EFFECTS OF PLANTING DATE ON THE GROWTH AND DEVELOPMENT OF NARROW-LEAVED HAWK’S-BEARD

1978 ◽  
Vol 58 (4) ◽  
pp. 1087-1094 ◽  
Author(s):  
A. L. DARWENT ◽  
J. S. McKENZIE
Keyword(s):  
Dark Period ◽  
Growing Season ◽  
Planting Date ◽  
Light Period ◽  
Crepis Tectorum ◽  
Winter Annuals ◽  
Winter Annual ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Mature Seeds

Narrow-leaved hawk’s-beard (Crepis tectorum L.) planted prior to 6 June bolted and produced mature seeds as a summer annual. Plantings on 16 June bolted but not all reached maturity during the same growing season. Narrow-leaved hawk’s-beard planted in early July developed in one of three ways: (1) bolted and produced mature seeds as a summer annual, (2) bolted but produced no mature seeds in the year of planting, or (3) developed as a winter annual. Plantings made after 15 July developed as winter annuals. Survival of winter annuals the following spring ranged from 12 to 46% for July plantings to 80 to 90% for August–September plantings. No plants survived from the mid-October plantings. In growth chamber studies at 20 °C, bolting occurred in all plants at an 18-h photoperiod but not in plants at a 14-h photoperiod. The percentage of plants bolting under photoperiods between 14 and 18 h was intermediate. When grown under the same photoperiod, reducing the temperature to 18 °C during the light period and 5 °C during the dark period did not affect the percentage of plants bolting. These results suggest that photoperiod plays a major role in determining the pattern of development of narrow-leaved hawk’s-beard.

FACTORS INFLUENCING THE DEVELOPMENT OF PRIMARY DORMANCY IN WILD OAT SEEDS

1979 ◽  
Vol 59 (3) ◽  
pp. 777-784 ◽  
Author(s):  
STEVEN G. RICHARDSON
Keyword(s):  
Gibberellic Acid ◽  
Wild Oat ◽  
Night Temperature ◽  
Primary Dormancy ◽  
Factors Influencing ◽  
Seed Maturity ◽  
Oat Seeds ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Mature Seeds

Germination in response to gibberellic acid was used as an assay for wild oat seed dormancy. In growth chamber studies removal of glumes, a 5 °C reduction in night temperature (20 °C day/15 °C night vs. constant 20 °C), and a shorter photoperiod (12 vs. 18 h) during the period following panicle emergence reduced subsequent germination (increased dormancy) of mature seeds. Dormancy of field-grown wild oat seeds increased with increasing seed maturity and was affected by planting location and associated crop.

Life Cycles of Field Pennycress in the Subarctic as Influenced by Time of Seed Germination

Weed Science ◽  
1969 ◽  
Vol 17 (4) ◽  
pp. 563-566 ◽  
Author(s):  
L. J. Klebesadel
Keyword(s):  
Seed Germination ◽  
Seed Production ◽  
Growing Season ◽  
Life Cycles ◽  
Planting Date ◽  
Annual Plants ◽  
Thlaspi Arvense ◽  
South Central ◽  
Field Pennycress ◽  
Winter Annuals

Field pennycress (Thlaspi arvense L.) was seeded in rows at approximately 10-day intervals from June 1 to August 30, 1963, and from July 12 to August 31, 1966, in subarctic, south-central Alaska (61.5° N.). Plants from June 20 and earlier seedings produced mature seed as summer annuals; those from seedings during the first 3 weeks of July produced elongated stems and green pods, while those from later seedings produced unelongated, basal rosettes. Seedlings that emerged during July or later were potential winter annuals. No study plants survived the 1963-64 winter. The 1966 plantings survived the 1966-67 winter as follows: July 12, 50%, July 20, 54%, August 1, 93%, and August 12, 23, and 31, 100%. Morphology, time of flowering, and seed pod production of plants surviving the winter also were influenced by planting date the previous growing season. To prevent field pennycress from producing seed as a summer annual, plants that emerge before the middle of July must be eradicated. Plants that emerge during July or later should be destroyed as seedlings or prior to seed production time the following year.

