Differential effects of light quantity and spectral light quality on growth, morphology and development of two stoloniferous Potentilla species

Plant species from open habitats often show pronounced responses to shading. Apart from a reduction in growth, shading can lead to marked changes in morphology and architecture, and it may affect the rate of plant development. Natural shade comprises two basically different features, a reduction in light quantity (amount of radiation) and changes in the spectral light quality. The first aspect represents changes in resource availability, while the latter acts as a source of information for plants and can prompt morphogenetic responses. A greenhouse experiment was carried out to study the effects of changes in light quality and quantity on the growth, morphology and development of two stoloniferous Potentilla species. Individual plants were subjected to three light treatments: (1) full daylight (control); and two shade treatments, in which (2) light quantity (photon flux density) and (3) light spectral quality (red/far-red ratio) were changed independently. Plant development was followed throughout the study. Morphological parameters, biomass and clonal offspring production were measured at the end of the experiment. Morphological traits such as petiole length, leaf blade characteristics and investment patterns into spacers showed high degrees of shade-induced plasticity in both species. With a few exceptions, light quality mainly affected morphological variables, while production parameters were most responsive to changes in light quantity. Potentilla anserina allocated resources preferentially to established rosettes at the cost of stolon growth and branching, while in P. reptans, all parameters related to development and allocation were slowed down to the same extent by light limitation. Light quality changes also positively affected biomass production via changes in leaf allocation. Changes in the spectral light quality had major effects on the size of modular structures (leaves, ramets), whereas changes in light quantity mainly affected their numbers. Received: 12 December 1997 / Accepted: 8 July 1998     

Effect of titanium-ion on the growth of various bacterial species

There are a number of studies that explain the metabolism and roles of metallic titanium and titaniumion. One of the most intriguing results from these studies is the finding of metallic titanium having no bacteriostatic effects on oral bacterial species. In this research, the effects of titanium-ion on the growth of twenty-two bacterial species, some of which are commonly found in foods such as yoghurt, kimchi, and soy fermented products, were investigated. All but two bacteria, Escherichia coli and Pseudomonas aeruginosa appeared to be sensitive to titanium-ion. These two species were grown on 360 microg/ml of titanium-ions, and they were found to be resistant to the titanium-ion. Both the wild-type and plasmid-cured E. coli showed good growth in a medium with 200 microg/ml of titanium-ions. These results suggest that titanium-resistance was independent from the effects of the plasmid in E. coli.     

Effects of light quality and quantity on growth of the clonal plant Eichhornia crassipes

Summary Plant canopy shade reduces photosynthetic photon flux density (PPFD) and ratio of red to far-red light (z). Both effects can cause plants to increase potential for light acquisition through vertical growth and leaf area expansion. Clonal plants such as Eichhornia crassipes might alternatively increase light interception via horizontal growth of stolons or rhizomes and placement of new ramets in less shaded microsites. Effect of simulated canopy shade and component effects of PPFD and z were tested by filtering or adding light uniformly, to a whole group of connected ramets, or locally, to individual ramets within a group. In uniform treatments, low PPFD reduced total growth but low z did not. Low PPFD and low z independently reduced stolon and ramet production and caused etiolation of petioles; effect of low PPFD plus low z on ramet production was greater than that of either factor alone. Lateral clonal growth thus did not seem to be a response to uniform shading; instead, uniformly low PPFD or low z increased partitioning to established ramets. Low z changed partitioning without changing total growth. In local treatments, reduction of growth of individual ramets due to low PPFD and inhibition of new ramet production attributable to spectral composition of light were mitigated when connected ramets were unshaded; plants may respond differently to patchy than to uniform shade.     

Combined effects of enhanced UV-B radiation and additional nutrients on growth of two Mediterranean plant species

Seedlings of two Mediterranean plants, the slow-growing, evergreen sclerophyll Ceratonia siliqua L. and the fast growing drought semi-deciduous Phlomis fruticosa L., were grown for one year in the field at ambient or ambient plus supplemental UV-B radiation (equivalent to a 15% ozone depletion) and two levels of applied fertilizers (NPK). The effects on growth, morphological, anatomical and physiological parameters were measured at final plant harvest. Additional nutrients increased leaf nitrogen, improved growth and reduced the root/shoot ratio in both plants, yet these effects were more pronounced in the fast growing P. fruticosa. A nutrient-induced increase in chlorophyll content was also observed in this plant. The growth responses to UV-B radiation were different for the two species. Growth in C. siliqua was not affected by UV-B radiation at both nutrient levels and the same was true for P. fruticosa at low nutrients. However, at the high nutrient level, supplemental UV-B radiation improved growth in P. fruticosa, indicating a strong interaction between the treatments. Photosystem II (PSII) photochemical efficiency, methanol-extractable UV-B absorbing capacity, total phenolics and tannins were not affected by either treatment in both plants. It is concluded that nutrient levels can strongly modify the UV-B radiation effects on growth of P. fruticosa. We presume that this may be correlated to the fast growing habit of this species.     

