Growth,allocation of N and carbohydrates,and stomatal conductance of greenhouse grown apple treated with prohexadione-Ca and gibberellins

Summary

Potted M.26 apple (Mahis domestica) liners were treated with the gibberellin biosynthesis inhibitor prohexadione-Ca (Apogee®) at 0 to 500 mg l”¹ as a foliar spray. Apogee inhibited stem elongation, leaf formation, total leaf area and shoot dry weight, while significantly increasing specific leaf weight, root dry weight and root: shoot ratio, regardless of rate. Foliar application of gibberellin A4₊₇ (GA4₊₇) at 200 mg l”¹ to Apogee-treated plants one day later reversed these effects, especially stem elongation, root dry-matter production and root: shoot ratio. Apogee increased N concentration in stems but not in leaves and roots. There was no effect on the pattern of N allocation amongst organs. GA4+7 increased leaf N concentration but decreased stem and root N concentrations compared with untreated controls, with N allocation shifting from roots to stem. Total nonstructural carbohydrates (TNC), expressed either on a concentration or content basis, increased in all parts of the Apogee-treated plants, due to increased levels of starch rather than soluble sugars, without altering allocation pattern. Conversely, GA4₊₇ reduced TNC levels (mainly starch levels) in all parts, with the pattern of allocation slightly shifted from roots to stem. The afternoon decline in stomatal conductance occurred earlier in the Apogee treated plants, measured 10 d after stem elongation had ceased. Starch buildup in the Apogee-treated plants appeared to be associated with this effect, suggesting an involvement of a feedback inhibition of photosynthesis in the Apogee-induced stomatal control.     

Effects of growth retarding treatments on apple tree growth,fruit maturation and fruit abscission

SUMMARY

Eight days after petal fall in 1991, mature 'Delicious'/MM. 106 apple trees and four days after petal fall in 1992, mature 'McintoshVMM. 106 were ringed, scored, root pruned (1 m from the trunk, two sides, 30 cm deep), or treated with ethephon (500 mg 1¹). Only ringing and scoring reduced vegetative growth. Ethephon advanced fruit maturation and fruit abscission, but root pruning did not affect the trees or fruit significantly. Mature 'Cort-land'/M.7a apple trees were root pruned 8 d after petal fall in 1991 and/or at full bloom in 1992. Root pruning reduced shoot growth, even in the year after treatment. Fruit abscission was reduced in 1991 and 1992 by root pruning in 1991, but root pruning in 1992 had no impact on abscission, in 1992. In an additional experiment, mature 'Mcintosh'/ MM.106 were root pruned 4 d after petal fall in 1991 or root pruned both in 1991 and at full bloom in 1992. Growth and preharvest fruit abscission were reduced in both the year of root pruning and the year after.     

The effect of pre-planting desiccation stress and root pruning on the physiological condition and subsequent field performance of one year old Prunus avium and P. cerasifera seedlings

Summary

Severe desiccation of dormant seedlings of wild cherry (Prunus avium) and cherry plum (P. cerasifera) did not affect their immediate survival, but caused significant reductions in subsequent shoot growth and root volume which were not recovered in a single growing season. Damage to the fine roots, as indicated by the physiological plant quality measures of tetrazolium absorbance and root electrolyte leakage, increased rapidly over drying periods of ca. 6 h, further damage requiring progressively longer periods of desiccation. Root pruning prior to planting did not mitigate desiccation damage and severe pruning was highly injurious to subsequent growth. Generally the removal of the fine roots was equivalent to a relatively short desiccation period, but pruning of fine roots prior to, instead of after, desiccation in P. cerasifera resulted in more lateral shoots, possibly indicating the production of growth retardant substances by the dried root systems. All measures of physiological plant quality at the beginning of the growing season were effective as predictors of plant performance at the end. In the species tested, the most cost-effective routines are likely to be fine root electrolyte leakage and root moisture content, with tetrazolium testing and stem water potential measurements requiring both greater reproducibility and more sophisticated equipment.     

