scholarly journals First year seed softening in three Hedysarum spp. in southern Queensland

2003 ◽  
Vol 43 (11) ◽  
pp. 1303 ◽  
Author(s):  
L. W. Bell ◽  
D. L. Lloyd ◽  
K. L. Bell ◽  
B. Johnson ◽  
K. C. Teasdale
Keyword(s):  
Soil Surface ◽  
First Year ◽  
Hard Seed ◽  
Seed Content ◽  
Constant Rate ◽  
Significant Difference ◽  
Hard Seeds ◽  
Hedysarum Coronarium ◽  
Seed Characteristics ◽  
Selection Of

Seed softening was investigated in 41 lines of Hedysarum coronarium, 5 lines of H. carnosum and 8�lines of H. flexuosum grown at Oakey, Queensland in 2000. After testing for initial hard seed content in each line, the remaining hard seeds were placed on the soil surface at Kingsthorpe on 15 January 2001. Changes in hard seed levels over the ensuing summer-autumn seed softening period were measured. The initial hard seed content in each species ranged from 20 to 79% in H. coronarium; 31 to 79% in H. carnosum; and 54 to 83% in H. flexuosum. No significant difference in the time of seed softening between accessions or species was identified. Despite the similar timing, the extent of softening varied greatly between accessions and species. The proportion of initially hard seed that softened ranged from 54 to 95% in H. coronarium; 27 to 45% in H. carnosum; and 50 to 74% in H. flexuosum. Accessions of H. coronarium and H. flexuosum softened the greatest proportion of seed between 15 January and 22�February with reducing amounts thereafter. Accessions of H. carnosum softened less seed over this period, appearing to display a slower, more constant rate of softening. Although total hard seed levels were relatively low, there was sufficient variability in hard seed levels to provide some scope for selection of desired hard seed characteristics.

Hard-seed content of alfalfa grown in Canada

1991 ◽  
Vol 71 (2) ◽  
pp. 437-444 ◽  
Author(s):  
D. T. Fairey ◽  
L. P. Lefkovitch
Keyword(s):  
British Columbia ◽  
Geographic Location ◽  
Viable Seed ◽  
Hard Seed ◽  
Peace River ◽  
Seed Content ◽  
River Region ◽  
Hard Seeds ◽  
Viable Seeds ◽  
Production Areas

The hard-seed content of alfalfa (Medicago spp.) grown in Canada in relation to genotype and geographic location of production was surveyed for the commercial growing regions in Manitoba, Saskatchewan, Alberta and British Columbia. The average hard-seed content of all pedigreed production over a 5-yr period, ranged from 22 to 37% and that in nonpedigreed production was between 14 and 30%. A database of the five widely grown cultivars revealed that the hard-seed content of alfalfa in the most northerly growing areas in the Peace River region of Alberta and British Columbia ranged from 31 to 51%, while hard seed content of alfalfa produced elsewhere varied from 22 to 38%. There was no apparent effect of latitude on the proportion of hard seeds, while there was a small increase for two of the five cultivars in production areas further west. Of particular interest was the trend in viable seed production. There was consistent evidence suggesting that the proportion of viable seeds decreased in production areas further north, but increased in production areas further west. However, the minimum viability was always in excess of 85%. There was no correlation between hard and viable seed. Key words: Medicago spp., alfalfa, lucerne, hard seeds, viable seeds

scholarly journals EVALUATION OF INUNDATIVE RELEASES OF TRICHOGRAMMA EXIGUUM (HYMENOPTERA: TRICHOGRAMMATIDAE) FOR SUPPRESSION OF NANTUCKET PINE TIP MOTH (LEPIDOPTERA: TORTRICIDAE) IN PINE (PINACEAE) PLANTATIONS

