scholarly journals PLANT GROWTH AND THE AERIAL ENVIRONMENT. VII. THE GROWTH OF IMPATIENS PARVIEEORA IN VERY LOW LIGHT INTENSITIES

1965 ◽  
Vol 64 (1) ◽  
pp. 55-64 ◽  
Author(s):  
A. P. HUGHES
Keyword(s):  
Plant Growth ◽  
Low Light ◽  
Light Intensities

Growth kinetics of Marquis wheat. IV. Temperature dependence

1973 ◽  
Vol 51 (4) ◽  
pp. 729-736 ◽  
Author(s):  
F. D. H. Macdowall
Keyword(s):  
Light Intensity ◽  
Plant Growth ◽  
Net Photosynthesis ◽  
Absolute Maximum ◽  
Temperature Optimum ◽  
Differential Growth ◽  
Low Light ◽  
Growth Coefficient ◽  
Light Intensities ◽  
Kinetics Of

Earlier described data from this laboratory were subjected to primary growth analysis. The plants had been grown in constant conditions of light intensity (200 to 2500 ft-c) and temperature (10° to 30 °C) at five different settings each. Multiple temperature optima were revealed and interpreted. The computed maximum plant growth coefficient was highest in value at 25 °C (plant kmL = 0.44 day−1) and secondarily so at 15 °C, but at the experimental light intensities the plant growth coefficient was maximal at 15 °C. The higher temperature optimum was characteristic of roots and "stems" (stem plus leaf sheaths) whose growth coefficients displayed a prominent peak at 25 °C (root kmL ~ 0.8 day−1, "stem" kmL = 0.4 day−1). This optimum was shifted downward with decreasing light intensity until temperature insensitivity was attained at low light intensity. The low-temperature optimum at 15 °C was principally displayed by leaf blades (lamina kmL = 0.47 day−1) whose computed maximum growth coefficient also showed a secondary maximum at 25°, but the 15 °C peak was the only one evident at low light intensities. It was tentatively concluded that the 25 °C temperature optimum was that of net translocation, and that the 15 °C temperature optimum was that of net photosynthesis in which photosynthesis was primarily balanced by photorespiration in wheat. The differential growth of the organs represented their relative sink strengths for attracting growth substrate, as dependent on light intensity and temperature. The availability of photosynthate was considered to be the dominating factor in the kinetics of growth free from inorganic limitations. When there was very little photosynthate the tissues benefited from translocation on a "first come first serve" basis. The high values of kmL pushed the absolute maximum plant growth coefficient, kM, of Marquis wheat toward 0.5 or 50% per day, and the basis of the advantage over previous approximations must be elucidated by further experiments. The computed relative efficiency of the use of photosynthate for growth was temperature dependent, but its value at optimum temperature was similar to previous estimates.

A laboratory study of vertical migration

1955 ◽  
Vol 144 (916) ◽  
pp. 329-354 ◽  
Keyword(s):  
Light Intensity ◽  
Vertical Migration ◽  
Time Course ◽  
Tap Water ◽  
Low Light ◽  
Overhead Light ◽  
Light Intensities ◽  
Orientation Response ◽  
Reduced Light ◽  
Characteristic Maximum

In a tank filled with a suspension of indian ink in tap water, a population of Daphnia magna will undergo a complete cycle of vertical migration when an overhead light source is cycli­cally varied in intensity. A ‘dawn rise’ to the surface at low intensity is followed by the descent of the animals to a characteristic maximum depth. The animals rise to the surface again as the light decreases, and finally show a typical midnight sinking. The light intensities at the level of the animals in this experiment are of the same order as those which have been reported in field observations; the time course of the movement also repeats the natural conditions in the field. The process is independent of the duration of the cycle and is related only to the variation in overhead light intensity. At low light intensity the movement of the animal is determined solely by positive photo-kinesis; the dawn rise is a manifestation of this, and is independent of the direction of the light. At high light intensities there is an orientation response which is superimposed upon an alternating positive (photokinetic) phase and a negative phase during which movement is inhibited. The fully oriented animal shows a special type of positive and negative phototaxis, moving towards the light at reduced light intensities and away from it when the light intensity is increased. In this condition it follows a zone of optimum light intensity with some exactness. Experiments show that an animal in this fully oriented condition will respond to the slow changes of intensity characteristic of the diurnal cycle, while being little affected by tran­sient changes of considerable magnitude.

COMBINATION AND DISPROPORTIONATION OF ETHYL RADICALS: INFLUENCE OF THE REACTION H+C2H5 = C2H6

1955 ◽  
Vol 33 (5) ◽  
pp. 821-829 ◽  
Author(s):  
Moyra J. Smith ◽  
Patricia M. Beatty ◽  
J. A. Pinder ◽  
D. J. Le Roy
Keyword(s):  
Light Intensity ◽  
Excellent Agreement ◽  
Mercury Concentration ◽  
Rate Constants ◽  
Room Temperature ◽  
Low Light ◽  
Ethylene Concentration ◽  
Light Intensities ◽  
Ethyl Radicals ◽  
Hydrogenation Of Ethylene

The mercury (3P1) photosensitized hydrogenation of ethylene has been studied at room temperature as a function of ethylene concentration, mercury concentration, and light intensity. In addition to combination and disproportionation, ethyl radicals have been shown to take part in the reaction[Formula: see text]The conditions favoring this reaction have been established and anomalous values previously found for the ratio of ethane to butane have been explained. The value obtained for the ratio of the rate constants for the disproportionation and combination of ethyl radicals, 0.15 ±.01, is in excellent agreement with the values obtained by other methods. Hexane formation is of some importance at low light intensities and high ethylene concentrations, and is adequately accounted for by the reactions[Formula: see text]

scholarly journals THE EFFECTS OF ILLUMINATION ON THE EARLY DEVELOPMENT OF AMPHIBIANS (AMPHIBIA: ANURA AND CAUDATA)

2018 ◽  
Vol 15 (30) ◽  
pp. 152-159
Author(s):  
A. B. RUCHIN
Keyword(s):  
Survival Rate ◽  
Early Development ◽  
Rana Arvalis ◽  
Low Light ◽  
Amphibian Species ◽  
Triturus Cristatus ◽  
Lissotriton Vulgaris ◽  
Light Intensities ◽  
Tailless Amphibians

The effects of illumination on the early development of four amphibian species — Lissotriton vulgaris (Linnaeus, 1758), Triturus cristatus (Laurenti, 1768), Rana arvalis (Nilsson, 1842), and R. temporaria (Linnaeus, 1758) — have been studied. In general, the rate of their early development is rather independent of illumination. The eggs of tailless amphibians develop almost similarly under any illumination conditions, whereas the eggs of tailed amphibians better develop at an illumination of 700 lx. Illumination mainly influences the survival rate of embryos and prolarvae, which increases at low light intensities and decreases in the dark. Possible mechanisms and causes underlying the observed facts are discussed.

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