Genotypic variation of cut chrysanthemum response to high CO2 concentration: Growth, time to flowering and visual quality

In this study sixteen cut chrysanthemum cultivars were used to evaluate the effects of high CO2 concentration (1500 µmol mol-1) on growth, time to flowering and visual quality as compared to the concentration used in commercial greenhouses (600 µmol mol-1). CO2 enrichment increased light use efficiency (11-41%) and total plant dry mass (TDM) (5-40%) in a cultivar dependent manner. This TDM increase was a result of: (i) higher relative growth rate during the long day period (i.e., 0 to 2 weeks; LD); and (ii) higher absolute growth rate both during the period between 2 to 6 weeks (SD1), and 6 weeks to final harvest (SD2). Cultivar differences in TDM at flowering between the two CO2 concentrations could be explained by differences in growth rate during the LD and SD2 periods. Furthermore, growing at high CO2 regime enhanced the number of flowers and flower buds per plant (NoF, 4-48%). Interestingly, the cultivars that showed the highest percentage of TDM increase, with CO2 enrichment, were not the ones that had the highest increase in the percentage of NoF. In contrast, high CO2 concentration had only a minor or no effect on the number of internodes on the main stem and on the reaction time in all the cultivars examined. From this research it is concluded that there is a large variation in the response of cut chrysanthemum cultivars to CO2 enrichment, in terms of TDM and NoF, which gives possibilities for breeding

Identifying Low-Back Stabilization in Low-Back Pain and the Influence of Tactile Information

Dieen, J.H. van [Promotor]Veeger, H.E.J. [Promotor

EFFECTS OF TYPES OF MEDIA AND NPK FERTILIZER ON THE ROOTING CAPACITY OF CHRYSANTHEMUM CUTTINGS

Physiological status of chrysanthemum cuttings during rooting process highly influences plant growth and flower production. Amongst other aspects, rooting capacity of the cuttings is the most important. Rooting capacity is influenced by environmental conditions such as growing medium and nutrition. The study was aimed to analyze the effects of different types of media, fertilizer concentration, and frequency of fertilizer application on the rooting capacity of chrysanthemum cuttings. The experiment was conducted at the Segunung Experimental Station of the Indonesian Ornamental Crops Research Institute from February to May 2005. The treatments consisted of four different rooting media, i.e. carbonized rice husk, coco peat, perlite, and mixture of perlite and vermiculite (1:1 v/v); two concentrations of NPK (25:7:7) fertilizers, i.e. 1.75 and 2.5 g 1-l; and four frequencies of fertilizer application, i.e. every 1 day, 2 days, 3 days, and 4 days. The experiment was designed in a completely randomized block with four replications. Parameters observed were rooting capacity and cutting performances such as cutting height, cutting diameter, number of leaves, number of visible roots, and root length at 16 days after planting. The results showed that chrysanthemum cuttings rooted in carbonized rice husk had better performance than those rooted in coco peat, vermiculite, and mixture of perlite + vermiculite. Higher concentration of fertilizer solution up to 2.5 g l-1 also gave significant effect on the root formation and further root growth of cuttings. However, the rooting capacity of cuttings was not affected by the frequency of fertilizer application. This study implied that carbonized rice husk growing medium supplemented with NPK (2.5 g l-l) every 4 days during rooting period is the choice for traditional chrysanthemum growers to increase the perform-ance and quality of the cut flowers

EFFECTS OF IRRIGATION FREQUENCY AND LEAF DETACHMENT ON CHRYSANTHEMUM GROWN IN TWO TYPES OF PLASTIC HOUSE

Chrysanthemum is one of important ornamentals in Indonesia and it ranks in the first quantity of cut flower marketed every year. In most cases, the low productivity is still a constraint for the traditional growers to make production process profitable. Several problems revealed in chrysanthemum production were investigated. The study dealt with the effect of two types of plastic house constructions, irrigation frequency, and leaf detachment on the growth and development of chrysanthemum. The experiment was conducted at Segunung, Indonesian Ornamental Plants Research Institute during the dry season of 2005. A nested design with six replications was used. The results showed that plants grown in wood-constructed plastic house had better growth performance and flower quality than those under bamboo plastic house. Longer stem and higher plant fresh weight with more flowers and longer life span were also observed on chrysanthemum irrigated four times per week than those irrigated twice per week. Leaf removal often practiced by the growers is no longer recommended, since the number of leaves on the plant influenced all parameters observed. The more leaves were detached, the more negative impacts on plant growth were found