2000 ◽  
Vol 132 (3) ◽  
pp. 373-386 ◽  
Author(s):  
David B. Orr ◽  
Charles P-C. Suh ◽  
Kenneth W. Mccravy ◽  
C. Wayne Berisford ◽  
Gary L. Debarr
Keyword(s):  
Loblolly Pine ◽  
Soil Surface ◽  
First Year ◽  
Egg Survival ◽  
Significant Difference ◽  
Nantucket Pine Tip Moth ◽  
Rhyacionia Frustrana ◽  
Female Longevity ◽  
And Control ◽  
Inundative Releases

AbstractInundative releases of Trichogramma exiguum Pinto and Platner were evaluated for suppression of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), in first-year loblolly pine, Pinus taeda L., plantations. Three releases, spaced 7 d apart, were made in three 0.4-ha plots during second-generation R. frustrana egg deposition. Each release included three cohorts of T. exiguum developmentally separated by 25 degree-days. Mean ± SD field release rate for each cohort was 328 238 ± 88 379 females/ha. Mean T. exiguum emergence under laboratory conditions for released cohorts was 96 ± 2%, with 74 ± 3% females, of which 1 ± 1% of females displayed brachyptery; female longevity was 18 ± 3 d. Field emergence averaged 96 ± 4%. Parasitism of R. frustrana eggs was significantly increased, ranging from 40 ± 19 to 73 ± 22% in T. exiguum-treated plots and 17 ± 17 to 67 ± 21% in control plots. Data from all treated plots combined showed R. frustrana egg survival (hatching) was significantly reduced by 46%, and larval populations were significantly reduced by 60%. There was no significant difference in the percentage of terminals damaged between T. exiguum-treated (31 ± 16%) and control plots (45 ± 10%); however, length of terminal damage was significantly lower in treated plots. The percentage of damage to top whorl shoots was significantly lower in T. exiguum-treated plots compared with control plots, but there was no significant difference in length of tunneling damage. Damage to remaining shoots was not significantly different between T. exiguum-treated and control plots. Microhabitat significantly influenced both mean maximum and minimum temperature and the number of consecutive hours per day that were at or above 35 °C (critical temperature for T. exiguum survival). Soil surface with no cover had the greatest number of hours at or above 35 °C, followed by soil surface with herbaceous cover, and canopies of small trees (0.4 m tall). Canopy habitats in larger trees (0.9–1.8 m tall) had the most moderate temperature conditions. Parasitoid emergence was significantly reduced in response to increasing number of consecutive hours at or above 35 °C. Predation of parasitoids prior to emergence was significantly affected by microhabitat and by the length of time capsules were in the field before T. exiguum emergence (i.e., cohort number).

Incidence and measurement of autumn seed softening within Medicago polymorpha L

1996 ◽  
Vol 47 (4) ◽  
pp. 575 ◽  
Author(s):  
GB Taylor
Keyword(s):  
Soil Surface ◽  
Temperature Fluctuations ◽  
The Other ◽  
Laboratory Simulation ◽  
First Year ◽  
Medicago Polymorpha ◽  
Softening Behaviour ◽  
Hard Seeds ◽  
Total Seed

Softening of hard seeds during autumn rather than summer is a desirable characteristic for reducing seed losses in annual legumes from false breaks of season in Mediterranean environments. The incidence of this characteristic in Medicago polymorpha L. was determined in 34 lines grown at Toodyay, Western Australia, in 1993 and collected in December. Patterns of seed softening during summer and autumn 1993-94 were studied in pods placed on the soil surface in the field at Merredin, and in laboratory and glasshouse simulations at Perth. Summer seed softening was simulated in the laboratory by the removal of seeds from pods by hand, subjecting them to a diurnally fluctuating temperature of 60/15�C for 16 weeks, and testing their permeability. Residual hard seeds were subjected to 4 gradual diurnal temperature fluctuations of 35/10�C and re-tested for permeability as a measure of autumn seed softening. In the glasshouse study, pods were placed on the surface of soil in boxes, and emerged seedlings were counted after watering in March and June. Field softening in the first year ranged from 6.8 to 69.6%, but exceeded 40% in only 6 of the 34 lines. Proportions of total soft seeds present in the field in June that had softened after 1 March in the 34 lines were normally distributed, and ranged from 2.5 to 78.7%. The laboratory simulation markedly underestimated both autumn and total seed softening in 13 of the lines but effectively predicted field softening behaviour in the other 21 lines. The glasshouse technique overestimated the proportions of seeds softening in autumn in most lines and underestimated total softening in 12 of the 34 lines. A technique involving the use of a rain-out shelter is proposed for routine determination of the incidence of autumn seed softening in medic evaluation programs.

