Short Light Periods Research Articles

SEASONAL PRODUCTIVITY OF TWO RED ALGAE IN A CENTRAL CALIFORNIA KELP FOREST1

ABSTRACTThe in situ productivity of Botryocladia pseudodichotoma (Farl.) Kyl. and Rhodymenia californica var. californica Kyl., two common understory macrophytes in Macrocystis pyrifera (L.) C. Ag. forests, was determined once per month for one year. Gross productivity for B. pseudodichotoma was highest in October (1.23 mgC · g dry wt.−1· h−1), but rates were generally greater in spring and lower in summer. Respiration was variable throughout the year, especially in proportion to gross productivity. Gross productivity for R. californica var. californica was also highest in October (4.62 mgC · g dry wt.−1· h−1), and lowest in summer. Respiration was highly variable throughout the year. Deep (11 m) populations o/B. pseudodichotoma had 50% higher productivity than shallow (3 m) populations when incubated in shallow water, and 45% higher productivity when incubated in deep water. Populations of B. pseudodichotoma growing in shade at 3 m had 77% higher productivity than populations growing in sun at the same depth when incubated in a sun exposed location at 3 m. Respiration of the shade‐adapted plants was only one‐half that of the sun‐adapted plants. In comparison with similar studies in other sub‐tidal communities, net productivity of these two understory red algae is somewhat lower. Lack of strong seasonal productivity patterns and the highly variable underwater light regime suggests that understory algae may be adapted for rapid growth during short periods of high light, regardless of the time of year.

The existence of a critical period for the abscission and a non-critical period for blasting of flower-buds of Lilium ‘Enchantment’; influence of light and ethylene

Flower-bud blasting and abscission, 2 dissimilar phenomena occurring in buds of Lilium ‘Enchantment’, can both be evoked by darkness or ethylene (C 2H 4). Flower-bud abscission is influenced more strongly than bud blasting by short light periods and C 2H 4. Flower-bud blasting can occur through out inflorescence development, abscission only during a critical stage of development of the flower-buds, which proved to coincide with a peak in the endogenous production of C 2H 4 by the buds and with the end of the meiotic phase of the stamens. Both C 2H 4 production by the buds and the occurrence of flower-bud abscission were influenced by the length of time the bulbs had been stored before planting.

Modulation of gonadal activity by timed injections of melatonin in pinealectomized or intact ferrets kept under two photoperiods.

These experiments investigated the way that the effects of melatonin on gonadal activity of ferrets depended upon either reproductive status or environmental lighting conditions. Melatonin (1 mg/day) injected once daily 8 h into the photoperiod prevented the retiming of oestrus by long photoperiods; oestrus occurred in animals treated in this way at the same time as in controls kept under short non-stimulatory photoperiods of 8 h light: 16 h darkness (8L : 16D). This suggests that the 'intrinsic' timing mechanism was not altered by melatonin. Melatonin injected daily into oestrous ferrets terminated oestrus prematurely when the injection was given either 8 or 14 h after the onset of the photoperiod in animals kept under either long (14L : 10D) or short (8L : 16D) photoperiods, though injections given 14 h after onset were more potent in long (but not short) light periods. Melatonin was equally effective in driving pinealectomized ferrets out of oestrus as it was in intact animals. Melatonin could also induce as well as terminate oestrus in ferrets, but only if injections were discontinued. Thus, shifting the time of two daily injections from 8 and 11 h after 'lights on' to 14 and 17 h was ineffective, but withdrawal of melatonin from anoestrous ferrets (pinealectomized or intact) reliably induced oestrus 4–6 weeks later, irrespective of the lighting conditions. Withdrawal of oil injections had no effect. These experiments suggest that melatonin acts on the neural mechanisms resetting the timing of oestrus, rather than by a direct 'anti-gonadotrophic' effect. Furthermore, the effect of changes in duration of photoperiod could not be replicated by simply changing the time of melatonin injections to correspond with the presumed night-time surge of endogenous melatonin. Some of the effects of melatonin on retiming oestrus can only be expressed in the absence of melatonin itself.

