丁香种子萌发的影响。结果表明:低浓度的NaCl溶液对紫丁香种子的萌发没有明显的促进作用,高浓度则有抑制作用;而Na2SO4溶液只具有抑制作用,并且同一浓度Na2SO4溶液的抑制作用比NaCl溶液更强。解除盐胁迫(150mmol/L的NaCl溶液和150、250mmol/LNa2SO4溶液)后的第1天就有种子萌发,且低浓度盐处理后的复萌效果要比高浓度的效果好,同一浓度下NaCl溶液的复萌效果比Na2SO4溶液好。     

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。     

翠菊种子萌发期耐盐性评价

以翠菊种子为试材,研究了种子萌发期对Na2 SO4胁迫的耐受范围。结果表明：翠菊种子萌发期耐盐适宜浓度为44．05mmol/L ,耐盐半致死浓度为78．92mmol/L ,耐盐极限浓度为133．78mmol/L。     

混合盐碱胁迫对金山绣线菊Na+和K+分布影响的研究

将中性盐NaCl和Na2SO4、碱性盐NaHCO3和Na2CO3按不同比例混合,模拟出24种盐碱度各不相同的复杂盐碱条件,并对金山绣线菊进行盐碱混合胁迫处理,测定金山绣线菊叶片及根部的Na+、K+含量.测定结果表明:随着盐浓度、pH值的增加,金山绣线菊根部、叶片中的Na+含量逐渐增加,K+的含量逐渐减少,Na+/K+的比值逐渐上升;金山绣线菊体内Na+的分布为根＞叶;K+的分布为叶＞根;抑割Na+向上运输的根部可能是金山绣线菊受盐害的主要部位.     

盐胁迫下刺槐叶片线粒体功能及超微结构的变化

为了揭示四倍体刺槐的耐盐机制,以刺槐Robinia pseudoacacia的二倍体和四倍体为材料,分别在盐胁迫处理前、处理10 d、处理20 d时进行叶片取材,比较了二者在NaCl和Na2SO4胁迫下叶片线粒体功能及超微结构的变化。结果表明,在2种盐胁迫下,二倍体刺槐细胞色素Cyt c/b的比值和SOD酶活性均呈下降趋势,而四倍体刺槐呈上升趋势;二者的H2O2和MDA含量均呈上升趋势。在盐胁迫处理前,二者叶片细胞中线粒体均表现结构完整、基质均匀、被膜清晰、嵴均匀分布且结构完整等特点。在NaCl处理10 d时,二倍体刺槐叶片细胞中部分线粒体出现变形、中空、膜模糊、嵴不均匀分布等现象;在NaCl处理20 d时,线粒体受损情况进一步加重。而Na2SO4胁迫下叶片细胞线粒体的损伤更为严重。四倍体刺槐在NaCl和Na2SO4处理时,线粒体受损情况差异较大,其中Na2SO4对四倍体刺槐叶片线粒体超微结构影响较大。     

沙棘对碱性盐胁迫的形态和生理响应

采用50、100、150 mmol·L-1 3种浓度的Na2CO3、NaHCO3及二者混合盐对2年生沙棘幼苗进行胁迫处理,通过比较分析胁迫后沙棘幼苗的形态和细胞膜透性、脯氨酸含量、可溶性糖含量的变化,探讨沙棘对Na2CO3、NaHCO3和混合盐胁迫的适应能力。结果表明:在胁迫条件下,沙棘出现枯黄、落叶等盐害症状,随着胁迫浓度的加大和时间的延长,症状表现逐渐加重;电导率、脯氨酸含量、可溶性糖含量均随胁迫程度的加深呈上升趋势,胁迫前期变化相对稳定,后期变化幅度较大;形态表现和生理指标实验均反映出,不同类型盐碱胁迫对沙棘的伤害程度不同,单盐的迫害作用大于复盐,碱性盐的伤害作用大于酸性盐,即Na2CO3>NaHCO3>混合盐碱。此结果对提高沙棘在东北地区护坡工程中的应用提供了技术支持。     

硅对盐胁迫下杨树根系中离子微域分布的影响

运用X-身于线电子探针研究了硅对盐胁迫下杨树根系中离子微域分布的影响.结果表明:盐胁迫(NaCl)浓度分别为0 g/L、2 g/L、3 g/L、4 g/L处理使杨树苗根系表皮、皮层和中柱细胞中Na 、Cl-的X-射线峰明显升高,K 峰降低;而盐胁迫后加浓度为0.5 g/L硅处理后根系表皮、皮层和中柱细胞中Na 、Cl-的X射线明显降低,而K 峰则大幅度提高,Na 在根系各部分呈均匀分布.表明盐胁迫下水培杨树苗适当加硅可以改变其体内养分离子的吸收和离子分布,从而缓解了盐离子对杨树的毒害作用.     