The effect of a Mediterranean summer environment on the permeability of hard seeds of subterranean clover

1962 ◽  
Vol 13 (3) ◽  
pp. 377 ◽  
Author(s):  
BJ Quinlivan ◽  
AJ Millington
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Maximum Level ◽  
Bare Soil ◽  
Early Summer ◽  
Hard Seed ◽  
Seed Content ◽  
Artificial Environment ◽  
Different Strains

Burr samples of nine strains of subterranean clover (Trifolium subterraneum L.) were collected from field sward trials at monthly intervals during the summer and autumn months and tested for hard seed content. Similar tests were carried out on burrs exposed to an artificial environment in a laboratory oven, which simulated the temperature conditions on a bare soil surface during the hot summer months in the agricultural districts of Western Australia. The maximum level of hard-seededness for all strains was achieved in the late spring or early summer soon after field maturity. There was significant variation in the maximum hard seed content of the different strains. Over the summer and autumn months the hard seed content of all strains declined in the samples from the field and the laboratory. There was considerable variability among strains in the rate and pattern of decline in hard seed content, and in the percentage of hard seed remaining in the autumn. The agronomic significance of the strain variability and the possibility of its inclusion in a breeding and selection programme are discussed.

Long-term softening of surface and buried hard seeds of yellow serradella grown in a range of environments

1998 ◽  
Vol 49 (4) ◽  
pp. 673 ◽  
Author(s):  
C. K. Revell ◽  
G. B. Taylor ◽  
P. S. Cocks
Keyword(s):  
Laboratory Tests ◽  
Soil Surface ◽  
First Year ◽  
Mediterranean Environment ◽  
The Third ◽  
Hard Seeds ◽  
Ornithopus Compressus ◽  
Alternating Temperature ◽  
One Year

A 3-year field experiment was conducted to investigate seed softening in yellow serradella (Ornithopus compressus L.) in a low rainfall Mediterranean environment at Merredin, Western Australia. The study examined seeds of 4 accessions of serradella from separate growing sites (Pindar, Merredin, and Badgingarra), and included the effect of pod burial (only for accessions grown at Merredin). Pods were placed on the soil surface in December 1992 and sampled in March, June, and October for the next 3 years. Burial treatments (2 and 6 cm beneath the surface) commenced in June 1993 after pods had been on the soil surface for one summer. Samples were collected in June for the next 2 years. Softening of seeds over the first summer in the field was compared with that obtained in the laboratory with 16 weeks at a diurnally alternating temperature of 60/15ºC. Few seeds of any accession softened (generally <6%) at the soil surface during the first summer but the rate of softening increased over the next 2 years. The highest annual rate of softening was about 55% in the third year in accessions GEH72-1A and GEH72-2A. Accession of serradella hadmore influence on pattern of seed softening than site at which seeds were produced. Burial of pods at 2 cm markedly accelerated seed softening in all strains, particularly GEH72-1A and cv. Madeira, in which over 95% of hard seeds softened during the first year of burial. Softening at 6 cm was similar to that at the soil surface. Shallow burial of pods, as would occur during cereal cropping in one year,could improve regeneration of serradella, but reduce the longevity of its seed bank. Laboratory treatment at 60/15ºC generally over-estimated field softening during the first summer.The spread of germination in time in laboratory tests differed between accessions and was much wider in GEH72-2A than in others, extending up to 35 days. Such behaviour could provide insurance against total seedling loss following false breaks of season.

