Seed softening, imbibition time, and seedling establishmentin yellow serradella

2002 ◽  
Vol 53 (9) ◽  
pp. 1011 ◽  
Author(s):  
G. B. Taylor ◽  
C. K. Revell
Keyword(s):  
Marked Effect ◽  
Soil Surface ◽  
First Year ◽  
Large Numbers ◽  
Buried Seeds ◽  
Ornithopus Compressus ◽  
Intermediate Time ◽  
Softening Process ◽  
Viable Seeds ◽  
The Times

The first (preconditioning) and final stages of seed softening were studied over a 4-year period in 4 lines of yellow serradella (Ornithopus compressus L.): cvv. Santorini and Charano, and accessions GEH72-1A and GRC5045-2-2. Pods grown in 1997 were collected in December (start of summer) and placed on the soil surface or buried at a depth of 1 cm. Measurements of seed softening between years were made from pod samples removed in June each year. The progress of preconditioning and seed softening within the first 3 years was determined from samples taken at the end of February. Numbers of soft and viable seeds were determined from each sampling. Preconditioned seeds were identified by subjecting seeds to 7 gradual diurnal temperature cycles of 48/15°C in darkness before testing for permeability. Seed softening was markedly accelerated by pod burial in all 4 lines, with most buried seeds of GEH72-1A and Santorini softening during the first year. Seed softening was slower in GRC5045-2-2 and Charano, approaching a constant annual rate over the 4 years of the experiment. Despite this marked effect of burial the differences between lines in rates of softening of buried seeds were sufficient to have important implications for persistence under some management systems. Most seeds of all lines softened between February and June, indicating that shallow pod burial could be delayed in these lines until at least the end of February to promote the final stage of seed softening. Although large numbers of seeds of GEH72-1A and GRC5045-2-2 had preconditioned at the soil surface by the end of February, few went on to complete the softening process by June, when most had lost their preconditioned state. Treatment at 48/15°C was less successful in identifying preconditioned seeds of Santorini and Charano. Rates of imbibition differed markedly between lines. Most soft seeds of GEH72-1A and GRC5045-2-2 imbibed within days, whereas they took weeks in Santorini and an intermediate time in Charano. Seedling age distributions in the 4 lines in June closely reflected the times their soft seeds took to imbibe in the laboratory. Imbibition time can be an important germination regulating mechanism having implications that may be either favourable or unfavourable depending on rainfall distribution around the break of season and the system of management.

Effect of pod burial, light, and temperature on seed softening in yellow serradella

1999 ◽  
Vol 50 (7) ◽  
pp. 1203 ◽  
Author(s):  
G. B. Taylor ◽  
C. K. Revell
Keyword(s):  
Final Stage ◽  
Soil Surface ◽  
Light Level ◽  
Inhibitory Effect ◽  
Temperature Treatment ◽  
Diurnal Temperature ◽  
Light Levels ◽  
Buried Seeds ◽  
Softening Process ◽  
A Site

Studies were made on the preconditioning stage (which produces latent soft seeds) and the final stage of seed softening in newly ripened seeds of the GEH72-1A accession of yellow serradella (Ornithopus compressus L.). Pods grown at Yelbeni, Western Australia, in 1996 were collected in December and placed on the soil surface or buried at a depth of 0.5 cm at a site near Perth. Other pods were subjected to a gradual diurnal temperature fluctuation of 60/15°C in darkness in a laboratory chamber. Pod samples were taken from the field at intervals from January to June in 1997, and over 336 days from the 60/15°C treatment. Pods were broken into segments and the number of soft seeds determined. Numbers of latent soft seeds were then determined by subjecting residual hard seeds to 7 gradual diurnal temperature cycles of 48/15°C in darkness and retesting for permeability. In a second experiment, seeds preconditioned at the soil surface until 3 March were subjected to a range of light levels in the field in March before testing for permeability. The time taken for seeds to precondition under a range of constant temperatures between 30° and 70°C was determined in a third experiment. Preconditioning commenced early in summer in both surface and buried seeds. All buried seeds that preconditioned completed the softening process to produce about 80% soft seeds, with most seeds softening in March when diurnal temperatures fluctuated between maxima of 45–50°C and minima of 10–20°C. Only 15% of the seeds at the soil surface softened so that relatively few preconditioned seeds completed the softening process. Preconditioning occurred more rapidly than did the completion of softening in the 60/15°C treatment, indicating that this temperature regime was above optimum for the final stage of softening. Reversal of the preconditioning process took place in the field as temperatures declined during May. Effects of reduced temperatures in causing this reversion were confirmed in the laboratory on seeds preconditioned at 60/15°C. The final stage of softening was inhibited in some seeds by light levels as low as 0.3% of daylight, and in all seeds at a light level between 5 and 25%. A close negative linear relation was obtained between the log of the time taken for 50% of seeds to precondition and the constant temperature treatment between 30°C and 70°C, with the rate of preconditioning doubling with every 5.2°C rise in temperature within this range. Although many seeds preconditioned at the soil surface, the main constraint to completion of the seed softening process during autumn was the inhibitory effect of light.

