The effects of a continued water supply during and beyond seed development on seed production and losses in subterranean clover swards

1980 ◽  
Vol 31 (2) ◽  
pp. 287 ◽  
Author(s):  
WJ Collins ◽  
BJ Quinlivan
Keyword(s):  
Seed Germination ◽  
Water Supply ◽  
Seed Development ◽  
Subterranean Clover ◽  
Moisture Stress ◽  
Pathogenic Microorganisms ◽  
Marked Decline ◽  
Beginning Of Flowering ◽  
Seed Yields ◽  
Number Of Seeds

Four strains of subterranean clover were grown in swards and mown regularly until the beginning of flowering. During the period of flowering and seed development, the swards were irrigated as required to prevent moisture stress. Watering was then continued to keep the burrs and seeds moist for a further 5 months. Depending on the strain, seed yields reached a peak between 74 days and 86 days after the onset of flowering (late August-early September). Then followed a sudden and marked decline in both the amount and number of seeds present in the four strains. By the end of February less than 20% of the seeds produced were still present in the soil. Seed germination accounted for less than 50% of the seed losses. The remainder (unrecovered seed) was presumably lost as a result of attack by pathogenic microorganisms in the soil. The results suggest that it may be difficult to obtain maximum seed yields in swards of subterranean clover. Even a relatively small (3 weeks) decrease or increase in the period for which moisture is available, compared with the optimum, can lead to markedly reduced seed yields.

The influence of shading on seed yield in subterranean clover

1978 ◽  
Vol 29 (6) ◽  
pp. 1167 ◽  
Author(s):  
WJ Collins ◽  
RC Rossiter ◽  
MA Ramas
Keyword(s):  
Solar Radiation ◽  
Seed Yield ◽  
Unit Area ◽  
Subterranean Clover ◽  
Curvilinear Relationship ◽  
Light Supply ◽  
Beginning Of Flowering ◽  
Seed Yields ◽  
Agro Forestry

Swards of three strains of subterranean clover (Woogenellup, Clare and Seaton Park) were subjected to three shading treatments (30%, 55% and 100% of daylight) from the beginning of flowering onwards. For the 100% daylight (unshaded) treatment the incoming daily solar radiation averaged between 20 and 30 MJ/m2. In the unshaded treatment, seed yields for the three strains ranged from about 120 to almost 200 g/m2. These yields were invariably decreased by shading. Moreover the evidence indicated a curvilinear relationship between seed yield and light supply such that at 50% of daylight there was a reduction of rather more than 50% in seed yield. Shading mainly affected the number of inflorescences produced per unit area, although other components of seed yield were also affected adversely. Even late shading (towards the end of flowering) led to lower seed yield, partly associated with lower inflorescence numbers and partly with lower seed numbers per burr. The results are considered to have significance for clover regeneration in mixed clover/grass pastures and also in the cloveritree associations of agro-forestry.

Effects of phosphorus on seed yields of subterranean clover, serradella and annual medics

1985 ◽  
Vol 25 (3) ◽  
pp. 595 ◽  
Author(s):  
MDA Bolland
Keyword(s):  
Seed Yield ◽  
Subterranean Clover ◽  
Average Weight ◽  
The Third ◽  
Hard Seeds ◽  
Annual Medics ◽  
Alternating Temperature ◽  
Seed Yields ◽  
The Relationship ◽  
Number Of Seeds

In three experiments located near Esperance, Western Australia, the effect of superphosphate phosphorus on seed yields of subterranean clover, serradella and annual medics was measured on newly-cleared soils, using low seeding rates. In two experiments, the relationship between seed yield and the amount of phosphorus applied was linear for subterranean clover and serradella; seed yields increasing by 7-24 kg/ha for each kg/ha of phosphorus applied, depending on species, strain or cultivar, and location. In the third experiment, seed yields of annual medic species also increased markedly with increasing amounts of applied superphosphate phosphorus, this response also depended on species and strain or cultivar, but the responses become less marked with increasing amounts of phosphorus. For the annual medic species, the phosphorus treatments had no effect on average weight of one burr, number of seeds per burr, weight of one seed, or the rate of softening of hard seeds as measured both in a 15/60� alternating temperature oven (one cycle/day) or for samples of burrs collected periodically during summer from the field. For all legumes, the appearance of first flowers was not affected by phosphorus treatment.