INFLUENCE OF PHOTOPERIOD ON SURVIVAL AND GROWTH OF LARVAL AMERICAN LOBSTERS (Homarus americanus)

AbstractThirty thousand American lobsters were hatched, stocked at a density of 2,000 per 40‐liter planktonkriesel, and exposed to one of three photo‐periods (LD 01:23, LD 12:12, LD 23:01) at constant 20°C. Five replicates were completed from March through May. The shortest photoperiods produced the most rapid development and the best survival to Fourth Stage. The longest daily light period produced the largest mean size and greatest size range. At all photoperiods the first larvae to reach Fourth Stage were the largest, and mean size decreased thereafter. Short daily light periods appear to be the most advantageous for larval culture under these conditions because, in addition to producing the best development and survival rates, short light periods reduce algal growth and tank maintenance requirements.

Seasonal changes in metabolic capacity and norepinephrine thermogenesis in the alaskan red-backed vole: Environmental cues and annual differences

1. 1. Wild red-backed voles ( Clethrionomys rutilus) were tested for maximum metabolic rate ( M max) and for metabolic response to norepinephrine ( M NE ) in September, November and January. During the same period, voles born and raised in the laboratory were acclimated (for 3.5 months) in the following groups: (1) +20 C and 24 hr light daily (LD 24:0): (2) +20 C and LD 4:20: (3) gradual change from + 5 C and LD 14:10 to −5 C and LD 4:20; (4) gradual change from +5 C to −5 C and continuous LD 4:20, and tested for M max. 2. 2. During acclimatization of wild voles from September to January M max increased 42% to 23.05 ± 1.19ml O 2·g −1 · hr −1 and M NE increased 59% to 14.12 ± 0.86 ml O 2·g −1·hr −1. Peak winter M max and M NE in these wild voles were lower than found in a previous winter. 3. 3. In voles acclimated to +20 C and either long or short daily light period M max remained unchanged. In voles acclimated to increasing cold and decreasing or short light period M max increased 39% to 20.0 ml O 2·g −1·hr −1. 4. 4. The results indicate that the magnitude of seasonal change of M max and M NE may vary from year to year and suggest that cold is essential to stimulate these seasonal changes in red-backed voles.

Photocontrol of spore germination in the fern Thelypteris kunthii

The light requirement for germination in spores of the fern Thelypteris kunthii (Desv.) Morton was fully satisfied by a long period of continuous red light or partially by intermittent, short periods of red light. Red light‐potentiated spore germination was inhibited by brief far‐red light irradiation, indicating phytochrome involvement. Repeated exposure of spores to prolonged red and short far‐red irradiations, or exposure of red‐potentiated spores to far‐red light after an extended period in darkness, led to their escape from inhibition of germination by far‐red light. Prolonged irradiation of spores with blue light before or after red light treatment partially antagonized the effect of red light.

Effect of photoperiod and cold acclimation on survival of mice in cold

Male albino mice (Swiss-Webster) were raised at 5 °C under short (8L:16D) and long (16L:8D) light periods. All mice were housed in groups of three to five individuals in plastic mouse cages (16 × 12 × 28 cm) until 42 days of age with food and water ad libitum and cold exposed to −40 °C between 10:00 am and 4:00 pm to determine survival time or time until loss of righting response occurred (CT min). Under short photo-periods, survival time was 49.3 ± 4.4 min and under long photoperiods it was 38.7 ± 1.9 min ( P < 0.05). A second group of mice was maintained from birth at thermoneutral temperature (22 °C) under constant darkness, short day lengths (4L:20D), or constant light in the same fashion as mentioned above. When exposed to −20 °C survival time was found to be 80.0 ± 5.0 min for the animals kept in constant darkness, 61.1 ± 2.3 min for animals raised in short photo-periods (4L:20D) ( P < 0.01), and 52.4 ± 2.3 min for mice raised in constant light ( P < 0.05). After 30 min mean rectal temperature was 32.1 ± 0.47 °C for constant-darkness animals, 30.5 ± 0.43 °C for short-day animals ( P < 0.02), and 28.5 ± 0.74 °C for animals raised in constant light ( P < 0.05). After 60 min mean rectal temperatures for constant-dark, 4L:20D, and constant-light animals were compared and body temperature was found to be 23.7 ± 1.6, 17.3 ± 1.5 ( P < 0.01), and 12.8 ± 0.87 °C ( P < 0.05), respectively. From these data, it is obvious that photoperiod influences cold resistance at both cold and thermoneutral acclimation temperatures although when considered individually, cold acclimation enhances cold survival to a greater degree than does reduced light exposure.

