Growth and biomass production in Azadirachta indica seedlings in response to nutrients (N and P) and moisture stress

Production of quality seedlings is an important aspect of successful tree planting. No information is available on the effect of nutrients and water on the growth and development of the seedlings of neem (Azadirachta indica A. Juss), an important component of many tropical agroforestry systems. In an experiment in central India, the growth and nutrient-use efficiency of neem seedlings grown at various levels of light, nutrients (N and P), and water stress were determined. Seedlings were given light (diffused and complete) and nutrient (N and P) treatments comprising either high N-high P, high N-low P, low N-high P, or low N-low P. Seedlings grown in complete light (800 mol/m²/s) had four times more biomass than those grown in diffused light (200 mol/m²/s). Significant increase in seedling biomass was observed with nitrogen application, while phosphorus had no effect on biomass. Leaves contributed maximum biomass, followed by roots and stem. Nutrient use efficiency decreased with an increase in the supply of nutrients. In another experiment, containerized and bare-root seedlings were subjected to five watering treatments, viz., watering twice a week, watering weekly, watering every alternate week, watering every third week, and natural precipitation. Plant moisture stress affected both growth and survival of neem seedlings. Only 50 per cent of seedlings survived in severe drought treatment (no. 4) whereas 90 to 95 per cent seedlings showed growth in all other treatments. Plant moisture stress in severe drought treatment averaged –21 bar while in other treatments it ranged from –9 to –12 bar. Shoot-root ratio was high in bare-root seedlings as compared to containerized seedlings. Containerized seedlings had shown better endurance against drought than the bare-root seedlings. The results suggest that neem seedlings adjust their nutrient use efficiency and can be grown even under limited available resources. It is also inferred that the species can tolerate soil resource depletion caused by competitor species.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Survival and growth of drought hardened <Emphasis Type="Italic">Eucalyptus pilularis</Emphasis> Sm. seedlings and vegetative cuttings

Forestry requires low mortality of transplanted seedlings. Mortality shortly after planting is often associated with inadequate hydration of transplants. Seedlings can be hardened to the drought conditions they may experience after transplanting by exposing them to controlled drought conditions in the nursery. Eucalyptus pilularis Sm. seedlings were drought hardened by providing nil (severe treatment) or half (mild treatment) the daily irrigation routinely received (control treatment) for up to two non-consecutive days per week during the last 4 weeks of growth in the nursery. Drought hardening reduced stem diameter, seedling leaf area, leaf area per root biomass and seedling quality measured by the Dickson quality index, but increased root:shoot ratio. Hardened seedlings had lower stomatal conductance and leaf water potential on the days they received less irrigation that the control treatment. Hardened seedlings had greater stomatal conductance and were less water stressed than seedlings experiencing drought for the first time indicating hardened seedlings had adjusted physiologically to drought. Survival after transplanting in the controlled drought environment in a glasshouse was enhanced by the hardening treatments. Non hardened seedlings that had had their upper leaves manually removed immediately prior to transplanting to reduce leaf area (top-clipped) had similar survival to hardened seedlings. Stomatal conductance and leaf water potential after transplanting were higher in hardened and top-clipped seedlings than unhardened control seedlings or vegetative cuttings. Survival in the field trial was over 95% for all treatments, possibly as rain fell within 4 days of planting and follow-up rain occurred in the subsequent weeks. Neither the hardened or top-clipped seedlings planted in the field trial had reduced growth, increased propensity to form double leaders or worse stem form than control seedlings when measured at age 3 years.     

Periodic chilling exposure during nursery culture

Five week old white spruce [Picea glauca (Moench) Voss] seedlings were placed within controlled-temperature growth chambers, and subjected to one of four periodic, chilling treatments for approximately 16 weeks. The treatments differed in the frequency of 24 hour exposure to 5 °C the seedlings received, and ranged from no chilling (control), to once every two, three or four days. After 25 weeks of growth, the control seedlings were significantly taller than all chilling-exposed seedlings, but stem diameters were similar. Chilling did not affect either needle length or needle density compared to control seedlings. During a water deficit test, frequently chilling-exposed seedlings maintained significantly higher mid-day shoot water potentials under extreme water stress. Re-watering after the drought resulted in all chilling-treated seedlings recovering faster to pre-stress shoot water potential levels than the control seedlings. Measurements of new root growth after 21 days at 10 °C indicated that previous chilling exposure delayed or inhibited new root production.     

