Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Acute effects of ∆9-tetrahydrocannabinol (THC) on resting state brain function and their modulation by COMT genotype
Bossong, Matthijs G. ; Hell, Hendrika H. van; Schubart, Chris D. ; Saane, Wesley van; Iseger, Tabitha A. ; Jager, Gerry ; Osch, Matthias J.P. van; Jansma, J.M. ; Kahn, René S. ; Boks, Marco P. ; Ramsey, Nick F. - \ 2019
European Neuropsychopharmacology 29 (2019)6. - ISSN 0924-977X - p. 766 - 776.
Arterial spin labelling - Cannabis - Catechol-methyl-transferase (COMT) - Delta9-tetrahydrocannabinol (THC) - Resting state connectivity - Salience

Cannabis produces a broad range of acute, dose-dependent psychotropic effects. Only a limited number of neuroimaging studies have mapped these effects by examining the impact of cannabis on resting state brain neurophysiology. Moreover, how genetic variation influences the acute effects of cannabis on resting state brain function is unknown. Here we investigated the acute effects of ∆9-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, on resting state brain neurophysiology, and their modulation by catechol-methyl-transferase (COMT) Val158Met genotype. Thirty-nine healthy volunteers participated in a pharmacological MRI study, where we applied Arterial Spin Labelling (ASL) to measure perfusion and functional MRI to assess resting state connectivity. THC increased perfusion in bilateral insula, medial superior frontal cortex, and left middle orbital frontal gyrus. This latter brain area showed significantly decreased connectivity with the precuneus after THC administration. THC effects on perfusion in the left insula were significantly related to subjective changes in perception and relaxation. These findings indicate that THC enhances metabolism and thus neural activity in the salience network. Furthermore, results suggest that recruitment of brain areas within this network is involved in the acute effects of THC. Resting state perfusion was modulated by COMT genotype, indicated by a significant interaction effect between drug and genotype on perfusion in the executive network, with increased perfusion after THC in Val/Met heterozygotes only. This finding suggests that prefrontal dopamine levels are involved in the susceptibility to acute effects of cannabis.

Object discrimination in poultry housing using spectral reflectivity
Vroegindeweij, Bastiaan A. ; Hell, Steven van; IJsselmuiden, Joris M.M. ; Henten, Eldert J. van - \ 2018
Biosystems Engineering 167 (2018). - ISSN 1537-5110 - p. 99 - 113.
To handle surrounding objects, autonomous poultry house robots need to discriminate between various types of object present in the poultry house. A simple and robust method for image pixel classification based on spectral reflectance properties is presented. The four object categories most relevant for the autonomous robot PoultryBot are eggs, hens, housing elements and litter. Spectral reflectance distributions were measured between 400 and 1000 nm and based on these spectral responses the wavelength band with lowest overlap between all object categories was identified. This wavelength band was found around 467 nm with an overlap of 16% for hens vs. eggs, 12% for housing vs. litter, and less for other combinations. Subsequently, images were captured in a commercial poultry house, using a standard monochrome camera and a band pass filter centred around 470 nm. In 87 images, intensity thresholds were applied to classify each pixel into one of four categories. For eggs, the required 80% correctly classified pixels was almost reached with 79.9% of the pixels classified correctly. For hens and litter, 40–50% of the pixels were classified correctly, while housing elements had lower performance (15.6%). Although the imaging setup was designed to function without artificial light, its optical properties influenced image quality and the resulting classification performance. To reduce these undesired effects on the images, and to improve classification performance, artificial lighting and additional processing steps are proposed. The presented results indicate both the simplicity and elegance of applying this method and are a suitable starting point for implementing egg detection with the robot.
