The influence of plant raising conditions on the head weight of crisp lettuce at maturity

1982 ◽  
Vol 99 (2) ◽  
pp. 417-423 ◽  
Author(s):  
D. C. E. Wurr ◽  
Jane R. Fellows
Keyword(s):  
Environmental Conditions ◽  
Coefficient Of Variation ◽  
Artificial Lighting ◽  
Lower Amplitude ◽  
Head Weight ◽  
Similar Weight ◽  
Supplementary Lighting ◽  
And Tungsten

SUMMARYTwo experiments investigated the effects of raising crisp lettuce seedlings under different environmental conditions prior to transplanting, on transplant size and weight and head weight at maturity.The use of tungsten lighting for 4 h after the end of a 12 h period of fluorescent and tungsten lighting increased transplant size and weight and the weight of heads at maturity compared with fluorescent and tungsten lighting only. Glasshouse-raised transplants were larger than those raised under artificial lighting but gave heads of similar weight to transplants which had supplementary tungsten lighting for 2 weeks. Both these treatments gave significantly heavier heads than a drilled crop or plants raised without supplementary tungsten lighting. Increasing the number of weeks of the supplementary lighting treatment tended to increase the coefficient of variation (c.v.) of head weight. Nevertheless the drilled crop had a higher c.v. of head weight than any transplanted treatment.The variety Pennlake produced pointed (‘coned’) heads when grown in the open and its leaves were shorter and broader than those of plants grown in polyethylene tunnels, which did not show ‘coning’. It is suggested that ‘coning’ occurs primarily as a result of either lower mean temperatures or a lower amplitude of temperature when grown in the open. It occurred most frequently with glasshouse-raised plants indicating that a higher raising temperature may also contribute to the problem.

Thermal sensitivity of reptilian melatonin rhythms: "cold" tuatara vs. "warm" skink

1989 ◽  
Vol 256 (5) ◽  
pp. R1160-R1163 ◽  
Author(s):  
B. T. Firth ◽  
M. B. Thompson ◽  
D. J. Kennaway ◽  
I. Belan
Keyword(s):  
Environmental Conditions ◽  
Thermal Sensitivity ◽  
Cold Temperature ◽  
Daily Rhythm ◽  
Threshold Temperature ◽  
Daily Rhythms ◽  
Thermoregulatory Behavior ◽  
Lower Amplitude ◽  
Sphenodon Punctatus ◽  
Reptilian Species

Daily rhythms in plasma melatonin levels were compared in two ecologically diverse reptilian species under natural environmental conditions in autumn. The nocturnal, cold temperature-adapted tuatara (Sphenodon punctatus) had a melatonin rhythm of much lower amplitude than did the diurnal desert-adapted sleepy lizard (Tiliqua rugosa). Experiments in controlled laboratory environments showed that, although both species are capable of attaining a comparable melatonin peak (approximately 750 pmol/l), the threshold temperature at which a significant daily rhythm occurs is approximately 15 degrees C in S. punctatus compared with approximately 25 degrees C in T. rugosa. This difference probably reflects the disparate thermoregulatory adaptations of the two species, S. punctatus favoring mean activity temperatures of 11.5 degrees C and T. rugosa, 32.5 degrees C. In ectotherms such as reptiles, therefore, species-typical thermoregulatory behavior may provide thermal cues that interact with photoperiod to provide the appropriate melatonin signal for the regulation of annual physiological cycles.

Evaluation of Sample Preparation Parameters in the Compressive Strength of Cementitious Composites

2016 ◽  
Vol 869 ◽  
pp. 93-97 ◽  
Author(s):  
Ana Luiza de Figueiredo Maia ◽  
Natalia Oliveira Sena ◽  
Laura Luíza de Melo Sapori Oliveira ◽  
Gabriela Melo Pereira ◽  
Mateus Justino da Silva ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Sample Preparation ◽  
Compression Strength ◽  
Environmental Conditions ◽  
Coefficient Of Variation ◽  
Experimental Evaluation ◽  
Laboratory Tests ◽  
Load Application ◽  
Cementitious Composites

This paper presents an experimental evaluation of how variations in proposed parameters interfere with compressive strength resistance of mortar and concrete specimens. The results were obtained through laboratory tests in which samples were tested under varying conditions. These conditions were as follows: speed of load application (0.25, 0.50, 0.75, and 1.00 MPa/s), environmental conditions (saturated, 2 h dried, and 24 h dried specimens), curing (dry and wet), and specimen ends preparation (sulphur, neoprene, rectification, and without regularization). Comparisons were made on the basis of the compression strength resistance results and the coefficient of variation in order to analyse the homogeneity and dispersion among variables. It was found that in the case of capping, the best results were obtained by the rectification of concrete specimens. In the case of loading speed, the best results were obtained at a speed of 1 MPa/s. Dry curing showed the best results, even though not resulting in the highest resistance. The results for specimen conditions were in accordance with the expectations, with lower dispersion for saturated specimens.