Early season short-day treatment did not affect the field performance of Pinus sylvestris container seedlings in summer planting

Abstract

When Scots pine (Pinus sylvestris L.) seedlings are short-day (SD) treated in May or early June, height growth ceases but seedlings reflush within a few weeks and grow secondary needles (later referred to as early SD treatment). These “2-year-old-like” seedlings have been thought to be more stress tolerant than traditional 1-year-old pine seedlings, and thus suitable for summer and autumn plantings. To test this, seedlings sown in April were early SD treated over a 3-week period from the beginning of June and the seedlings were planted at 10-day intervals from the beginning of July until the end of September, and also during the following spring. Neither survival nor height growth of early SD-treated seedlings differed from untreated (1-year-old) seedlings. Moreover, for both early SD-treated seedlings and 1-year-old seedlings, those planted in summer grew and survived better after planting but had more multiple leaders than seedlings planted in autumn or spring.     

水松幼苗的水分和铜胁迫试验

应用盆栽试验方法,比较研究了水松幼苗在不同水分和铜胁迫条件下的生长表现。结果表明:①在渍水(Wa)、隔天渍水(Wb)及3天浇水1次(Wc)和7天浇水1次(Wd)等4种水分胁迫条件下,Wc处理组幼苗生长表现最好;Wa和Wb处理组次之,Wd处理组幼苗在第7 d就出现萎焉,至第10天时全部死亡。②在Cu2+50(Cu50)、100(Cu100)、200(Cu200)、500mg·L-1(Cu500)等4种铜胁迫条件下,水松裸根苗在第10天时全部死亡;水松土培苗也出现不同程度的死亡和生长受抑现象,随着铜胁迫时间的延长,其成活率和生长量与对照组(Cu0)的差异增大;至90 d时,Cu500处理组的苗木存活率只有22.2%,其幼苗高增长量仅为对照组的38.2%。     

Improving drought tolerance of <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> seedlings by arbuscular mycorrhizas under glasshouse conditions

Effects of mycorrhizal association on improving tolerance of host plant under stress environments have received attentions in recent years. In this paper, six isolates of AMF (arbuscular mycorrhizal fungus) were inoculated to Casuarina equisetifolia seedlings under glasshouse conditions to investigate the effects of AMF on growth and drought tolerance of host plants. All the six isolates which belong to Glomus showed high mycorrhizal colonization (88.5–96.0%) with C. equisetifolia seedlings. Seedlings were subjected to drought stress without watering for 7 days and survival of the seedlings inoculated with Glomus caledonium Gc90068, G. versiforme Gv9004 and G. caledonium Gc90036 increased by 36.6, 23.3 and 16.6%, respectively compared with uninoculated seedlings. Limited influence of AMF on seedling height growth was found, but the effects of AMF on total biomass increment were very significant; the increment ranged from 25.7 to 118.9% compared with uninoculated treatment, and it was noted that AMF exerted more influences on root biomass than shoot biomass. Based on the changes in physiological and biochemical parameters among different treatments caused by drought stress, it was concluded that AM (arbuscular mycorrhizal) associations improve the drought tolerance of C. equisetifolia seedlings by means of some physiological and biochemical responses, such as lowering permeability of plasma membrane and MDA (malondialdehyde) contents, enhancing concentrations of P nutrition, soluble sugar, soluble protein and activities of POX (Peroxidase) of C. equisetifolia seedlings.     

Use of short-day treatment in the production of Norway spruce mini-plug seedlings under plant factory conditions

Mini-plug transplant seedlings of Norway spruce have been cultivated in closed growth systems, so-called plant factories, for few years. The aim of the experiment was to define a short-day treatment (SD) that harden seedlings to sustain 3 months of cold storage, but does not have adverse effects on growth, morphology, and vitality. The seedlings were subjected to one of the following treatments: (1) 12?h photoperiod + 3 weeks duration; (2) 8?h photoperiod + 3?wk duration; (3) 12?h photoperiod + 5?wk duration; and (4) 8?h photoperiod + 5?wk SD. All the SD treatments yielded healthy seedlings that grew well after the cold storage. The frost hardiness of the seedlings improved when the photoperiod was reduced from 12 to 8?h, and when the SD duration was increased from 3 weeks to 5 weeks, but reducing the photoperiod from 12?h to 8?h caused growth reductions. The root and shoot regrowth after cold storage was highest in seedlings that had received 12?h photoperiod and 5?wk duration. However, 12?h photoperiod and 3?wk duration may be an adequate practice for nurseries that treat multiple crops in their SD facilities.     