Diversity in secondary metabolites including mycotoxins from strains of aspergillus section nigri isolated from raw cashew nuts from benin, west africa
Lamboni, Yendouban ; Nielsen, Kristian F. ; Linnemann, Anita R. ; Gezgin, Yué Ksel ; Hell, Kerstin ; Nout, Rob ; Smid, Eddy J. ; Tamo, Manuele ; Boekel, M.A.J.S. van; Hoof, Jakob Blñsbjerg ; Frisvad, Jens Christian - \ 2016
PLoS ONE 11 (2016)10. - ISSN 1932-6203

In a previous study, raw cashew kernels were assayed for the fungal contamination focusin on strains belonging to the genus Aspergillus and on aflatoxins producers. These sample showed high contamination with Aspergillus section Nigri species and absence o aflatoxins. To investigate the diversity of secondary metabolites, including mycotoxins, th species of A. section Nigri may produce and thus threaten to contaminate the raw cashe kernels, 150 strains were isolated from cashew samples and assayed for their productio of secondary metabolites using liquid chromatography high resolution mass spectrometr (LC-HRMS). Seven species of black Aspergilli were isolated based on morphological an chemical identification: A.Tubingensis (44%), A. niger (32%), A. brasiliensis (10%), A. carbonariu (8.7%), A. luchuensis (2.7%), A. aculeatus (2%) and A. aculeatinus (0.7%). Fro these, 45 metabolites and their isomers were identified. Aurasperone and pyranonigrin A produced by all species excluding A. aculeatus and A. aculeatinus, were most prevalen and were encountered in 146 (97.3%) and 145 (95.7%) isolates, respectively. Three mycotoxin groups were detected: fumonisins (B2 and B4) (2.7%) ochratoxin A (13.3%), an secalonic acids (2%), indicating that these mycotoxins could occur in raw cashew nuts Thirty strains of black Aspergilli were randomly sampled for verification of species identit based on sequences of β-Tubulin and calmodulin genes. Among them, 27 isolates wer positive to the primers used and 11 were identified as A. niger, 7 as A.Tubingensis, 6 as A carbonarius, 2 as A. luchuensis and 1 as A. welwitschiae confirming the species names a based on morphology and chemical features. These strains clustered in 5 clades in A. sectio Nigri. Chemical profile clustering also showed also 5 groups confirming the speciespecific metabolites production.

Occurrence of Aspergillus section Flavi and section Nigri and aflatoxins in raw cashew kernels (Anacardiumoccidentale L.) from Benin
Lamboni, Y. ; Frisvad, J.C. ; Hell, K. ; Linnemann, A.R. ; Nout, M.J.R. ; Tamo, M. ; Nielsen, K. ; Boekel, M.A.J.S. van; Smid, E.J. - \ 2016
Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 70 (2016). - ISSN 0023-6438 - p. 71 - 77.
The objective of this study was to evaluate the presence of Aspergillus section Flavi and A. section Nigri in cashew nuts harvested in the Northern Guinea (NG) and Southern Sudanian (SS) agro-ecological zones of Benin. Also, the presence of aflatoxins was investigated. For detection of fungal contamination, a total of
100 kernels/sample (with disinfection) and 40 kernels/sample (without disinfection) were plated. Seventy samples from fourteen villages were used. Aflatoxins occurrence was analysed on 84 samples by ultraehigh performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The average water content and the cashew nuts count were respectively 8.6% and 172 nuts/kg in NG and 8.7% and 174 nuts/kg in SS. Significant differences between villages in both zones were found for both water content and nuts count. In disinfected samples, strains of Aspergillus section Nigri were predominant, in
NG and SS zones (90.2% and 87.2%) respectively. When non disinfected kernels were plated, A. section Nigri was predominant in both NG and SS zones, with percentages of 89.7% and 93.4%, respectively. None of the 84 nuts samples were positive for natural occurrence of aflatoxins with a detection limit of 0.05
e0.2 mg/kg.
Object segmentation in poultry housings using spectral reflectivity
Vroegindeweij, B.A. ; Hell, Steven van; Ijsselmuiden, J.M.M. ; Henten, E.J. van - \ 2015
- 6 p.
poultry housing - object segmentation - spectral reflectivity
The endocannabinoid system and emotional processing: A pharmacological fMRI study with Delta 9-tetrahydrocannabinol
Bossong, M.G. ; Hell, H.H. van; Jager, G. ; Kahn, R.S. ; Ramsey, N.F. ; Jansma, J.M. - \ 2013
European Neuropsychopharmacology 23 (2013)12. - ISSN 0924-977X - p. 1687 - 1697.