Effect of light on seed germination and seedling growth ofMerremia species

The seeds ofMerremia aegyptia are indifferent to light conditions for germination, which becomes 100% in the first 24 hrs. On the contrary, inM. dissecta the highest percentage was found in red light within the first 24 hrs. This difference was lost later on except in far-red. The seedling growth of the two species was least in blue and red lights, respectively. However, the growth of hypocotyl in the former species was faster than the latter.     

Effect of ammonia on the growth of Bacillus species and some other bacteria

The tolerance of 26 Bacillus species isolated from alkaline fermented foods, five other bacilli and nine non spore-forming bacteria to alkaline pH and ammonia was determined. All grew at pH 7, 8 and 9 in the presence of 930 mmol l-1 NH4 + at pH 7.0, and in the presence of NH3 concentrations up to 5 mmol l-1 at pH 7.0 and 8.0. At higher NH3 concentrations, growth of some of the bacteria was inhibited and at 500 mmol l-1 only B. pasteurii and B. pumilus grew. Bacteria from alkaline food fermentations included strains relatively sensitive to NH3 (inhibited by 50 mmol l-1) and relatively tolerant strains (grew in the presence of 300 mmol l-1) and there was no evidence that they were more tolerant to NH3 than bacteria not associated with these fermentations.     

Effect of some plant growth regulator treatments on apple fruit ripening

The activity of IAA oxidase (IAAox), peroxidases (POD), and polyphenoloxidases (PPO), as affected by different pre-harvest growth regulator treatments (ABA, AVG, NAA, PDJ), was determined in on-tree ripening apples (cv. Golden Delicious) before and during the ethylene climacteric. The production of ethylene was inhibited by AVG and delayed by NAA, whereas ABA and PDJ treatments caused, in the on-tree remaining fruits, a marked fruit drop and a decrease or a slight increase in ethylene levels respectively. While all treatments reduced POD activity, jasmonate increased IAAox and PPO activity. The inhibitory effect of NAA on all enzyme activity seems related to interference with C₂H₂ action or to a reduced sensitivity of the fruit abscission zone tissues to the hormone. The observed high fruit drop induced by ABA treatment made it impossible to detect differences in enzyme activity. AVG-treated fruits showed no substantial effects on IAAox and PPO activity in comparison to the control, a finding that seems to be related to a delay in all senescence processes caused by the very low level of the inhibited ethylene production. In control fruits IAAox activity increased during the initial ripening stages and decreased thereafter, POD activity increased throughout ripening and PPO showed little variation.     

Effect of plant VOCs and light intensity on growth and reproduction performance of an invasive and a native Phytolacca species in China

Invasive plants often pose great threats to the growth of co‐occurring native plant species. Identifying environmental factors that facilitate exotic plant invasion and native species decline are important. In this study, we measured the effects of plant volatile organic compounds (VOCs), light intensity, and their interactions on the growth and reproduction performance of indigenous Phytolacca acinosa, and invasive Phytolacca americana, which has largely replaced the former in China. VOCs of invasive P. americana and low light levels both had negative effects on P. acinosa morphological and reproductive traits (stem length, average leaf number, total number, and length of racemes), and biomass allocation (total biomass, and leaf and flower mass fraction); low light also affected photosynthesis‐related trait (specific leaf area) of P. acinosa. In contrast, VOCs of P. acinosa had no significant effect on P. americana, but low light levels adversely affected its morphological and reproductive traits (stem length, total number, and length of racemes) and biomass allocation (total biomass, stem, and leaf mass fraction). Interactions between plant VOCs and light intensity had no significant effects on P. acinosa or P. americana. Under all experimental treatments, stem length, average leaf area, total number, and length of racemes, Root/Shoot ratio, root and flower mass fraction of P. americana were higher than those of P. acinosa, while average leaf number, specific leaf area, and leaf mass fraction was lower. These results indicated that P. acinosa was sensitive to P. americana VOCs and low light, which might affect the growth of sympatric P. acinosa. P. americana was negatively influenced by low light, but higher plant height and more reproductive organ resource allocation relative to sympatric P. acinosa might contribute to invasion success.     

Short-term effects of litter from 21 woody species on plant growth and root development

Background and aims

Plant litter has an important role in terrestrial ecosystems (Lambers et al. 2008). Our aim was to assess the short-term effect of litter from 21 woody species (deciduous and evergreens) on plant growth and root development.