Effects of Variations in Daylength and Temperature on Net Rates of Photosynthesis, Dark Respiration, and Excretion by Isochrysis galbana Parke

The effects of variable daylength and temperature on net rates of photosynthesis, dark respiration, and excretion of a unicellular marine haptophyte, Isochrysis galbana Parke, were examined and related to division rates. Six combinations of daylength (18:6, 12:12, 6:18 light:dark, LD) and temperature (20, 25 C) were used. Daily rates of net photosynthesis were closely correlated to division rates, suggesting a direct relationship, and were maximal when cells were grown at 12:12 LD at both temperatures and 18:6 LD at 20 C. A daylength of 6 hours decreased daily rates by decreasing the time for carbon uptake. Further, cells grown with this daylength had maximal chlorophyll a contents, suggesting a physiological adaptation by photosynthetic units to short light periods. A photoperiod of 18:6 LD at 25 C decreased daily rates of net photosynthesis by reducing the hourly rate of net photosynthesis via an unidentified mechanism. The importance of rates of net dark respiration in controlling daily net photosynthesis was small, with carbon lost during dark periods varying between 4 and 14% of that gained during light periods. Also, the influence of net excretion was small, varying between 1.0 and 5.5% of daily net photosynthesis.

‘Paradoxical Driving’ of Walking Activity in Locusts

ABSTRACT Gregarious fifth-instar larvae of Locusta migratoria migratorioides were placed singly on a counterbalanced, recording treadmill providing precise measurements of (i) walking bout length, (ii) non-walking bout length, (iii) walking speed and (iv) distance walked, over periods of hours. Under constant conditions in light the walking activity was often inter-rupted but gradually built up to a high intensity which was then sustained for 1−2 h before finally declining; there were orderly relations between the measured behavioural components. In continuous darkness walking activity was less interrupted but less intense and quickly declined; there were less orderly relations between the components. Under alternating 10 min periods of light and darkness the relations between the behavioural components were again more orderly in the light than the dark. However, walking activity was sharply depressed in these short light periods but was promptly resumed in each subsequent dark period and grew stronger as the fight–dark alternation continued. These diverse and at first sight paradoxical results are all consistent with the principle of post-inhibitory rebound (‘antagonistic induction’). This type of behavioural after-effect, acting on different time scales, is exemplified by the surge of walking observed in the dark on the release of the experimentally applied inhibition of walking by light, as well as by the build-up and sustained walking in continuous light (‘paradoxical driving’).

Enhancement of paradoxical sleep by short light periods in the golden hamster

In hamsters exposed to short light-dark (LD) cycles, paradoxical sleep (PS) predominated during the light periods, whereas slow wave sleep (SWS) was not affected by the lighting conditions. Thus a selective effect of lighting conditions on paradoxical sleep which so far has been documented only for the rat, occurs in a further rodent species.

Persistency of egg production of common coturnix is affected by early light regimens

The quantity and quality of light during the growing period was studied in 3 experiments to determine the effect on subsequent egg production of Coturnix coturnix japonica . Females were individually caged and kept in climatic chambers. Either short days (LD 8:16), or long days (LD 16:8) were given from hatching until 10 weeks of age. Later the birds were exposed to short and long light periods of 6 weeks duration alternately, until 34 or 36 weeks of age. Parameters measured were age at first egg, total egg production, and rate of lay under LD 8:16. Although no treatment resulted in all of the birds of a group being persistent layers, rearing on short-days, blinding and fluorescent light each contributed to persistency in adults. Early light regimens in coturnix are important in establishing persistency of egg production performances as adults.

Growth, flowering and runnering of strawberry after daylength extension with tungsten and fluorescent lighting

Fluorescent lighting, with low emission in the far red spectral region, and red light from filtered fluorescent lamps inhibited flower formation, promoted runnering, increased laminae sizes and gave moderate increase in petiole length when given at low intensity from midnight to dawn, but not (or very much less so) when given from dusk to midnight, following a short main light period. Unfiltered incandescent lighting gave similar plant responses whether given from dusk to midnight or from midnight to dawn, and always gave much longer petioles than did unfiltered fluorescent lighting. Fluorescent lighting during the second part of the night, because of its smaller effect on petiole length, gave a more compact type of plant than incandescent lighting, whilst still promoting runnering and inhibiting flower initiation.

Melanin deposition in the hyphae of a species of Phomopsis.

