The Influence of Photoperiod and Temperature on the Development of Frost Hardiness in Seedlings of Pinus silvestris and Picea abies

The influence of short days and low temperature on the development of frost hardiness in seedlings of Scots pine (Pinus silvestris L.) and Norway spruce [Picea abies (L.) Karst.], grown for 6 months in glasshouses and climate chambers, was investigated. The degree of hardiness was estimated by freezing the shoots of the seedlings to predetermined temperatures. After 8 weeks in a glasshouse the viability of the seedlings was determined by establishing bud flushing. The most effective climate for the development of frost hardiness was short days (SD) and low temperature (2°C); the next most effective was SD and room temperature (20°C). However, long days (LD) and low temperature also had a marked effect on the development of hardiness. A combination of 3 weeks’treatment with SD and 20°C, and 3 weeks with SD and 2°C gave the same results as 6 weeks with SD and 2°C. The results clearly demonstrate the importance of the photoperiod prior to low temperature for the development of frost hardiness. In conclusion both short days and low temperature induce frost hardiness development. Probably this occurs by initiation of different processes in the two cases. The degree of frost hardiness development appears to depend on the sum of these different processes and on the timing between them.     

Seasonal ionic fluctuations and annual growth rates in stands of Pinus silvestris L. and Picea abies Karst. (L.)

Seasonal variations in potassium, calcium, nitrogen, phosphorus, and magnesium contents of needles from two different stands of Pinus silvestris L. and Picea abies (L.) Karst. were determined monthly during a period of two years, and the growth rates once a year during five years. The stands were growing on sand or on clay. The supposed transport of potassium to the shoot during autumn could not be demonstrated. The nutrient status of pine and spruce growing on sand and clay was very similar, except for calcium and magnesium. There were only small differences in ion contents between pine and spruce, except for calcium. On soils with low water-holding capacity, the available water in dry years is the limiting factor affecting the growth rate of spruce but not of pine. It is concluded that the nutrient status of the leaves, the growth rates and the available water in the soil are factors that should have an important part in any discussion of fertilization of coniferous forests.     

Uptake of benzyladenine in explants of Picea abies and Pinus sylvestris

Primary explants of Picea abies (L.) Karst. and Pinus sylvestris L. were incubated for various periods in solutions containing different concentrations of [¹⁴C]-benzyladenine. Time course analysis showed that uptake was linear for the initial 60 min; after this time linear uptake continued but at a much reduced rate. The amount of benzyladenine taken up by the explants saturated at a concentration about one third of that of the medium, Concentration dependence experiments showed that BA uptake was directly proportional to the external concentration. These results and those from experiments in which uptake was examined at different temperatures are consistent with a passive mode of BA uptake. The results are discussed with respect to in vitro micropropagation.     

A Definition of Optimum Nutrient Requirements in Birch Seedlings

Birch seedlings (Betula verrucosa Enrh.) were grown in nutrient solutions with pH varied in the range 2.5 to 6.8 or temperature varied in the range 2.5 to 35°C. The criteria for maximum growth previously established for birch seedlings were used and maintained by means of automatic pH and conductivity titrations with stock solutions containing the optimum nutrient proportions. Both nitrogen sources, NH₄ and NO₃, were present in the solutions. Growth rate was maximum or close to maximum between pH 4.0 and 6.8, whether kept at a specific level or allowed to vary between the extremes. At pH 3.5 and lower, the calcium uptake was decreased and root damage was observed. The seedlings has also a high dry matter content and obviously an unsatisfactory water balance. pH 2.5 was rapidly lethal. Growth rate was linearly correlated with solution temperature up to 20°C. Temperatures above 30°C, especially in the range 32.5 to 35°C, resulted in rapid decrease in growth rate. The nutrient contents in the seedlings were strongly affected by solution temperature in the low as well as in the high range when expressed on a dry weight basis. However, this effect was almost entirely attributable to changes in dry matter content. When expressed on a fresh weight basis, nutrient uptake and nutrient status of the seedlings appeared to be optimum throughout, although a variation remained since the varying dry matter content is included in the fresh weight basis. The results indicate, in agreement with the literature, that disturbed water uptake and water balance is the way in which growth is affected by root medium temperature. Similarly, extremely low pH levels in the nutrient solution meant root damage, although birch seedlings appear comparatively insensitive to pH variations. Thus, the growth technique used supplied the seedlings with adequate nutrients, so that the criteria used in the definition of nutrient requirements in birch seedlings are valid within wide ranges of solution pH and temperature; and other factors than nutrition determine growth.     

