Flower initiation in pasture legumes. I. Factors affecting flower initiation in Trifolium subterraneum L.

1955 ◽  
Vol 6 (2) ◽  
pp. 211 ◽  
Author(s):  
Y Aitken
Keyword(s):  
Low Temperature ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Cold Period ◽  
Effect Of Temperature ◽  
Flower Initiation ◽  
Temperature Level ◽  
Factors Affecting ◽  
Pasture Legumes ◽  
Precise Knowledge

The value of the annual legume Trifolium subterraneum L. (subterranean clover) in Australian agriculture warrants more precise knowledge of factors affecting flowering and prolific seeding. The effect of temperature and photoperiod on flower initiation in early and later flowering varieties has been investigated in an effort to determine the geographical limits of the use of subterranean clover in Australia. At any time of sowing, the length of the growing season of a variety depends greatly on the variety's response to the temperature level and to the photoperiod of the first few weeks after germination. In all varieties of subterranean clover so far examined flower initiation is accelerated by a period of low temperature. In the later varieties, flower initiation is prevented by an insufficient period of low temperature. The length of the necessary cold period is shortened under longer photoperiod. Early varieties are early flowering because they do not require so long a cold period or so low a temperature as late varieties.

Flower initiation in pasture legumes. III. Flower initiation in Medicago tribuloides Desr. and other annual medics.

1955 ◽  
Vol 6 (2) ◽  
pp. 258 ◽  
Author(s):  
Y Aitken
Keyword(s):  
Low Temperature ◽  
Subterranean Clover ◽  
Late Summer ◽  
Flower Initiation ◽  
Commercial Variety ◽  
Barrel Medic ◽  
Pasture Legumes ◽  
Annual Medics ◽  
Long Photoperiod

Observations on barrel medic (Medicago tribuloides Desr., commercial variety) sown throughout the year in the field showed that the flower initiation of the winter sowings was the most rapid and that of the late summer sowings the most delayed. This delay was due to the absence of sufficiently low temperature following germination. Low temperature and long photoperiod accelerate flower initiation in barrel medic as in subterranean clover. Five types of annual medic that persist under Mallee conditions are similar in their flower initiation character to that of the "second-early" varieties of subterranean clover.

Flower initiation in pasture legumes. II. Geographical implications of cold temperature requirements of varieties of Trifolium subterraneum L.

1955 ◽  
Vol 6 (2) ◽  
pp. 245 ◽  
Author(s):  
Y Aitken
Keyword(s):  
Low Temperature ◽  
Trifolium Subterraneum ◽  
Growing Season ◽  
Flower Initiation ◽  
Summer Drought ◽  
Productive Capacity ◽  
Northern Australia ◽  
Mild Winter ◽  
Temperature Requirement ◽  
Temperature Requirements

In Trifolium subterraneum L. (subterranean clover) the low temperature requirements of its range of varieties, together with the mild winter of southern Australia, result in a lengthened growing season compared with that usual in northern Europe, and hence in greater productivity. Over much of southern Australia, some degree of summer drought prevents the use or reduces the yield of perennial species and so the productive capacity of this particular clover has made it of major importance in pastures. The low temperature requirement, however, reduces the value of the species as a self-regenerating annual where temperatures of both summer and winter seasons are too high for flower initiation. This occurs with the later varieties when sown in northern Australia. Temperatures of the summer growing season in the tropics are likely to be too high even for the short low temperature requirement of the earliest flowering group, with its high critical upper margin of about 75°F mean weekly temperature. The dry winter months are cooler, and, if water supply is available, flower initiation is possible, though retarded with consequent leafiness of the plant. Hence in northern Australia, only varieties in the early flowering group may be of use in pastures, and then only in the cooler parts of the region.

Some characteristics of "Carnamah", a very early-flowering strain of Trifolium subterraneum L., when grown as single plants

1961 ◽  
Vol 12 (1) ◽  
pp. 27 ◽  
Author(s):  
RC Rossiter ◽  
AJ Millington
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Early Flowering ◽  
Winter Period ◽  
Flower Initiation ◽  
Total Production ◽  
Initiation Rate ◽  
The Difference ◽  
Early Flower ◽  
Early Strain

A very early-flowering strain of subterranean clover was discovered in 1957 at Carnamah, W.A. From extensive studies at several field centres, it was demonstrated that the new strain – now called Carnamah – commenced flowering from 30 to 10 days before Dwalganup (the standard commercial "early" strain) when sown in the autumn-early winter period. With very early planting – late March – the difference in flowering time was even greater (about 45–50 days). The very early-flowering nature of the Carnamah strain is associated with early flower initiation. Rate of flower development (from flower initiation to flower appearance) in relation to temperature was similar for Carnamah and Dwalganup. Under spaced-plant conditions the total production of Carnamah was much less than that of Dwalganup, a finding which conforms to the results of previous single-plant studies. The new strain was not readily distinguished from Dwalganup, but several minor differences in morphology are mentioned. The chromosome number was normal for the species (2n = 16). The relevance of these data to sward conditions is discussed briefly, and it is suggested that the Carnamah strain may be more effective than Dwalganup in extending the "clover belt" inland in southern Australia.

