scholarly journals Photopreiodic and Temperature Control of Flower Initiation in the Late Pea Cultivar Greenfeast

1968 ◽  
Vol 21 (4) ◽  
pp. 609 ◽  
Author(s):  
DM Paton
Keyword(s):  
Temperature Control ◽  
Low Temperatures ◽  
Continuous Light ◽  
Flower Initiation ◽  
Temperature Responses

The number of green foliage leaves at initiation is related to a quantitative leaf requirement for flowering in the late pea cultivar Greenfeast. When grown in various temperature and photoperiod regimes the leaf requirement is least in continuous light and low temperatures. The additive nature of the photoperiodic and temperature responses suggests that photoperiod and temperature probably act independently.

Flowering in Pisum: Does Gibberellic Acid Directly Influence the Flowering Process?

1977 ◽  
Vol 4 (4) ◽  
pp. 479 ◽  
Author(s):  
JB Reid ◽  
PJ Dalton ◽  
IC Murfet
Keyword(s):  
Gibberellic Acid ◽  
Direct Effect ◽  
Continuous Light ◽  
Flower Initiation ◽  
Small Delay ◽  
Effect Of Age ◽  
Flowering Process

Gibberellic acid is shown to cause a substantial delay in the flowering node, time of flower initiation and leaf requirement for flowering in the late pea cultivar line 24, grown under an 8-h photoperiod. In continuous light, gibberellic acid caused only a small delay in the flowering node and leaf require- ment. As the plants became older the effect of applied gibberellic acid decreased. This was not due to initiation having already occurred or to the gibberellic acid not penetrating the plant. It is suggested that gibberellic acid has a direct effect on the flowering process in line 24 plants grown under an 8-h photoperiod and that it may act by reducing the effect of age on the gene Sn.

Delayed Emission from Green Algae “Chlorella pyrenoidosa” at Various Temperatures

1977 ◽  
Vol 32 (1) ◽  
pp. 88-95 ◽  
Author(s):  
F. Drissler ◽  
W. Hägele ◽  
D. Schmid ◽  
H. C. Wolf
Keyword(s):  
Linear Dependence ◽  
Low Temperatures ◽  
Continuous Light ◽  
Chlorella Pyrenoidosa ◽  
Excitation Intensity ◽  
Whole Cells ◽  
Light Pulses ◽  
Light Production ◽  
Quantum Mechanism ◽  
Prompt Emission

Abstract Comparative studies of prompt and delayed emission from whole cells of Chlorella pyrenoidosa are presented for various temperatures between 4.2 and 300 K. Prompt emission was excited with continuous light (wavelengths between 420 and 670 nm). Light pulses (duration 6.9 msec) have been used to excite delayed emission. Their wavelength had to be shorter than 600 nm for investigations at 77 K.A linear dependence of the delayed emission intensity on the excitation intensity at low temperatures (4.2 and 77 K) favours a one-quantum-mechanism to be responsible for delayed light production.The response of the total intensities on temperature shows a similar behaviour for both types of emission up to 200 K. Above 200 K they behave quite differently.

Equipment for Preparing Electropolished TEM Specimens at Controlled and Low Temperatures

1987 ◽  
Vol 115 ◽  
Author(s):  
Vjekoslav Franetovic
Keyword(s):  
Stainless Steel ◽  
Temperature Control ◽  
Low Temperatures ◽  
Control Unit ◽  
Cooling Device ◽  
Dry Ice ◽  
Temperature Control Unit ◽  
Copper Coil ◽  
Heat Buildup

ABSTRACTA cooling device for use with the Fishione twin-jet electropolisher Model 110 has been developed for electropolishing TEM specimens at controlled and low temperatures necessary for some materials. This consists of an explosion-proof pump circulating methanol through a specially designed stainless steel bath, and a copper coil immersed in a mixture of methanol and dry ice in a dewar. A thermocouple with a temperature control unit provides precise temperature control.With this device, electropolishing can be conducted at temperatures as low as −55°C. This allows electropolishing of certain materials which cannot be polished with conventional equipment. The precisely controlled temperature also improves the performance of the electropolishing equipment at all temperatures because the success of electropolishing depends on maintaining constant conditions during the process. The unit further allows the use of aggressive electrolytes and preparation of solutions which could otherwise become hazardous due to heat buildup during electropolishing or preparation.