cb1 cannabinoid receptors - happy facial expressions - healthy-volunteers - antagonist rimonabant - major depression - memory function - functional mri - amygdala - brain - involvement
Various psychiatric disorders such as major depression are associated with abnormalities in emotional processing. Evidence indicating involvement of the endocannabinoid system in emotional processing, and thus potentially in related abnormalities, is increasing. In the present study, we examined the role of the endocannabinoid system in processing of stimuli with a positive and negative emotional content in healthy volunteers. A pharmacological functional magnetic resonance imaging (fMRI) study was conducted with a placebo-controlled, cross-over design, investigating effects of the endocannabinoid agonist Delta 9-tetrahydrocannabinol (THC) on brain function related to emotional processing in 11 healthy subjects. Performance and brain activity during matching of stimuli with a negative ('fearful faces') or a positive content ('happy faces') were assessed after placebo and THC administration. After THC administration, performance accuracy was decreased for stimuli with a negative but not for stimuli with a positive emotional content. Our task activated a network of brain regions including amygdala, orbital frontal gyrus, hippocampus, parietal gyrus, prefrontal cortex, and regions in the occipital cortex. THC interacted with emotional content, as activity in this network was reduced for negative content, while activity for positive content was increased. These results indicate that THC administration reduces the negative bias in emotional processing. This adds human evidence to support the hypothesis that the endocannabinoid system is involved in modulation of emotional processing. Our findings also suggest a possible role for the endocannabinoid system in abnormal emotional processing, and may thus be relevant for psychiatric disorders such as major depression. (C) 2013 Elsevier B.V. and ECNP. All rights reserved.
Default Mode Network in the Effects of ¿9-Tetrahydrocannabinol (THC) on Human Executive Function
Bossong, M.G. ; Jansma, J.M. ; Hell, H.H. van; Jager, G. ; Kahn, R.S. ; Ramsey, N.F. - \ 2013
PLoS ONE 8 (2013)7. - ISSN 1932-6203 - 10 p.
deficit hyperactivity disorder - working-memory - endocannabinoid system - healthy-volunteers - prefrontal cortex - synaptic plasticity - error awareness - brain-function - neural basis - fmri
Evidence is increasing for involvement of the endocannabinoid system in cognitive functions including attention and executive function, as well as in psychiatric disorders characterized by cognitive deficits, such as schizophrenia. Executive function appears to be associated with both modulation of active networks and inhibition of activity in the default mode network. In the present study, we examined the role of the endocannabinoid system in executive function, focusing on both the associated brain network and the default mode network. A pharmacological functional magnetic resonance imaging (fMRI) study was conducted with a placebo-controlled, cross-over design, investigating effects of the endocannabinoid agonist ¿9-tetrahydrocannabinol (THC) on executive function in 20 healthy volunteers, using a continuous performance task with identical pairs. Task performance was impaired after THC administration, reflected in both an increase in false alarms and a reduction in detected targets. This was associated with reduced deactivation in a set of brain regions linked to the default mode network, including posterior cingulate cortex and angular gyrus. Less deactivation was significantly correlated with lower performance after THC. Regions that were activated by the continuous performance task, notably bilateral prefrontal and parietal cortex, did not show effects of THC. These findings suggest an important role for the endocannabinoid system in both default mode modulation and executive function. This may be relevant for psychiatric disorders associated with executive function deficits, such as schizophrenia and ADHD
THC reduces the anticipatory nucleus accumbens response to reward in subjects with a nicotine addiction
Jansma, J.M. ; Hell, H.H. van; Vanderschuren, L.J.M.J. ; Bossong, M.G. ; Jager, G. ; Kahn, R.S. ; Ramsey, N.F. - \ 2013
Translational Psychiatry 3 (2013). - ISSN 2158-3188 - 10 p.
endogenous cannabinoid anandamide - increasing monetary reward - endocannabinoid system - drug-addiction - cb1 receptors - brain - dependence - rats - inhibition - humans
Recent evidence has implicated the endocannabinoid (eCB) system in nicotine addiction. The eCB system also has an important role in reward mechanisms, and nicotine addiction has been associated with aberrant reward processing. Motivated by this evidence, we tested the hypothesis that eCB modulation of reward processing is altered in subjects with a nicotine addiction (NAD). For this purpose, we compared reward-related activity in NAD with healthy controls (HC) in a pharmacological magnetic resonance imaging (MRI) study using ¿9-tetrahydrocannabinol (THC) administration to challenge the eCB system. Eleven HC and 10 NAD participated in a 3-T functional MRI (fMRI) study with a double-blind, cross-over, placebo-controlled design, using a Monetary Incentive Delay (MID) paradigm with three reward levels. Reward activity in the nucleus accumbens (NAcc) and caudate putamen during anticipation and feedback of reward was compared after THC and placebo. fMRI results indicated a significant reduction of reward anticipation activity in the NAcc in NAD after THC administration, which was not present in HC. This is indicated by a significant group by drug by reward interaction. Our data show that THC significantly reduces the NAcc response to monetary reward anticipation in NAD. These results suggest that nicotine addiction is associated with altered eCB modulation of reward processing in the NAcc. This study adds important human data to existing evidence implicating the eCB system in nicotine addiction.