The growth of barley grass (Hordeum leporinum) in annual pasture. 3. Some factors affecting balance with subterranean clover (Trifolium subterraneum)

1968 ◽  
Vol 8 (35) ◽  
pp. 702 ◽  
Author(s):  
DF Smith
Keyword(s):  
Soil Nitrogen ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Moisture Stress ◽  
Nitrogen Addition ◽  
The Other ◽  
Early Start ◽  
Factors Affecting ◽  
Two Factors ◽  
Hordeum Leporinum

Mixed swards of barley grass (Hordeum leporinum) and subterranean clover (Trifolium subterraneum) of two densities were grown at two levels of nitrogen. Growth was started at two different times mid- April and mid-May-and at each time half the plots were subjected to moisture stress. The swards were harvested after nine weeks of growth. The survival of clover plants was reduced by an early start, moisture stress and nitrogen addition : much more so than barley grass. The root : shoot ratios of both species were calculated ; both showed some sensitivity to the time of break and moisture stress, and the grass was also affected by the other two factors. Total sward production and the ratios of clover to grass varied widely Grass daminance was favoured by moisture stress or a late break, and both of these factors tended to override the effect of higher soil nitrogen in determining clover-grass balance. Total sward production more dependent on density than any other factor, especially with the later start. Higher nitrogen was effective in boosting production only if the break was early and there was no moisture stress.

Seed production and persistence of Carnamah and other early strains of Trifolium subterraneum in the wheatbelt of Western Australia

1967 ◽  
Vol 7 (24) ◽  
pp. 25 ◽  
Author(s):  
GB Taylor ◽  
RC Rossiter
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Western Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Growing Season ◽  
Early Flowering ◽  
The Other ◽  
Factors Affecting ◽  
Seed Yields

Seed production and persistence of the Carnamah, Northam A, Dwalganup, and Geraldton strains of subterranean clover (Trifolium subterraneum L.) were examined in undefoliated swards in the wheatbelt of Western Australia. The early flowering characteristic of Carnamah was not always associated with higher seed yields. Only when there was a well-defined, early finish to the growing season, or when flowering was very much earlier in Carnamah (viz., following an early 'break' to the season), did this strain clearly outyield both Northam A and Geraldton. The seed yield of Dwalganup was generally inferior to that of the other strains. Factors affecting regeneration are discussed. Under low rainfall conditions, poorer germination-regulation of Carnamah, compared with Geraldton and Northam A, would be expected to result in poorer persistence unless offset by higher seed yields in the Carnamah strain.

Nitrogenase Activity by Subterranean Clover and Other Temperate Pasture Legumes

1988 ◽  
Vol 15 (5) ◽  
pp. 657 ◽  
Author(s):  
AG Davey ◽  
RJ Simpson
Keyword(s):  
Root Respiration ◽  
Nitrogenase Activity ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Acetylene Reduction Activity ◽  
Diffusion Resistance ◽  
Pasture Legumes ◽  
Reduction Activity ◽  
Decline Rate ◽  
Nodulated Root

Nitrogenase (C2H2-reduction) activity and nodulated root respiration of intact plants of subterranean clover (Trifolium subterraneum L.) cv. Seaton Park nodulated by Rhizobium trifolii WU95 were measured in a flow-through system. Simultaneous declines in nitrogenase activity and respiration were exhibited 2 min after 10% C2H2 had been introduced into the gas stream. Declines in nitrogenase activity and nodulated root respiration provided an estimate of the efficiency of nitrogenase activity (mol CO2 evolved/mol C2H4 produced). The pre-decline rate of nitrogenase activity at time zero was thus calculated as the product of the respiration associated with nitrogenase activity and the reciprocal of the efficiency of nitrogenase activity. Pre-decline rates of nitrogenase activity were similar to peak rates for several pasture legumes. However, post-decline rates of activity were as much as 70% lower than the pre-decline rate. The age of subterranean clover plants had an important influence on the magnitude of the C2H2-induced decline; young plants exhibited the largest C2H2-induced inhibition of nitrogenase activity. Neither sainfoin (Onobrychis viciifolia Scop.) cv. Othello nodulated by Rhizobium sp. CC1108 nor yellow serradella (Ornithopus compressus L.) cv. Pitman nodulated by R. lupini WU425 exhibited C2H2-induced declines in nitrogenase activity. Nitrogenase-linked respiration of subterranean clover at the 14-leaf stage accounted for 50% of total nodulated root respiration. The oxygen diffusion resistance of the nodules increased in the presence of C2H2 but the effect was reversible once C2H2 was removed from the gas atmosphere. The pre-decline rate of acetylene reduction activity of subterranean clover reached a maximum at 10% C2H2. The C2H2-induced decline in nitrogenase activity was lower at subsaturating pC2H2 and was not detected at 0.4% C2H2.