Betacyanin accumulation, chlorophyll content, and flower initiation in Chenopodium rubrum as related to endogenous rhythmicity and phytochrome action

1970 ◽  
Vol 48 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Edgar Wagner ◽  
Bruce G. Cumming
Keyword(s):  
Gibberellic Acid ◽  
Chlorophyll Content ◽  
Dark Period ◽  
Continuous Light ◽  
High Energy ◽  
Hypocotyl Elongation ◽  
Chenopodium Rubrum ◽  
Physiological Status ◽  
Flower Initiation ◽  
Endogenous Rhythmicity

In Chenopodium rubrum seedlings (ecotypes 50°10′ N and 49°58′ N) betacyanin synthesis is light dependent (completely dark-grown seedlings contain no betacyanin) and is under phytochrome control via both the low energy and the high-energy (HER) reactions of photomorphogenesis. In continuous light, accumulation of betacyanin is linear with time. However, when a single dark period interrupts continuous light, the amount of both betacyanin and chlorophyll synthesized during a given period of time after the dark interruption shows a rhythm reflecting differences in the rate of, and (or) the capacity for, pigment accumulation that are dependent on the duration of the dark period. The rhythm in chlorophyll content was higher in frequency than circadian, with a period of about 15 h, while rhythmicity in the rate of synthesis of betacyanin was circadian. These results suggest that there is endogenous rhythmicity in the metabolic state of the system in darkness. The imposition of light after darkness apparently stabilizes the specific physiological status attained at that respective time of darkness and thus determines the metabolic activity of the seedlings.When glucose was supplied throughout darkness interrupting continuous light, the phasing of the rhythm of betacyanin synthesis was positively correlated with the rhythm of flower initiation, but this was not so when phenylalanine was supplied during darkness. In contrast, when glucose was supplied for a varied length of time in continuous light, there was rhythmicity in the rate of betacyanin accumulation, with a periodicity of about 15 h, that was dependent on the duration of the glucose application.When seedlings were supplied with 10−6 M gibberellic acid during darkness there was a rhythm in the amount of hypocotyl elongation that depended on the length of a single dark period interrupting continuous light. Other evidence has suggested that there is a rhythm in the stability of the cellular membranes; this rhythm was assayed (non-physiologically) by the time of onset of betacyanin leakage from seedlings into an extraction medium and was apparent only after application of 10−10 M gibberellic acid. The rhythms in hypocotyl elongation and in membrane stability that were revealed after the application of gibberellic acid suggest that there may be a rhythm in the rate of differentiation and (or) development of the system.It is postulated that endogenous rhythmicity is due to the spatial separation of energy production and use in different cell particulates, with phytochrome acting as a membrane operator.

Flower initiation in Trifolium subterraneum L. II. Limitations by vernalization, low temperatures, and photoperiod, in the field at Canberra

1959 ◽  
Vol 10 (1) ◽  
pp. 17 ◽  
Author(s):  
FHW Morley ◽  
LT Evans
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Day Length ◽  
Flower Initiation ◽  
Inhibitory Effects ◽  
Low Field ◽  
The Times ◽  
Short Days

At various times throughout the winter, autumn-sown plants of five strains of subterranean clover were removed from the field to a series of day length and temperature treatments. The times to inflorescence initiation in all treatments were determined by dissection. As vernalization proceeded the requirement of all strains for long days was progressively reduced until, by midwinter, several strains had become virtually independent of day length. Similarly, with the progress of vernalization the inhibitory effects of high temperatures during short days became progressively less marked. Whereas exposure to long days at high temperatures greatly accelerated inflorescence initiation in all strains, long days at low field temperatures had little effect. Evidence is presented which suggests that the limiting effect of very low temperatures on initiation is due not only to retardation of the rate of inflorescence primordium formation (realization), but also to limitation of an inductive process other than vernalization and dark period inhibition. The flowering behaviour of the various strains is discussed in terms of their responses to the partial processes leading to inflorescence initiation, and the interrelationships of these processes are considered.

Flower initiation in pasture legumes. IV. Flower initiation in Trifolium pratense L.