Seedbank Dynamics of Two Swallowwort (Vincetoxicum) Species

2017 ◽  
Vol 10 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Antonio DiTommaso ◽  
Lindsey R. Milbrath ◽  
Scott H. Morris ◽  
Charles L. Mohler ◽  
Jeromy Biazzo
Keyword(s):  
United States ◽  
Management Strategy ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Growing Season ◽  
First Year ◽  
Northeastern United States ◽  
The Third ◽  
Viable Seeds ◽  
Filled Seeds

Pale swallowwort and black swallowwort are European viny milkweeds that have become invasive in many habitats in the northeastern United States and southeastern Canada. A multiyear seedbank study was initiated in fall 2011 to assess annual emergence of seedlings and longevity of seeds of pale swallowwort and black swallowwort at four different burial depths (0, 1, 5, and 10 cm) over 4 yr. One hundred swallowwort seeds were sown in seed pans buried in individual pots, and emerged seedlings were counted and removed from May through September each year. A subset of seed pans was retrieved annually in October, and recovered seeds were counted and tested for viability. The majority of seedling emergence occurred during the first year (92% in 2012), and no new seedlings emerged in the third (2014) or fourth (2015) years. Pale swallowwort had relatively poor emergence at sowing depths of 0 cm (11%), 5 cm (6%), and 10 cm (0.05%—only one seedling), while 37% of pale swallowwort seeds emerged at 1 cm. The larger-seeded black swallowwort was more successful, with two-thirds of all sown seeds emerging at depths of 1 cm (71%) and 5 cm (66%), and 26% emerging at 10 cm. Only 16% of the surface-sown black swallowwort emerged. A large portion of the seeds that germinated at 10 cm, as well as at 5 cm for pale swallowwort, died before reaching the soil surface. Of filled seeds that were recovered in 2012 (black swallowwort at the 0-cm depth), 66% were viable. No viable seeds were recovered after the second growing season. Seeds recovered following the third year had become too deteriorated to accurately assess. Swallowwort seeds do not appear to survive more than 2 yr in the soil, at least in our experiment, suggesting that the elimination of seed production over 3 yr will exhaust the local seedbank. Seeds would need to be buried at least 10 cm for pale swallowwort but more than 10 cm for black swallowwort to prevent seedling emergence. Burial of swallowwort seeds as a management strategy may, however, only be practical in natural areas where high swallowwort densities occur.

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.

Decline of Weed Seeds and Seedling Emergence Over Five Years as Affected by Soil Disturbances

Weed Science ◽  
1990 ◽  
Vol 38 (6) ◽  
pp. 504-510 ◽  
Author(s):  
Grant H. Egley ◽  
Robert D. Williams
Keyword(s):  
Seedling Emergence ◽  
Soil Surface ◽  
First Year ◽  
Weed Species ◽  
Native Seed ◽  
Seed Population ◽  
Soil Disturbances ◽  
Viable Seeds ◽  
Prickly Sida ◽  
Weed Emergence

Weed emergence and viable weed seed numbers were determined in field plots during a 5-yr period where reseeding was prevented. Known numbers of seeds of seven weed species were added to the native seed population at the beginning of the study. Plots were nontilled or tilled to depths of 0, 5, 10, and 15 cm early in the spring of each year. Velvetleaf, spurred anoda, hemp sesbania, morningglory species, and pigweed species emergence was significantly greater from the nontilled plots during the first year after seeds were added to the native seed population. Tillage, regardless of depth, reduced weed emergence during the first year where seeds were added to the plots but had no effect on emergence from plots where no seeds were added. Tillage during the second through the fifth year did not affect emergence regardless of the addition of seeds. of the 5-yr emergence totals, 61 to 88% of all weeds in all plots emerged during the first year and 9 to 23% emerged during the second year. The 5-yr decline rate for emergence of all weeds was exponential. Viable seeds of prickly sida, spurges, and pigweeds in the nontilled plots declined from 590, 1531, and 4346 m−2, respectively, to zero by the third year. Tillage did not affect the decline. However, weed emergence in the field indicated that a few (1.0 to 5.6 m−2) seeds of those weeds were still viable after 3 yr. In nontilled plots, many recently added seeds were on or near the soil surface and germinated during the first year. Tillage moved many seeds to sites that were unfavorable for germination and emergence during the first year.