Mechanism of chemical root pruning in kangaroo paw (Anigozanthos flavidus) by selected heavy metal carbonates

Summary

Heavy metal carbonates/hydroxides of copper (Cu), cobalt (Co) and zinc (Zn) were tested for their ability to induce root pruning in container-grown Anigozanthos flavidus (kangaroo paw). Co (1 and 2 mol eq 1^–1) and Cu (2 and 5 mol eq 1^–1) were the best heavy metals for root pruning, while Zn was only effective at 5 mol eq 1^–1. Successful root pruning was accompanied by 80% of root tips at or near the container wall being morphologically dead, whilst within the media a maximum of 25% of roots were dead. Increase in shoot/root ratios and a decrease in the root branching coefficient were strongly correlated with root pruning ability. The mitotic index was significantly lower in heavy metal pruned root tips, and this was accompanied by an uptake of the respective heavy metal. Heavy metals also significantly reduced the amounts of potassium present in root tips at or near the container wall, demonstrating some nutritional imbalances, and that potassium levels may be a sensitive indicator of heavy metal toxicity. During the eight-week experimental period, heavy metals were slowly released into the media water, the amounts were low and below water quality guidelines. The moderate effects of Co in affecting mitosis and potassium nutrition during root pruning, and its general lower toxicity in the environment suggest that Co may be utilized as a suitable and effective chemical root pruning agent.     

四种嫁接方法对甜瓜嫁接苗生长的影响

以‘特选一号’甜瓜为接穗,‘银光’南瓜为砧木,采用了顶插接、改良插接、断根插接和断根贴接4种嫁接方法,研究了不同嫁接方法对甜瓜嫁接苗生长的影响,以期为甜瓜育苗提供指导。结果表明:甜瓜顶插接嫁接速率最快、嫁接工效最高,嫁接后在昼/夜温度为28℃/18℃条件下,改良插接的嫁接成活率最高,改良插接和断根贴接的愈合时间短。在一叶一心时期,改良插接和顶插接的嫁接苗有明显的生长优势,改良插接的嫁接苗根系生长最好;而到三叶一心时期,断根插接和断根贴接的甜瓜嫁接苗生长快,壮苗指数显著高于顶插接和改良插接,断根插接的嫁接苗叶面积最大。不同嫁接方法所需除萌蘖次数和时间也存在差异,断根插接除萌蘖次数最少,除萌蘖用时仅为顶插接的46.3%。     

不同整枝方式对管棚越夏栽培番茄生长的影响

在管棚田间状况下,对越夏栽培的番茄进行单秆整枝、双秆整枝及连续摘心处理,测定番茄的生长、产量及品质指标,研究不同的整枝方式对越夏栽培番茄生长的影响.研究结果表明,连续摘心处理的植株在株高、茎粗、产量、叶绿素含量及根系活力指标方面均优于单秆整枝和双秆整枝处理;双秆整枝处理的植株叶片中丙二醛含量最高,番茄果实中VC含量也有...     

Effect of pruning and plant spacing on the growth of cherry rootstocks and their influence on stem water potential of sweet cherry trees

Summary

The aims of this work are to describe the effects of pruning and planting density on growth and water relations of ungrafted and grafted sweet cherry trees. A trial with cherry rootstocks ‘Prunus avium’, ‘CAB 11E’, ‘Maxma 14’, ‘Gisela 5’ and ‘Edabriz’ was begun in 1997. Pruning severities were applied to the rootstocks (0, 30, 60 and 90% of the vegetative growth was removed corresponding to P1, P2, P3 and P4 treatments, respectively) after planting to two plant spacings (S1 = 0.25 × 1.0 m and S2= 0.45 × 1.5 m). Canopy, root growth and leaf water potential (ψ_leaf) were quantified throughout the growing season. Pruning significantly affected root length and root weight of the rootstocks. Uncut plants (P1) showed a heavier and expanded root biomass (231 g and 108 m) than the intensively pruned plants (P4) (187 g and 75 m). The greater root biomass was obtained with the spacing/pruning combination, S1/P1 (285 g), and the smaller with S1/P4 (180 g) and S2/P4 (176 g). ψ_leaf varied significantly between the rootstocks and plant spacing but not with pruning. ‘Maxma 14’ and ‘P. avium’ attained the lowest values of midday ψ_leaf, –2.28 and –2.04 MPa, but the highest values of predawn ψ_leaf, –0.29 and –0.25 MPa, respectively. Generally, with high density (S1), the rootstocks exhibited lower predawn and midday ψ_leaf. In 1998, cultivars ‘Burlat’, ‘Summit’ and ‘Van’ were grafted onto rootstocks and a trial was installed in 1999. Predawn and midday stem water potential (ψ_stem) on cherry trees, measured in 2002, were affected significantly by the rootstock/genotype combination. Cultivars grafted on ‘P. avium’ and ‘Maxma 14’ showed the less negative midday ψ_stem, –1.36 and –1.42 MPa respectively, so these rootstock genotypes perhaps induced a higher drought resistance to the scion. Recorded data show that the scion-rootstock interaction with regard to production performance under water deficits may be an important consideration in cherry tree planting strategies.     