Novel root & tuber crops and food security in West Africa : Factors influencing successful introduction of new R&T crops for food security in West Africa - cases of Benin and Ghana
Opoku, M. ; Ingenbleek, P.T.M. ; Hell, K. - \ 2012
Saarbrücken, Germany : LAP Lambert Academic Publishing - ISBN 9783659000829 - 192
marketing - wortelgewassen - knollen - voedselzekerheid - west-afrika - ghana - benin - introductie - consumentengedrag - root crops - tubers - food security - west africa - introduction - consumer behaviour
Microbiological and physicochemical characterization of shea butter sold on Benin markets
Honfo, G.F. ; Hell, K. ; Akissoe, N.H. ; Linnemann, A.R. ; Coulibaly, O. - \ 2012
Journal of Stored Products and Postharvest Research 3 (2012)3. - ISSN 2141-6567 - p. 24 - 29.
Shea butter, a fat from the nuts of shea tree, is of great nutritional and commercial value for local communities of Africa. The sanitary and physicochemical qualities of shea butter sold in Benin markets are unknown. This study assesses the quality characteristics of 54 samples of shea butter collected from eight markets in Benin, West Africa. Total germs, yeasts and mould varied with markets. Moisture content ranged between 2.5 to 6.2%. Iodine index was around 49 mgI2/100 g, but acid index (4.1 to 6.0 mgKOH/g), peroxide value (9.4 to 11.8 meq O2/kg) and saponification values (186.4 to 193.7 mgKOH/g) showed high variability both within and between samples of different markets. Quality characteristics were poorer for butter collected in the main urban markets (Cotonou, Bohicon and Malanville), due mainly to poor storage conditions. Shea butter could be stored in a clean package before sale to preserve its beneficial qualities.
Effects of ¿9-Tetrahydrocannabinol Administration on human encoding and recall memory function: a pharmacological fMRI study
Bossong, M.G. ; Jager, G. ; Hell, H.H. van; Zuurman, L. ; Jansma, J.M. ; Mehta, M.A. ; Gerven, J. van; Kahn, R.S. ; Ramsey, N.F. - \ 2012
Journal of Cognitive Neuroscience 24 (2012)3. - ISSN 0898-929X - p. 588 - 599.
long-term-memory - impairs spatial memory - medial temporal-lobe - recognition memory - episodic retrieval - prefrontal cortex - smoked marijuana - semantic memory - oral delta(9)-tetrahydrocannabinol - healthy-volunteers
Deficits in memory function are an incapacitating aspect of various psychiatric and neurological disorders. Animal studies have recently provided strong evidence for involvement of the endocannabinoid (eCB) system in memory function. Neuropsychological studies in humans have shown less convincing evidence but suggest that administration of cannabinoid substances affects encoding rather than recall of information. In this study, we examined the effects of perturbation of the eCB system on memory function during both encoding and recall. We performed a pharmacological MRI study with a placebo-controlled, crossover design, investigating the effects of ¿9-tetrahydrocannabinol (THC) inhalation on associative memory-related brain function in 13 healthy volunteers. Performance and brain activation during associative memory were assessed using a pictorial memory task, consisting of separate encoding and recall conditions. Administration of THC caused reductions in activity during encoding in the right insula, the right inferior frontal gyrus, and the left middle occipital gyrus and a network-wide increase in activity during recall, which was most prominent in bilateral cuneus and precuneus. THC administration did not affect task performance, but while during placebo recall activity significantly explained variance in performance, this effect disappeared after THC. These findings suggest eCB involvement in encoding of pictorial information. Increased precuneus activity could reflect impaired recall function, but the absence of THC effects on task performance suggests a compensatory mechanism. These results further emphasize the eCB system as a potential novel target for treatment of memory disorders and a promising target for development of new therapies to reduce memory deficits in humans
Effects of ¿9-Tetrahydrocannabinol on human working memory function
Bossong, M.G. ; Jansma, J.M. ; Hell, H.H. van; Jager, G. ; Oudman, E. ; Saliasi, E. ; Kahn, R.S. ; Ramsey, N.F. - \ 2012
Biological Psychiatry 71 (2012)8. - ISSN 0006-3223 - p. 693 - 699.