Pt菌剂对尾叶桉苗木抗旱性的影响

对尾叶桉苗木采用Pt菌剂(Pisolithus tinctorius)和水分胁迫处理,研究不同处理对该苗木生长及营养物质积累方面抗旱性的影响.结果表明:接种菌剂后水分胁迫条件比常规供水更利于苗高生长.无论常规供水还是水分胁迫条件下,接种菌剂10 g地径增长量都最大,高Pt菌剂施用量对地径增长量有一定的抑制作用.菌剂处理能提高苗木生长质量.常规条件下,菌剂5 g处理苗木质量最高;胁迫条件下,菌剂10 g处理苗木质量最高,而对总体抗旱性而言,菌剂15 g处理效果最好.     

红塔区施肥、浇水措施对漾濞泡核桃苗木生长的影响研究

2009年玉溪红塔区引种漾濞泡核桃,恰逢2009～2012年连续4年异常干旱,本研究针对该区域凤凰街道办事处灵秀二组种植的漾濞泡核桃,采用尿素、复合肥、磷复肥、核桃专用肥、缓释肥5种不同肥料施肥,并进行春季浇水次数为0次、1次、2次、3次试验,检测核桃苗木地径、高生长及桂果情况。试验结果表明,漾濞泡核桃按照每年浇水3次,并对其进行修剪（整形）、病虫防控管理的条件下,不同种类肥料促进漾濞泡核桃苗高生长差异性显著,缓释肥促进苗木高生长效果最显著,施用4年后,苗高可达3．50±0．68m,苗木地径达11．2±1．25em;不浇水漾濞泡核桃苗木基本不长,浇水次数越多苗木高生长越大、地径也越大;在供水条件跟上,每年春季浇水3次的情况下,试验用的尿素、复合肥、磷复肥、核桃专用肥、缓释肥5种肥料,施用3年均可挂果;肥料充足,都施用缓释肥,每年春季浇水次数不同,挂果历时明显不同,浇水3次,定植3年就开始挂果;浇水2次,定植4年开始挂果;浇水1次和不浇水,不挂果。     

Impacts of nursery cultural treatments on stress tolerance in 1 + 0 container white spruce (<Emphasis Type="Italic">Picea glauca</Emphasis> [Moench] Voss) seedlings for summer-planting

Impacts of nursery cultural treatments (T) on stress tolerance of greenhouse-grown 1 + 0 container white spruce (Picea glauca [Moench] Voss) seedlings (mean height 24 cm, root collar diameter 3.1 mm) for summer planting were studied. Seedlings were subjected to 12-h short-day treatments of 0 (T0), 3 (T3), 7 (T7), 10 (T10), or 15 (T15) days, followed by 0, 7, 17, 40, or 46 days of reduced N supply, respectively. Relevant physiological and morphological factors were examined concurrently. Foliar N concentrations exceeded optimal levels and differed little among treatments, suggesting a minor confounding role for N reduction. Both frost and drought tolerance increased incrementally from T0 through T15. Electrolyte leakage index decreased steadily from T0 (25% for roots, 17% for needles) to T15 (1% for roots, 2% for needles) after 2-h exposure of fine roots to − 2°C and of needles to − 8°C. Withholding soil watering for 19 days caused 80% mortality among seedlings in T0, 50% in T3, and < 10% in T7–T15. The transpiration decline curve suggested that enhanced drought tolerance was largely attributable to quicker stomatal closure during water stress and lower cuticular transpiration rate. The treatments increased root growth capacity on a per-seedling, but not per-root-mass, basis. Needle primordia were developed in all T7-T15 seedlings but not in T0 and T3 treatments, suggesting that nurseries may need no more than 7 days of blackout application for conditioning spruce seedlings for summer planting. Shoot dry weight fraction increased gradually from T0 through T15 and was linearly correlated with needle specific weight and frost tolerance, and may thus be useful in monitoring progress of conditioning treatments.     

