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.     

Frost hardiness development in Pinus silvestris seedlings in response to fertilization

The effects of different levels of nitrogen on freezing survival, the amounts of chlorophylls and β-carotene, the ratios Chl a/Chl b, and (Chl a + Chl b)/β-carotene in hardened and unhardened seedlings of Scots Pine (Pinus silvestris L.) have been investigated. There was. no correlation between frost hardiness and nitrogen content in the unhardened seedlings. However, the hardy seedlings with the highest nitrogen content, showed a decrease in frost hardiness of 3°C. The amounts of chlorophylls and β-carotene increased for all the treatments during hardening, except for the seedlings that had the highest nitrogen content; so that the effect of fertilizer was more evident in non-hardened than in hardened plants. The ratios Chl a/Chl b decreased during hardening in all the treatments. This was an effect of a larger increase of Chl b than Chl a. The ratios of Chl a + Chl b/β-carotene also decreased during hardening except for the plants that were fertilized with the second lowest amount of nitrogen. Since the amounts of Chl a and Chl b increase during hardening the amount of β-carotene increases even more.
The growth rates of the seedlings were closely related to the nitrogen content for the different treatments. All plants were infected with ectotrophic mycorrhizae, which resulted in an enhancement of ion transportation from the soil to the plants. This is important when the supply of ions is low.     

Development of photosynthetic electron transport in Pinus silvestris

Photosynthetic electron transport activity has been measured in chloroplasts isolated from dark-grown seedlings of Pinus silvestris L. and in chloroplasts isolated from seedlings subjected to illumination for periods of up to 48 h. Activities of photosystem 2, photosystem 1 and photosystem 2 plus 1 have been measured. Chloroplasts isolated from dark-grown seedlings showed significant electron transport activity through both photosystems and through the entire electron transport chain from water to NADP. Illumination of the seedlings for only 5 min markedly promoted photosystem 2 activity. The artificial electron donor, diphenylcarbazide. promoted activity in chloroplasts from dark-grown seedlings and in chloroplasts from seedlings illuminated for up to 30 min. In comparison to photosystem 2 and overall electron transport from water to NADP, photosystem 1 activity increased only slightly during illumination. Measurements of electron transport and fluorescence kinetics have confirmed that photosynthetic electron transport capacity is limited on the water splitting side of photosystem 2 in dark-grown seedlings, whereas the primary and secondary electron acceptors of photosystem 2 are fully synthesized and functioning in darkness. Polyethylene glycol must be used as a protective agent when isolating photoactive chloroplasts from secondary needles of conifers. However, the presence of polyethylene glycol, when isolating chloroplasts from dark-grown pine cotyledons, caused a total inhibition of the activity of photosystem 2. The failure of others to show a substantial electron transport activity in chloroplasts from dark-grown Pinus silvestris might depend on their use of polyethylene glycol in the preparation medium and/or on their use of suboptimal reaction conditions for the electron transport measurements.     

Short and Long Term Investor Synchronization Caused by Decoupling

The dynamics of collective decision making is not yet well understood. Its practical relevance however can be of utmost importance, as experienced by people who lost their fortunes in turbulent moments of financial markets. In this paper we show how spontaneous collective “moods” or “biases” emerge dynamically among human participants playing a trading game in a simple model of the stock market. Applying theory and computer simulations to the experimental data generated by humans, we are able to predict the onset of such moments before they actually happen.     

Short and Long Term Outcome of Bilateral Pallidal Stimulation in Chorea-Acanthocytosis

Background

Chorea-acanthocytosis (ChAc) is a neuroacanthocytosis syndrome presenting with severe movement disorders poorly responsive to drug therapy. Case reports suggest that bilateral deep brain stimulation (DBS) of the ventro-postero-lateral internal globus pallidus (GPi) may benefit these patients. To explore this issue, the present multicentre (n=12) retrospective study collected the short and long term outcome of 15 patients who underwent DBS.

Methods

Data were collected in a standardized way 2-6 months preoperatively, 1-5 months (early) and 6 months or more (late) after surgery at the last follow-up visit (mean follow-up: 29.5 months).

Results

Motor severity, assessed by the Unified Huntington’s Disease Rating Scale-Motor Score, UHDRS-MS), was significantly reduced at both early and late post-surgery time points (mean improvement 54.3% and 44.1%, respectively). Functional capacity (UHDRS-Functional Capacity Score) was also significantly improved at both post-surgery time points (mean 75.5% and 73.3%, respectively), whereas incapacity (UHDRS-Independence Score) improvement reached significance at early post-surgery only (mean 37.3%). Long term significant improvement of motor symptom severity (≥20 % from baseline) was observed in 61.5 % of the patients. Chorea and dystonia improved, whereas effects on dysarthria and swallowing were variable. Parkinsonism did not improve. Linear regression analysis showed that preoperative motor severity predicted motor improvement at both post-surgery time points. The most serious adverse event was device infection and cerebral abscess, and one patient died suddenly of unclear cause, 4 years after surgery.