Light Quality Effects on the Life Cycle of Common Purslane

Weed Science ◽  
1970 ◽  
Vol 18 (5) ◽  
pp. 611-613 ◽  
Author(s):  
Stuart Dunn
Keyword(s):  
Life Cycle ◽  
High Temperature ◽  
Light Quality ◽  
Dark Period ◽  
Green Light ◽  
Growing Season ◽  
Light Period ◽  
Yellow Light ◽  
The Common ◽  
Common Purslane

The common purslane plant(Portulaca oleraceaL.) flowered and produced seeds throughout the growing season. Seeds were mature about 15 days after flowering. Increased light intensity and temperature stimulated growth. In general greater yields were obtained under cool white light, followed by yields under green, blue, red, and yellow light, in that order. With high temperature during the light period and low temperature during the dark period, best growth occurred under green light.

scholarly journals Growth, maturity and flowering of pigeon peas, Cajanus cajan L. Millsp., at high latitudes

1969 ◽  
Vol 73 (3) ◽  
pp. 223-229 ◽  
Author(s):  
Rubén Vélez-Colón ◽  
Stephen A. Garrison
Keyword(s):  
Field Studies ◽  
Pigeon Pea ◽  
Germination Percentage ◽  
Planting Date ◽  
Mechanical Equipment ◽  
Vegetative Development ◽  
Planting Dates ◽  
Early Maturity ◽  
Chamber Studies ◽  
Growth Chamber Studies

The effects of temperature and planting dates on germination, emergence, growth, vegetative development, and time to flowering and maturity of the pods of pigeon pea were evaluated. Growth chamber studies were conducted to determine the effects of 12.5°, 15°, and 20° C on the germination of pigeon pea cultivar 2B-Bushy. Germination percentage was low (1.0 and 2.0%) at 15° and 12.5° C, respectively. At 17.5°, germination increased to 18% (average) and required 4 to 9 days. At 20° C, germination was 48° (average) and required 2 to 5 days. The vigor of the seed lot appeared to be low. Replicated field studies were conducted with large plant populations to determine the effect of planting date on emergence, growth, flowering and maturity of the pods of the commercial cultivar 2B-Bushy and two lines (PR2 7/13 and PR2 7/16) for early maturity in New Jersey (40° N fat,). Pigeon peas seeded May 19 emerged in 12 days at a mean soil temperature of 19° C at 2.5-crn depth. At later planting dates (2 June, 16 June, 1 July and 14 July) pigeon peas emerged in 6 or 7 days. Plant height and height to the first branch at flowering decreased in all three genotypes at the later planting dates. Pigeon peas planted at all sowing dates were tall but could be harvested with mechanical equipment. Planting date had a significant effect on the earliness of flowering and the percentage of plants that flowered. All plants of the PR2 selections flowered at all planting dates. The 2B-Bushy cultivar flowered only the first three planting dates; and not all the plants flowered. The 2B-Bushy flowered in the upper one-third of the plant, whereas the PR2 lines flowered in the upper two thirds. None of the plants of the 2B-Bushy genotype produced pods by the termination of the experiment, 15 October, just before frost. The PR2 lines seeded May 19 and June 2 produced 12% of the plants with mature green pods, and 6% of the plants with some dry pods, respectively, by 15 October. About 3% of these PR2 plants had 90% of their pods dry by 15 October. Thus, the PR2 lines were highly variable for maturity at 40° N lat. Therefore, pigeon peas could be selected for adaptation to this location and even more northerly areas.

Immunocytochemical studies on the behavior of RuBisCO and LHCP II during the cell cycle of synchronized Euglena gracilis

1990 ◽  
Vol 48 (3) ◽  
pp. 662-663
Author(s):  
Tetsuaki Osafune ◽  
Shuji Sumida ◽  
Tomoko Ehara ◽  
Eiji Hase ◽  
Jerome A. Schiff
Keyword(s):  
Cell Cycle ◽  
Immunoelectron Microscopy ◽  
Growth Phase ◽  
Euglena Gracilis ◽  
Dark Period ◽  
Light Period ◽  
Carboxylase Activity ◽  
Immunocytochemical Studies ◽  
Lhcp Ii

Changes in the morphology of pyrenoid and the distribution of RuBisCO in the chloroplast of Euglena gracilis were followed by immunoelectron microscopy during the cell cycle in a light (14 h)- dark (10 h) synchronized culture under photoautotrophic conditions. The imrnunoreactive proteins wereconcentrated in the pyrenoid, and less densely distributed in the stroma during the light period (growth phase, Fig. 1-2), but the pyrenoid disappeared during the dark period (division phase), and RuBisCO was dispersed throughout the stroma. Toward the end of the division phase, the pyrenoid began to form in the center of the stroma, and RuBisCO is again concentrated in that pyrenoid region. From a comparison of photosynthetic CO2-fixation with the total carboxylase activity of RuBisCO extracted from Euglena cells in the growth phase, it is suggested that the carboxylase in the pyrenoid functions in CO2-fixation in photosynthesis.

