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.

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.

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.

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.

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.

Changes with time in the germination of buried scentless chamomile (Matricaria perforata Mérat) seeds

1995 ◽  
Vol 75 (1) ◽  
pp. 277-281 ◽  
Author(s):  
G. G. Bowes ◽  
A. G. Thomas ◽  
L. P. Lefkovitch
Keyword(s):  
Seed Bank ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Growing Season ◽  
Early Spring ◽  
First Year ◽  
Temperature Regimes ◽  
Buried Seed ◽  
Second Year ◽  
Persistent Seed Bank

Change with time in the germination of scentless chamomile (Matricaria perforata Mérat) seeds was investigated. Seeds were placed in nylon net bags, buried 7 cm deep in soil, exhumed at monthly intervals for 2 yr and allowed to germinate in temperature regimes of 10/2 °C, 20/5 °C, 25/10 °C and 35/20 °C (16/8 h), simulating temperatures found during early spring or late fall, spring or fall, summer and mid-summer on the soil surface, respectively. Exhumed and refrigerator-stored (2 °C) check seeds exhibited no yearly dormancy/nondormancy germination cycle, but mortality of buried seed increased to 36%, after 10 mo in contrast with that of the check seeds which remained low for two years. Light was required for germination during the first year but was not required for a portion of the seed during the second year. The retention of viability in buried seed explains the persistent seed bank and seedling emergence throughout the growing season when moisture and temperature are nonlimiting. Key words: Seed burial, germination, Matricaria perforata Mérat

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.

Clover and crop production under 13- to 15-year-old Pinus radiata

1979 ◽  
Vol 19 (98) ◽  
pp. 362 ◽  
Author(s):  
GW Anderson ◽  
FE Batini
Keyword(s):  
Pinus Radiata ◽  
Crop Production ◽  
Subterranean Clover ◽  
Growing Season ◽  
Tree Density ◽  
First Year ◽  
Adjacent Area ◽  
The Third ◽  
One Year ◽  
Seed Yields

A thirteen-year-old Pinus radiata plantation was thinned to 143 or 261 stems ha-1 and pruned to 6 m at Mundaring, Western Australia. The production of the Daliak, Seaton Park and Woogenellup cultivars of subterranean clover sown under the trees and on an adjacent area under pasture only was measured for two years. The yields of oats and lupins sown for two successive years following one year of clover pasture were also measured. No seedling establishment problems were encountered and healthy, productive pastures resulted. In the first year, Daliak was inferior to the other cultivars for both herbage and seed production. Seed yields were highest under the low tree density. By the third growing season herbage yields had fallen under the trees to 84% of the control pastures (4800 kg ha-1) at 143 stems ha-1 and 68% at 261 stems ha-1. The yields of oats were usually higher on the control plots but those of lupins seldom so.

scholarly journals REDUCTION IN GROWTH OF WHITE SPRUCE AFTER OUT-PLANTING

1964 ◽  
Vol 40 (4) ◽  
pp. 488-502 ◽  
Author(s):  
R. E. Mullin
Keyword(s):  
Growing Season ◽  
White Spruce ◽  
First Year ◽  
Age Classes ◽  
Nursery Stock ◽  
Before And After

Several age-classes of nursery stock were sampled before and after the 1963 growing season by excavation of trees. Samples were also planted out and later excavated. Studies of several criteria to express check were made and leader length selected as the most practicable.It is suggested that, by definition, a tree be considered in check until it has achieved a rate of terminal growth equivalent to that it would have attained in the next season in the nursery. Average leader lengths of unchecked trees are suggested for 2-0, 3-0 and 2-2 stock. Check was found to reduce leader length by about 50% in the first year after outplanting. Other experiments indicate that the effect continued for ten years or more in many instances.

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.

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