Hyaline hyphae of Phomopsis become pigmented when exposed to short periods of light. Pigment was deposited in the form of melanin granules both within the cell wall and within mucilaginous excrescences that were developed irregularly over the hyphal surface. Analysis of the pigment showed it to have properties similar to that of "Dopa" melanin and to pigments previously isolated from fungal cell walls. Lysis of both hyaline and pigmented hyphal walls by means of lytic enzymes was minimal. It is suggested that the major role of melanin in this fungus is the protection of cellular organelles from harmful ionizing radiations.

Diapause in the phytoseiid mite, Neoseiulus (T.) fallacis

Female Neoseiulus (Typhlodromus) fallacis exhibited an adult reproductive diapause. Induction of diapause was dependent upon both photoperiod and temperature. The critical photoperiod at 15·6°C occurred between 11·75 and 12·0 hr light/day for a strain collected at Brunswick, New Jersey and reared in the laboratory under long light periods for ca. 2 years prior to testing. When the F 1 progeny of a strain collected at Wilkesboro, North Carolina was reared under a 11·75 hr light/day, 15·6°C régime along with the New Brunswick strain the photoperiodic response of the two strains was similar. Further studies with the New Jersey strain showed that the incidence of diapause at a short light period was averted entirely at 26·7°C. Little difference was shown in the developmental rates of mites under a short and long light period. Diapause duration was reduced at 15·6°C by exposure to a long light period. When held constantly at a short light period, an increase in temperature from 21·1 to 26·7°C reduced the duration of diapause. This reduction may reflect an effect of temperature on diapause termination as well as post-diapause development. Although diapause termination was influenced by both photoperiod and temperature, it occurred eventually under all experimental conditions, including those initiating diapause. There was no significant parental effect on the incidence of diapause in F 1 and F 2 progeny of adults reared under either a short or long light period. However, parental preconditioning did alter diapause intensity. When parents and offspring experienced a short light period, the resulting diapause duration was significantly longer than when parents experienced a long light period and the offspring experienced a short light period.

ECOLOGICAL FACTORS OF THE NORTHERN REGION AND HIGHLAND ZONE INFLUENCE ON YIELD FORMATION OF EARLY MATURING POTATOES VARIETIES

The aim of the research was to study the yield indicators of 36 early maturing potato varieties in the northern region (Arkhangelsk region) and the highlands of the North Caucasus (an altitude of 2500 m above sea level). The experimental work was carried out in 2015–2020. The characteristic features of the northern region are the light period (up to 21 hours in June – July), &#x0D; which contributes to an increase in the duration of the interphase periods of plant development, in the highlands – a short light period (14 hours), a sharp temperature drop in the daytime (15.1 – 25.8 °С) and night (7.8 – 15.2 ° C) hours, intense solar insolation. The peat-podzolic-gley soils of the northern region were characterized by a lower humus content (3.7%) and a high content of potassium (240 – 267 mg / kg) in comparison with the mountain meadow subalpine soils of the highlands (6.7% and 102 – 120 mg / kg, respectively). Potatoes were planted in early June and harvested in early September, 25 tubers of each variety according to the scheme 0.7×0.3 m, the area of the registration plot was 5.25 m². Using the methods of cluster and discriminant analyzes, the varieties were grouped and the most productive genotypes were identified by a set of indicators: the multiplication factor, plant productivity and the average tuber weight. In the northern region, the best varieties were Gulliver, Udacha, Krepysh, Solist, Leader, Darenka, Breeze, Red Lady, Riviera and Vineta, which formed from 8.1 to 11.4 tubers per plant with an average weight of 37.0 – 67.9 g and productivity 400 – 633 g. In the highlands, the most productive varieties were Gulliver, Yakutyanka, Yugana, Darenka, Leader, Breeze, Red Lady, Impala and Rosara, which formed from 11.8 to 19.8 tubers per plant with an average weight of 56.5 – 70, 6 g and productivity 830 – 1140 g.

