An ‘ecobox’ with a discontinuous temperature gradient and a continuous light intensity gradient

The speed of sustained migration of Dictyostelium discoideum slugs was similar in a temperature gradient and at different light intensities, including a light intensity sufficient to cause significant disorientation of slugs. No change was observed in slug speed in the presence of high levels of Slug Turning Factor (STF), a low molecular weight compound through which phototaxis and thermotaxis are mediated. Thus orientation of D. discoideum slugs is not mediated by a sustained changed in slug speed and we propose that slug movement is not directly coupled to tactic responses. Slug speed depended on the size, age and genotype of slugs as well as the nature of the substratum (charcoal-containing water agar versus water agar).

Download Full-text

The effects of continuous light and light intensity on the reproduction rates of twenty-two species of marine phytoplankton

Journal of Experimental Marine Biology and Ecology ◽

10.1016/0022-0981(81)90045-9 ◽

1981 ◽

Vol 50 (2-3) ◽

pp. 119-132 ◽

Cited By ~ 135

Author(s):

L.E. Brand ◽

R.R.L. Guillard

Keyword(s):

Light Intensity ◽

Continuous Light ◽

Marine Phytoplankton

Download Full-text

THE CONTROL OF GROWTH AND DEVELOPMENT IN RED CLOVER (TRIFOLIUM PRATENSE L.): II. LIGHT, TEMPERATURE, AND THE INFLUENCE OF GROWTH REGULATORS

Canadian Journal of Botany ◽

10.1139/b59-082 ◽

1959 ◽

Vol 37 (5) ◽

pp. 1027-1048 ◽

Cited By ~ 4

Author(s):

Bruce G. Cumming

Keyword(s):

Light Intensity ◽

Growth Regulators ◽

Growth And Development ◽

Trifolium Pratense ◽

Stem Elongation ◽

Indirect Evidence ◽

Continuous Light ◽

Red Clover ◽

Auxin Level ◽

Increased Sensitivity

Morphogenesis of Dollard red clover clones has provided indirect evidence that endogenous auxin level and, or, sensitivity of response of tissues to auxin vary according to light and temperature and as a function of genotype.The amount of growth and development was less in autotetraploid than in diploid plants.Root formation on propagules was influenced by relatively short-term different daylength pretreatments of intact plants; also, by the daylength and light intensity imposed during rooting.Under reduced light intensity extension growth already initiated was increased and this was related to increased "sensitivity" of growth response of stems and petioles to applied auxin.Morphogenetic effects relatively similar to those caused, respectively, by shortening the daylength and by lengthening the daylength resulted from antiauxin (TIBA) as compared with auxin (IAA) treatments.Concentrations of IAA that were primarily stimulatory to growth under shorter daylengths were inhibitory under continuous light. The primary stimulatory effect of IAA was on bud formation under SD but on stem elongation under LD.The relatively similar and additive effects of photoperiod, applied auxin, and cold pretreatment are discussed. It is postulated that in red clover a greater endogenous diffusible auxin level is required for optimum formation of stems and inflorescences than for buds and roots.Manipulation of light and temperature and the use of growth regulators provide added precision in the control of growth and development in red clover.

Download Full-text

LIGHT-STIMULATED LEAF GROWTH ON INTACT AND EXCISED BEAN PLANTS (PHASEOLUS VULGARIS L.) III. EFFECT OF LIGHT INTENSITY

Israel Journal of Plant Sciences ◽

10.1080/07929978.1999.10676778 ◽

1999 ◽

Vol 47 (4) ◽

pp. 231-236

Author(s):

Shimon Lavee ◽

Elizabeth Van Volkenburgh ◽

Robert Cleland E.

Keyword(s):

Light Intensity ◽

Leaf Growth ◽

Energy Requirement ◽

Red Light ◽

Continuous Light ◽

Leaf Expansion ◽

Minimal Amount ◽

Light Intensities ◽

Bean Plants ◽

Effect Of Light

The effect of light intensity on primary bean leaf unfolding and elongation was studied with intact and excised 10-day-old plants grown under red light. Continuous light of 40 μmol; m−2S−1 was enough to induce maximal leaf expansion both on intact and excised bean plants. Lower light intensities had a partial effect. The growth rate during the first 24 h in light was linearly related to light intensity up to 130 μmol; m−2S−1, although this light intensity was already supra-optimal for final leaf size. The minimal amount of light energy needed for full leaf expansion was about 15 mol photons m−2. The mode of light application, level of intensity, and irradiance duration were not critical when the total energy requirement was fulfilled. Under insufficient light applications for full leaf expansion, interrupted irradiance and longer low light intensity application induced leaf elongation more efficiently. Generally, the effect of different white light intensities on primary bean leaf expansion was the same on both intact and excised red-light-grown plants.