Effect of length of growing season on development of hard seeds in yellow serradella and their subsequent softening at various depths of burial

1999 ◽  
Vol 50 (7) ◽  
pp. 1211 ◽  
Author(s):  
C. K. Revell ◽  
G. B. Taylor ◽  
P. S. Cocks
Keyword(s):  
Soil Surface ◽  
Growing Season ◽  
First Year ◽  
Variable Effect ◽  
Softening Mechanism ◽  
Hard Seeds ◽  
Before And After ◽  
Viable Seeds ◽  
A Site ◽  
Seed Yields

Effects of withholding water at 4 (W4) and 8 (W8) weeks after commencement of flowering on seed development in 2 accessions of yellow serradella (Ornithopus compressus L.), cv. Avila and accession GEH72-1A, were investigated in swards at a site near Perth, Western Australia. Softening of resulting hard seeds during the following summer and autumn was then studied in newly ripened pods placed at the soil surface, and at depths of 0.5 and 2 cm in the soil at Merredin in the first week of January. Proportions of soft seeds were determined in the original seed populations and in pods taken from the field in March and June. In 2 further treatments, proportions of soft seeds were determined in June in (i) pods that had been at the soil surface until they were buried at 2 cm in March, and (ii) in pods that had been buried at 2 cm until March, when they were returned to the soil surface. Seed yields from W4 were about 35% of those from W8 owing to reductions in pod numbers (partly as a result of more flower shedding in W4), number of seeds per pod, and seed size. Developing seeds became germinable between 21 and 29 days after anthesis when seed dry weights were between 0.9 and 1.4 mg, which was about the same time that they developed the capacity for seed coat impermeability. Viability of hard seeds was almost 100% from W8 but only 65% from the W4 treatments. Less than 5% of the newly ripened viable seeds were soft in any of the treatments. Length of growing season had no effect on seed softening at the soil surface and only a relatively small and variable effect on softening in buried pods. At the June sampling, up to 16% of Avila and 5% of GEH72-1A seeds had softened at the soil surface. Burial of pods increased proportions of soft seeds up to 85% in Avila and 53% in GEH72-1A. Whereas most of the seed softening in Avila occurred before March, similar amounts of softening occurred before and after the March sampling in GEH72-1A. Burial of pods in March increased seed softening by June in GEH72-1A but reduced softening in Avila, whereas transfer of buried pods to the soil surface in March had the reverse effect. This seed softening behaviour is explained in terms of the 2-stage seed softening mechanism. Burial of newly ripened seeds by tillage or stock trampling during the first summerŒautumn appears a feasible management option for improving first year regeneration in at least the softer seeded accessions of yellow serradella.

scholarly journals SELECTION OF MEDICAL PROFESSION BY FIRST YEAR MEDICAL STUDEN

2009 ◽  
Vol 16 (04) ◽  
pp. 556-563
Author(s):  
FATIMA MUKHTAR ◽  
Sidra Zaman ◽  
SEEMA DAUD ◽  
Ammad Masood ◽  
NOREEN RAHAT HASHMI ◽  
...  
Keyword(s):  
Financial Incentives ◽  
Medical Profession ◽  
First Year ◽  
Fisher Exact Test ◽  
Personal Interest ◽  
Cross Sectional Survey ◽  
Medical Specialties ◽  
Career Opportunities ◽  
Significant Difference ◽  
Selection Of