Henbit (Lamium amplexicaule), Common Chickweed (Stellaria media), Shepherd's-Purse (Capsella bursa-pastoris), and Field Pennycress (Thlaspi arvense): Fecundity, Seed Dispersal, Dormancy, and Emergence

Weed Science ◽  
2014 ◽  
Vol 62 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Erin C. Hill ◽  
Karen A. Renner ◽  
Christy L. Sprague
Keyword(s):  
Seed Production ◽  
Seedling Emergence ◽  
Crop Productivity ◽  
Seed Fate ◽  
Stellaria Media ◽  
Thlaspi Arvense ◽  
Emergence Patterns ◽  
Field Pennycress ◽  
Winter Annuals ◽  
Winter Annual

Winter annual weeds protect the soil from erosion and retain nutrients during the winter; however, they can also act as a host for crop pests and pathogens and impede planting. Increased knowledge of the reproductive biology and the seed fate of winter annuals would be useful to improve management and crop productivity. The objectives of this research were to determine the recruitment biology of shepherd's-purse, henbit, common chickweed, and field pennycress, including seed production, dispersal, dormancy, and seedling emergence, based on growing degree days (GDD). Henbit was the least prolific of the four weeds studied, producing 800 to 40,000 seeds m−2at naturally occurring densities; shepherd's-purse was the most prolific, producing 11,000 to 400,000 seeds m−2with 40 to 230 plants m−2. Fifty percent seed rain occurred for henbit, common chickweed, shepherd's-purse, and field pennycress at 620, 790, 880, and 1300 GDDBase,0C, respectively. Overall, seeds were dormant for all species at the time of dispersal. In 2 of 3 yr, dormancy of later-dispersed common chickweed decreased after 6 mo of storage at natural, fluctuating temperatures in the absence of water. The emergence patterns of the four species followed the Gompertz equation and were indicative of facultative winter annuals. The emergence patterns by rate were similar between henbit and common chickweed and between shepherd's-purse and field pennycress. Seed production, dispersal, dormancy, and seedling emergence were influenced by moisture; therefore, including a precipitation or soil moisture component into a GDD model (such as the use of hydrothermal time) would improve the accuracy of predicting winter annual reproduction, seed fate, and emergence.

scholarly journals Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea Mays)

PLoS ONE ◽  
2012 ◽  
Vol 7 (3) ◽  
pp. e33741 ◽  
Author(s):  
Paul Szpak ◽  
Fred J. Longstaffe ◽  
Jean-François Millaire ◽  
Christine D. White
Keyword(s):  
Zea Mays ◽  
Stable Isotope ◽  
Growth Chamber ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Seabird Guano

Biocontrol of seed-borne Alternaria raphani and A. brassicicola

1987 ◽  
Vol 33 (10) ◽  
pp. 850-856 ◽  
Author(s):  
G. Vannacci ◽  
G. E. Harman
Keyword(s):  
Biological Control ◽  
Host Range ◽  
Trichoderma Harzianum ◽  
Pythium Species ◽  
Biological Control Agents ◽  
Fusarium Sp ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Radish Seedlings

Forty-two microorganisms were tested as biological control agents against Alternaria raphani and A. brassicicola. Tests were conducted for in vitro antagonistic ability, for ability to control the pathogens on naturally infected seeds germinated on moistened blotters, and in planting mix in growth chamber studies, and for their ability to reduce pod infection. The organisms tested were obtained from cruciferous seeds or were strains already identified as being effective against soil-borne Pythium species. The blotter test indicated that six organisms increased both the number of healthy seedlings and the number of seedlings produced from A. raphani infected radish seeds. An additional seven strains improved either germination or increased the number of healthy seedlings. Twenty-nine organisms increased the number of healthy cabbage seedlings from A. brassicicola infected seeds, but total germination was not modified by any treatment. Experiments in planting mix showed that five antagonists (Chaetomium globosum, two strains of Trichoderma harzianum, T. koningii, and Fusarium sp.) increased the number of healthy plants in both radish samples tested, while four additional antagonists provided a significant increase in only one of the samples tested. The five antagonists that consistently increased numbers of healthy radish seedlings also decreased pod infection by A. raphani. None were as effective as iprodrone, however. Several effective antagonists were found to be mycoparasitic against Alternaria spp. Some strains of Trichoderma previously found to be effective against Pythium spp. were also effective against Alternaria spp., indicating that these strains have a wide host range.