Download Full-text

THE EFFECT OF PHOTOPERIOD ON WHITE PINE SEEDLING GROWTH

The Forestry Chronicle ◽

10.5558/tfc37133-2 ◽

1961 ◽

Vol 37 (2) ◽

pp. 133-143 ◽

Cited By ~ 1

Author(s):

D. P. Fowler

Keyword(s):

Light Intensity ◽

Soil Fertility ◽

Root Length ◽

Continuous Light ◽

Stem Diameter ◽

Day Length ◽

Time Data ◽

White Pine ◽

Hypocotyl Length ◽

Light Intensities

White pine seedlings from freshly germinated seed were subjected to different photoperiods and light intensities for a period of nine months. The photoperiods consisted of normal, normal plus eight hours, and continuous day length while the supplementary light intensities were 25-50 foot candles and 200-400 foot candles. Three levels of soil fertility obtained from mixtures of acid sand and white pine humus were also tested.Observations were recorded over the nine month period and at the termination of this time data from the following measurements were obtained: hypocotyl length, top length, root length, stem diameter, and oven-dry weight.Hypocotyl length was found to be independent of soil fertility, whereas both continuous light and light of high intensity caused seedlings to have short hypocotyls.Top length and root length were found to be dependent upon soil fertility as well as upon photoperiod but were independent of light intensity. Continuous light caused the greatest root length whereas eight hours additional light caused the greatest crown length.Stem diameter was found to be dependent upon soil fertility, photoperiod and light intensity. No significant differences in this respect were found between photoperiods consisting of eight hours additional light and continuous light. The greatest stem diameter resulted from high light intensity.Oven-dry weight was found to depend upon soil fertility, photoperiod, and light intensity. The richer the soil, the longer the photoperiod, and the greater the light intensity, the greater was the weight of the seedlings produced.

Download Full-text

Influence of Medium Frequency Light/Dark Cycles on the Cultivation of Auxenochlorella pyrenoidosa

Applied Sciences ◽

10.3390/app10155093 ◽

2020 ◽

Vol 10 (15) ◽

pp. 5093

Author(s):

Zhijie Chen ◽

Bosheng Su

Keyword(s):

Light Intensity ◽

Biomass Production ◽

Cycle Time ◽

Biomass Yield ◽

Continuous Light ◽

Biomass Productivity ◽

Chlorella Pyrenoidosa ◽

Dark Cycle ◽

Medium Frequency ◽

Intermittent Light

Light (wavelength, intensity, and light/dark cycle) have been considered as one of the most important parameters for microalgae cultivation. In this paper, the effect of medium frequency intermittent light on Auxenochlorella pyrenoidosa (formerly Chlorella pyrenoidosa) cultivation was investigated. Three parameters of intermittent light, light intensity, light/dark ratio, and light/dark cycle were employed and the influence of these parameters on the productivity of Auxenochlorella pyrenoidosa was studied. The biomass yield and growth rates were mainly affected by the light fraction and cycle time. Light with 220 μE m−2 s−1 light intensity was determined as the optimal light intensity for biomass production. At the light intensity of 420 μE m−2 s−1, the results indicated that the intermittent light improved the biomass production with larger light/dark ratio compared with the continuous light. At a lower mean light intensity over time, the intermittent light should be more suitable for biomass growth and the decrease in the light/dark ratio (L/D) will lead to a higher biomass productivity. The light/dark cycle time has little influence on the biomass yield.

Download Full-text

Influence of light and calcium on guanosine 5'-triphosphate in isolated frog rod outer segments.

The Journal of General Physiology ◽

10.1085/jgp.74.6.649 ◽

1979 ◽

Vol 74 (6) ◽

pp. 649-669 ◽

Cited By ~ 37

Author(s):

M S Biernbaum ◽

M D Bownds

Keyword(s):

Light Intensity ◽

Calcium Concentration ◽

Control Mechanism ◽

Continuous Light ◽

Ionophore A23187 ◽

Rod Outer Segments ◽

Outer Segments ◽

Induced Changes ◽

Hydrolysis Of ◽

External Calcium

Frog rod outer segments contain approximately 0.25 mol of GTP and 0.25 mol of ATP per mol of rhodopsin 3 min after their isolation from the retina. UTP and CTP are present at 10-fold and 100-fold lower levels, respectively. Concentrations of GTP and ATP decline in parallel over the next 4 min to reach relatively stable levels of 0.1 mol per mol of rhodopsin. Illumination reduces the concentration of endogenous GTP but not ATP. This light-induced decrease in GTP can be as large as 70% and has a half-time of 7 s. GTP is reduced to steady intermediate levels during extended illumination of intermediate intensity, but partially returns to its dark-adapted level after brief illumination. The magnitude of the decrease increases as a linear function of the logarithm of continuous light intensity at levels which bleach between 5 X 10(2) and 5 X 10(6) rhodopsin molecules/outer segment per second. This exceeds the range of intensities over which illumination causes decreases in the cyclic GMP content and permeability of isolated outer segments (Woodruff and Bownds. 1979. J. Gen. Physiol. 73:629-653). Thus, over 4 log units of light intensity, a sensitivity control mechanism functions to make extended illumination less effective in stimulating a GTP decrease. GTP levels in dark-adapted outer segments are sensitive to changes in calcium concentration in the suspending medium. If the external calcium concentration is reduced to 10(-8) M, GTP concentration is lowered to the same level caused by saturating illumination, and the GTP remaining is no longer light-sensitive. Lowering calcium concentration to intermediate levels between 10(-6) and 10(-8) M reduces GTP to stable intermediate levels, and the GTP remaining can be reduced by light. Restoration of millimolar calcium drives synthesis of GTP, but not of ATP, and GTP lability towards illumination is again observed. These calcium-induced changes in GTP are diminished by the addition of the divalent cation ionophore A23187. Lowering or raising magnesium levels does not influence the GTP concentration. These data raise the possibility that light activates either a calcium transport mechanism driven by the hydrolysis of GTP, or some other calcium-sensitive GTPase activity of unknown function. Known light-dependent reactions involving cyclic nucleotide transformations and rhodopsin phosphorylation appear to account for only a small fraction of the light-induced GTP decrease.

Download Full-text