Performance of carrot seeds possessing different germination rates within a seed lot

1988 ◽  
Vol 110 (1) ◽  
pp. 93-99 ◽  
Author(s):  
W. E. Finch-Savage ◽  
C. I. McQuistan
Keyword(s):  
Environmental Conditions ◽  
Coefficient Of Variation ◽  
Germination Rate ◽  
Seedling Emergence ◽  
Seedling Performance ◽  
Controlled Conditions ◽  
Carrot Seed ◽  
The Relationship ◽  
Fluid Drilling

SummaryThe relationship between germination rate within a carrot seed lot and subsequent seedling performance was studied in four seed lots of different viability. Seedling performance was assessed using slope tests conducted under controlled conditions and in the field following fluid drilling under a range of environmental conditions. Germination rate within a seed lot was positively related to vigour measured by slope tests, percentage emergence and seedling weight, and was negatively related to the spread of emergence times (In variance days) and the coefficient of variation (c.v.) of seedling weights. Sowing seeds selected as fast germinating resulted in greater seedling emergence percentages over a range of environmental conditions than when sowing seeds selected as slowly germinating.

An evaluation of feedblocks as a means of providing supplementary nutrients to ewes grazing upland/hill pastures

1981 ◽  
Vol 33 (1) ◽  
pp. 51-57 ◽  
Author(s):  
M. J. Ducker ◽  
P. T. Kendall ◽  
R. G. Hemingway ◽  
T. H. McClelland
Keyword(s):  
Environmental Conditions ◽  
Individual Variation ◽  
Coefficient Of Variation ◽  
Chromium Content ◽  
Chromic Oxide ◽  
Grazing Area

ABSTRACTA series of trials was conducted to measure the extent of individual variation in feedblock intake for ewes on upland/hill farms. From 15 flocks on nine farms 4284 ewes were selected with a range of environmental conditions and levels of performance. Ewes were given either Rumevite, Norbloc or Wintawell feedblocks containing chromic oxide. Faecal grab samples were taken per rectum from individual ewes and analysed for their chromium content to obtain estimates of feedblock consumption.The results showed that provision of feedblocks does not ensure a uniform intake of supplementary nutrients by sheep in upland/hill situations. On average, 19% of the 2931 ewes sampled had not eaten the feedblock on offer. The proportion of ewes not consuming feedblock varied from flock to flock (0 to 67%). The coefficient of variation of faecal chromium concentrations varied between flocks (46 to 231%). The reasons for the large variation in intakes observed are discussed. Feedblock intake was significantly affected by the grazing area per ewe (P<0·01) and the age of ewes (P<0·05 to P< 0·001).

Effets d'un éclairage d'appoint sur la croissance et le métabolisme azoté primaire de la laitue mâche et de l'épinard cultivés en serre

1999 ◽  
Vol 79 (3) ◽  
pp. 421-426 ◽  
Author(s):  
Hassan Chadjaâ ◽  
Louis-Philippe Vézina ◽  
André Gosselin
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Climatic Conditions ◽  
Nitrate Accumulation ◽  
Artificial Lighting ◽  
Spinacea Oleracea ◽  
Supplementary Lighting ◽  
Nitrates Content ◽  
High Yields

Two cultivars of Lamb's lettuce (Valerianella sp. 'Valgros' et 'Vit') and one cultivar of spinach (Spinacea oleracea L. 'Martine RZ F1') were subjected to three light treatments. Two photoperiods, 12 h and 16 h were compared to natural light between January and April 1994. A photosynthetic flux of 50 µmol m–2 s–1 was provided as supplementary lighting using HPS lamps. The use of artificial lighting significantly increased biomass and nitrate reductase activity, while also reducing nitrate accumulation in leaves. The 16 h-photoperiod increased biomass and reduced nitrates content in leaves more than the 12 h photoperiod. In Lamb's lettuce, Valgos was more productive than Vit but accumulated more nitrates. The use of supplementary lighting gave high yields of lamb's lettuce and spinach in greenhouse under northern climatic conditions. Key words: Lamb's lettuce, spinach, nitrate reductase activity, nitrate, Valerianella sp., Spinacea oleracea L.

scholarly journals Effects of Host Physiology on the Development of Core Rot, Caused by Alternaria alternata, in Red Delicious Apples

2012 ◽  
Vol 102 (8) ◽  
pp. 769-778 ◽  
Author(s):  
D. Shtienberg
Keyword(s):  
Environmental Conditions ◽  
Coefficient Of Variation ◽  
Alternaria Alternata ◽  
Large Variability ◽  
Yield Load ◽  
Fungicide Application ◽  
Host Physiology ◽  
Pathogen Occurrence ◽  
Core Symptoms ◽  
Morisita's Index