Identifying intrinsic and reflexive contributions to low-back stabilization

Motor control deficits have been suggested as potential cause and/or effect of a-specific chronic low-back pain and its recurrent behavior. Therefore, the goal of this study is to identify motor control in low-back stabilization by simultaneously quantifying the intrinsic and reflexive contributions. Upper body sway was evoked using continuous force perturbations at the trunk, while subjects performed a resist or relax task. Frequency response functions (FRFs) and coherences of the admittance (kinematics) and reflexes (sEMG) were obtained. In comparison with the relax task, the resist task resulted in a 61% decrease in admittance and a 73% increase in reflex gain below 1.1 Hz. Intrinsic and reflexive contributions were captured by a physiologically-based, neuromuscular model, including proprioceptive feedback from muscle spindles (position and velocity) and Golgi tendon organs (force). This model described on average 90% of the variance in kinematics and 39% of the variance in sEMG, while resulting parameter values were consistent over subjects

The Identification of Zebrafish Mutants Showing Alterations in Senescence-Associated Biomarkers

There is an interesting overlap of function in a wide range of organisms between genes that modulate the stress responses and those that regulate aging phenotypes and, in some cases, lifespan. We have therefore screened mutagenized zebrafish embryos for the altered expression of a stress biomarker, senescence-associated β-galactosidase (SA-β-gal) in our current study. We validated the use of embryonic SA-β-gal production as a screening tool by analyzing a collection of retrovirus-insertional mutants. From a pool of 306 such mutants, we identified 11 candidates that showed higher embryonic SA-β-gal activity, two of which were selected for further study. One of these mutants is null for a homologue of Drosophila spinster, a gene known to regulate lifespan in flies, whereas the other harbors a mutation in a homologue of the human telomeric repeat binding factor 2 (terf2) gene, which plays roles in telomere protection and telomere-length regulation. Although the homozygous spinster and terf2 mutants are embryonic lethal, heterozygous adult fish are viable and show an accelerated appearance of aging symptoms including lipofuscin accumulation, which is another biomarker, and shorter lifespan. We next used the same SA-β-gal assay to screen chemically mutagenized zebrafish, each of which was heterozygous for lesions in multiple genes, under the sensitizing conditions of oxidative stress. We obtained eight additional mutants from this screen that, when bred to homozygosity, showed enhanced SA-β-gal activity even in the absence of stress, and further displayed embryonic neural and muscular degenerative phenotypes. Adult fish that are heterozygous for these mutations also showed the premature expression of aging biomarkers and the accelerated onset of aging phenotypes. Our current strategy of mutant screening for a senescence-associated biomarker in zebrafish embryos may thus prove to be a useful new tool for the genetic dissection of vertebrate stress response and senescence mechanisms

Odor supported place cell model and goal navigation in rodents

Experiments with rodents demonstrate that visual cues play an important role in the control of hippocampal place cells and spatial navigation. Nevertheless, rats may also rely on auditory, olfactory and somatosensory stimuli for orientation. It is also known that rats can track odors or self-generated scent marks to find a food source. Here we model odor supported place cells by using a simple feed-forward network and analyze the impact of olfactory cues on place cell formation and spatial navigation. The obtained place cells are used to solve a goal navigation task by a novel mechanism based on self-marking by odor patches combined with a Q-learning algorithm. We also analyze the impact of place cell remapping on goal directed behavior when switching between two environments. We emphasize the importance of olfactory cues in place cell formation and show that the utility of environmental and self-generated olfactory cues, together with a mixed navigation strategy, improves goal directed navigation