dorsolateral prefrontal cortex - catechol-o-methyltransferase - endogenous cannabinoids - genetic-variation - brain-function - schizophrenia - dysfunction - fmri - mri - cognition
Background Evidence indicates involvement of the endocannabinoid (eCB) system in both the pathophysiology of schizophrenia and working memory (WM) function. Additionally, schizophrenia patients exhibit relatively strong WM deficits. These findings suggest the possibility that the eCB system is also involved in WM deficits in schizophrenia. In the present study, we examined if perturbation of the eCB system can induce abnormal WM activity in healthy subjects. Methods A pharmacological functional magnetic resonance imaging study was conducted with a placebo-controlled, cross-over design, investigating effects of the eCB agonist ¿9-tetrahydrocannabinol on WM function in 17 healthy volunteers, by means of a parametric Sternberg item-recognition paradigm with five difficulty levels. Results Performance accuracy was significantly reduced after ¿9-tetrahydrocannabinol. In the placebo condition, brain activity increased linearly with rising WM load. ¿9-Tetrahydrocannabinol administration enhanced activity for low WM loads and reduced the linear relationship between WM load and activity in the WM system as a whole and in left dorsolateral prefrontal cortex, inferior temporal gyrus, inferior parietal gyrus, and cerebellum in particular. Conclusions ¿9-Tetrahydrocannabinol enhanced WM activity network-wide for low loads, while reducing the load-dependent response for increasing WM loads. These results indicate that a challenged eCB system can induce both abnormal WM activity and WM performance deficits and provide an argument for the possibility of eCB involvement in WM deficits in schizophrenia
Involvement of the endocannabinoid system in reward processing in the human brain
Hell, H.H. van; Jager, G. ; Bossong, M.G. ; Brouwer, A. ; Jansma, J.M. ; Zuurman, L. ; Gerven, J. van; Kahn, R.S. ; Ramsey, N.F. - \ 2012
Psychopharmacology 219 (2012)4. - ISSN 0033-3158 - p. 981 - 990.
acute oral delta(9)-tetrahydrocannabinol - cannabinoid cb1 receptors - healthy-volunteers - clinical-research - dopamine release - decision-making - human striatum - neural-basis - thc - delta-9-tetrahydrocannabinol
Rationale Disturbed reward processing in humans has been associated with a number of disorders, such as depression, addiction, and attention-deficit hyperactivity disorder. The endocannabinoid (eCB) system has been implicated in reward processing in animals, but in humans, the relation between eCB functioning and reward is less clear. Objectives The current study uses functional magnetic resonance imaging (fMRI) to investigate the role of the eCB system in reward processing in humans by examining the effect of the eCB agonist ¿9-tetrahydrocannabinol (THC) on reward-related brain activity. Methods Eleven healthy males participated in a randomized placebo-controlled pharmacological fMRI study with administration of THC to challenge the eCB system. We compared anticipatory and feedback-related brain activity after placebo and THC, using a monetary incentive delay task. In this task, subjects are notified before each trial whether a correct response is rewarded (“reward trial”) or not (“neutral trial”). Results Subjects showed faster reaction times during reward trials compared to neutral trials, and this effect was not altered by THC. THC induced a widespread attenuation of the brain response to feedback in reward trials but not in neutral trials. Anticipatory brain activity was not affected. Conclusions These results suggest a role for the eCB system in the appreciation of rewards. The involvement of the eCB system in feedback processing may be relevant for disorders in which appreciation of natural rewards may be affected such as addiction
Endocannabinoid involvement in reward and impulsivity in addiction
Hell, H.H. van - \ 2011
Rijksuniversiteit Utrecht. Promotor(en): N.F. Ramsey, co-promotor(en): Kees de Graaf. - Utrecht : Universiteit Utrecht - ISBN 9789053354704
Addiction is one of the most disabling diseases in the world. An important neurotransmitter system that has recently been implicated in addiction is the endocannabinoid system. The endocannabinoid system consists of cannabinoid receptors and endocannabinoid ligands that work on these receptors. Animal studies have shown that blocking the cannabinoid system prevents relapse to addiction, while activating the cannabinoid system with an agonist evokes relapse. Still, the involvement of the endocannabinoid system in addiction in humans remains unclear. The current thesis aimed to clarify the role of the endocannabinoid system in reward processing in nicotine addiction in humans. Brain function during reward processing was assessed using functional Magnetic Resonance Imaging (fMRI). In the first study described in this thesis, we have shown that both chronic nicotine and cannabis use attenuates reward-related brain activity in the nucleus accumbens, a brain area well known for its involvement in reward processing. Next, the endocannabinoid system was challenged using the partial cannabinoid agonist THC, the main psychoactive constituent of cannabis. When comparing nicotine users with non-using controls, we showed that a THC challenge did not affect reward processing in the nucleus accumbens in controls, while it was attenuated in nicotine users. Thus, altered reward processing as is found in nicotine addiction is associated with increased sensitivity of the cannabinoid system. In contrast, the endocannabinoid system seems to play a limited role in normal reward processing. Together, these data indicate that the endocannabinoid system is involved in addiction, and possibly other diseases in which reward processing is impaired, such as depression and ADHD
Evidence for involvement of the insula in the psychotropic effects of THC in humans: a double-blind, randomized pharmacological MRI study
Hell, H.H. van; Bossong, M.G. ; Jager, G. ; Kristo, G. ; Osch, M.J.P. ; Zelaya, F. ; Kahn, R.S. ; Ramsey, N.F. - \ 2011
International Journal of Neuropsychopharmacology 14 (2011)10. - ISSN 1461-1457 - p. 1377 - 1388.
