Acclimatization of Codiaeum variegatum L. ‘Aucubaefolia’ to changes in photon flux density. II. Net photosynthesis,dark respiration and chlorophyll content

Summary

Net photosynthesis, dark respiration and chlorophyll content were studied in plants of Codiaeum when transferred” from a glasshouse to photon flux densities 6, 18, or 66 μE m^?2s^?1 in growth rooms. The diurnal patterns of daily net photosynthesis and dark respiration were recorded during the first 12 days and 3, 7, 11 and 19 weeks after the transfer. Only plants transferred to 66 μE m^?2s^?1 reached a positive total net photosynthesis per day within the first 12 days. This was achieved only between the 12th day and 3 weeks when transferred to 6 μE m^?2s^?1. The rate of net photosynthesis increased until the 11th week and then declined, while dark respiration decreased until the 11th week and then increased. The diurnal patterns of net photosynthesis and dark respiration changed significantly with time of acclimatization. The rate of change in daily net photosynthesis and dark respiration was highest in the plants transferred to the lowest photon flux density. Changes in chlorophyll content of the leaves were similar to those in net photosynthesis.     

Growth and mortality in underplanted tree seedlings in response to variations in canopy closure of Norway spruce stands

Six broadleaved tree species and Picea abies (L.) Karst. wereplanted under spruce plantations of varying densities, in Sweden.Treatments included control (994 stems ha^–1), dense (538stems ha^–1), sparse (294 stems ha^–1) and gap (0stems ha^–1) overstory treatments. There was an increasein height and diameter growth from control to sparse overstorytreatment of all underplanted tree species except for ash (Fraxinusexcelsior L.) and Norway maple (Acer platanoides L.). Site conditionsmay have hampered the growth of these species, as well as wildcherry (Prunus avium L.). Both oak (Quercus robur L.) and sprucehad greater growth in the gap treatment, relative to the othertreatments. Insecticide application did not influence seedlinggrowth or survival. The performance of beech (Fagus sylvaticaL.), lime (Tilia cordata Mill.), spruce and oak was consistentwith shade tolerance ranking. Beech and lime had a very highsurvival rate, even under the densest canopy. The growth andmortality of ash, maple and wild cherry differed significantlyfrom what was expected. This experiment demonstrated significantvariation in interspecific growth and mortality between sevenplanted tree species in relation to canopy density. Correctsite and species selection is crucial when underplanting inshelterwood systems.     

Influence of environment, fertilizer and genotype on shoot morphology and subsequent rooting of birch cuttings

Differences in rooting ability of birch (Betula pubescens J.F. Ehrh.) cuttings were observed as a result of differences in genotype and physiology of the stock plants. The uniformity in response among cuttings from micropropagated plants compared with cuttings from seed plants confirmed the advantage of using micropropagated plants to study environmental effects. Shoot morphology of the seed stock plants was influenced by both photoperiod and thermoperiod. A day/night temperature of 15/25 degrees C reduced stem elongation compared with a day/night temperature of 25/15 degrees C regardless of photoperiod, and a continuous light regime resulted in more shoots per plant in both temperature regimes than a 16-h photoperiod. A reduction in the supply of macronutrients did not influence shoot morphology, but increased rooting substantially and seemed to override the effects of environmental factors. In cuttings of seed plants, the highest rooting percentage and number of roots were obtained in a 16-h photoperiod with a day/night temperature of 15/25 degrees C. In micropropagated stock plants, there was a positive correlation between shoot length and number of leaves per shoot and topographical distribution of light within the plants, but there was no correlation between these parameters and rooting ability of the cuttings. A rooting temperature of 16 degrees C delayed the rate of root production compared with the rate at higher temperatures, but the final rooting percentage was the same over the range from 16 to 28 degrees C. Root branching increased with temperature. At all temperatures, there was a large increase in sucrose content at the base of the cuttings during rooting, whereas the concentration of nontranslocated sugars remained constant. The carbohydrate content at the base of cuttings from micropropagated stock plants was three times higher than at the base of cuttings from seed stock plants, but the higher carbohydrate content was not correlated with a higher rooting potential.     

Herbivory by the pine weevil (Hylobius abietis L.) and short-snouted weevils (Strophosoma melanogrammum Forst. and Otiorhynchus scaber L.) during the conversion of a wind-thrown Norway spruce forest into a mixed-species plantation

The influence of above-ground insect herbivory and other agents of damage to seedlings was studied in a field experiment. Nine different tree species were planted in each of five randomised blocks. The species were: Alnus glutinosa (L.) Gaertner, Betula pendula Roth., Fagus sylvatica L., Fraxinus excelsior L., Larix eurolepis Henry, Picea abies (L.) Karst., Prunus avium L., Quercus robur L. and Tilia cordata Mill. The seedlings were monitored through the 2000–2002 growing seasons. Pine weevils (Hylobius abietis L.) fed significantly more on Norway spruce seedlings than on all other tree species. The following rough preference order was obtained: Norway sprucelarch>birch, beech, oak>cherry>alder, ash, lime. Thus, during the conversion of single-species coniferous plantations to mixed-species broadleaved stands, the use of costly insecticides against pine weevil is not required. Short-snouted weevils (e.g. Strophosoma melanogrammum Forst. and Otiorhynchus scaber L.) and other insects caused leaf and needle area loss primarily during the first growing season.     

