Environmental influences on juvenile shoot growth in Picea abies

Under certain environmental conditions, juvenile shoot growth characters might give early indications of adaptability and growth potential. Therefore, the reaction patterns of predetermined and free shoot growth were studied on Picea abies (L.) Karst, plants, which at different times during the growth period were treated by (1) application of nutrients, (2) defoliation, and (3) short days. Fertilization caused an increase in both predetermined and free growth, while defoliation and short day treatment caused a decrease in both forms of shoot growth and short days did not allow any free growth to occur. In the growth period following the treatments, fertilization caused more predetermined and less free growth to occur, while defoliation caused less predetermined and more free growth. Predetermined growth is explainable by the finite number of predetermined needle primordia. Free growth is initiated thereafter. It is influenced strongly by the environmental conditions and seems not to be influenced by the amount of preceding predetermined growth. Free growth enables young plants to utilize favourable growth conditions in summer for height growth precociously, which might increase their adaptability and competitive value. However, predetermined growth is the preferable mode of shoot growth because favourable conditions in successive growth periods induce more predetermined than free growth. Predetermined and free growth are well integrated forms of shoot growth giving no supporting evidence to the hypothesis that free and predetermined growth are inherited independently of each other. Rank changes in provenance development are probably not explainable by a loss in height growth when free growth occurs no more due to age, but by other causes.     

Causal relationship between juvenile shoot growth characters in picea abies

The causal relationships between shoot growth variables were analysed on the basis of a study in the Phytotron where six full‐sib families of Picea abies L. (Karst.) were grown for six growth periods. Phenotypic correlations and path analysis were used for the analysis of causes. The phenotypic correlations were estimated in three different ways: 1) separate analyses within each growth period based on individual tree data, 2) based on family means at different growth periods (0, and 3) using differences in family means between two consecutive growth periods (dt). The two methods based on t or dt‐values gave different results in a number of cases. We argue that, because of the rapid concurrent changes that occurred between growth periods, we could not conclude that the correlations based on family means (t) reflected causal relations and, also, that the method based on dt‐values gives a better indication of causal relationships between different variables. Using dt‐values, the variation in shoot elongation period was mainly explained by the variation in free growth (82%) while the variation in shoot growth initiation only explained a minor fraction. Variation in leader length was mainly explained by growth rate and only to a minor extent by shoot elongation period, meaning that the observed decrease in shoot elongation period did not cause a corresponding changé in leader length. One conclusion from this finding is that we do not necessarily lose growth capacity if we breed for a better adapted growth rhythm (i.e. shorter shoot elongation period) of the seedlings.     

Spring growth of Douglas-fir seedlings from two bud development regimes

The effect of two bud development treatments on post-dormancy shoot growth was investigated with 1-year-old container-grown Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings. A difference in the date of budset and number of overwintering primordia was obtained by applying 8-hour or 17-hour photoperiods in growth rooms during summer months. Seedlings were then chilled for 14 weeks at 4 °C and finally held 2 months at 22 °C under either an 8-hour or 16-hour photoperiod. The new shoot growth of seedlings with early budset had greater length, stem unit numbers, average stem unit length, and dry weight. Stem unit number of the post-dormancy seedlings was unaffected by photoperiod during flushing. Significant free growth occurred only in late budset seedlings and accounted for 40% and 46% of the fixed growth under 16-hour and 8-hour flushing photoperiods, respectively.     

Needle growth in Sitka spruce (Picea sitchensis): effects of nutrient deficiency and needle position within shoots

Needle development and shoot growth were studied in 14- and 20-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) planted on an oligotrophic peat and fertilized with N, P and K (control), N and P (-K), N and K (-P) or unfertilized (-NPK). Shoot extension, needle number, and the size and number of needle cells were observed throughout the season. Beginning with bud burst in early May, needle growth continued for nine weeks in the control treatment. Needle growth in the mineral deficiency treatments terminated at the same time as in the controls, although it did not begin until up to three weeks later than in the control trees. Needles developed acropetally along the shoot, with basal needles completing their development first. Cell division in needles of control trees lasted about 3 weeks, with cell expansion continuing for a further 3 weeks. Initial mean cell cycle times were shortest for proximal needles following bud burst, but lengthened as the season progressed. Cell number increased from 6600 in the primordia to 200 000 in mature needles. Final needle dimensions and cell number varied according to the position of the needle on the shoot. The largest needles with the most cells were near the middle of the shoot. Relative to the controls, all mineral deficiency treatments reduced shoot length, bud and needle dimensions, and needle cell number, particularly the -P treatment. Potassium and P deficiency treatments reduced primordial cell number by up to 42%, whereas final mean cell size was 30% greater in the -P treatment, 17% greater in the -NPK treatment, but 14% smaller in the -K treatment. Mean cell size was constant for needles at all positions in any particular treatment at any time, so that final needle size was determined by cell number alone. Needle dry weight/fresh weight ratio continued to increase until early August, with significantly higher ratios in the -K and -P treatments than in the controls.     