A Novel Paradigm for Engineering Education: Virtual Internships With Individualized Mentoring and Assessment of Engineering Thinking

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Naomi C. Chesler ◽  
A. R. Ruis ◽  
Wesley Collier ◽  
Zachari Swiecki ◽  
Golnaz Arastoopour ◽  
...  
Keyword(s):  
Engineering Education ◽  
First Year ◽  
Collaborative Environment ◽  
Large Numbers ◽  
Engineering Problems ◽  
Complex Engineering ◽  
Potential Impact

Engineering virtual internships are a novel paradigm for providing authentic engineering experiences in the first-year curriculum. They are both individualized and accommodate large numbers of students. As we describe in this report, this approach can (a) enable students to solve complex engineering problems in a mentored, collaborative environment; (b) allow educators to assess engineering thinking; and (c) provide an introductory experience that students enjoy and find valuable. Furthermore, engineering virtual internships have been shown to increase students'—and especially women's—interest in and motivation to pursue engineering degrees. When implemented in first-year engineering curricula more broadly, the potential impact of engineering virtual internships on the size and diversity of the engineering workforce could be dramatic.

Direct seeding of black spruce in northwestern Ontario: Seedbed relationships

1994 ◽  
Vol 70 (2) ◽  
pp. 151-158 ◽  
Author(s):  
R. L. Fleming ◽  
D. S. Mossa
Keyword(s):  
Seedling Establishment ◽  
Black Spruce ◽  
Mineral Soil ◽  
Soil Surface ◽  
Direct Seeding ◽  
First Year ◽  
Strongly Correlated ◽  
Seedling Mortality ◽  
Northwestern Ontario ◽  
Seedbed Preparation

A series of spot seeding experiments was set out on coarse-textured upland sites in northwestern Ontario to investigate how black spruce (Picea mariana [Mill.] B.S.P.) seedling establishment and growth could be improved by site selection and seedbed preparation. Virtually all germination occurred within the first growing season. Annual seedling mortality rates were greatest during the first year, then declined steadily and stabilized at low levels (<10%) after the third year. The highest fifth-year establishment ratios (seedlings/viable seed sown) were found on seedbeds derived from materials near the mineral soil/humus interface. On wetter sites (i.e., higher Soil Moisture Regimes) the best seedbeds occurred closer to the soil surface. Mean fifth year establishment ratios for the best seedbeds were 0.032 on moderately fresh to fresh sites, 0.146 on very fresh to moderately moist sites, and 0.082 on moist to very moist sites. On adjacent lowland sites, slow-growing, compact Sphagnum mosses had a mean establishment ratio of 0.179. Mean fifth-year seedling heights on upland sites ranged from 12 to 14 cm, and were not strongly correlated with site or seedbed type. Key words: direct seeding, black spruce, seedbed, seedling establishment, site type and germination

Teaching Enterprise — Can it Be Done in Large Groups?

2003 ◽  
Vol 17 (1) ◽  
pp. 37-44
Author(s):  
Raymond D. Donnelly
Keyword(s):  
Market Research ◽  
Business Plan ◽  
Management Programme ◽  
First Year ◽  
Large Numbers ◽  
Commercial Sources ◽  
To Come ◽  
The University ◽  
Large Groups

This paper reports on work carried out in the School of Management at Heriot-Watt University in Edinburgh. Following a wide-ranging review of the first-year management programme, a module on enterprise was introduced. As part of that module students had to compete in a game, the object of which was to come up with a business idea, conduct market research and present a business plan and proposal to a panel of judges. The number of students was 225 in year one but reached around 500 within five years. The module has generated many good ideas and has attracted sponsorship from commercial sources. As yet the university has been unable to take the ideas further. It is possible that enterprise can be learned by people in large numbers, but perhaps universities are not the places in which to attempt such work.