Lodging studies in Lolium perenne grown for seed: 1. Seed yield and seed yield components

1978 ◽  
Vol 90 (2) ◽  
pp. 261-267 ◽  
Author(s):  
P. D. Hebblethwaite ◽  
A. Burbidge ◽  
D. Wright
Keyword(s):  
Seed Development ◽  
Lolium Perenne ◽  
Seed Yield ◽  
Perennial Ryegrass ◽  
Yield Components ◽  
Field Experiments ◽  
Unit Area ◽  
Seed Yield Components ◽  
Seed Yields ◽  
Number Of Seeds

SummaryThe effects of lodging on the seed yield of S. 23 and S. 24 perennial ryegrass were investigated in a series of field experiments from 1973 to 1976. Natural lodging severely reduced seed yield in all years as a result of a decrease in the number of seeds per unit area. Controlled lodging at different stages of crop growth produced more variable results, indicating that lodging may affect both pollination and seed development. Disturbance of the crop during anthesis in order to aid pollination did not improve seed yields, possibly as a result of damage incurred.

The inhibitory effect of light on seed development in subterranean clover (Trifolium subterraneum L.)

1976 ◽  
Vol 27 (2) ◽  
pp. 207 ◽  
Author(s):  
GB Taylor
Keyword(s):  
Seed Development ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Moisture Stress ◽  
Inhibitory Effect ◽  
Atmospheric Moisture ◽  
Dark Treatment ◽  
Poor Seed ◽  
Development Processes ◽  
Effect Of Light

Explanations were sought for the poor seed development commonly found in unburied burrs of subterranean clover. In the first of two experiments, the effects of light and of atmospheric moisture stress on seed development in subterranean clover (cv. Daliak) were examined. Burrs produced from spaced laterals were enclosed in plastic tubes variously shaded to permit the entry of 0, 5, 19, 48 and 100% daylight. The tubes were further allocated to two groups. Air was continuously passed through tubes of one group to produce an atmospheric moisture stress, while those of the other group were not subjected to air flow. There was a marked effect of light on seed development. Mean seed weight was reduced from c. 11 mg in the dark treatment to 4 mg at only 5% daylight and to 2 mg in the 100% daylight treatment. Seed numbers were reduced significantly, from four to c. two seeds per burr, in the 100% daylight treatment only. There was virtually no effect of atmospheric moisture stress on either seed set or seed size. In the second experiment, a study was made of the effect of timing of burr burial on seed development processes. Fertilization does not appear to be implicated but both cell division and cell enlargement were influenced by the state of burial and, presumably, by light.

The effect of some environmental conditions on seed development and hard-seededness in subterranean clover (Trifolium subterraneum L.)

1979 ◽  
Vol 30 (1) ◽  
pp. 65 ◽  
Author(s):  
GB Taylor ◽  
MJ Palmer
Keyword(s):  
Seed Development ◽  
Seed Size ◽  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Moisture Stress ◽  
Effect Of Temperature ◽  
Temperature Regimes ◽  
Increasing Temperature ◽  
Dry Out

Subterranean clover (cv. Daliak) was grown in boxes with provision for unrestricted lateral growth. At the commencement of flowering, plants were allocated to three day/night temperature regimes of 12/7°, 18/13° and 24/19°C in controlled-temperature glasshouses and well watered until maturity (unstressed). In two additional treatments at 18/13°, plants were either subjected to intermittent moisture stress throughout the flowering period (stressed) or well watered for the first 6 weeks of flowering and then allowed to dry out (droughted). Increasing temperature resulted in more rapid inflorescence production, seed development and earlier plant maturation. The overall mean seed size was lower at 24/19° than at the other two temperatures. The stressed and droughted treatments produced fewer and smaller seeds than the corresponding unstressed treatment. There was a small effect of temperature on the degree of hard-seededness as determined from the mean softening time of seed subjected to daily alternating temperatures of 60/15°. Softening time was not significantly affected by watering treatments. There were small differences in softening time due to the position of the burr on the lateral, with a slight trend for seeds from the first-formed burrs to soften more rapidly. Most of the variation in softening time between seeds was due to variation within burrs. The sequence of seed softening within burrs was related to seed size, the larger seeds generally softening first, but no single regression could be used to describe this relationship for different burr positions or treatments. The absence of major treatment effects on the degree of hard-seededness indicates that varying the length of the seed development period does not necessarily result in differences in hard-seededness, as has been suggested from field experiments.