水分胁迫对宜昌楠外部形态的影响

对1年生宜昌楠幼苗进行水分胁迫实验,做6个处理,分别为：不浇水、每日浇水、隔日浇水;水痕于盆迹的1/3、1/2、全部淹没。处理后观察幼苗的外形变化,测定幼苗的生长高度。实验表明：宜昌楠幼苗在干旱情况下出现枯死现象,在涝渍情况下叶片出现红色,排水试验后叶片开始恢复,叶片红色变浅。水分胁迫在不同程度上对宜昌楠的生长造成了影响,影响由胁迫程度、胁迫时间的不同而异。证明宜昌楠具有一定的抗涝渍能力,经过一定时间的水分胁迫后,解除水分胁迫,仍可恢复生长,不同的处理恢复情况有所差异。     

An irrigation control system with a web-based interface for the management of Eucalyptus planting stock in a nursery

Efficient nursery irrigation is a key factor for the production of high-quality forestry planting stock. Conventional timer-based irrigation systems used by most forestry nurseries have some drawbacks that, if not properly managed, can lead to over-irrigation and water wastage, leaching of nutrients and contribute to increased incidences of pests and/or diseases. A practical method to accurately measure media water content and control irrigation more carefully could prevent some of these issues. To evaluate the potential use of an automated irrigation system, commercially available Decagon EC-5 dielectric soil water content sensors were laboratory-calibrated against the gravimetric method using coir/pine bark/vermiculite, coir/perlite and pine bark media to measure water content of nursery seedling containers. Using Eucalyptus dunnii seedlings raised in polystyrene seedling containers to test the irrigation system, a datalogger was programmed to control irrigation for low (0.22–0.26 m³ m^?3), medium (0.26–0.32 m³ m^?3) and high (0.32–0.41 m³ m^?3) watering treatments. The measurements were displayed in near real-time using a web-based system, which allowed for system checking and from which data could be downloaded. The Decagon EC-5 sensors were successfully calibrated for all media (R² > 0.97) and provided a better estimation of media water content than the manufacturer-supplied calibration equation better-suited for soils. The automated irrigation system effectively maintained the specified media water content for E. dunnii seedlings. The high watering treatment seedlings had the highest growth rates, although this treatment also had increased leaching of nutrients. By contrast, the low watering treatment seedlings showed the lowest growth rates, although these seedlings seemed to be more robust and tolerant of water stress. This study showed that the automated irrigation system, based on measurements of the media water content, can be successfully used in scheduling irrigation for Eucalyptus seedlings, leading to potential water savings.     

Stress responses of <Emphasis Type="Italic">Salix gracilistyla</Emphasis> and <Emphasis Type="Italic">Salix subfragilis</Emphasis> cuttings to repeated flooding and drought

To compare the responses to repeated flooding and drought of Salix gracilistyla, which grows on coarse gravel substrates, and Salix subfragilis, which grows on fine silt or clay substrates, we measured pre-dawn leaf water potential (Ψw _pd), osmotic adjustment (Ψw _tlp, Ψo _sat), and biomass production of cuttings under greenhouse conditions. The experimental design involved a control and four treatments that crossed 1 or 3-week flooding (F) with 1 or 2-week droughts (D). Ψw _pd was reduced after 2 weeks of drought when preceded by 1 week of flooding. Neither species increased osmotic adjustment in response to increased duration of drought between repeated 3-week flooding. Moreover, a decrease in the ratio of leaf biomass to total biomass or an increase in the ratio of root biomass to total biomass with longer drought repetitions was not observed for either species. The root ratio of S. gracilistyla was more strongly inhibited by flooding than that of S. subfragilis. The shoot-to-root ratio of S. subfragilis was higher than that of S. gracilistyla in all F combinations. The hypertrophied lenticel ratio of S. gracilistyla after 1 week of flooding was nearly the same as that after 3 weeks of flooding, whereas values for S. subfragilis after 1 week of flooding were lower than those after 3 weeks of flooding. The low allocation to roots and the generation of hypertrophied lenticels by S. gracilistyla in response to flooding, as compared with S. subfragilis, seem to be related to the different habitat substrate conditions of the two species.     