Effects of aluminium on growth and nutrient uptake of small Picea abies and Pinus sylvestris plants

Summary The effects of aluminium concentrations between 0.2 and 30 mM at pH 3.8 ±0.2 on small plants of Norway spruce [(Picea abies (L.) Karst], Scots pine (Pinus sylvestris L.), and Scots pine infected with the ectomycorrhizal fungus Suillus bovinus (L. ex Fr.) O. Kuntze were investigated. The plants were grown at maximum relative growth rate (R_G % day^–1) with free access but very low external concentrations of nutrients. Steady-state conditions with respect to relative growth rate (R_G) and internal nutrient concentrations were achieved before addition of aluminium, which was added as AlCl₃ and/or Al(NO₃)₃. There were reductions in rg at aluminium concentrations of 0.3 mM in spruce, 6 mM in pine and 10 mM in ectomycorrhizal pine, i. e. at aluminium concentrations considerably higher than those normally occurring in the top layer of the mineral soil where most fine roots are found. Nutrient uptake rate per unit root growth rate was calculated for different nutrient elements. The uptake rate of calcium and magnesium was reduced at aluminium concentrations of 0.2 mM (spruce), 1 mM (pine) and 3 mM (ectomycorrhizal pine), without influencing R_g. The results question the validity of the hypothesis of aluminium toxicity to forest tree species at low external concentrations.     

Relationships Between Tree and Soil Properties in Picea abies and Pinus sylvestris Forests in Sweden

The exchange of elements between plants and the soil in which they are growing creates reciprocal control of their element composition. Within plants, the growth rate hypothesis from ecological stoichiometry implies a strong coupling between C, N, and P. No similar theory exists for predicting relationships between elements in the soil or relationships between plants and the soil. We used a data set of element concentrations in needles and humus of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) forests in Sweden to investigate the extent to which relationships between elements (C, N, P, S, K, Ca, Mg, Fe, Mn, Al) can be observed within and between plants and soils. We found element composition to be more strongly controlled in needles than in humus. Elements that are covalently bound were also more strongly controlled, with no apparent differences between macro- and micronutrients. With the exception of N/C, there were surprisingly few relationships between elements in needles and humus. We found no major differences between the two tree species studied, but investigations of additional forest types are needed for firm conclusions. More control over element composition was exercised with respect to N than C, particularly in needles, so it might be advantageous to express nutrient concentrations relative to N rather than on a dry weight or carbon basis. Variations in many ecosystem variables appeared to lack ecological significance and thus an important task is to identify the meaningful predictors.     

On the Reason for the Different Photosynthetic Rates of Seedlings of Pinus silvestris and Betula verrucosa

The growth and net photosynthetic properties of seedlings of Pinus silvestris L. and Betula verrucosa Ehrh., grown under identical conditions in a controlled environment chamber, were compared. The relative growth rate of birch was about twice that of pine. The rates of in situ net photosynthesis were 1.50 and 2.30 micromoles CO₂ meter⁻² second⁻¹ and the photosynthetic quantum yields under light-limiting conditions were 0.022 and 0.032 for pine and birch, respectively. The total leaf surface areas were used for calculating the CO₂ flux densities. The difference in the rates of in situ net photosynthesis depended equally on morphological and metabolic factors. It was assumed that a pronounced mutual shading and an unfavorable leaf inclination made the pine seedlings less efficient in absorbing the unidirectional light of the climate chamber than the broadleaved seedlings of birch. Both pine and birch were adapted to the growth conditions so the flux densities of absorbed quanta were rate-limiting for in situ net photosynthesis. It was concluded that the difference in the photosynthetic quantum yields (i.e. the linear slope of the photosynthetic light curve) of the two species defined the metabolically controlled part of the difference in the rate of in situ net photosynthesis. The quantum yield of pine was lower than that of birch and was partly explained by pine having a higher rate of photorespiration than birch. The remaining difference was most likely controlled by the properties of the chloroplast thylakoids, e.g. energy transfer efficiency between pigments, photosynthetic electron transport, or coupling between electron transport and photophosphorylation.     

油松、白皮松和青木千花粉营养成分的研究

通过对我国有巨大生产量和应用潜力的油松、白皮松和青木千花粉的18种氨基酸、蛋白质、维生素A、维生素E、维生素C、磷脂、葡萄糖氧化酶等重要营养成分含量的测定,发现这三种花粉的以上成分含量都很高.其中青木千花粉的维生素A含量达70641.6IU/100g,氨基酸总量达24.443mg/100mg.从营养的角度来看,青木千花粉是较优秀的花粉.     