Summer pruning reduces whole-canopy carbon fixation and transpiration in apple trees

Summary

Canopy size control is one of the major purposes of summer pruning. However, reducing canopy size might also result in less light interception, consequently decreasing canopy photosynthetic efficiency and carbohydrate production, which might lead to the imbalance of carbohydrate supply and fruit demand. To document the effectiveness of summer pruning on canopy control and the impact on canopy gas exchange, pruning treatments at four levels of intensity (unpruned, light, moderate, and severe) were carried out on mature ‘Empire’/M.9 slender spindle apple trees (Malus domestica Borkh.) on 30 July 1998 and 4 August 1999. Changes in canopy leaf area after summer pruning were estimated. Canopy net carbon exchange rate (NCER) and canopy transpiration before and after summer pruning were monitored. Canopy growth was suppressed by summer pruning and the post-pruning regrowth was insignificant. Canopy NCER was reduced in proportion to the amount of leaf area removed by summer pruning. The result suggests that commercial pruning intensity similar to the moderate to severe treatments in this study could cause a significant reduction in canopy NCER and carbohydrate production. In addition, canopy transpiration was reduced in proportion to pruning intensity. Lower water consumption and improved water status during the growing season after summer pruning might benefit fruit growth and relieve the potential detriment due to carbohydrate shortage.     

Effect of electrical conductivity,fruit pruning,and truss position on quality in greenhouse tomato fruit

Summary

The combined effects of electrical conductivity (an EC of 2.5 dS m^–1 or 8 dS m^–1 in the root zone) and fruit pruning (three or six fruit per truss) on tomato fruit quality were studied in a greenhouse experiment, planted in January 2005. Taste-related attributes [dry matter content (DM), total soluble solids content (SSC), titratable acidity (TA), glucose, fructose and citric acid content] and health-promoting attributes (lycopene, βcarotene, vitamin C, and total anti-oxidant activity) of tomato fruits harvested on the vine from the fifth or tenth truss positions were determined. The quality of tomato fruits was improved by high EC. A high EC in the root zone increased the DM content, total SSC, TA, as well as glucose, fructose and citric acid contents. A significantly higher lycopene and βcarotene content was also observed [on a fresh weight (FW) and dry weight (DW) basis] with a high EC in the root zone. The accumulation of different compounds that determine tomato fruit quality differed between the fifth and tenth truss. In particular, the lycopene content was reduced, whereas the βcarotene content was increased in the tenth truss with respect to the fifth truss, most likely because of higher temperatures during ripening of the tenth truss. Fruit pruning increased fruit FW by 42% and positively influenced the DM content and total anti-oxidant activity, while a negative effect was observed on lycopene and citric acid contents (on a FW and DW basis). EC and fruit pruning both had a strong effect on fruit size; however, EC had a much stronger impact on taste and health-related fruit quality attributes. A small interaction between EC and fruit pruning was found for marketable yield, fructose and glucose content, fruit firmness, and P and Ca concentrations in fruits.     

Girdling and summer pruning in apple increase soil respiration

The root system of plants derives all its energy from photosynthate translocated from the canopy to the root system. Canopy manipulations that alter either the rate of canopy photosynthesis or the translocation of photosynthate are expected to alter dry matter partitioning to the root system. Field studies were conducted to evaluate the effect of trunk girdling (2008 and 2009) and summer pruning (2009) on soil respiration, maximum quantum yield efficiency of photosystem II and leaf carbohydrate content. In apple trees, following trunk girdling there was increased soil respiration in association with a significant rainfall event suggesting rapid release of organic matter and subsequent microbial decomposition of the carbon. Soil respiration rates returned to baseline levels over time. Reduction in midday maximum quantum efficiency of photosystem II (RPSII) was increased by girdling when crop load was low and this reduction was not related to leaf carbohydrate levels. Girdling reduced leaf sucrose and sorbitol levels in both years, however, total leaf carbohydrates were not affected by girdling. Summer pruning increased soil respiration within 2 weeks of treatment in association with a significant rainfall event, also suggesting a release of organic matter and microbial decomposition of the carbon. Cultural practices that severely affect canopy sink source relationships such as girdling and summer pruning increase soil respiration, however these effects appear to be very short lived, 3–10 days, followed by recovery of the soil/root system to similar levels of soil carbon dioxide efflux. These cultural practices do not likely pose a long-term detrimental effect on root system efficiency because the effects are of short duration with apparent recovery.     