The effect of defoliation on inflorescence production, seed yield and hard-seededness in swards of subterranean clover

1978 ◽  
Vol 29 (4) ◽  
pp. 789
Author(s):  
WJ Collins
Keyword(s):  
Seed Yield ◽  
Yield Components ◽  
No Reduction ◽  
Initial Level ◽  
Subterranean Clover ◽  
Flower Initiation ◽  
Flowering Period ◽  
Beginning Of Flowering ◽  
Cutting Height ◽  
Seed Yields

Swards of three strains of subterranean clover (Seaton Park, Yarloop, Midland B) were subjected to a range of defoliation treatments. In all strains, cutting at weekly intervals at a height of 1.5–2 cm from 1 month after sowing until the onset of flowering led to a slight delay in flower initiation but the time of flowering was little affected. The rate of inflorescence production, however, was always increased, as was the total number of inflorescences produced by the end of flowering. In particular, seed yields were increased by at least 30% compared with uncut controls. This effect was attributable partly to increased inflorescence numbers and partly to increases in other yield components as a consequence of the burial of a large proportion of burrs. Cutting increased the initial level of hard-seededness in Seaton Park and Yarloop; in addition the rate of breakdown of hard-seededness in all strains was slower in seed from the defoliated swards. When cutting was continued until midway through flowering (with the cutting height progressively raised) the seed yield in Yarloop and especially in Midland B was much lower than that obtained when cutting was stopped at the beginning of flowering; but in Seaton Park there was no reduction. With further cutting-until the end of flowering-seed yields were less than when cutting was stopped midway through flowering. Extending cutting into the flowering period (compared with cutting only until the onset of flowering) resulted in a decline in the initial level of hard-seededness and an increase in the rate of breakdown of hard-seededness in Midland B but had little effect in Yarloop or Seaton Park.

Corrigendum - The effect of defoliation on inflorescence production, seed yield and hard-seededness in swards of subterranean clover

1978 ◽  
Vol 29 (4) ◽  
pp. 789
Author(s):  
WJ Collins
Keyword(s):  
Seed Yield ◽  
Yield Components ◽  
No Reduction ◽  
Initial Level ◽  
Subterranean Clover ◽  
Flower Initiation ◽  
Flowering Period ◽  
Beginning Of Flowering ◽  
Cutting Height ◽  
Seed Yields

Swards of three strains of subterranean clover (Seaton Park, Yarloop, Midland B) were subjected to a range of defoliation treatments. In all strains, cutting at weekly intervals at a height of 1.5–2 cm from 1 month after sowing until the onset of flowering led to a slight delay in flower initiation but the time of flowering was little affected. The rate of inflorescence production, however, was always increased, as was the total number of inflorescences produced by the end of flowering. In particular, seed yields were increased by at least 30% compared with uncut controls. This effect was attributable partly to increased inflorescence numbers and partly to increases in other yield components as a consequence of the burial of a large proportion of burrs. Cutting increased the initial level of hard-seededness in Seaton Park and Yarloop; in addition the rate of breakdown of hard-seededness in all strains was slower in seed from the defoliated swards. When cutting was continued until midway through flowering (with the cutting height progressively raised) the seed yield in Yarloop and especially in Midland B was much lower than that obtained when cutting was stopped at the beginning of flowering; but in Seaton Park there was no reduction. With further cutting-until the end of flowering-seed yields were less than when cutting was stopped midway through flowering. Extending cutting into the flowering period (compared with cutting only until the onset of flowering) resulted in a decline in the initial level of hard-seededness and an increase in the rate of breakdown of hard-seededness in Midland B but had little effect in Yarloop or Seaton Park.