Background: The factors which influence medical students' selection of specific medical specialties have been analyzed by anumber of studies in the literature. However, very few studies have been carried out to ascertain the factors which influence students selectionof the medical profession itself. The literature review did not identify any such study conducted in Pakistan, therefore this particular venturewas undertaken. Objectives: To establish a baseline of factors that affect student's decision in selecting medical profession and to determineif there was a significant difference in factor by gender. Place a n d Duration of Study: Lahore Medical and Dental College, between Januaryand February 2009. Methodology: The present study was a cross-sectional survey in which the first year MBBS class of Lahore Medical andDental College, comprising ninety students were part of the study. Data was collected using a pre-formed structured questionnaire, which waspretested before adoption of the final version. The collected data was analyzed using version 16 of the statistical package for social sciences(SPSS). Data is presented in the form of tables and figures. It is described in the form of frequencies and percentages. Inferential statistics weredone using Fisher Exact test at 5% level. Results: Among 90 respondents, 58(64%) were females, 74(82%) were between 18-20 years of age,81(90%) had their residence in Pakistan, 57(63%) of the respondents' fathers and 26(29%) of their mothers had attained postgraduateeducation. Of the respondents' parents, 29(32%) of the fathers and 12(14%) of the mothers belonged to the medical profession. All studentstaking two attempts at FSc/A-level/American high examination also took two attempts at the entry test to a medical college (p<0.001). A largeproportion 10(59%), of students who attempted the entry test twice had fathers who were doctors. The popular reasons for selection of medicalprofession by the respondents included personal interest (89%), parental wish (58%) and a desire to serve humanity (41%). Among therespondents 100% males had a personal interest in medical profession in contrast to 83% female respondents (p=0.012), 100% malerespondents were influenced by parental wish compared to 34% females (p<0.001), 100% males in contrast to 9% females identifiedhumanitarian concern (p<0.001) as factors influencing selection of medical profession. The prestigious status of the profession, parents beingdoctors, financial incentives, better career opportunities and a better chance to go abroad were the factors identified by only the malerespondents as compared to the female respondents in influencing their choice of medical field (p<0.05). C o n c l u s i o n : The overall frequentchoices for selection of medical profession included personal interest in the profession, parental wish and a desire to serve humanity. Whereas,parents being in the same profession, financial incentives, better career opportunities and the prestige associated with the profession wereidentified as motivating factors by only the male respondents.

Hardseededness and the pattern of softening in Biserrula pelecinus L., Ornithopus compressus L., and Trifolium subterraneum L. seeds

1999 ◽  
Vol 50 (6) ◽  
pp. 1073 ◽  
Author(s):  
A. Loi ◽  
P. S. Cocks ◽  
J. G. Howieson ◽  
S. J. Carr
Keyword(s):  
Seed Bank ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Farming System ◽  
First Year ◽  
Ley Farming ◽  
Sufficient Variation ◽  
Depth Of Burial ◽  
Selection Of

Experiments measuring seed bank size, hardseededness, and seed softening of biserrula (Biserrula pelecinus L.) were conducted at Merredin and Perth in Western Australia. At Merredin, a mixture of 2 biserrula accessions was grazed, shallow cultivated, or left uncultivated and ungrazed. Seed bank size, seedling regeneration, and seed softening were measured over 2 years. At Perth, softening of biserrula, yellow serradella, and subterranean clover seeds grown at 2 sites (Binnu and Northam) was compared on the soil surface and after burial at 2 and 10 cm over a period of 2 years. Seed bank size of biserrula at Merredin ranged from 14000 to 17500 seeds/m2. Regeneration was greater in the second year (800–1700 seedlings/m2) than in the first year (40–600 seedlings/m2). In both years the shallow cultivated treatment recorded the highest number of seedlings. About 90% of biserrula and serradella seed remained hard after 2 years on the soil surface, compared with only about 10% of subterranean clover. Serradella softened more rapidly when buried 2 cm below the soil surface (8–12% hard) than it did on the soil surface (84–92% hard) (P<0.05). In contrast, the softening of subterranean clover decreased with increasing depth. Biserrula was intermediate, although it too softened most rapidly at 2 cm (78–95% hard compared with 82–97% on the surface) (P<0.05). Rate of seed softening in all species decreased with increasing depth of burial below 2 cm. Of the 4 accessions of biserrula, an accession from Greece (83% hard after 2 years exposure) was significantly softer than the other accessions. The results indicate that biserrula is very hardseeded, although there is sufficient variation in hardseededness for the selection of somewhat softer lines. Its pattern of softening suggests that biserrula may be successful in the ley farming system (crop/pasture rotations) of southern Australia.