Vegetative Growth,Productivity, Berry Quality Attributes and Leaf Macronutrients Content of Currants as Affected by Species and Cultivars

Bush vigor, berry physical traits and chemical composition, seasonal changes of leaf macronutrients content and leaf mineral status at mid-summer (120 DAFB, Days After Full Bloom) were evaluated in black, red and white currants and their cultivars which are grown on heavy soil, and with reduced cultural practices, except pruning, fertilization with cattle manure and weed control with herbicide, under western Serbian conditions. Results indicated that black currant had lower bush size, yield, bunch weight and number of berries per bunch, but had significantly higher berry weight as compared to red and white currants. Red and white currants had similar bush size, yield and bunch weight. Berries of black currant contained much higher levels of soluble solids content, acidity, vitamin C, total phenolics and flavonoids content than both red and white currants, whereas ripening index was similar. Leaf of black currants had lower macronutrients content, except leaf Mg, as compared with others. Very high excesses of all leaf macronutrients content, except in some cases for leaf N and Mg, were observed in currants in mid summer, i.?e. at 120 DAFB. Black currant showed the best balanced nutritional values, whereas red currant showed a wider imbalance in nutritional values. Beside currant species, strong effect of cultivar per se was found on the most of evaluated features. Generally, black currant cv. ‘Eva’, red currant cv. ‘Slovakia’, somewhat ‘Detvan’, and white currant cv. ‘Primus’ had higher bush size, better berry physico-chemical attributes and higher leaf macronutrients content than others. Finally, ‘Eva’, ‘Tatran’ and ‘Meridian’ showed the best balanced nutritional values at 120 DAFB.     

断根和剪枝对盆栽苹果叶片光合蒸腾及WUE的影响

 以5 年生盆栽苹果(Malus domestica Borkh/Malus hupenensis Rhed) 为试材, 研究了断根和剪枝等处理对叶片净光合速率(Pn) 、蒸腾速率(Tr) 、气孔导度(Gs) 、水分利用效率(WUE) 的影响及引起WUE变化的原因。结果表明, 断根明显提高了WUE , 处理后第2～42 天逐渐升高。同时, 断根后Tr、Gs 明显下降, 而Pn 和羧化效率(CE) 迅速恢复, 并在第7 天以后明显高于对照; 新根总数及叶片玉米素核苷(ZR)浓度则于第28 天后恢复至对照水平。剪枝使Pn、CE、Tr、Gs 及叶片ZR 浓度升高, 但WUE 只在28 d 后稍高于对照。断根结合剪枝后第2 天, Pn、CE、Tr 及Gs 下降; 21 d 后Pn 和CE 高于对照, 而Tr 及Gs 与对照相近, WUE 在后期稍有升高。分析认为, 断根通过降低气孔导度极显著地提高了叶片WUE , 剪枝则通过提高CE 而使WUE 升高。     

The effect of root restriction on the incidence of blossom-end rot in bell pepper (Capsicum annuum L.)

Summary

Water and calcium uptake are important factors affecting the incidence of fruit blossom-end rot (BER) in tomato and pepper. In the present study an attempt was made to manipulate these factors by severe root pruning and to examine the effect on BER in greenhouse-grown bell pepper (Capsicum annuum L., cv. Mazurka). Pepper plants were transplanted, with the root system split into four separated compartments, each containing a single root quarter. Removal of half, or three quarters, of the root from fruit-bearing plants significantly reduced fruit BER incidence compared with plants with intact roots, especially in fruits which were at the rapid expansion stage at the beginning of the treatments. Removal of three quarters of the root reduced midday leaf water potential, stomatal conductance, and plant height. The number and weight of fruits were not affected by these treatments. Root pruning caused only a slight reduction in stem sap flow, as measured by the heat pulse technique. Calcium concentrations in the distal part of fruits from quarter-root-plants were higher than in fruits from non-pruned plants, whereas magnesium and potassium concentrations were not affected. On the other hand, in the leaves, calcium, magnesium and potassium concentrations were all reduced by root pruning. The K/Ca ratio decreased in the blossom-end of the fruits and increased in the leaves of root-pruned compared with control plants. The results suggest that root pruning did not affect the total uptake of calcium, apparently driven by transpiration, but did enhance calcium partitioning to the developing fruit. Root pruning also affected calcium distribution within the fruit and therefore attenuated BER incidence.     