Effect of temperature on flowering in Primula vulgaris

When grown in a glasshouse, flowering in Primula vulgaris ‘Aalsmeer Giant’ (yellow) and ‘Ducat’ (blue) was delayed with increasing temperature from approximately 12°C to 18°C. In addition, size of the first open flower and the number of flowering axillary shoots decreased, whereas the number of leaves and leaf area increased with the temperature increase. All temperature responses were greater in ‘Aalsmeer’ than in ‘Ducat’.When grown in growth rooms at 9°C, flowering in P. vulgaris ‘Aalsmeer Giant’ (yellow) was inhibited compared with 15°C. However, when 9 weeks of 15°C was applied to plants grown for 9 weeks at 9°C, the inhibition was overcome; longer periods of 15°C being no more effective. This indicates than an early stage of flower formation, probably the initiation, in Primula vulgaris is inhibited by 9°C, and not the further development of the buds towards open flowers.     

Circulating cytokine concentrations in dogs with different degrees of myxomatous mitral valve disease

Cytokines have been associated with the progression of congestive heart failure (CHF) in humans and may be implicated in the pathophysiology of myxomatous mitral valve disease (MMVD) in dogs. The aim of this study was to determine the serum concentrations of cytokines in dogs with MMVD. The study included 16 Cairn terriers with no or minimal mitral regurgitation (MR), 41 Cavalier King Charles Spaniels (CKCS) with different degrees of MR and 11 dogs of different breeds with CHF due to MMVD. Granulocyte-macrophage colony-stimulating factor, interferon-γ, interleukin (IL)-2, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, keratinocyte-derived chemokine, interferon-γ-induced protein and monocyte chemoattractant protein-1 (MCP-1) were measured using a canine-specific multiplex immunoassay. CHF dogs had significantly higher MCP-1 concentrations than dogs with no or minimal MR. Among the CKCS, IL-2 and IL-7 decreased with increasing left atrial size and IL-7 also decreased with increasing MR. IL-8 decreased with increasing left ventricular end-systolic internal dimensions. MCP-1 was increased in CHF dogs compared to healthy control dogs and IL-2, IL-7 and IL-8 decreased with increasing indices of disease severity. The results suggest a role for these cytokines in canine MMVD and CHF.     

Adventitious shoot regeneration from leaf segments of in vitro cultured shoots of the apple rootstock Jork 9

SUMMARY

Adventitious shoot formation was investigated using leaf segments of in vitro cultured shoots of the apple rootstock Jork 9. Regeneration capacity was influenced by the pretreatment of the mother shoots, macroelements, hormone concentrations, the gelling agent and the carbohydrate source. The highest regeneration rate and most shoots per leaf explant resulted from young leaves on a medium based on MS macroelements supplemented with 22 µM BAP and 0.1 µM_NAA together with sorbitol, at concentrations of 165 mM or 220 mM. Sorbitol was more effective than sucrose, glucose, fructose or a combination of these sugars. A cold and dark pretreatment of the shoots enhanced the formation of adventitious shoots.     

Micropropagation of gooseberry, Ribes grossularia

A method for rapid micropropagation of gooseberry (Ribes grossularia cultivar ‘Hinnonmäki Yellow’) was established. The optimum concentration for shoot production was obtained at 2.2 μM BAP and 0.05 μM IBA with MS nutrient medium. The Lepoivre salt medium with no hormones was used for elongation of shoot clusters, and in this medium about 50% of the shoots formed roots. For both rooted and unrooted shoots, 100% survival was obtained after transfer to soil. It was possible to store shoots in vitro for 130 days without any sub-culture and with 100% survival if the temperature was increased successively after cold storage.     

Dogs with heart diseases causing turbulent high-velocity blood flow have changes in platelet function and von Willebrand factor multimer distribution

The purpose of this prospective study was to investigate platelet function using in vitro tests based on both high and low shear rates and von Willebrand factor (vWf) multimeric composition in dogs with cardiac disease and turbulent high-velocity blood flow. Client-owned asymptomatic, untreated dogs were divided into 4 groups: 14 Cavalier King Charles Spaniels (Cavaliers) with mitral valve prolapse (MVP) and no or minimal mitral regurgitation (MR), 17 Cavaliers with MVP and moderate to severe MR, 14 control dogs, and 10 dogs with subaortic stenosis (SAS). Clinical examinations and echocardiography were performed in all dogs. PFA100 closure times (the ability of platelets to occlude a hole in a membrane at high shear rates), platelet activation markers (plasma thromboxane B2 concentration, platelet surface P-selectin expression), platelet aggregation (in whole blood and platelet-rich plasma with 3 different agonists), and vWf multimers were analyzed. Cavaliers with moderate to severe MR and dogs with SAS had longer closure times and a lower percentage of the largest vWf multimers than did controls. Maximal aggregation responses were unchanged in dogs with SAS but enhanced in Cavaliers with MVP (regardless of MR status) compared with control dogs. No significant difference in platelet activation markers was found among groups. The data suggest that a form of platelet dysfunction detected at high shear rates was present in dogs with MR and SAS, possibly associated with a qualitative vWf defect. Aggregation results suggest increased platelet reactivity in Cavaliers, but the platelets did not appear to circulate in a preactivated state in either disease.