Photoperiod and temperature as factors controlling the diapause of the sunflower moth, Homoeosoma electellum

Induction of larval diapause of the sunflower moth, Homoeosoma electellum (Hulst), was found to be dependent upon both temperature and photoperiod. Diapause was induced more readily at 21 than at 27°C, but only in photoperiods having 11 hr or less of light/day. Greatest percentages of diapausing larvae occurred among larvae subjected to 10 hr or less light time/day at 21°C, regardless of the photoperiodic exposure of the parents and eggs. The incidence of diapause was extremely low when larvae were subjected to periodic reductions in either temperature or day-length. A concomitant reduction of temperature and day-length increased the percentage of diapausing larvae to some degree, but this was small compared to percentages obtained among larvae maintained in days of 11 hr or less at 21°C. Diapause termination may be influenced by temperature and photoperiod. Diapause termination required less time at 27° than 21°C. Also, larvae which were subjected to photoperiods having 11 hr or more light/day resumed development more rapidly than larvae held in shorter light periods.

Changes in Succinyl CoA Synthetase Activity in Etiolated Bean Leaves Caused by Illumination

The illumination of etiolated bean leaves (Phaseolus vulgaris) causes an increase in the activity of succinyl coenzyme A synthetase. Continuous white light or short periods of red or blue light followed by darkness will induce an increase with the highest activity at about 6 hr after the onset of illumination. Thereafter the activity decreases so that at 12 hr it is the same as the initial dark activity. Treatment with cycloheximide before illumination prevents the increase in activity. A number of other enzymes have been studied in an attempt to determine the significance of the transient nature of the changes in succinyl CoA synthetase activity.

Light-dependent hydrogen evolution by Scenedesmus

The effect of glucose and the uncoupler Cl-CCP upon hydrogen production was studied in adapted cells of Scenedesmus obliquus D3. Cl-CCP at 10(-5)M concentration completely inhibited the evolution of H2 in the dark and increased the apparent rate of H2 evolution in the light. At 10(-5)M Cl-CCP, photosynthesis and photoreduction by anaerobically adapted algae were only temporarily inhibited; O2 evolution reappeared after approximately 1 hr of illumination if CO2 was present. Increasing the Cl-CCP concentration to 5 x 10(-5)M led to a maximum rate of photohydrogen production and fully inhibited H2 evolution, photoreduction and dark H2 evolution. H2 evolution was accompanied by a release of varying amounts of CO2 in the light, as well as in the dark. Dark CO2 production was stimulated by Cl-CCP. H2 evolution in the light was stimulated by adding glucose to autotrophically grown cells or by growing the cells heterotrophically with glucose; starvation had an opposite effect. Adapted cells released (14)CO2 from the 3 and/or 4 position of specifically labeled glucose, indicating that degradation occurred via the Embden-Meyerhof pathway. The amount of H2 released by autotrophically grown cells was the same either with continuous illumination or with short periods of light, followed by darkness. Scenedesmus mutant No. 11, which is unable to evolve O2 was not inhibited in its capacity to evolve H2 in the light. These data indicate that the evolution of H2 in the light by adapted Scenedesmus depends upon the degradation of organic material and does not require the production of free O2 by photosystem II.

Versuche zur Phasenverschiebung endogener Rhythmen: Blütenblattbewegung von Kalanchoe blossfeldiana

Studies on phase shifts of endogenous rhythms: The petal movement of Kalanchoe blossfeldiana. It takes up to 5 cycles until the phase shifts of the diurnal petal movement of Kalanchoe by short light periods are constant. Effects of a second light break are explainable neither by the suggestion of BUNNING and ZIMMER that the behaviour of the oscillator is immediately reflected in the course of the curves of the movement nor by that of PITTENDRIGH that an A-oscillator is immediately phase shifted by light, with several cycles being required for phase control of the B-oscillator. We propose to explain the results, especially those shown in curve 5 of fig. 2, in terms of a coaction of on- and off-rhythms.

Length of Light Period for Maximum Broiler Weight

NUMEROUS studies have been conducted concerning the length of light period necessary for maximum growth in broilers. Clegg and Sanford (1951) found that body weight was increased when broilers were exposed to short periods of intermittent light and darkness compared to when exposed to longer periods. Moore (1957) reported that broilers up to 4 weeks of age grew faster when exposed to continuous light compared to shorter periods. Shutze et al. (1960) indicated that the ability of the chick to grow more rapidly when subjected to continuous light was consistent in all their experiments. Beane et al. (1963) noted a growth advantage in broiler stock subjected to continuous light when compared to those exposed to shorter light regimes. Cherry and Barwick (1962) with small pens where the chicks were given a one week preliminary training found that the subsequent pattern of lighting had no effect on body weight at broiler …