Changes in chlorophyll,ribulose bisphosphate carboxylase-oxygenase,glycine betaine content,photosynthesis and transpiration in Amaranthus tricolor leaves during salt stress

Summary

We examined changes in leaf growth and chemical composition, including chlorophyll content, ribulose bisphosphate carboxylase-oxygenase (RuBisCO), and glycine betaine (GB) in relation to photosynthesis and transpiration responses to salt stress in Amaranthus tricolor leaves. To induce salt stress, plants were transferred to a growth medium containing 300 mM NaCl for 7 d followed by 7 d of relief from salinity. A decrease in leaf enlargement began 3 d after salt stress, and leaves subsequently showed the same degree of regrowth as controls after relief in non-salt medium. Chlorophyll content expressed on a leaf-area basis increased under conditions of salinity due to a reduction in leaf tissue water content. The decrease in chlorophyll content continued throughout the 7 d of relief from salinity. The RuBisCO and soluble protein contents when expressed on a leaf dry-weight basis decreased in response to salinity, and then gradually increased during the relief period. GB content increased slightly up to 3 d of salt stress, and showed typical accumulation during salt stress. GB content decreased sharply immediately after plants were transferred to non-stress medium, but remained at a higher level throughout the relief period. A decrease in photosynthetic activity and transpiration rate preceded any changes in leaf area, RuBisCO or GB content. During relief from salinity, photosynthesis and transpiration rates gradually recovered to control levels with restoration of stomatal conductance. The above findings suggest that the increase in GB content is important in adaptation to salt stress in Amaranthus plants, although photosynthesis and transpiration responses occurred immediately after salt-stress.     

Effect of harvest date on onion yield in a northern climate

Summary

Timing of harvest is an essential factor affecting the quantity, quality and storability of onion yield. This study aimed to establish when no further yield increase is to be expected and to determine the relationship between maturity stage and yield development. Experiments on 4-6 harvests at 9-14 d intervals were conducted at several locations in southern Finland in 1996-1999. Generally little, if any, yield increase was recorded after plants had reached 100% maturity, but in some cases bulb growth continued after complete fall-down of leaves. On the other hand, harvesting before 100% maturity resulted in a yield loss of 0-45% of final yield. Weight loss, and thus energy consumption during drying, was still reduced after complete leaf fall-down. Therefore, it may be concluded that delaying harvest up to 100% maturity, or even longer, ensures that highest yield and lowest drying costs.     

Effect of soil salinity levels on growth and chemical composition of Syzygium cumini L.

Seedlings of Syzygium cumini were grown in artificially salinized soils of conductivities 0 to 20 mmhos cm^-1 for 19 months. Adverse effects on growth were seen at and above a conductivity level of 16 mmhos cm^-1 of the saturation extract. As the conductivity increased, the adverse effects of growth and the extent of plant injury were intensified As salinity increased, the leaf chlorophyll content at the end of the experiment decreased. The leaf N content did not differ significantly, but the root N content was significantly lower at higher salinity levels. With increased salinity the K, Ca, Mg, Zn and Fe in the leaves and roots lessened, but leaf Na rose in concentration with increasing salinity. The Mn and Cu contents of leaves and roots did not differ significantly.     

The effect of split-root salinity stress on tomato leaf expansion,fruit yield and quality

Summary

A crop-scale experiment between March and October 2000 investigated the effects of split-root salinity stress and rooting volume on the expansion of leaves, fruit yield and quality in two standard round fruited cultivars of tomato (Lycopersicon esculentumMill) Solairo and Espero, grown in rockwool. To implement the treatments, a split-root method was utilized whereby different levels of salinity (expressed as EC), adjusted by the addition of NaCl, was administered to two halves of a root system. The split-root high EC (2.8/8.0 dS m^–1) treatment enhanced fruit quality by increasing the concentrations of sugar, acid, total soluble solids and reducing the incidence of visual defects such as uneven ripening and gold-spot. Split-root high EC did however reduce leaf area that corresponded with low K concentration in the leaf tissue. The split-root method utilized doubled the rooting volume compared with the standard single rockwool slab, but this extra rooting capacity had no detectable effect on leaf expansion, yield or fruit quality. Although there was little impact on yield for ten weeks after the imposition of the high EC split-root treatment, mean reductions in weekly yield occurred thereafter and were of the order of 9 and 13% for ‘Solairo’ and ‘Espero’ respectively through to the end of the experiment. The fall in yield was due, in part, to a decrease in fruit size. Whilst water uptake was reduced it was unclear how the effects on leaf growth and fruit yield were mediated in the shoot. Possible processes that coordinate responses to root-zone salinity stress are discussed. The potential use of the split-root system in commercial production is considered.     