1964 ◽  
Vol 15 (1) ◽  
pp. 21 ◽  
Author(s):  
Y Aitiken
Keyword(s):  
Trifolium Pratense ◽  
Continuous Light ◽  
Red Clover ◽  
Flower Initiation ◽  
Pasture Legumes ◽  
Flowering Season ◽  
Short Period ◽  
Trifolium Pratense L ◽  
Long Photoperiod ◽  
Early Strain

An early strain (Cowgrass) and a late-maturing strain (Montgomery) of red clover (Trifolium pratense L.) were grown at Melbourne, lat. 38°S., to study flower initiation and the relationship between initiation and flowering, because of the importance of flowering to the use of the species as a source of hay. The terminal inflorescence in red clover arises from a lateral bulge at the shoot apex, and the main shoot of the plant is strongly vegetative, only becoming reproductive in a proportion of plants under long photoperiod, particularly continuous light. In both strains, whether first-year or older plants, flower initiation and therefore flowering were confined to a short period of the year, the early strain having the longer period. Sowing the two strains at intervals through the year in the field, under natural and long photoperiods, showed the importance of both photoperiod and temperature to initiation. Both strains were hastened by a long photoperiod whatever the temperature, and initiated at a similar low leaf number, but the early strain was able to initiate at a shorter photoperiod than the late one. Seed vernalization had almost no effect; but at photoperiods of 14 to 11 hr, high temperatures strongly retarded Cowgrass and appeared to prevent initiation in Montgomery. The capacity of Cowgrass to initiate at a shorter photoperiod and at higher temperatures than Montgomery explains its longer flowering season in temperate latitudes. These genetic differences suggest that an appropriate environment can be used to differentiate early and late-flowering strains for seed certification, and that late strains would stay vegetative at low latitudes and would therefore be less useful as a source of hay than early ones.

scholarly journals Thermal cycling of DNA devices via associative strand displacement

2019 ◽  
Vol 47 (20) ◽  
pp. 10968-10975 ◽  
Author(s):  
Jaeseung Hahn ◽  
William M Shih
Keyword(s):  
Thermal Cycling ◽  
Low Temperatures ◽  
Logic Circuits ◽  
Design Parameters ◽  
Strand Displacement ◽  
Base Pairs ◽  
Transient Heating ◽  
Displacement Reactions ◽  
Temperature Responses ◽  
Net Release

Abstract DNA-based devices often operate through a series of toehold-mediated strand-displacement reactions. To achieve cycling, fluidic mixing can be used to introduce ‘recovery’ strands to reset the system. However, such mixing can be cumbersome, non-robust, and wasteful of materials. Here we demonstrate mixing-free thermal cycling of DNA devices that operate through associative strand-displacement cascades. These cascades are favored at low temperatures due to the primacy of a net increase in base pairing, whereas rebinding of ‘recovery’ strands is favored at higher temperatures due to the primacy of a net release of strands. The temperature responses of the devices could be modulated by adjustment of design parameters such as the net increase of base pairs and the concentrations of strands. Degradation of function was not observable even after 500 thermal cycles. We experimentally demonstrated simple digital-logic circuits that evaluate at 35°C and reset after transient heating to 65°C. Thus associative strand displacement enables robust thermal cycling of DNA-based devices in a closed system.

FLORAL INITIATION IN STRAWBERRY AND SOME EFFECTS OF RED AND FAR-RED RADIATION AS COMPONENTS OF CONTINUOUS WHITE LIGHT

1966 ◽  
Vol 44 (5) ◽  
pp. 663-668 ◽  
Author(s):  
W. B. Collins
Keyword(s):  
White Light ◽  
Concentration Gradient ◽  
Red Light ◽  
Continuous Light ◽  
High Energy ◽  
Clear Distinction ◽  
Flower Initiation ◽  
Floral Initiation ◽  
Mother Plants ◽  
Red Radiation

The effects of different ratios of red to far-red radiation in continuous light on flower initiation in strawberry are described. A correlation was found between flower promotion and the content of far-red light in the supplied radiation which may be related to the red/far-red ratio of light and therefore to the level of phytochrome-Pfr in the plants. However, since relatively high energy (white) light was the only radiation used, a clear distinction between photosynthetic and red/far-red photoreversible effects is not possible. Flowering did not occur on all runner plants. Where flowering was promoted it invariably occurred first on the second- or third-formed runner plants on the stolon. Flowering was delayed on the proximal runner plants and never occurred on the mother plants. The results support the premise that a flower-inhibiting system was present along a concentration gradient in the runner.

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