Methods

We conducted a short-term experiment (10 weeks) under controlled conditions adding litter from 21 woody species to pots with Dactylis glomerata (target species). We determined plant biomass and root development and related these variables to decomposition rate and litter quality.

Results

Litter from two species enhanced plant growth whereas litter of five species inhibited it. Considering all species in the data set, plant growth was associated to litter with high decomposition rate and high litter quality: high Ca and N concentration and low polyphenols concentration. However, excluding from the analyses the two species that increased growth, litter inhibition effect on plant growth was related to the litter-polyphenols concentration. Plants growing with nutrient-richer litter had a lower proportion of fine roots which could be related to a litter mediated increase in soil nutrient.

Conclusions

Enhanced plant growth or, on the contrary, plant growth inhibition could be the result of a positive or, in turn, negative balance between nutrient and polyphenols concentration in litter.     

The effect of light quality on the growth and development of in vitro cultured Doritaenopsis plants

The influence of light quality on growth and development of in vitro grown Doritaenopsis hort. (Orchidaceae) plants was investigated. Growth parameters like leaf and root fresh/dry mass and leaf area were highest with plants grown under red plus blue light emitting diodes (LEDs). Leaf length was greater with the plants grown under red LED. Carbohydrate (starch, sucrose, glucose and fructose) and leaf pigment (chlorophylls and carotenoids) biosynthesis of the plants was significantly increased in plants grown under red plus blue LEDs compared to red or blue LED and fluorescent light treatments. This study suggests that the production of quality Doritaenopsis plants is possible by culturing the plants in vitro under a mixture of blue plus red light sources.     

Effect of fire-derived chemicals on germination and seedling growth in Mediterranean plant species

The promoting effect of smoke-derived chemicals (e.g. karrikinolide and cyanohydrin) on germination in many plants from Mediterranean-type ecosystems such as South Africa and south-western Australia is well documented. However, very little is known about (1) the relative importance of different compounds and their possible interactive effects, (2) their role in enhancing seedling growth in wild plants, and (3) their effect on the germination of plants in the Mediterranean Basin. To fill these gaps in knowledge, we performed experiments to evaluate the effect of smoke water, karrikinolide, mandelonitrile (a cyanohydrin analogue), potassium nitrate and gibberellic acid on the germination and seedling growth of 37 species from the Mediterranean Basin. The results suggest that germination and/or seedling growth of 21 species are enhanced by at least one of the fire-derived chemicals. There were positive correlations between most of the compounds tested in terms of germination response, but synergetic and inhibitory effects were also detected. Stimulation of germination was most prominent in species with annual life cycles. Fire-derived chemicals were more effective in stimulating root growth than shoot growth. In conclusion, we provide novel evidence that the recruitment of different Mediterranean species may be enhanced by different smoke compounds, and that synergetic and inhibitory effects of chemical compounds are important in the germination ecology of plants.     

Under low irradiation,the light regime modifies growth and metabolite production in various species of microalgae

The effects of continuous light exposure (24L:0D) and a 12 h:12 h light/dark regime (12L:12D) were compared on the growth and carotenoid, protein, sugar, lipid, and fatty acid contents in Chlorella vulgaris, Nannochloropsis sp., Isochrysis galbana, and Dunaliella salina cultured in a batchwise facility. These microalgae were grown axenically under a low photon flux density (PFD) of 27 μmol photons m^?2 s^?1. C. vulgaris, Nannochloropsis sp., and I. galbana exhibited the highest cell densities when cultured under 24L:0D, whereas D. salina grew better under the alternating light/dark regime. I. galbana accumulated high levels of proteins, sugars, and lipids and exhibited the highest carotenoid content under 24L:0D. Protein production was enhanced in C. vulgaris under 24L:0D. The highest total lipid content was recorded for D. salina, reaching 74.6 % of total proteins, sugars, and lipids in cells at the stationary phase when grown under 12L:12D. The light/dark regime at low PFD was sufficient to stimulate the accumulation of monounsaturated and polyunsaturated fatty acids in all four algae. Their levels, like those of saturated fatty acids, did not differ significantly under the two light regimes. D. salina was an important source of tetradecenoic acid 14:1(n-5). Nannochloropsis sp. produced a large amount of the essential eicosapentaenoic acid, which reached 20 % of total fatty acids under 12L:12D, while I. galbana exhibited the highest level of docosahexaenoic acid, which reached 21 % under both light regimes. This study demonstrated the feasibility of culturing microalgae under low PFD in order to produce large quantities of valuable metabolites, especially various lipids with neutraceutical value.     