The effect of defoliation on seed yield of two strains of subterranean clover grown in monocultures and in binary mixtures

1983 ◽  
Vol 34 (6) ◽  
pp. 671 ◽  
Author(s):  
WJ Collins ◽  
I Rhodes ◽  
RC Rossiter ◽  
MJ Palmer
Keyword(s):  
Competitive Advantage ◽  
Seed Production ◽  
Seed Yield ◽  
Unusual Case ◽  
Subterranean Clover ◽  
Replacement Series ◽  
Competitive Relations ◽  
Beginning Of Flowering ◽  
Seed Yields ◽  
Competition For Resources

The effect of defoliation on seed production was examined in swards of Seaton Park and Midland B grown in a de Wit replacement series in the field. The three defoliation treatments were: D0, uncut (control); D1, defoliated at weekly intervals until the beginning of flowering; and D3, as for D1 but with cutting continued until the end of flowering. Defoliation up to the commencement of flowering (D1) had no significant effect on seed yield in the monocultures of either strain. However, with severe defoliation (D3) seed yields were reduced in both strains, although more so in Midland B than in Seaton Park. This greater sensitivity of Midland B supports the results of earlier work. The most important finding from this study was that cutting influenced the competitive relations between the two strains. For both the D0 and D1 treatments there was competition for the same resources ('space' of de Wit); in D0 neither strain had a competitive advantage, whereas in D1 Midland B appeared to be the better competitor. By contrast, in the D3 treatment there was the relatively unusual case of competition for resources which were not entirely the same; and here Seaton Park was the better performer. Possible explanations for this response are suggested.

An analysis of seed yield in some strains of subterranean clover (Trifolium subterraneum L.) when grown in binary mixtures

1981 ◽  
Vol 32 (3) ◽  
pp. 445 ◽  
Author(s):  
RC Rossiter ◽  
MJ Palmer
Keyword(s):  
Competitive Advantage ◽  
Seed Yield ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
The Other ◽  
Pair Member ◽  
Replacement Series ◽  
Beginning Of Flowering ◽  
Seed Yields

Two experiments using various strains of subterranean clover are described. The first experiment was conducted in the field with mixtures of Dwalganup/Northam A, DwalganupI/Daliak and Yarloop/Seaton Park, and the second in an open-sided glasshouse with Yarloop/Seaton Park. In the field experiment, the plots were grazed continuously from late July until early November when the swards were completely dry; in the glasshouse experiment, the swards were defoliated weekly until shortly after the beginning of flowering. Mixtures were arranged according to the de Wit replacement series. Seed yields for the Dwa1ganup/Northam A mixture showed the classical (de Wit) competition for the same resources, with Northam A the better competitor. On the other hand, for the Dwalganup/Daliak and Yarloop/Seaton Park mixtures there was no clear evidence of a competitive advantage of one strain over the other pair member, at least under our defoliated conditions. Whether or not this absence of 'competition' (as usually understood) is common in clover-strain mixtures is as yet unknown. We emphasize, however, that long-term success of clover strains in mixtures is not invariably associated with competitive advantage.

Microflora in External Auditory Canals of Recreational Scuba-Divers and Swimmers Related to the Tropical Waterflora of a Coral Island

1993 ◽  
Vol 27 (3-4) ◽  
pp. 187-193
Author(s):  
T. Haider ◽  
R. Sommer ◽  
G. Stanek
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Water Supply ◽  
External Auditory Canal ◽  
Pathogenic Microorganisms ◽  
Lagoon Water ◽  
Scuba Divers ◽  
Tropical Coral ◽  
Coral Island ◽  
Recreational Scuba ◽  
The Tropics

Recent studies described the acute diffuse external otitis frequently observed in recreational scuba-divers and swimmers in the tropics. In this study the microflora of the external auditory canal of 90 persons was determined. Additionally, a group of 17 persons was examined before, during and at the end of a two weeks vacation on a tropical coral island as well as three months after. Further, samples from sea, lagoon water and the water supplies used for the showers were microbiologically examined. 14 different and fecultatively pathogenic microorganisms were isolated from the external auditory canals. We found a temporary colonization with those microorganisms during the two weeks. Above all Pseudomonas aeruginosa was predominant during and at the end of the vacation especially in children. Before the vacation and three months after P. aeruginosa could not be found. The samples of sea and lagoon waters did not seem to be noticeably polluted, whereas the samples of the water supply were extremely contaminated with Pseudomonas aeruginosa. It was concluded that besides indirect factors such as tropical climate and intensive exposition to water, the insufficient treatment of the water from the supply could also be a reason for the temporary microbiological colonization of the external auditory canal.

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