Age, stucture, growth rates and movements of sea mullet, Mugil cephalus L., and Yellow-eye Mullet, Aldrichetta forsteri (Valenciennes), in the Swan-Avon river system, Western Australia

1981 ◽  
Vol 32 (4) ◽  
pp. 605 ◽  
Author(s):  
CF Chubb ◽  
IC Potter ◽  
CJ Grant ◽  
RCJ Lenanton ◽  
J Wallace
Keyword(s):  
Growth Rates ◽  
River System ◽  
First Year ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Using Data ◽  
The Times ◽  
First Year Of Life ◽  
Breeding Seasons ◽  
System 1

The age structure, growth rates and movements of M. cephalus and A forsteri in the Swan-Avon river system have been investigated using data obtained from beach seining and gill netting carried out between February 1977 and June 1980. Length-frequency data and scale readings show that the populations of both species consist predominantly of 0+ and 1 + fish. From the times when the smallest fry (20-30 mm) were present in the lower part of the river system, and from the condition of the gonads of older fish, the breeding seasons of the sea and yellow-eye mullets have been estimated as extending from March to September and from March to August respectively. The bimodality or polymodality exhibited by the length-frequency distributions for the 0 + year classes suggest that in both species groups of individuals spawn at slightly different times. The range of mean total lengths and weights of animals caught in May near the end of the first year of life was 178-222 mm and 64-119 gin M. cephalus and 136-154 mm and 19-30 g in A. forsteri, which shows that the growth of each of these two species of mullet is relatively very rapid in the Swan-Avon river system. 1 + and 2 + fish tend to leave the estuary for varying periods. Although 0+ fish of both species utilized the shallow banks of the estuary throughout the year. the sea mullet moved further upstream and were not as consistently abundant in the lower estuary. Since 0+ yellow-eye mullet 40-100 mm long were also abundant in marine coastal waters between January and May. and sea mullet of comparable age were rarely observed in these regions, it would appear that M. cephalus is the more estuarine-dependent of the two species. Commercial catches of M. cephalus were greater than those of A. forsteri. This feature can be related in part to the much faster growth rate of M. cephalus, which results in a larger proportion of its youngest year classes reaching the minimum legal size for capture prior to the time when they leave the estuary in large numbers.

Amelioration of subsurface acidity in sandy soils in low rainfall regions .2. Changes to soil solution composition following the surface application of gypsum and lime

Soil Research ◽  
1994 ◽  
Vol 32 (4) ◽  
pp. 847 ◽  
Author(s):  
CDA Mclay ◽  
GSP Ritchie ◽  
WM Porter ◽  
A Cruse
Keyword(s):  
Ionic Strength ◽  
Soil Solution ◽  
Ion Pairs ◽  
Chemical Properties ◽  
Sandy Soils ◽  
Soil Surface ◽  
Field Trials ◽  
Annual Rainfall ◽  
First Year ◽  
Solution Composition

Two field trials were sampled to investigate the changes to soil solution chemical properties of a yellow sandplain soil with an acidic subsoil following the application of gypsum and lime to the soil surface in 1989. The soils were sandy textured and located in a region of low annual rainfall (300-350 mm). Soil was sampled annually to a depth of 1 m and changes in soil solution composition were estimated by extraction of the soil with 0.005 M KCl. Gypsum leaching caused calcium (Ca), sulfate (SO4) and the ionic strength to increase substantially in both topsoil and subsoil by the end of the first year. Continued leaching in the second year caused these properties to decrease by approximately one-half in the topsoil. Gypsum appeared to have minimal effect on pH or total Al (Al-T), although the amount of Al present as toxic monomeric Al decreased and the amount present as non-toxic AlSO+4 ion pairs increased. Magnesium (Mg) was displaced from the topsoil by gypsum and leached to a lower depth in the subsoil. In contrast, lime caused pH to increase and Al to decrease substantially in the topsoil, but relatively little change to any soil solution properties was observed in the subsoil. There was an indication that more lime may have leached in the presence of gypsum in the first year after application at one site. Wheat yields were best related to the soil acidity index Al-T/EC (where EC is electrical conductivity of a 1:5 soil:water extract), although the depth at which the relationship was strongest in the subsoil varied between sites. The ratio Al-T/EC was strongly correlated with the activity of monomeric Al species (i.e. the sum of the activities of Al3+, AlOH2+ and Al(OH)+2 in the soil solution. An increase in the concentration of sulfate in the subsoil solution (which increased the ionic strength, thereby decreasing the activity of Al3+, and also increased the amount of Al present as the AlSO+4 ion pair) was probably the most important factor decreasing Al toxicity to wheat. The results indicated that gypsum could be used to increase wheat growth in aluminium toxic subsoils in sandy soils of low rainfall regions and that a simple soil test could be used to predict responses.

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