盐胁迫对银白杨苗高和地径的影响

采用不同浓度的Nacl、Na2CO3和NaHCO3溶液对银白杨幼苗模拟盐胁迫环境,测定银白杨苗高和地径.试验结果表明:随着Nacl、Na2CO3和NaHCO3溶液浓度的增加,银白杨的苗高和地径呈下降趋势,当浓度达到5％时,死亡率明显升高.由此可知:银白杨对低浓度的盐胁迫具有较强的适应性.     

NaCl胁迫对宁夏4种灌木生长及光合特性的影响

以黑果枸杞、沙棘、银水牛果和柽柳的幼苗为研究对象,研究不同NaCl浓度(0、250mmol/L、500mmol/L、750mmol/L和1 000mmol/L)对宁夏4种常见耐盐植物生长及光合作用的影响。结果表明,(1)当NaCl浓度达到750mmol/L时,沙棘植株死亡,当浓度增加到1 000mmol/L时银水牛果植株死亡,黑果枸杞和柽柳也出现不同程度的盐害症状;(2)4种灌木的株高与基径增长量在NaCl胁迫下均呈下降趋势,高浓度盐胁迫明显抑制了4种灌木生物量(P0.05),低浓度盐胁迫对黑果枸杞和柽柳的生物量的影响不明显;(3)在NaCl胁迫下4种植物的净光合速率、蒸腾速率、叶绿素相对值均表现出不同程度的降低,并随着胁迫浓度的增加而下降,而水分利用效率则升高,NaCl胁迫对4种植物的光合特性有显著影响(P0.05);(4)综合分析各树种生长和生理表现,沙棘耐盐性较弱,银水牛果具有中度耐盐性,黑果枸杞和柽柳可忍受中高浓度的盐胁迫。     

控根育苗技术引进试验初步效果

为提高森林城市建设工程质量,赤峰市林业科学研究所从陕西杨凌引进澳大利亚先进的控根快速育苗技术,对17种树木分3种不同规格容器进行培育试验,对树木成活率、生长量和增根效果进行调查分析,结果表明:树木成活率为97%,当年高度生长量在0.3~0.9m不等,均优于大田树木;用纵切1/4根系的方法测量根系鲜重,平均鲜重为0.120kg,约是大田对照鲜重的2倍。       

Stockplant Management for Optimized Rhizogenesis in Tectona grandis Stem Cuttings

A 5-year stand of teak (Tectona grandis L. f.) was coppiced in 1999 and converted into a vegetative multiplication garden. Subsequently, three harvesting regimes for the collection of single node stem cuttings were imposed: (1) once – in March (H₁), (2) twice – in March and September (H₂) and (3) three times in March, July and November (H₃). Cuttings were treated basally with either:- T₀ – control (6 h in water), T₁ – half the recommended dose of a mixture of IBA and thiamine (500 ppm IBA + 400 ppm thiamine) or T₂ – the full dose of the same mixture (1000 ppm IBA + 800 ppm thiamine). Cuttings receiving IBA + thiamine rooted significantly better than untreated cuttings, but even the best treatment only resulted in 38.3 ± 3.8% rooting. This treatment produced the greatest number of roots (5.2–12.1). The full dose treatment appears to have been supra-optimal. Rooting ability was also affected by the frequency of stockplant pruning, with cuttings from stockplants pruned twice per year having the greatest rooting percentage (27.8 ± 3.8%) and the most roots (9.2 ± 4.8). This bi-annual pruning (H₂) resulted in the greatest number of rooted propagules (2.6 and 4.2 times more than H₁ and H₃, respectively). There was a significant interaction between Treatment × Pruning frequency. Bi-annual hedging of teak stockplants is recommended for practical purposes, although further work is required to achieve commercially acceptable levels of rooting from coppiced tree stumps.     