Short-term patterns of seed softening in Trifolium subterraneum, T. glomeratum and Medicago polymorpha

1996 ◽  
Vol 47 (5) ◽  
pp. 775 ◽  
Author(s):  
FP Smith ◽  
PS Cocks ◽  
MA Ewing
Keyword(s):  
Selection Criterion ◽  
Trifolium Subterraneum ◽  
First Year ◽  
Stage Model ◽  
Mediterranean Environment ◽  
Short Term ◽  
Medicago Polymorpha ◽  
Pasture Legumes ◽  
Hard Seeds ◽  
Selection Of

The short-term (within-year) dynamics of the softening of hard seeds in a number of accessions of Trifolium subterraneum L., T. glomeratum L., and Medicago polymorpha L. were monitored in the field. There were distinct differences in the patterns of seed softening between and within species and between years. Seed softening was accurately described by logistic curves with calculated half-lives of hard seeds (within a given year) a good indicator of differences in the softening patterns between species and accessions. T. subterraneum cv. Nungarin softened most rapidly over summer, ceasing by March (half-life in the first year 45 days), whereas M. polymorpha cv. Serena and 2 accessions of T. glomeratum softened mainly during the autumn (half-lives of 126, 104, and 136 days, respectively) First year half-lives of 4 other accessions of T. subterraneum ranged from 64 to 79 days. The results showed that large seeds were more likely to soften in the first year than were small seeds. The different patterns can be explained using Taylor's 2-stage model of seed softening. The implications of different patterns are discussed in terms of adaptation to a Mediterranean environment. T. glomeratum and M. polymorpha cv. Serena are considered to have a short-term pattern of seed softening well adapted to an environment where false breaks to the growing season are likely. The pattern of T. subterraneum is considered to be less well adapted to such an environment. However, variation within the species indicates the potential for selection of better adapted varieties. The inclusion of the short-term seed softening pattern as a selection criterion for pasture legumes is recommended.

Cultivar and storage effects on germination and hard seed content of alfalfa

1999 ◽  
Vol 79 (2) ◽  
pp. 201-208 ◽  
Author(s):  
S. N. Acharya ◽  
D. G. Stout ◽  
B. Brooke ◽  
D. Thompson
Keyword(s):  
Medicago Sativa ◽  
Liquid Nitrogen ◽  
Storage Conditions ◽  
Temperature Treatment ◽  
Short Exposure ◽  
High Temperature Treatment ◽  
Hard Seed ◽  
Seed Content ◽  
Hard Seeds ◽  
And Storage

The impermeable coat of alfalfa (Medicago sativa L.) seed can reduce germination to an extent unacceptable for commercial use. The usual method of increasing germination of lots with high proportion of impermeable or hard seeds, mechanical scarification, can damage seeds. Experiments were conducted to determine the effect of cultivar, year of production and storage conditions on germination and hard seed content in alfalfa. Experiments with four Canadian cultivars indicated a significant effect of cultivar on seed weight, germination and hard seed content in freshly harvested seed. Year of production had a greater influence on these seed traits than cultivar. Under uncontrolled storage conditions, germination of 35 alfalfa synthetics increased and hard seed content decreased with time, although not at the same rate for all synthetics. Storage at 20 °C for up to 64 mo did not significantly decrease hard seed content. At 35 °C, hard seed content decreased continuously for all cultivars (for one cultivar to <5%) after 64 mo. Over 80.5 mo storage at room temperature (22 ± 2 °C), germination increased in a nonlinear fashion. Storing seed in sealed plastic bags at 35 °C delayed seed dehydration and the loss of hard seeds. Levels of nonviable seed were low (<10%), even after storage at 35 °C for 64 mo. Brief (1 min) exposure to liquid nitrogen increased germination of freshly harvested alfalfa seed to >90%. The results indicate that the germination percent of alfalfa can be increased and hard seed content reduced by short exposure to liquid nitrogen or storage at nonlethal high temperatures (35 °C) such that mechanical scarification may be unnecessary. Key words: Medicago sativa, hard seed, stored seed, seed dehydration, high temperature treatment, liquid nitrogen treatment

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