Vigilance states, EEG spectra, and cortical temperature in the guinea pig

1993 ◽  
Vol 264 (6) ◽  
pp. R1125-R1132 ◽  
Author(s):  
I. Tobler ◽  
P. Franken ◽  
K. Jaggi
Keyword(s):  
Guinea Pig ◽  
Rem Sleep ◽  
Guinea Pigs ◽  
Process Model ◽  
Dark Period ◽  
Nrem Sleep ◽  
Light Period ◽  
Recording Time ◽  
Cortical Temperature ◽  
Eeg Power

Vigilance states, electroencephalogram (EEG) power spectra (0.25-25.0 Hz), and cortical temperature (TCRT) were obtained in nine guinea pigs for 24 h in a 12:12-h light-dark (LD 12:12) schedule. Sleep was markedly polyphasic and fragmented and amounted to 32% of recording time, which is a low value compared with sleep in other rodents. There was 6.8% more sleep in the light period than in the dark period. EEG power density in non-rapid eye movement (NREM) sleep showed no significant temporal trend within the light or the dark period. The homeostatic aspects of sleep regulation, as proposed in the two-process model, can account for the slow-wave activity (SWA) pattern also in the guinea pig: The small 24-h amplitude of the sleep-wakefulness pattern resulted in a small, 12% decline of SWA within the light period. In contrast to more distinctly nocturnal rodents, SWA in the dark period was not higher than in the light period. TCRT showed no difference between the light and the dark period. TCRT in REM sleep and waking was higher than TCRT in NREM sleep. TCRT increased after the transition from NREM sleep to either REM sleep or waking, and decreased in the last minute before the transition and after the transition from waking to NREM sleep. Motor activity measured in six animals for 11 days in constant darkness showed no apparent rhythm in three animals and a significant circadian rhythm in three others. Our data support the notion that guinea pigs exhibit only a weak circadian rest-activity rhythm.

Stimulation of Melatonin Receptors Decreases Calcium Levels in Xenopus Tectal Cells by Activating GABAC Receptors

2005 ◽  
Vol 94 (2) ◽  
pp. 968-978 ◽  
Author(s):  
Claudia Prada ◽  
Susan B. Udin ◽  
Allan F. Wiechmann ◽  
Irina V. Zhdanova
Keyword(s):  
Receptor Antagonist ◽  
Dark Period ◽  
Light Period ◽  
Melatonin Receptors ◽  
Receptor Activity ◽  
Calcium Dynamics ◽  
Rt Pcr ◽  
Dark Cycle ◽  
Bath Application ◽  
Stimulation Of

To investigate the physiological effects of melatonin receptors in the Xenopus tectum, we have used the fluorescent indicator Fluo-4 AM to monitor calcium dynamics of cells in tectal slices. Bath application of KCl elicited fluorescence increases that were reduced by melatonin. This effect was stronger at the end of the light period than at the end of the dark period. Melatonin increased γ-aminobutyric acid-C (GABAC)–receptor activity, as demonstrated by the ability of the GABAC-receptor antagonists, picrotoxin and TPMPA, to abolish the effects of melatonin. In contrast, neither the GABAA-receptor antagonist bicuculline nor the GABAB-receptor antagonist CGP 35348 diminished the effects of melatonin. RT-PCR analyses revealed expression of the 3 known melatonin receptors, MT1 (Mel1a), MT2 (Mel1b), and Mel1c. Because the effect of melatonin on tectal calcium increases was antagonized by an MT2-selective antagonist, 4-P-PDOT, we performed Western blot analyses with an antibody to the MT2 receptor; the data indicate that the MT2 receptor is expressed primarily as a dimeric complex and is glycosylated. The receptor is present in higher amounts at the end of the light period than at the end of the dark period, in a pattern complementary to the changes in melatonin levels, which are higher during the night than during the day. These results imply that melatonin, acting by MT2 receptors, modulates GABAC receptor activity in the optic tectum and that this effect is influenced by the light–dark cycle.

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