cerebral-blood-flow - low-frequency fluctuation - central-nervous-system - resting-state fmri - neural-basis - anterior insula - healthy-volunteers - marijuana smoking - functional mri - cannabis use
The main reason for recreational use of cannabis is the ‘high’, the primary psychotropic effect of ¿9-tetrahydrocannabinol (THC). This psychoactive compound of cannabis induces a range of subjective, physical and mental reactions. The effect on heart rate is pronounced and complicates bloodflow-based neuroimaging of psychotropic effects of THC. In this study we investigated the effects of THC on baseline brain perfusion and activity in association with the induction of ‘feeling high’. Twenty-three subjects participated in a pharmacological MRI study, where we applied arterial spin labelling (ASL) to measure perfusion, and resting-state functional MRI to assess blood oxygen level-dependent signal fluctuation as a measure of baseline brain activity. Feeling high was assessed with a visual analogue scale and was compared to the imaging measures. THC increased perfusion in the anterior cingulate cortex, superior frontal cortex, and insula, and reduced perfusion in the post-central and occipital gyrus. Baseline brain activity was altered, indicated by increased amplitude of fluctuations in resting-state functional MRI signal after THC administration in the insula, substantia nigra and cerebellum. Perfusion changes in frontal cortex were negatively correlated with ratings of feeling high, suggesting an interaction between cognitive control and subjective effects of THC. In conclusion, an acute THC challenge altered baseline brain perfusion and activity, especially in frontal brain areas involved in cognitive and emotional processes, and the insula, associated with interoceptive awareness. These changes may represent the THC-induced neurophysiological correlates of feeling high. The alterations in baseline brain perfusion and activity also have relevance for studies on task-related effects of THC on brain function.
Nix fixes depency hell on all Linux distributions
Prins, J.C.P. ; Suresh, J. ; Dolstra, E. - \ 2008
Linux (2008).
Vegetative propagation of Strelitzia reginae.
Pol, P.A. van de; Hell, T.F. van - \ 1988
Acta Horticulturae 226 (1988). - ISSN 0567-7572 - p. 581 - 586.
Strelitzia reginae is propagated either by division of naturally developed branches known as fans or by seeds. Vegetative propagation by division is limited by a low rate of multiplication being 0.5–1.5 divisions per branch per year. Branching originates in the division of the apical dome with an absolute abscence of branching from axillary buds. Propagation by seeds is undesirable due to juvenility and genetic variation. Therefore induction of branching to increase the multiplication rate of Strelitzia by elimination of apical dominance was the purpose of this study. Selected plants were excavated and divided in fans. After shortening the roots to 20 cm, the fans were planted in containers and left for recovery and root regeneration. Then the apex was reached by a triangular excision of a part of the plant with a transversal cut 8–12 mm above the basal plate throughout the basal leaf sheaths keeping the leaves in contact with the roots. Thereafter the apex was removed and after 2–6 months lateral sprouts developed, varying in number from 2 to 30 per fan depending on age and size of the fan. In order to obtain shoots with roots most of the old roots were removed and during the next 6 months the newly formed laterals, rooted and could be divided in individual plants. These plants could be treated again from one year on. The total period for the sequential processes took one year
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