Preformation in vegetative buds of Prunus persica: factors influencing number of leaf primordia in overwintering buds

We investigated the influence of bud position, cultivar, tree age, tree carbohydrate status, sampling date, drought and light exposure on the number of leaf primordia formed in dormant vegetative peach buds (Prunus persica (L.) Batsch) relative to the number of primordia formed after bud break (neoformed). During winter dormancy, vegetative peach buds from California and Italy were dissected and the number of leaf primordia recorded. Between leaf drop and bud break, the number of leaf primordia doubled from about five to about 10. Parent shoot length, number of nodes on the parent shoot, cross-sectional area of the parent shoot, bud position along the parent shoot and bud cross-sectional area were correlated with the number of leaf primordia. Previous season light exposure, drought and tree carbohydrate status did not affect the number of leaf primordia present. The number of leaf primordia differed significantly among peach varieties and tree ages at leaf drop, but not at bud break. Our results indicate that neoformation accounted for all shoot growth beyond about 10 nodes. The predominance of neoformed shoot growth in peach allows this species great plasticity in its response to current-season conditions.     

Promotion of cone production on white spruce grafts by Gibberellin A4/7 application

White spruce [Picea glauca (Moench) Voss] grafts growing in a seed orchard were sprayed with gibberellin A_4/7 (GA_4/7), either at different periods of time during the growing season or in different concentrations, for a 3-year period. Whole-tree spraying in May through July 1983 significantly increased cone production in 1984, while spraying in June through August of the same year was not effective. The best treatment in branch spraying was at the highest concentration (800 mg/L GA_4/7). The spray was effective in a good, but not a poor, crop year. Vegetative budburst occurred in the first half of May and shoot elongation ended in late June. Needle primordia in a newly formed bud were not discernible until the end of June. Application of GA_4/7 during the period of bud scale initiation and shoot elongation, and before needle primordial initiation, could have influenced the course of bud differentiation to increase the formation of reproductive buds.     

Genetic control and age‐related changes of juvenile growth characters in Picea abies

In full‐sib families of Picea abies (L.) Karst. (Norway spruce) the dynamics of juvenile growth and the inheritance of the most important growth characters were analysed in six growth periods in climate chambers followed by two additional growing seasons in a nursery. The full‐sib families were of French and North Swedish origin including both within and between provenance crosses. All growth rhythm characters changed over time. For instance, number of days to budbreak increased, whereas days to budset decreased, as growth periods advanced. Concurrent with the changes in growth rhythm, free growth decreased with increasing age. Half of the total variation for different growth rhythm characters within a growth period could in most cases be explained by provenance effects. Early selection is, therefore, meaningful to reduce damage by frost and mortality. Furthermore, the actual distances between family means decreased substantially with increasing age, and the actual length of the shoot elongation period decreased from 31 days during the second growth period to 16 days during the sixth. We suggest therefore that selection together with some treatment in the nursery that alters the growth rhythm of the seedlings are the best ways to increase frost resistance. Tree height was influenced by a set of complex gene actions that changed over time. Provenance effects were important during the first two growth periods. Subsequently, non‐accumulative within provenance family variance took over. If this pattern holds true in general, juvenile selection for height growth in Norway spruce cannot be made as early as that for growth rhythm.     