A Method for obtaining Samples of the Population of Collembola (Symphypleona) in Pastures

1933 ◽  
Vol 24 (3) ◽  
pp. 351-352 ◽  
Author(s):  
J. Davidson ◽  
D. C. Swan
Keyword(s):  
Moisture Content ◽  
Total Population ◽  
Surface Soil ◽  
Relative Proportion ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Food Plants ◽  
Simple Method ◽  
Factors Affecting

In our investigations on Smynthurus viridis, L., a study has been made of the population of this species, in an area of lucerne, at intervals of three and four days throughout the season.The density of the population of the species in a favourable pasture is markedly affected by the relative abundance of certain food-plants, especially leguminous species and particularly clovers such as subterranean clover (Trifolium subterraneum) and lucerne (Medicago sativa).The activity of the insect is intimately associated with the moisture of its environment, and the moisture content of the surface soil is one of the most important factors affecting the environmental conditions.Considering the habits of the insect, it was felt that the sweeping method would not give a reliable record of the total population in a given area of pasture. A sample obtained by sweeping with a net does not include individuals on or near to the surface of the soil. The relative proportion of individuals situated on or near the soil surface and those situated further up the plants varies considerably from time to time, according to the meteorological conditions, the growth of the herbage and the moisture content of the surface soil. It was necessary therefore to devise a simple method by means of which a more accurate record of the total population in a given area could be obtained.

Flower initiation in Trifolium subterraneum L. II. Limitations by vernalization, low temperatures, and photoperiod, in the field at Canberra

1959 ◽  
Vol 10 (1) ◽  
pp. 17 ◽  
Author(s):  
FHW Morley ◽  
LT Evans
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Day Length ◽  
Flower Initiation ◽  
Inhibitory Effects ◽  
Low Field ◽  
The Times ◽  
Short Days

At various times throughout the winter, autumn-sown plants of five strains of subterranean clover were removed from the field to a series of day length and temperature treatments. The times to inflorescence initiation in all treatments were determined by dissection. As vernalization proceeded the requirement of all strains for long days was progressively reduced until, by midwinter, several strains had become virtually independent of day length. Similarly, with the progress of vernalization the inhibitory effects of high temperatures during short days became progressively less marked. Whereas exposure to long days at high temperatures greatly accelerated inflorescence initiation in all strains, long days at low field temperatures had little effect. Evidence is presented which suggests that the limiting effect of very low temperatures on initiation is due not only to retardation of the rate of inflorescence primordium formation (realization), but also to limitation of an inductive process other than vernalization and dark period inhibition. The flowering behaviour of the various strains is discussed in terms of their responses to the partial processes leading to inflorescence initiation, and the interrelationships of these processes are considered.

Long-term patterns of seed softening in some annual pasture legumes in a low rainfall environment

1992 ◽  
Vol 32 (3) ◽  
pp. 331 ◽  
Author(s):  
GB Taylor ◽  
MA Ewing
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Medicago Polymorpha ◽  
Pasture Legumes ◽  
Burr Medic ◽  
Growing Environment ◽  
Simulated Field ◽  
Favourable Environment

Annual rates of seed softening were determined from 4 lines of burr medic (Medicago polymorpha), 1 barrel medic (M. truncatula), and 1 subterranean clover (Trifolium subterraneum) grown at Merredin in the 1 year. Measurements were also made on one of the lines of burr medic grown in 2 other environments, Gnowangerup and Eneabba, in the same year. Burrs were placed on the soil surface at Merredin and the numbers of residual hard seeds determined each year for up to 5 years in this one environment. Patterns of softening of seeds from the same seed populations were also determined in a laboratory oven with a diurnal temperature fluctuation of 60/15�C. In the field, the softening rates of the 5 medics grown at Merredin were similar, averaging 21% of the original seeds each year for the first 4 years. Seeds of the burr medic grown in a more favourable environment at Eneabba were much slower to soften (averaging 14%); hence, hardseededness in these medics was influenced more by the growing environment than by genotype. More than half of the seeds of subterranean clover softened in the field over the first summer, with declining annual proportions thereafter. There were clear differences between the clover and medics in both pattern and rate of seed softening. The lower seed-softening rate of medics than of subterranean clover was more favourable for ley systems involving frequent cropping, especially in low rainfall areas. Treatment of seeds at 60/15�C simulated field softening for subterranean clover well but produced misleading results for the medics.

Vernalization as a factor influencing the rate of development in subterranean clover (Trifolium subterraneum L.)

1975 ◽  
Vol 26 (6) ◽  
pp. 959 ◽  
Author(s):  
WJ Collins ◽  
DF Smith
Keyword(s):  
Environmental Conditions ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Flower Initiation ◽  
Rate Of Development ◽  
Practical Consequence ◽  
Normal Field ◽  
Delayed Flowering

An investigation of the influence of vernalization on the rate of development in three cultivars of subterranean clover was conducted under controlled environmental conditions. Effects were evaluated in terms of the time from imbibition to flower initiation or flowering, i.e. including the time during which vernalization was imposed. In these terms, vernalization actually delayed flowering in the Yarloop and Mt. Barker cultivars, hastening it only in Tallarook. Some practical considerations are discussed. The effects of periods of higher temperatures after vernalization on the rate of development were also studied. No evidence was found for the occurrence of devernalization. If devernalization docs occur in subterranean clover, it is unlikely to be of practical consequence in normal field situations.

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