Mineral Nutrient Requirements of Vaccinium vitis idaea and V. myrtillus

The mineral nutrient requirements of Vaccinium vitis idaea L. and V. myrtillus L. have been studied. It is found that the optimum nutrient proportions are similar to those of birch seedlings except for a relatively low potassium requirement. The nitrogen sources ammonium and nitrate are both usable at low concentrations. A system with both sources present seems preferable. The ammonium uptake is then much more rapid than the nitrate uptake. The optimum total concentration falls within the low salt range and is about the same as found for birch seedlings, but the sensitivity to high salt concentrations is more pronounced in the Vaccinium species. A very marked characteristic of the nutrient absorption is the rapid calcium uptake. The results are discussed in relation to similar experiments with birch and cucumber seedlings, representing species with a wide or calcareous ecological adaptation.     

油松、白皮松和青杄花粉营养成分的研究

通过对我国有巨大生产量和应用潜力的油松、白皮松和青木千花粉的 1 8种氨基酸、蛋白质、维生素A、维生素E、维生素C、磷脂、葡萄糖氧化酶等重要营养成分含量的测定 ,发现这三种花粉的以上成分含量都很高。其中青木千花粉的维生素A含量达 70 641 .6IU/ 1 0 0g ,氨基酸总量达 2 4 .443mg/ 1 0 0mg。从营养的角度来看 ,青木千花粉是较优秀的花粉。     

The hydraulic conductivity of the xylem in conifer needles (Picea abies and Pinus mugo)

Main resistances of the plant water transport system are situated in leaves. In contrast to angiosperm leaves, knowledge of conifer needle hydraulics and of the partitioning of resistances within needles is poor. A new technique was developed which enabled flow-meter measurements through needles embedded in paraffin and thus quantification of the specific hydraulic conductivity (K(s)) of the needle xylem. In Picea abies, xylem K(s) of needle and axes as well as in needles of different age were compared. In Pinus mugo, resistance partitioning within needles was estimated by measurements of xylem K(s) and leaf conductance (K(leaf), measured via 'rehydration kinetics'). Mean K(s) in P. abies needles was 3.5×10(-4) m(2) s(-1) MPa(-1) with a decrease in older needles, and over all similar to K(s) of corresponding axes xylem. In needles of P. mugo, K(s) was 0.9×10(-4) m(2) s(-1) MPa(-1), and 24% of total needle resistance was situated in the xylem. The results indicate species-specific differences in the hydraulic efficiency of conifer needle xylem. The vascular section of the water transport system is a minor but relevant resistance in needles.     

Nitrate Uptake and Reduction of Aseptically Cultivated Spruce Seedlings, Picea abies (L.) Karst

Spruce (Picea abies (L.) Karst.) seedlings were asepticallycultivated and the effects of different N-nutrition on net uptakeand reduction of nitrate were investigated. The characteristicsof nitrate uptake were calculated, K_s as 0?2 mol m^–3 andV_max as 18 µmol g^–1 d^–1. Low pH, and Al³⁺ in the medium caused adecrease in nitrate uptake rate. An in vivo assay was set upwhich allowed the measurement of NRA in both roots and needlesof spruce seedlings. The in vivo nitrate reductase activitywas repressed by ammonium and stimulated by nitrate. Nitratereduction was similar to nitrate uptake, negatively affectedby low pH and ammonium. Therefore, a limited N-supply to spruceseemed to occur when pH was low in the rhizosphere combinedwith the presence of Al³⁺ and . Key words: Spruce, nitrate uptake, nitrate reduction     

A Definition of Optimum Nutrient Requirements in Birch Seedlings. II

The aim of the experiments described was to specify further the nutrient requirements of birch seedlings. A growth method is described in which the nutrients consumed at maximum growth of birch seedlings can be replaced, without change of the nutrient solution, by means of additions made as pH and conductivity titrations so that three conditions are satisfied: 1) All necessary mineral nutrients are present in the plant in optimum proportions. 2) The nitrogen sources NH⁴+ and NO₃- are present in the nutrient solution in an optimum ratio. 3) Total concentration in the solution is optimum. The three conditions may be regarded as criteria in a definition of nutrient requirements. The possible use of criterion 1 as an expression of the optimum nutrient status is also discussed. A considerable increase in light intensity had no significant effect on the optimum nutrient proportions or the optimum total concentration. A tendency to lower ammonium uptake in relation to nitrate was induced when both nitrogen sources were present. Simple stock nutrient solution systems are listed and discussed.     