等渗胁迫及其钙调节下青钱柳幼苗叶肉细胞中ATP酶的细胞化学定位及亚细胞变化

研究了等渗的盐和水分胁迫及其钙调节下,青钱柳幼苗叶肉细胞中ATP酶活性在亚细胞中的分布及其超微结构变化。在人工气候室中采用水培法,将青钱柳幼苗进行5个不同浓度处理：对照,85mMNaCl,85mMNaCl＋12mMCa（NO3）2,PEG（渗透势等于85mMNaCl）及PEG（渗透势等于85mMNaCI）＋12mMCa（NO3）2。结果表明：正常生长条件下,ATP酶活性较低并主要定位在细胞核中 等渗胁迫12d以后,ATP酶活性增大并以液泡中居多。等渗水分胁迫下出现的嗜锇颗粒较等渗盐胁迫下的多。由于外源钙的调节作用,等渗胁迫下ATP酶活性增加并主要转移至细胞核上,且在等渗水分胁迫下的嗜锇颗粒明显减少。ATP酶定位在细胞核中表明幼苗遭受胁迫伤害程度较轻,而定位在液泡中则表明受伤害程度较重。等渗处理4和20d后,等渗胁迫及其钙调节下青钱柳幼苗叶片超微结构被破坏程度较无钙调节处理,尤其是较等渗水分胁迫下的轻。初步认为,等渗盐胁迫下青钱柳幼苗遭受的胁迫伤害程度较等渗水分胁迫下的轻,而钙调节作用则以等渗水分胁迫下的效果较佳。     

不同土壤水分胁迫格局对印度沙漠中的黄檀种苗营养吸收和生物量的影响

1998年7月,利用非称重式蒸渗池种植单一种源的一年生黄檀种苗,研究在印度沙漠地区培养黄檀种苗的合理灌水技术参数。当各处理（W1、W2、W3、W4）的土壤水分含量分别降低到7.56%、5.79%、4.44%和3.23%时,通过灌溉使苗木生长保持在一定的土壤的水分状况,如36.2mm（W1）、26.5mm（W2）、20.2mm（W3）和18.1mm（W4）。结果表明,在36.2mm（W1）水平时,种苗的株高、冠径、叶数和叶面积达到最大值（p〈0.01）。在W1和W2处理中,虽然上述参数没有明显差异,但在W2处理中,种苗的每升水分利用率的生物量最大。在W3、W4和W5灌溉水平下,不利于提高种苗的株高、生物量和营养积累。在W2水平以下（5.79%）,土壤水分有效率能提高根系生物量占总生物量的百分比。但在W3和W4处理中,叶干生物量百分比下降,同时在W5处理中,茎干生物量百分比下降。在W5处理中,土壤水势达到-196Mpa,种苗才可以成活。在W3和W4处理中,土壤水分有效率的限额影响黄檀种苗的生长和生物量。在W2处理中,土壤水分有效利用率最高,种苗的生长和生物量达到最高值。因此,在壤砂土条件下,通过灌溉维持幼苗土壤水分含量在5.79%以上时,可获得较好的黄檀种苗的生长和生物量产量。     

Effects of Acidic Precipitation and Ectomycorrhizal Inoculation on Growth,Mineral Nutrition,and Xylem Water Potential of Juvenile Loblolly Pine and White Oak

Abstract

Individual and interactive effects of simulated acidic rainfall and mycorrhizal inoculation on growth and nutrient and water relations of loblolly pine (Pinus taedaL.) and white oak (Quercus albaL.) grown in a loam soil were examined. Seedlings of each species inoculated with basidiospores of the ectomycorrhizal fungus Pisolithus tinctorius(Pers.) Coker and Couch, a known my-cobiont of both loblolly pine and white oak, and uninoculated control seedlings received two simulated rains per week of either pH 3.6, 4.2, or 4.8 for 26 weeks. Higher acidity rainfall reduced the growth but increased mycorrhizal colonization of loblolly pine, while both loblolly pine and white oak exposed to these rains exhibited greater foliar injury. Inoculation with P. tinctoriusincreased growth and reduced foliar injury of both species. Foliar concentrations of P, S, and Cu in loblolly pine and white oak, Ca in loblolly pine, and Fe and Zn in white oak decreased with increasing rain acidity while the Al concentration of both species increased. Higher rainfall acidity also reduced soil pH and Ca and Mg concentrations while increasing soil AI. Foliage of inoculated seedlings of both species had higher N and P concentrations and lower Al concentrations than control seedlings. Following the final rain applications, a drought cycle was simulated by withholding irrigation for two weeks during which seedling xylem pressure potential and soil water potential were measured. One day after cessation of irrigation, xylem pressure potential of loblolly pine that had received pH 3.6 rains was lower than that of other treatments. Thereafter, xylem pressure potential and soil water potential of the inoculated treatment decreased below those of the control treatment in both species. These results suggest that acid deposition is detrimental to juvenile loblolly pine and white oak, but the magnitude of this effect is less than the positive response to ectomycorrhizal inoculation.     