Conclusion

This study shows that bilateral DBS of the GPi effectively reduces the severity of drug-resistant hyperkinetic movement disorders such as present in ChAc.     

Impedance Spectroscopy in Frost Hardiness Evaluation of Rhododendron Leaves

Impedance spectroscopy was used in studying frost hardinessof leaves of two diploid rhododendron cultivars, RhododendronL. ‘PJM’ and R. ‘Cunningham's White’,and their tetraploid derivatives, R. ‘Northern Starburst’(NSB) and CW4. After the growing season and initial hardeningin a greenhouse, plants were subjected to an acclimation regimein a phytotron: 3 consecutive weeks at +5, +1 and -2°C each.Hardiness was studied with controlled freezing tests beforeeach decrease in temperature and at the end of the experiment,based on data of extracellular resistance r_eand relaxation time of the frost-exposed leaves. The correlation of the two estimateswas 0.92. Generally, the diploid clones had better frost hardinessthan the tetraploid clones. At the end of the experiment, frosthardiness of the diploid ‘PJM’ was -28.7°C andthat of the tetraploid NSB -20.6°C. Leaves of the diploid‘Cunningham's White’ and of the tetraploid CW4 hardenedto -32.0°C and -20.9°C, respectively. Frost hardinessestimated by impedance spectroscopy correlated well with earlierresults based on visual scoring (r = 0.81–0.86) and electrolyteleakage tests (r = 0.84–0.90), but results from impedancespectroscopy indicated weaker hardiness than the other tests.The difference between the results from impedance spectroscopyand the other tests was smaller and more coherent within the‘Cunningham's White’ clones than within ‘PJM’and NSB. Changes in extracellular and intracellular resistanceof non-frozen leaves during the acclimation correlated withthe changes in frost hardiness of ‘Cunningham's White’clones, but not with those of ‘PJM’ and NSB, whichbelong to another subspecies.Copyright 2000 Annals of BotanyCompany Cold resistance, evergreen, frost hardiness, impedance spectroscopy, polyploid, Rhododendron, tetraploid     

Short Term Interactions with Long Term Consequences: Modulation of Chimeric Vessels by Neural Progenitors

Vessels are a critical and necessary component of most tissues, and there has been substantial research investigating vessel formation and stabilization. Several groups have investigated coculturing endothelial cells with a second cell type to promote formation and stabilization of vessels. Some have noted that long-term vessels derived from implanted cocultures are often chimeric consisting of both host and donor cells. The questions arise as to whether the coculture cell might impact the chimeric nature of the microvessels and can modulate the density of donor cells over time. If long-term engineered microvessels are primarily of host origin, any impairment of the host''s angiogenic ability has significant implications for the long-term success of the implant. If one can modulate the host versus donor response, one may be able to overcome a host''s angiogenic impairment. Furthermore, if one can modulate the donor contribution, one may be able to engineer microvascular networks to deliver molecules a patient lacks systemically for long times. To investigate the impact of the cocultured cell on the host versus donor contributions of endothelial cells in engineered microvascular networks, we varied the ratio of the neural progenitors to endothelial cells in subcutaneously implanted poly(ethylene glycol)/poly-L-lysine hydrogels. We found that the coculture of neural progenitors with endothelial cells led to the formation of chimeric host-donor vessels, and the ratio of neural progenitors has a significant impact on the long term residence of donor endothelial cells in engineered microvascular networks in vivo even though the neural progenitors are only present transiently in the system. We attribute this to the short term paracrine signaling between the two cell types. This suggests that one can modulate the host versus donor contributions using short-term paracrine signaling which has broad implications for the application of engineered microvascular networks and cellular therapy more broadly.     

Adenosine Triphosphatase Activity in Cell-Wall Preparations and Excised Roots of Barley

Cell-wall preparations from barley roots contain about 20 percent of the ATP-ase activity of the whole homogenate. This activityis maximal near pH 7, activated by calcium and magnesium ionsand shows further activation when sodium and potassium chloridesare applied at alkaline pH values. High concentrations of sodiumchloride and ammonium sulphate are needed to elute the activityfrom the walls which suggests an ionic binding with the wallfraction. Excised root tips release inorganic phosphate fromATP with no lag phase, and this activity shows a response tovariation in substrate and magnesium concentration similar tothat of the cell-wall preparations, suggesting a surface locationof the enzyme. The properties of this hydrolytic activity arediscussed in relation to those described in other plant systemsand to animal transport ATP-ases.     