Frost hardiness, bud phenology and growth of containerized Picea mariana seedlings grown at three nitrogen levels and three temperature regimes

We studied the influence of temperature and near- and sub- optimal mineral nutrition of black spruce seedlings (Picea mariana [Mill.] B.S.P.) during their second growing period on bud set, bud development, growth, mineral content and cold tolerance. Bud break and growth after bud break were also studied. Seedlings were grown for 106 d in growth chambers under three temperature regimes in combination with three concentrations of a fertilizer. They were then cold hardened for 56 d and dehardened for 66 d.Under these near- and sub-optimal N levels, bud formation occurred during the growing season. Bud formation was accelerated with decreasing fertilization, but was not affected by temperature treatments. Needles from seedlings with 0.64% N (dry mass basis) before hardening did not harden. Those with 0.87% N showed a lesser degree of hardiness than those with 1.28% N. Stem diameter increased at the beginning of the hardening period. During this acclimation period, shoot dry mass decreased with time at a constant rate and at the same rate over time for all treatments whereas root dry mass was more variable. Total number of needle primordia was low and no difference was observed among growing conditions. Bud break was similar in all treatments. Following bud break, shoot height and stem diameter increases were small but their magnitude varied with the nutritional regimes applied during the previous growing period. During hardening, nitrogen concentration of shoot tissues first increased and then decreased; phosphorus concentration first increased and then remained stable; potassium concentration remained stable. Concentration of these three elements generally decreased in the roots during this hardening.     

Seedling shoot,needle and bud development in three provenances of Pinus sylvestris and Pinus contorta cultivated in northern Sweden

The patterns of current‐year shoot, needle and terminal bud elongation in seedlings of three Scots pine (Pinus sylvestris L.) and three lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) provenances were compared during the third and fourth growing seasons after planting. Lodgepole pine produced longer shoots and buds than did Scots pine, mainly because lodgepole pine formed more stem units and elongated at a faster rate. Stem unit length and the duration of shoot and bud elongation differed relatively little between species and provenances. Lammas or polycyclic growth occurred in some lodgepole pine provenances, but not in any Scots pine provenance, and was associated with enhanced shoot elongation. Needle elongation commenced earlier, proceeded at a faster rate, and was greater in lodgepole pine than in Scots pine, but ceased about the same time in all species and provenances. The heat sum required to attain 50% of final length was lower for shoots and needles in lodgepole pine than in Scots pine, and for shoots in northern provenances than in southern ones. Mitotic activity in the apical meristem of the terminal bud, which occurred less than one week after the seedlings were free from snow, started and ceased about the same time in each species, but was higher in lodgepole pine than in Scots pine early in the shoot elongation period.     

Terminal bud failure of black cottonwood (Populus trichocarpa) exposed to salt-laden winter storms

At coastal sites, trees are exposed to marine aerosols that may cause foliar necrosis and shoot dieback, which can result in deformed crowns and contorted stems. A six-year study of leaf primordia in terminal buds of black cottonwood trees (Populus trichocarpa Torr. & Gray) on Heimaey Island off the south coast of Iceland was undertaken to elucidate the physiological events associated with salt-deposition-related bud failure. Leaf and bud lengths, dry mass, water content and chloride concentrations were monitored and related to four phenological stages: (1) bud set; (2) dormancy induction; (3) dormancy release; and (4) bud break. The trees set buds in July and shed their leaves by late September. Leaf primordia generally stopped growing by September 10 +/- 22 days and attained midwinter water content in late September. Leaf growth commenced in the terminal buds by March 2 +/- 16 days, but mean dates of bud swelling and bud break were April 29 +/- 19 and May 10 +/- 12 days. In summer and until November, chloride concentrations in leaf primordia were low, but increasing. Chloride concentrations remained stable from December to February, even though the dormant trees were exposed to large amounts of marine aerosols. In February and March, three events occurred more or less simultaneously: (1) leaf extension growth commenced; (2) chloride concentration surged in the leaf primordia; and (3) the leaf primordia began to hydrate. Following dormancy release, growth and hydration of leaf primordia were negatively related to chloride concentration in the leaf primordia, with inhibition of leaf growth, tissue hydration and chloride acquisition occurring at a chloride concentration threshold estimated at 7.3 mg Cl- g(-1) tissue water. Necrosis of leaf primordia was observed above 14 mg Cl- g(-1) tissue water. Growth and hydration of leaves at bud break in mid-May was explained by a three-parameter logistic model of chloride concentration in leaf primordia at the end of March. By mid-May, 90% of all buds remained non-necrotic, but only 56% the terminal buds had broken. Salt alone explained the observed growth suppression of leaf primordia in the buds and the resultant failure of terminal buds to break by mid-May.     