Planting frozen conifer seedlings: Warming trends and effects on seedling performance

In temperate climates, conifer seedlings are often held in frozen storage (–2 °C) for extended periods and then placed in cool storage (+2 °C) so the root plug can thaw prior to outplanting. Two plug temperature treatments were used to test the hypothesis that thawing seedlings prior to outplanting may be unnecessary: seedlings were planted with frozen root plugs (frozen seedlings) and with thawed root plugs (thawed seedlings). The experiment was conducted under two watering regimes (irregular, regular) and with three conifer species (lodgepole pine [Pinus contorta var. latifolia], western larch [Larix occidentalis], interior spruce [Picea glauca × engelmannii]) to increase the generality of the results. The warming of root plugs after planting was examined. Thawed root plugs warmed to soil temperature rapidly (about 30 min) while frozen root plugs took longer (to 2 h) because ice in the plug had to melt before temperatures rose. Larger root plugs took longer to warm to soil temperature. Several aspects of seedling field performance were also assessed. For all species, variable fluorescence did not differ between frozen and thawed seedlings. Bud break was faster for thawed than frozen western larch seedlings but did not differ between frozen and thawed seedlings for either lodgepole pine or interior spruce. Height increment differed significantly between frozen and thawed seedlings that received the irregular watering regime; this effect was likely a response to the positioning of irrigation nozzles, which resulted in sporadic and non-uniform irrigation patterns. Height increment did not differ between frozen and thawed seedlings that received the regular watering regime. Root collar diameter and volume increments were not significantly affected by plug temperature treatment under either watering regime. Planting seedlings with frozen root plugs did not hinder field performance over one growing season under these watering regimes.     

Interacting effects of irradiance and water stress on dry weight and biomass partitioning in Fagus sylvatica seedlings

Abstract

Actual climate models for central Europe predict prolonged summer droughts. Knowledge on how the interaction between light and water availability affects regeneration will hence be of major importance. In an experiment carried out under controlled conditions, newly emerged beech seedlings were grown in pots with sand during 54 days. Three treatments applying three different light levels (2, 9 and 43% relative light intensity) were combined with two soil water treatments (control and drought). At the end of the experiment, seedlings were separated into leaves, stem and root and the seedlings’ dry mass, leaf area and stem length was determined. Low irradiance (2%) had a strong negative effect on dry weights of seedling components, leaf area and specific leaf mass. Drought clearly affected biomass partitioning for seedlings at high irradiance levels (43%). An interaction between irradiance and drought on biomass partitioning in beech seedlings was observed at medium irradiance level (9%). Within a wide range of light levels in the forests, both light and drought may affect biomass partitioning in young seedlings.     

Induction of hairy and normal roots on Picea abies,Pinus sylvestris and Pinus cortorta by agrobacterium rhizogenes

Two‐ to three‐week‐old seedlings of Picea abies, Pinus sylvestris and Pinus contorta were inoculated with the supervirulent strain Agrobacterium rhizogenes R1600 2cm above the base of the hypocotyl; other treatments included inoculation with Agrobacterium tumefaciens strain A281 (pTVK291) or mock inoculation. Hairy or highly branched roots formed on 2–3% of seedlings of all 3 species that were infected by R1600 but on none of the other seedlings. Normal adventitious roots were also induced on 5–10% of Agrobacterium‐treated seedlings but none appeared on the other seedlings. Opine assays and growth rates of hairy and normal roots indicated that only roots with the hairy morphology were transformed.