Effect of static magnetic field on growth and sporulation of some plant pathogenic fungi

Growth and sporulation of phytopathogenic microscopic fungi were studied under a static magnetic field. The applied flux densities were 0.1, 0.5, and 1 mT. The magnetic field decreased the growth of colonies by 10% using this flux density region. At 0.1 mT flux density, the deviations are significant, P =.001, while in other cases the deviations generally are not significant. At the same time, the number of the developed conidia of Alternaria alternata and Curvularia inaequalis increased by 68-133%, but the number of Fusarium oxysporum conidia decreased by 79-83%. The deviations are generally significant at the P =.05 level.     

Clonal growth and plant species abundance

Background and Aims

Both regional and local plant abundances are driven by species'' dispersal capacities and their abilities to exploit new habitats and persist there. These processes are affected by clonal growth, which is difficult to evaluate and compare across large numbers of species. This study assessed the influence of clonal reproduction on local and regional abundances of a large set of species and compared the predictive power of morphologically defined traits of clonal growth with data on actual clonal growth from a botanical garden. The role of clonal growth was compared with the effects of seed reproduction, habitat requirements and growth, proxied both by LHS (leaf–height–seed) traits and by actual performance in the botanical garden.

Methods

Morphological parameters of clonal growth, actual clonal reproduction in the garden and LHS traits (leaf-specific area – height – seed mass) were used as predictors of species abundance, both regional (number of species records in the Czech Republic) and local (mean species cover in vegetation records) for 836 perennial herbaceous species. Species differences in habitat requirements were accounted for by classifying the dataset by habitat type and also by using Ellenberg indicator values as covariates.

Key Results

After habitat differences were accounted for, clonal growth parameters explained an important part of variation in species abundance, both at regional and at local levels. At both levels, both greater vegetative growth in cultivation and greater lateral expansion trait values were correlated with higher abundance. Seed reproduction had weaker effects, being positive at the regional level and negative at the local level.

Conclusions

Morphologically defined traits are predictive of species abundance, and it is concluded that simultaneous investigation of several such traits can help develop hypotheses on specific processes (e.g. avoidance of self-competition, support of offspring) potentially underlying clonal growth effects on abundance. Garden performance parameters provide a practical approach to assessing the roles of clonal growth morphological traits (and LHS traits) for large sets of species.     

Right place,right time: Spatiotemporal light regulation of plant growth and development

Recent advances in our understanding of the roles of photoreceptors in light-dependent regulation of plant growth and development have been rapid and significant. Developments have been reported for numerous plant photoreceptor signaling pathways, yet researchers have made the most progress in increasing our comprehension of the roles of phytochrome family members, as well as the intracellular roles of phytochromes and phytochrome-interacting proteins in light-dependent signaling. An understudied, but vitally important, area of phytochrome biology centers on the roles phytochromes play in intercellular and interorgan signaling at the molecular level that results in the coordination of growth responses between distinct tissues and organs. This frontier of research into the spatiotemporal roles of phytochromes, and more generally plant photoreceptors, which is only beginning to be investigated and understood at the molecular genetic level, has a rich history of physiological data.Key words: cryptochrome, photomorphogenesis, photoreception, photoreceptor, phytochrome, spatiotemporal     

Dynamics and attenuation characteristics of periphyton upon artificial substratum under various light conditions and some additional observations on periphyton upon Potamogeton pectinatus L.

The seasonal variation in periphyton dynamics has been studied upon artificial substratum (microscopic glass slides) under various light conditions during the periods May–October 1986 and May–September 1987, in Lake Veluwe. Some additional observations on the periphyton development upon leaves of Potamogeton pectinatus L. have been made simultaneously. Four different light conditions were created in an experimental setup by manipulating the photon flux density through artificial shading.Periphyton upon artificial substratum exhibited a relatively high abundance with a distinct seasonal pattern. Periphyton accrual rates were highest at the beginning of June and in August and September upon slides which were incubated for two weeks. Periphyton mass increased during May and June, decreased or remained about the same during July and subsequently increased until an upper plateau was reached upon slides which were incubated from the beginning of May onwards.Generally, periphyton mass was lower upon slides than upon P. pectinatus. The seasonal variation in periphyton mass was more pronounced upon P. pectinatus leaves than upon the slides.Attenuation by periphyton upon slides ranged from 5 to 65% after two weeks of incubation. Periphyton upon slides which had been incubated for more than two weeks demonstrated an attenuation of more than 85%.Water quality parameters other than photon flux density were probably more important in determining the periphyton dynamics, since only minor differences were observed in periphyton mass between the various light conditions. Chlorophyll-a content was higher with increased shading on various sampling dates.Periphyton, especially older periphyton consisted largely of settled silt and clay particles and to a lesser extent of detrital matter on both substrata. Living epiphytes were only a relatively small fraction.It is concluded that a reduction of resuspension of sediment particles, giving less suspended matter in the water column, will result in lower periphytic mass. Consequently, the quantity of photosynthetically active radiation reaching the submerged macrophytes is expected to increase considerably.