Structural and functional relationships in developing Pinus silvestris chloroplasts

The light dependent chloroplast development of dark grown seedlings of Pinus silvestris L. was followed by analyses of chlorophyll content, chlorophyll a/b ratios, chlorophyll/P700 ratios, chlorophyll-protein complexes and structural changes. Low-temperature fluorescence emission spectra of isolated chloroplasts and separation of sodium dodecyl sulphate solubilized chlorophyll-protein complexes by gel electrophoresis showed that the chlorophyll-protein complexes of photosystem 1 (P700-CPa), photosystem II (PS II-CPa) and the light-harvesting complex LH–CPa/b were present in dark grown seedlings. The low-temperature fuoorescence emission maxima of isolated P700–CPa and PS II–CPa shifted towards longer wavelengths during greening in light, indicating a light induced change of the chlorophyll organisation in the two photosystems. Illumination caused LH–CPa/b to increase relative to P700–CPa, whereas the ratio between LH–CPa/b and PS II–CPa remained essentially constant. Analyses of low-temperature fluorescence spectra with or without 0.01 M Mg²⁺ showed that the Mg²⁺ controlled distribution of excitation energy into PS I was activated upon illumination of the seedlings. The photosynthetic unit size, as defined by the chlorophyll/P700 ratio, did not change over a 96 h illumination period, although the chlorophyll content increased about 6–fold during that time. This result and the constant electron transport rate per unit chlorophyll and time during chlorophyll accumulation provided evidence for a sequential development of the photosynthetic units when illuminating dark grown pine cotyledons. Electron micrographs showed that exposure of dark grown seedlings to light for 2 h caused the prolamellar body to disappear and grana to form. These changes occurred prior to substantial accumulation of chlorophyll or change in the ratio between LH–CPa/b and P700–CPa. However, both the water-splitting system of photosystem II and the Mg²⁺ controlled redistribution of excitation energy was activated during this period.     

Comparison of Reductions in Adenosine Triphosphate Content, Plasma Membrane-associated Adenosine Triphosphatase Activity, and Potassium Absorption in Oat Roots by Diethylstilbestrol

The possibility was investigated that diethylstilbestrol (DES) inhibits potassium absorption in oat (Avena sativa L. cv. Goodfield) roots by inhibiting mitochondrial functions in addition to inhibiting the plasma membrane ATPase. DES at 10⁻⁶ molar stimulated the mitochondrial ATPase slightly, but higher concentrations had no effect. Oxidative phosphorylation by isolated mitochondria was inhibited 50% by 2.6 × 10⁻⁵ molar DES; concentrations of 10⁻⁴ molar or greater were completely inhibitory. After a lag of about 2 minutes, 10⁻⁴ molar DES produced a linear decrease in ATP content of excised roots. After 20 minutes, the ATP content of the tissue was about 50% of the control and remained at that level after 30 minutes in DES.     

Cytology of Potato Callus Cells in Relation to their Frost Hardiness

Structure of callus cells of frost-sensitive and frost-tolerant Solanum species and a frost-tolerant cell line (D20-1), selected from S. tuberosum cv. Desirée callus, was studied. Like frost-tolerant species S. commersonii, cells of the frost-tolerant cell line contained starch grains in their plastids. The cells of this frost-tolerant line also possessed an increased number of microbodies containing protein crystals which suggests the involvement of proteins in frost tolerance but the mechanism may differ from that in frost-tolerant species.     

Purification and Characterization of a Cation-stimulated Adenosine Triphosphatase from Corn Roots

A membrane-bound, monovalent cation-stimulated ATPase from Zea mays roots has been purified to a single band on sodium dodecyl sulfate gel electrophoresis. Microsomal preparations with K⁺ -stimulated ATPase activity were extracted with 1 m NaClO₄, and the solubilized enzyme was purified by chromatography on columns of n-hexyl-Sepharose, DEAE-cellulose, and Sephadex G-100 Superfine. A 500-fold purification over the activity present in the microsomes was obtained. The K⁺ -stimulated activity shows positive cooperativity with increasing KCl concentrations. The purified enzyme shows K⁺ -stimulated activity with ATP, GTP, UTP, CTP, ADP, α + β-glycerophosphate, p-nitrophenyl phosphate, and pyrophosphate as substrates. Under most conditions ATP is the best substrate. Although dicyclohexyl carbodiimide and Ca²⁺ inhibit and alkylguanidines stimulate the K⁺ -ATPase while bound to microsomes, they have no effect on the purified enzyme.     