Effects of temperature on shoot growth in northern provenances of Pinus sylvestris L

Effects of temperature on shoot growth in northern provenances of Pinus sylvestris L. were studied under natural long-day conditions (Lat. 69 degrees 39' N) at controlled temperatures. The optimum constant temperature for formation of stem unit primordia in the terminal resting bud was 18 to 21 degrees C. Stem unit number decreased linearly with temperature between 15 and 9 degrees C. Temperature during bud formation had a significant effect on final stem unit length achieved in the following year. Final shoot length was significantly affected by temperature during shoot elongation. The optimum constant temperature for elongation growth was 18 to 21 degrees C. The rate of shoot elongation was positively correlated with the number of stem units.     

Early shoot and root growth dynamics as indicators for the survival of black poplar cuttings

The relationship between early root and shoot formation at the beginning of the vegetation period and cutting survival on sandy and loamy fluvisol for 14 genotypes of black poplars was analyzed. Considerable cutting mortality was observed only within the first 80 days since planting. Intensive root formation in the first 20 days since the planting and vigorous shoot growth and development in subsequent 20 days was observed in easy-to-root genotypes. Coefficients of correlation revealed close relationship between early root and shoot growth and development and cutting survival of tested genotypes. The obtained results could be used in the breeding process, as well as for the design of cultivar-adjusted nursery and plantation establishment technology. Tested shoot characteristics, were found to be especially interesting since they could be measured rapidly, by non-destructive means.     

Frost hardening spruce container stock for overwintering in Ontario

Difficulties overwintering container stock in northern Ontario led to the development of the extended greenhouse culture hardening regime for spruce seedlings. Laboratories to measure shoot frost hardiness and evaluate terminal bud development were established to monitor nursery crops being hardened using this regime. Information on frost hardiness and bud development provided by these laboratories has been used by nursery managers to determine readiness of container seedlings for overwintering. Since 1982, over 200 stock lots have been monitored by these operational laboratories. This database can be used to determine the importance of nursery cultural factors and seed source on frost hardening. The database shows large differences between nurseries in approach to hardening seedlings which were reflected in levels of freezing damage, winter desiccation and overwintering success. Rates of frost hardening (i.e., the interval between terminal bud initiation and attainment of a --15°C level of shoot frost hardiness) of crops produced in north central Ontario failed to show significant seed source effects. The rate of frost hardening was faster in crops producing fewer needle primordia in terminal buds.     

Genetic Variation in Seedling Development of Sitka Spruce, Picea sitchensis (Bong). Carr.

The development of the terminal bud in one-year seedlings ofSitka spruce, Picea sitchensis (Bong.) Carr., is illustratedand described as a continuous process. The same sequence ofmorphological events occurred in forty-seven provenances examinedbut the timing was different. Buds formed in response to decreasingdaylength, and an essentially continuous relationship was demonstratedbetween time of bud formation and latitude of seed origin. Flushingwas controlled largely by temperature, and time of flushingreflected the nature of the temperature r?gime in the nativehabitat. The height attained at the end of the growing season was demonstratedto be related to date of bud formation and latitude of seedorigin, but the relationship was modified by temperature andphotoperiod. There was little genetic variation in rate of heightgrowth, and variability in time of bud formation was consideredto be the major factor causing provenance variation in totalheight growth. Bud size was correlated with the number of needle primordia,but the effect of bud size on height growth was secondary, aswas the effect of the number of lateral branches. The reactions of two provenances suggested that ecotypic differentiationhas occurred in response to specific, local, environmental selectionpressures. The results supplement the conclusions of earlier reports, namelythat there is a broad interaction of genotype with environmentthat should be evaluated before planting the species at anygiven site.     

The effect of late season damage on the apical bud development of Scots pine seedlings

The effect of Lygus rugulipennis Popp. feeding and artificial damage on the apical bud of Scots pine (Pinus sylvestris L.) late in the growing season was studied on two-year-old seedlings. Lygus feeding in late July and August caused inhibition of bud formation in the subsequent year's shoots, which led to loss of apical dominance and formation of interfascicular buds. Mechanical damage caused by piercing the apical bud with a needle in July, August and October produced scars and malformations on subsequent year's shoots and buds, but did not inhibit bud formation. Damage to the apical meristem could not be detected visually on the dormant bud before shoot elongation.     