Alternaria alternata is the predominant fungus involved in moldy core and core rot of Red Delicious apples. The effects of environmental conditions during bloom on moldy core and core rot, and on the need for fungicide application, were examined in 10 experiments carried out in 2007. In untreated experimental plots, typical moldy core symptoms were very common, with relatively low variability (coefficient of variation: 22.2%) among experiments; core rot incidence ranged from 2 to 26% with large variability (coefficient of variation: 90.0%) among experiments. No evidence of prevailing environmental conditions during bloom affecting the development of moldy core or core rot was detected. No effect of fungicide application (a mixture of bromuconazole + captan three times a week at bloom) on moldy core or core rot was found. A random distribution of moldy core and an occasional aggregation of core rot in the orchards were indicated from Morisita's index of dispersion (Iδ). The hypothesis that core rot incidence is governed by host physiology and that yield load can be used as an indicator of trees' susceptibility was examined in a set of eight observations and four experiments. No correlation was found between tree yield load and moldy core, but core rot incidence was inversely related to yield load. Furthermore, irrespective of tree yield load, core rot was more abundant on large compared with small fruits. It is concluded that host physiology, rather than pathogen occurrence or environmental conditions at bloom stage, governs the development of core rot in Red Delicious apples caused by A. alternata in Israel.

scholarly journals The Design of a Mini Plant Factory with Artificial Lighting and Application of Environmental Conditions Control System

2019 ◽  
Vol 7 (11) ◽  
pp. 1834
Author(s):  
Ali Çaylı ◽  
Emir Hüseyin Kaya
Keyword(s):  
Control System ◽  
Environmental Conditions ◽  
Production Systems ◽  
Low Cost ◽  
Climatic Conditions ◽  
Plant Production ◽  
Artificial Lighting ◽  
Plant Factory ◽  
Open Source Hardware ◽  
And Control

Due to rapidly increasing population and urbanization, agricultural lands are shrinking. However, environmental problems and pollution are constantly increasing. This poses a threat to agricultural production and food access. In order to overcome these threats, the use of fully controlled indoor production systems called plant factory is becoming widespread. The management of plant nutrition and monitor of environmental conditions is very important for production in the plant factory. Plant production is sensitive to environmental conditions. For this reason, it is necessary to make accurate measurements in order to ensure the correct climatic conditions. The high cost of control systems designed for this purpose is a problem for producers. In this study, a mini plant factory prototype and control system are presented which is developed by using open source hardware and software. In addition, the temperature, relative humidity and light measured by the low-cost sensors were compared with the reference devices and the system performance and stability were investigated.

The effect of amount and timing of nitrogen application to drilled crisp lettuce crops on head weight at maturity

1985 ◽  
Vol 105 (3) ◽  
pp. 727-729 ◽  
Author(s):  
D. C. E. Wurr ◽  
Jane R. Fellows
Keyword(s):  
Environmental Conditions ◽  
Plastic Film ◽  
Nitrogen Application ◽  
Iceberg Lettuce ◽  
Recent Increase ◽  
Head Weight ◽  
The Mean

Much of the recent increase in crisp lettuce production in the U.K. has been marketed as heavily trimmed solid ‘Iceberg’ heads, wrapped in plastic film. Supermarkets want ‘Iceberg’ lettuce with a minimum trimmed weight of 450 g (Anon. 1983) and consistency of product, but the mean head weight of crisp lettuce at maturity can vary considerably from one sowing to another as a result of environmental conditions earlier in growth (Pew, Gardner & Bessey, 1984; Wurr & Fellows, 1984). In midsummer, some sowings of the most popular variety Saladin can produce larger and heavier heads thanc supermarkets require and the cause of this variation needs to be understood in order to increase the proportion of crops meeting supermarket needs.

Testing of Tire Treadwear under Laboratory and under Service Conditions

1973 ◽  
Vol 1 (1) ◽  
pp. 39-46 ◽  
Author(s):  
J. C. Ambelang
Keyword(s):  
Tungsten Carbide ◽  
Environmental Conditions ◽  
Variable Speed ◽  
Service Conditions ◽  
And Tungsten

Abstract Four different laboratory machines for the evaluation of tire treadwear have been described which used concrete, steel, and tungsten carbide abrasion surfaces at variable speed and slip, but none has satisfactorily replaced highway testing. Predominant sources of wear on passenger tires appear to be cutting and frictional fatigue, the rates of which are influenced differently by temperature and load. Thus, seasonal or climatic, topographical, and geographical effects are evidenced. Treadwear cannot be expressed solely as a property of the tire since it is the resultant of the interaction of the tire with multivariate environmental conditions.

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