Correlations between Ion-stimulated Adenosine Triphosphatase Activities and Ion Influxes in Maize Roots

Two uptake-wash regimes were used to determine influxes of ⁸⁶Rbacross the plasmalemma and across an internal membrane of maizeroots. By using a variety of different conditions it was possibleto determine the magnitude of non-metabolic uptake at differentconcentrations and hence measure more accurately the magnitudeof the active influxes at each membrane. This data was usedto study possible correlations between ion influxes and theactivities of two different membrane-bound KCl-stimulated ATPasesisolated from maize roots. One of these ATPase activities wasassociated with a fraction enriched in plasmalemma and the otherwith a fraction containing a smooth internal membrane. Significant correlations were found between the influx of ⁸⁶Rbacross the plasmalemma and the plasmalemma-associated, KCl-stimulatedATPase activity and between the influxes and KCl-stimulatedATPase activities associated with an internal membrane. Thesecorrelations may be regarded as evidence for mediation of specificion influxes by ion-stimulated ATPases. However, a number ofsignificant cross-correlations could also be made (e.g. betweenthe influx across the plasmalemma and the inner membrane ATPaseactivity) which, together with problems of identification ofthe internal membrane and accurate flux measurement, make itdifficult to interpret the result unequivocally in terms ofthe above hypothesis.     

Correlation between Cold- and Drought-Induced Frost Hardiness in Winter Wheat and Rye Varieties

Exposure of six wheat (Triticum aestivum L.) and one rye (Secale cereale L.) cultivar to 40% relative humidity for 24 hours induced the same degree of freezing tolerance in seedling epicotyls as did cold conditioning for 4 weeks at 2°C.     

Inhibition of Adenosine Triphosphatase in Sheep Red Cell Membranes by Oxidized Glutathione

This paper reports inhibition of Na⁺ + K⁺-stimulated, ouabain-inhibited adenosine triphosphatase (S-ATPase) in sheep red cell membranes by oxidized glutathione (GSSG). The results are consistent with the hypothesis that this inhibition depends upon the formation of a mixed disulfide between glutathione and -SH group(s) in the enzyme protein. Thus, inhibition of S-ATPase by GSSG proceeds more rapidly at alkaline than at neutral pH and is reversed by the addition of an excess of a compound containing reduced -SH groups (e.g. dithiothreitol). ATP protects S-ATPase against inhibition by GSSG and this protection depends on both the monovalent and divalent cation composition of the medium. Protection by ATP is more complete in the presence of K⁺ than in the presence of Na⁺.     

Correlation between Ion Fluxes and Ion-stimulated Adenosine Triphosphatase Activity of Plant Roots

The energy-dependent influx of Rb(+) into excised roots of corn, wheat, and barley has been determined and compared to the Rb(+)-stimulated ATPase activity of membrane fractions obtained from root homogenates of these species. The external Rb(+) concentrations studied were in the range of 1 to 50 mm. The ratio of Rb(+) influx/Rb(+)-stimulated ATPase was approximately 0.85 and was nearly constant for all the species and Rb(+) concentrations studied. The correlation coefficient for Rb(+) influx versus Rb(+)-activated ATPase was 0.94. The results support the concept that ATP is the energy source for ion transport in roots and that an ATPase participates in the energy transduction process involved in energy-dependent ion transport.     

Mineral Nutrient Requirements of Pinus silvestris and Picea abies Seedlings

The mineral nutrient requirements of Pinus silvestris L. and Picea abies Karst. were studied according to previously published methods applied to a series of various plant species. The optimum nutrient proportions are similar to those of Vaccinium, with a lower relative potassium requirement than birch and other broad-leaf species. Various ratios between ammonium and nitrate nitrogen were about equally efficient except for a minor growth reduction with pure nitrate, which gave a comparatively low nitrogen content and a high cation/nitrogen ratio. The rate of ammonium uptake was much higher than that of nitrate when both sources were supplied. The required total concentration in the nutrient solution for maximum growth is lower in pine than in spruce, but both fall within the low salt range. Both species, especially pine, are sensitive to high salt concentrations. Although pine and spruce grow on the same type of soils as Vaccinium— leached soils with low base saturation – accumulation of calcium or other cations is not as pronounced as in Vaccinium, especially not in pine. The results are compared with results from similar experiments with a series of other conifers. All the conifers have more flexible cation uptake mechanisms than Vaccinium but the results indicate tendencies to accumulation of anions, nitrate and phosphate. Recommended fertilizer compositions for forest fertilization and nurseries are discussed.