刺楸埋根育苗技术研究

采用不同根穗长度、根穗粗度、不同树龄及不同激素等处理,对刺楸的埋根繁殖技术进行试验研究。结果表明,刺楸埋根育苗是一种切实可行的无性繁殖方法。     

Quantifying root system quality of nursery seedlings and relationship to outplanting performance

With over 1.5 billion forest tree seedlings produced annually in the USA, seedling quality assessment is critical to ensure reforestation success. While height and root-collar diameter are the most common traits evaluated during seedling quality assessment, above-ground morphology is not always an accurate predictor of performance after outplanting. Root system morphology and physiological status may provide a more accurate indication of seedling potential. However, relatively few studies have attempted to quantitatively assess root system quality in relation to outplanting success. Large root volume, high root fibrosity, and an increased number of first-order lateral roots have shown some correlation to improved field performance. Physiological seedling quality assessment is commonly practiced through evaluation of root growth potential. Other tests, such as root electrolyte leakage, have also shown some potential as measures of seedling physiological quality. This review identifies current methods of assessing seedling root system quality and discusses potential shortcomings of these methods. An increased understanding of the suitability of current tests, coupled with the development of new tests and multiple parameter relationships, may foster the development of species and site-specific targets for seedling root system quality assessment. The production of seedlings with root systems that meet high morphological and physiological standards better enables seedlings to rapidly establish and thrive upon outplanting.     

Root distribution of Eucalyptus grandis and Corymbia maculata in degraded saline soils of south-eastern Australia

Planting trees, in farm forestry enterprises, to control rising watertables is an increasing practice for both economic and environmental benefits. One central biophysical issue which determines the effectiveness of trees to control groundwater is the ability of trees to grow roots through degraded soils and take up groundwater. We investigated the effect of soil properties, especially the presence of shallow watertables and site preparation practice, on the vertical and horizontal distributions of Eucalyptus grandis W. Hill ex Maiden and Corymbia maculata (Hook.) K.D. Hill and L.A.S. Johnson roots. In order to improve the reliability of root data, we measured root growth and distribution by three different methods – (i) number of roots intercepting the vertical plane of the soil profile, (ii) root length density in soil cores taken at different depths but in the horizontal plane of the profile, and (iii) root length density in soil cores in the vertical plane at different radial positions from trees and compared the results. Two experimental sites were established in flood-irrigated, farm forestry plantations on contrasting soils in the Murray Riverina region of south-eastern Australia. At one site (Norwood Park), we studied a 58-month-old stand of E. grandis growing in clay loam overlaying medium clay, saline, sodic and alkaline subsoil with a saline (11.5 dS m⁻¹) watertable at 2.8 m depth. Here, there were few roots growing above the watertable. The Karawatha site had adjacent stands of 46-month old E. grandis and C. maculata growing in a sandy, neutral and non-saline soil with a shallow (3.1 m deep) non-saline (2.8 dS m⁻¹) watertable. Here roots proliferated above the watertable in both species but to a much greater extent under C. maculata than under E. grandis. Root distributions in the surface soil were similar at all sites but differences in root growth in the capillary zones paralleled differences in groundwater uptake by trees. We conclude (i) that appropriate matching of species with site characteristics, especially soil and groundwater properties, will enhance tree growth and groundwater uptake and (ii) that extensive planting of C. maculata over non-saline watertables maximises the chances of achieving the multiple objectives of regional groundwater control, fast growth rates and reduced irrigation demand.     

Field measures of the contribution of root respiration to soil respiration in an alder and cypress mixed plantation by two methods: trenching method and root biomass regression method

The contribution of root respiration to total soil respiration is one of the most interesting, important, and methodologically complicated problems in the study of the carbon budget in soils. A trenching method and a root biomass regression method were used to determine the contribution of root respiration to total soil respiration in a subtropical forest ecosystem. The average root respiration contributions were 37.15% with the range of 13.04–51.23% by trenching method and 31.80% with the range of 10.64–56.10% by root biomass regression method from August 2005 to July 2006. In growing season, the contributions of root respiration were 47.25 and 43.53% estimated by trenching method and root biomass regression method, respectively. There was no significant difference between the monthly attributions of root respiration to soil respiration estimated by two methods. Our results showed that trenching and root biomass regression methods were both suitable to estimate the root respiration in this forest.     