Circumnutation oscillations of the hypocotyl and hypocotyl hook formation: A comparison of Norway spruce (Picea abies (L.)Karst.) and Scots pine (Pinus silvestris L.) seedlings

Circumnutation oscillations of hypocotyls were studied in Norway spruce and Scots pine using time-lapse cinematography. It was found that the circumnutations were specific in species. The analysis of hypocotyl ontogeny (100 h) revealed a different duration of the phases I, II and III of nutation oscillations in the first and second taxon. From the quantitative point of view it can be stated that during the phase I of nutation oscillations the Norway spruce hypocotyls exhibited higher frequency activity (corrections in direction of the hypocotyl by an elongation-controlling system corrected by a feedback mechanism), while in the phase III of nutation oscillations higher growth rate and larger amplitudes were observed in the Scots pine hypocotyl when compared with those of Norway spruce. The hypocotyl hook appeared only in Norway spruce.     

Stem-growth response of Pinus sylvestris and Picea abies to nitrogen fertilization as related to needle nitrogen concentration

 Responses of stem-volume growth to N application were evaluated in relation to foliar N concentrations. Data from N-fertilization experiments in 28 Pinus sylvestris stands and 21 Picea abies stands were used. Relative stem-growth responses were negatively related to concentrations of N in current-year needles of unfertilized trees. There appeared to be a threshold value of 15–16 mg (g DM)^–1 N in current-year needles, above which N-application is unlikely to stimulate growth. However, relations were non-significant between N concentrations in current-year needles and the absolute stem-growth response [dm³ ha^–1 (5 years)^–1]. The indicated threshold values are discussed in relation to other variables reflecting the N richness of the environment.--> Received: 20 December 1996 / Accepted: 30 September 1997     

High-efficiency Agrobacterium-mediated transformation of Norway spruce (Picea abies) and loblolly pine (Pinus taeda)

Agrobacterium-mediated gene transfer is the method of choice for many plant biotechnology laboratories; however, large- scale use of this organism in conifer transformation has been limited by difficult propagation of explant material, selection efficiencies and low transformation frequency. We have analyzed co-cultivation conditions and different disarmed strains of Agrobacterium to improve transformation. Additional copies of virulence genes were added to three common disarmed strains. These extra virulence genes included either a constitutively active virG or extra copies of virG and virB, both from pTiBo542. In experiments with Norway spruce, we increased transformation efficiencies 1000-fold from initial experiments where little or no transient expression was detected. Over 100 transformed lines expressing the marker gene -glucuronidase (GUS) were generated from rapidly dividing embryogenic suspension-cultured cells co- cultivated with Agrobacterium. GUS activity was used to monitor transient expression and to further test lines selected on kanamycin-containing medium. In loblolly pine, transient expression increased 10-fold utilizing modified Agrobacterium strains. Agrobacterium-mediated gene transfer is a useful technique for large-scale generation of transgenic Norway spruce and may prove useful for other conifer species.     

Circadian Timekeeping for the Photoperiodic Control of Budset in Picea abies (Norway Spruce) Seedlings

Romanian populations of Norway spruce are induced to set terminal buds by four inductive cycles of 8 h light/16 h darkness. To distinguish between circadian and hourglass timekeeping for the photoperiodic control of budset, seedlings were raised in continuous light at 300 µmol m^-2s^-1 at 20°C for 10 weeks. They were then exposed to an extended night regime consisting of three cycles of 8 h light/40 h dark with 4-h or 1-h nightbreaks (120 µmol m^-2s^-1) applied to groups of plants at intervals during the extended night. Following a final cycle of 8 h light/16 h dark to maximize budset, the plants were transferred to continuous light. Budset was delayed when the night-break was applied close to the critical nightlength (CNL) of 6–7 h or about 22–23 h later in the extended night, consistent with circadian rather than hourglass timekeeping. Confidence intervals were calculated for the times to maximum effect of the night-breaks.     

Circadian Timekeeping for the Photoperiodic Control of Budset in Picea abies (Norway Spruce) Seedlings

Romanian populations of Norway spruce are induced to set terminal buds by four inductive cycles of 8 h light/16 h darkness. To distinguish between circadian and hourglass timekeeping for the photoperiodic control of budset, seedlings were raised in continuous light at 300 µmol m^-2s^-1 at 20°C for 10 weeks. They were then exposed to an extended night regime consisting of three cycles of 8 h light/40 h dark with 4-h or 1-h nightbreaks (120 µmol m^-2s^-1) applied to groups of plants at intervals during the extended night. Following a final cycle of 8 h light/16 h dark to maximize budset, the plants were transferred to continuous light. Budset was delayed when the night-break was applied close to the critical nightlength (CNL) of 6-7 h or about 22-23 h later in the extended night, consistent with circadian rather than hourglass timekeeping. Confidence intervals were calculated for the times to maximum effect of the night-breaks.