Morphology,yield and quality of ashwagandha (Withania somnifera L. Dunal) roots and its cultivation economics as influenced by tillage depth and plant population density

Summary

Ashwagandha (Withania somnifera L. Dunal; Solanaceae) is being cultivated around the world mainly for its root which has rejuvenative properties. Field experiments during 1999–2001 under semi-arid tropical conditions of Hyderabad, India studied the effect of tillage depths (15 and 30 cm) and plant population densities (20, 40, 60 and 80 plants m^–2) on root morphology, yield and quality and cultivation economics of ashwagandha. Preparatory tillage to 30 cm depth in combination with a density of 60 plants m^–2 gave the highest root yield of 1.2 t ha^–1 which was 50% higher than that following 15 cm tillage depth and the same density. This is attributed to the favourable effect of the former treatment leading to 33, 37 and 21% increases in plant height, number of branches per plant and shoot biomass yield, respectively. Further, this treatment produced most (68%) best quality root pieces. Main root length, length of lateral roots and diameter of lateral roots were significantly increased, while the diameter of main root and the number of laterals decreased. Furthermore, increase in plant density from 20–80 plants m^–2 increased production of best quality roots from 42% to 59% under shallow tillage and from 53% to 71% of root yield under deep tillage. The implications of change in root morphology are discussed in the light of production of different grades of roots, their market preferences and economics. Deep tillage was equally advantageous for seed production, but plant population density for maximum seed yield (211 kg ha^–1) was lower at 40 than at 60 plants m^–2 for maximum root yield. Maximum gross and net returns and benefit-cost ratio occurred following the highest root yield.     

Yield benefits associated with pre-blossom low-biuret urea sprays on Citrus spp.

Summary

This study evaluated the potential yield benefits of pre-blossom urea sprays on various Citrus spp. and to ascertain whether these yield benefits are as a result of altering the blossom composition or of supplying readily utilizable N during the critical flowering/fruit set period. Pre-blossom low-biuret urea sprays, 6–8 weeks before anthesis, at 1% concentration, one or two sprays 10–14 d apart, have resulted in significant (P<0.05) yield benefits in certain orchards. Experiments were conducted over a period of 2–4 years. Cultivars evaluated included ‘Shamouti’ oranges, ‘Ellendale’ tangor and ‘Minneola’ tángelo. In orchards where the leaf N level was below optimum the results were most significant while only slight or no yield responses were obtained in orchards where N levels approximated or exceeded 2.6%. Endogenous leaf ammonia levels were significantly increased for 14–30 d after the spray. This indicated a beneficial N level during the critical flowering and fruit set period. Because of large field variation no consistent trend with respect to the effect of the urea spray on changing the blossom composition (leafless vs. leafy inflorescences) could be demonstrated. Despite the increased ammonia levels recorded, no longer term increases in reserve leaf N levels were obtained.     

Spring growth of almond nursery trees depends upon nitrogen from both plant reserves and spring fertilizer application

Summary

June-budded ‘Nonpareil’/‘Nemaguard’ almond (Prunus dulcis (Mill) D. A. Webb) trees were fertigated with one of five nitrogen (N) concentrations (0, 5, 10, 15, or 20 mM) from July to September. The trees were sprayed with either water or 3% urea in October, then harvested bareroot after natural leaf fall, and stored at 2°C. One set of trees was destructively sampled for total N content; the remaining trees were transplanted into N-free media in the spring after cold storage. After budbreak, these trees were supplied for 70.d with either N-free Hoagland’s solution or Hoagland’s solution containing ¹⁵N-NH₄NO₃. Nitrogen concentrations in both stem and root tissues were positively correlated with the N-fertigation concentration. Fall foliar urea applications increased levels of stem and root N regardless of the N-fertigation concentration. During the first 70 d of spring growth, the trees utilized nitrogen from both their reserves and spring fertilizer applications. The amount of N reserves used for growth of new shoots and leaves was proportional to the total amount of reserves. Trees with low N reserves relied primarily on the spring fertilizer as their source of nitrogen. We conclude, therefore, that both reserve N and spring-applied N fertilizers are important for enhancing the regrowth of bareroot almond nursery trees during establishment after transplanting. Nitrogen fertilization in the spring can especially improve the performance of trees with low N reserves.