Vitality rating of picea abies by defoliation class and other vigour indicators

The study was made to assess the relationship between visually estimated defoliation class and a number of other variables depicting the vitality of Norway spruce (n=50). Variables characterizing crown size and condition were determined on the standing trees. Electrical impedance (an indication of the physiological status of a tree) was measured in the inner bark tissue of the living trees. Shoot growth and needle variables were determined from the detached sample branches. Negative correlations were found between defoliation class and the growth parameters (5‐year height, radial and volume growth of the trunk). Positive correlations were observed between the needle loss class and the abundance of branch damage, secondary shoots and impedance values. 18 variables (defoliation excluded) describing tree size and vitality were summarized in a factor analysis incorporating 5 factors. These were interpreted as 1) vitality, 2) foliage discoloration, 3) tree size, 4) needle number and 5) needle size factors. The tree‐specific score values for the first factor were interpreted as “vitality indices”;. The rank correlation between these score values and defoliation degree was 0.835. This result suggests that the defoliation class and vitality parameters contributing to the first factor give a consistent estimate of the tree condition.     

Effect of GA(4 + 7) on the initiation and development of the inflorescence bud of evergreen azalea

Apical buds of evergreen azalea (Rhododendron sp.) were treated with GA(4 + 7) at different stages of development. Treatment of vegetative buds stimulated shoot growth, slightly delayed both flower initiation and development, but increased the number of flower primordia. Treatment at the time of floral transition induced bud abortion at an early stage of the reproductive development. Treatment of inflorescence buds which contained at least one complete flower substituted for chilling in overcoming dormancy and prevented inflorescence bud abortion.     

Physiological and field growth responses of oak seedlings to warm storage

The effect of warm storage (15°C) for 0, 15 or 31 days, applied after cold storage until April, and date of lifting to cold storage on the physiological condition and field performance of two-year-old oak seedlings (Quercus robur L.) was investigated. Assessments before planting included plant moisture status, root and shoot dry weight, root growth potential (RGP), while after planting root growth, shoot growth phenology, shoot and root dry matter accumulation and stem quality were assessed. Warm storage effects were large, but lift date effects were small. Warm storage for 31 days reduced height and diameter growth, stem quality, total biomass, root growth, and reduced stem quality in the field, but 15 days storage had a smaller effect. Warm storage delayed bud break and shoot growth cessation but survival was unaffected. The depletion of food reserves during storage and low moisture availability might have caused shoot dieback leading to the development of poor quality stems. There was evidence that dry weight fraction of both the shoot tip and the taproot provided good information on the quality of the stock before planting. RGP was also a good indicator of quality. Electrolyte leakage readings from fine and taproots were not reliable indicators of plant quality.     

Heat damage in boxed white spruce (Picea glauca [Moench.] Voss) seedlings: Its pre-planting detection and effect on field performance

This study investigated the effects of holding 1+0 PSB313a white spruce (Picea glauca (Moench.) Voss) seedlings in storage boxes at air temperatures of 5, 10, 20, 30 and 40°C for 12, 24, 48, 72 and 96 h before planting. The ability to detect physiological damage to seedlings as a result of such treatment, before planting, was also examined. After one growing season, no needle damage or mortality >8% was found for temperature treatments up to 20°C for 4 days. At 30°C and above, seedling damage and mortality increased, while bud flush, shoot height, stem diameter and shoot dry weight decreased with increasing temperature and duration of treatment. Seedling mortality in the field was 100% after the 40°C treatment exposure for 72 h or longer. Pre-planting needle electrolyte leakage was indicative of visible needle damage 14 days after planting, whereas stem electrolyte leakage and root growth potential were more closely related to end of season plantation mortality. Despite the lack of damage observed at 20°C or below, preplanting exposure of white spruce seedlings to temperatures above 5°C, during transportation and field storage, is not recommended.     

深山含笑嫁接技术研究

对深山含笑苗圃嫁接时期、嫁接方法进行了研究。结果表明 :在用白玉兰作砧木嫁接深山含笑时 ,在各个时期进行嵌芽接的嫁接成活率均很低 ;枝接以 3月中下旬最理想。其中 :带顶芽切接成活率在 95 8% ,其次是不带顶芽包头切接 ,成活率达 85 0 % ,都显著高于或极显著高于同期进行的不带顶芽不包头切接