Relationships between the root system size and its hydraulic properties in white spruce seedlings

Seedlings grown under different N supply were examined for relationships between root system size attributes and its hydraulic properties. These relationships were also studied on seedlings of different stock types (grown in different container types). Measurements with root pressure probes were taken at various times after germination, under applied hydrostatic pressure and non-limiting soil moisture. Different N-treatments and stock types were used solely to produce seedling of different sizes, especially root system sizes. Specific root hydraulic conductivity (Lp_r) typically declined with an increasing root system size and correlations between Lp_r and the root system size attributes were often negative. The flow of water through the root system correlated well with root system size attributes only in young (3–4 month old) seedlings but the correlations were inconsistent among different N treatments and stock types. Neither the root system surface area nor dry weight reliably reflected its ability to absorb and conduct water. Generally, the amount of water delivered through the root system and available for transpiration per unit or leaf surface area or unit of leaf dry weight correlated poorly or negatively with the root system size. Practical and scientific implications of the findings are discussed. *Paper presented at Forest Seedling Root Development Conference: From the Nursery to the Field, Eugene, Oregon, May 12–13, 2004.     

Field Performance of Pinus radiata D. Don Produced in Nursery with Different Types of Containers

We have studied the development in nurseries of containerized Pinus radiata produced with different container systems in order to choose the most suitable system for producing well-balanced plants with an optimal root system. At the end of the production period, significant differences were found in morphological responses among the seedlings to the various container characteristics. Seedlings grown in containers that permitted lateral air puning presented less growth and lower biomass production. However, root deformations were more frequent and severe in plants produced in closed-wall containers. Field performance was likewise mainly affected by container type and plant growth rate, as faster grown plants showed more problems of stability than plants with a balanced root and stem development.     

Root carbohydrates and aspen regeneration in relation to season of harvest and machine traffic

Season of harvest has often been suggested as a driver for the erratic success of aspen (Populus tremuloides) sucker regeneration, partially due to root carbohydrate reserves and soil conditions at the time of harvest. A field experiment in western Manitoba, Canada, assessed root suckering and root carbohydrates of aspen in response to season of harvest and machine traffic. Six sites (120 m × 120 m) were selected within two large mature aspen stands slated for summer harvest. Plots (50 m × 50 m) were hand-felled (without machine traffic) in mid-summer, late summer, winter, and one plot was left uncut as a control. Season of cut with no traffic had no effect on sucker density, height or leaf dry mass per sucker. During the dormant season, root starch reserves were highest in the winter cut plots, however, just prior to suckering, this difference in carbohydrate reserves among the three seasons of harvest disappeared and by the end of the first growing season root reserves in all three seasons of cut had recovered to near control levels. Adjacent plots that were conventionally harvested in the summer and impacted by logging traffic had similar sucker densities but had 19% less height growth of suckers and 29% less leaf dry mass per sucker compared to suckers in plots harvested at the same time without traffic. After one growing season, root carbohydrate levels were similar whether or not machine traffic was used; however, the reduction in leaf dry mass in plots with machine traffic could have negative implications for carbohydrate accumulation and growth. The study suggests that the phenological state of the mature aspen plays a very small role in aspen regeneration and that harvesting practices and site conditions are likely the main drivers of aspen regeneration success.     

Root characteristics and growth potential of container and bare-root seedlings of red oak (<Emphasis Type="Italic">Quercus rubra</Emphasis> L.) in Ontario,Canada

Root characteristics and field performance of container and bare-root seedlings of red oak (Quercus rubra L.) were compared during the first growing season after planting. Sixty seedlings of each stock type were planted on a clearfell and weed-free site near Restoule, Ontario. Twenty-four additional seedlings from each stock type were compared at the start of the study in terms of shoot and root parameters. Measurement of root and shoot parameters were repeated at three dates during the first growing season in the field. The root systems of container stock had a larger number of first order lateral long roots and were significantly more fibrous than bare-root stock. These differences were sustained throughout the first growing season. In terms of field performance, container seedlings had 100% survival and achieved significant increases in both biomass and shoot extension. Bare-root seedlings suffered 25% mortality, significant shoot dieback and more variable growth. The mean relative growth rate (RGR) of container seedlings increased throughout the study period to a maximum of 30 mg/g/day, whereas the mean RGR of bare-root stock remained close to or below zero. Overall, the container seedlings proved less prone to transplanting shock than the bare-root seedlings, most likely due to favourable root architecture and the pattern of root development. Further work may be warranted in container design, growing regimes and root architecture to fully realise the potential of container systems for the production of high quality red oak seedlings across a range of site conditions.