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.

Effect of burial on the softening of hard seeds of subterranean clover

1984 ◽  
Vol 35 (2) ◽  
pp. 201 ◽  
Author(s):  
GB Taylor
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
The Other ◽  
Soil Tillage ◽  
Microbial Decomposition ◽  
Buried Seeds ◽  
Hard Seeds ◽  
Depth Of Burial

Burrs of eight varieties of subterranean clover (Trifolium subterraneum L.), which had experienced one summer at the soil surface, were placed on the soil surface and at depths of 2, 6 and 10 cm in the soil. The numbers of residual hard seeds were determined after 1, 2 and 3 years. The effects of laboratory treatment at a diurnally fluctuating temperature of 60/15�C on the softening of buried seeds and of seeds stored in the laboratory for 1 and 3 years were determined. Rate of seed softening in all varieties decreased with increasing depth of burial, apparently because the soil insulated the seeds from high soil surface temperatures. Few seeds of the varieties Northam and Geraldton softened during 3 years of burial at 6 or 10 cm; while, at the other extreme, few seeds of Yarloop survived 3 years at any depth. Some evidence was found for microbial decomposition of hard seeds in the field. Seeds softened more readily at 60/15�C (in the laboratory) as the preceding periods of either laboratory storage or field burial increased. Such storage or burial experiences have a preconditioning effect on hard seeds, making them more amenable to softening once they are subjected to wide diurnal temperature fluctuations. The results indicate that soil tillage associated with cropping should build up a useful soil seed reserve of the harder seeded varieties.

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.

The influence of the growing season and the following dry season on the hardseeedness of subterranean clover in different environments

1965 ◽  
Vol 16 (3) ◽  
pp. 277 ◽  
Author(s):  
BN Quinlivan
Keyword(s):  
Surface Temperature ◽  
Critical Factor ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
Growing Season ◽  
Growing Period ◽  
Hard Seeds ◽  
Soil Surface Temperature

The length of the growing period in the spring months appears to be a critical factor in the development of hardseededness in subterranean clover (Trifolium subterraneum L.). Environments with relatively long spring growing periods cause a higher proportion of hard seeds to form at field maturity, and increase the resistance which these hard seeds are capable of offering to the softening effects of the following summer environment. During the dry summer period the rate of softening of hard seeds is determined, not only by the previous growing season but also by the summer environment itself. Hot summer environments with wide soil surface temperature fluctuations are conducive to a relatively rapid rate of softening. Grazing or removal of the dry topgrowth from a pasture during the summer increases the daily soil surface temperature fluctuations, and results in the hard seeds softening at an increased rate. Differences in the overall environment manifest themselves in terms of site and seasonal variation in the proportion of hard seeds which survive beyond the opening of the following growing season. The scope for variation is wide, and this has agronomic significance from the aspect of long-term persistence of the species.

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.

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.

The effect of constant and fluctuating temperatures on the permeability of the hard seeds of some legume species

1961 ◽  
Vol 12 (6) ◽  
pp. 1009 ◽  
Author(s):  
BJ Quinlivan
Keyword(s):  
Constant Temperature ◽  
Temperature Fluctuation ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
Lupinus Luteus ◽  
Maximum Effect ◽  
Rate Of Increase ◽  
Hard Seeds ◽  
Temperature Ranges

Hard seeds of Lupinus digitatus Forsk., Lupinus luteus L., Medicago tribuloides Desr., and Trifolium subterraneum L. (Mt. Barker, Dwalganup, and Geraldton strains) were subjected to constant temperatures of 60 and 140°F, and to fluctuating temperature ranges of 60–115°F, 60–140°, and 60–165°, for a period of 5 months. The temperature fluctuation treatments were set to follow patterns similar to those experienced on the soil surface during the summer months in the agricultural districts of Western Australia. Increased permeability, i.e. an increase in the percentage of seeds permeable to water, took place under all temperature conditions. The lowest increase occurred at a constant temperature of 60°F. A constant temperature of 140° gave a relatively higher increase. All three temperature fluctuation treatments increased the permeability as compared with the constant temperatures, with maximum effect at a range of 60-140°F. Increasing the range to 60–165° did not increase the permeability. With the exception of L. digitatus all species subjected to temperature fluctuations showed a rapid increase in permeability over the first 2 or 3 months. Beyond this point the rate of increase was very slow. The permeability or softening pattern followed by L. digitatus was almost the direct opposite to that of the other species. Of the three strains of T. subterraneum, Mt.. Barker showed the highest increase in permeability under temperature fluctuations and Geraldton the least.

Determination of the lattice translation across {110} APBs in GaAs

1988 ◽  
Vol 46 ◽  
pp. 600-601
Author(s):  
D.R. Rasmussen ◽  
N.-H. Cho ◽  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Lower Energy ◽  
Antiphase Boundary ◽  
The Other ◽  
Boundary Structure ◽  
Interface Plane ◽  
Inversion Symmetry ◽  
High Angle ◽  
Equilibrium Distance

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

Determination of the Burgers vector of a dislocation in a Fe-Mn alloy by weak-beam image in HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 330-331
Author(s):  
Y. Ishida ◽  
H. Ishida ◽  
K. Kohra ◽  
H. Ichinose
Keyword(s):  
High Order ◽  
Simulation Technique ◽  
The Other ◽  
Image Simulation ◽  
Diffraction Vector ◽  
Burgers Vector ◽  
Weak Beam ◽  
Beam Image ◽  
Edge Component

IntroductionA simple and accurate technique to determine the Burgers vector of a dislocation has become feasible with the advent of HVEM. The conventional image vanishing technique(1) using Bragg conditions with the diffraction vector perpendicular to the Burgers vector suffers from various drawbacks; The dislocation image appears even when the g.b = 0 criterion is satisfied, if the edge component of the dislocation is large. On the other hand, the image disappears for certain high order diffractions even when g.b ≠ 0. Furthermore, the determination of the magnitude of the Burgers vector is not easy with the criterion. Recent image simulation technique is free from the ambiguities but require too many parameters for the computation. The weak-beam “fringe counting” technique investigated in the present study is immune from the problems. Even the magnitude of the Burgers vector is determined from the number of the terminating thickness fringes at the exit of the dislocation in wedge shaped foil surfaces.

Procedures for the Quantitative Determination of Autoprothrombin C

1962 ◽  
Vol 08 (03) ◽  
pp. 434-441 ◽  
Author(s):  
Edmond R Cole ◽  
Ewa Marciniak ◽  
Walter H Seegers
Keyword(s):  
Quantitative Determination ◽  
Plasma Sample ◽  
Quantitative Measure ◽  
The Other ◽  
Clotting Time ◽  
Bovine Plasma ◽  
Autoprothrombin C

SummaryTwo quantitative procedures for autoprothrombin C are described. In one of these purified prothrombin is used as a substrate, and the activity of autoprothrombin C can be measured even if thrombin is in the preparation. In this procedure a reaction mixture is used wherein the thrombin titer which develops in 20 minutes is proportional to the autoprothrombin C in the reaction mixture. A unit is defined as the amount which will generate 70 units of thrombin in the standardized reaction mixture. In the other method thrombin interferes with the result, because a standard bovine plasma sample is recalcified and the clotting time is noted. Autoprothrombin C shortens the clotting time, and the extent of this is a quantitative measure of autoprothrombin C activity.

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