Competition between plants of different initial seed sizes in swards of subterranean clover (Trifolium subterraneum L.) with particular reference to leaf area and the light microclimate

1958 ◽  
Vol 9 (3) ◽  
pp. 299 ◽  
Author(s):  
JN Black
Keyword(s):  
Leaf Area ◽  
Incident Light ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Light Energy ◽  
Light Extinction ◽  
Unexpected Finding ◽  
Sampling Occasion ◽  
Area Index ◽  
Initial Seed

A study was made of the development and fate of individual plants growing from contrasting seed sizes in swards of subterranean clover (var. Bacchus Marsh). Three sets of swards were grown in boxes, from large, small, and mixed (large and small) seeds respectively, all sown at the same number of plants per unit area; the swards were harvested on five occasions. Leaf area in each 2 cm layer of the sward was determined separately and measurements of the light intensity reaching each layer were obtained at each harvest. Counts of the plants on each occasion revealed a steady drop of about 30 per cent. over the whole period; in the "mixed" swards, only plants from small seed sizes died, the number of large-seeded plants remaining unchanged. The data of leaf area and numbers in each layer showed that leaf area is concentrated in a relatively shallow band at the top of the sward, the area attained by individual leaves increasing with height in the sward and with time. Leaves are not retained in the canopy at heights below that at which light extinction occurs. An unexpected finding was that, as the sward developed, the leaf area index (the ratio of leaf area to ground covered) required for the absorption of all incident light energy increases, and it is suggested that this is due to changes in leaf morphology. The importance of the position at which leaves of individual plants are held in the canopy is stressed; although at the first sampling occasion, the small-seeded plants had 25 per cent. of the leaf area of the mixed sward, they were so located as to absorb only 10 per cent. of the incident light energy; at the last sampling occasion, the values were 10 and 2 per cent. respectively. It is concluded that the disappearance of the small-seeded plants from the mixed swards was due to shading from the large-seeded plants.

Seed size as a factor in the growth of subterranean clover (Trifolium subterraneum L.) under spaced and sward conditions

1957 ◽  
Vol 8 (4) ◽  
pp. 335 ◽  
Author(s):  
JN Black
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Seed Size ◽  
Seed Weight ◽  
Agricultural Research ◽  
Incident Light ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Area Index ◽  
Significant Difference

The significance of seed weight in the growth of subterranean clover (Trifolium subterraneum L) , of the Bacchus Marsh strain, has been assessed under both spaced plant and sward conditions at the Waite Agricultural Research Institute. Under conditions of spacing, plants of three widely separated seed size grades were grown a t a density of 1 per 25 sq. links. The dry weights of the plants were proportional to seed weight from the time of sowing (in May) till the end of October – over almost the entire growing period of the crop. Three sets of swards were grown a t a density of 25 plants per sq. link, each sward being planted with seed of one of the three sizes. Dry weight was proportional to seed weight in the early part of the season but when the swards reached a leaf area index of about 4 (i.e. when there were 4 sq. links of leaf surface on 1 sq. link of ground), a reduction in growth rate occurred. This critical leaf area index was reached first in "large seed" swards, followed later by "medium seed" and finally by "small seed" swards. Thus there was a period in which the swards were growing at different rates, and in which the dry weights came to parity, so that on the final sampling occasion (in December) there was no significant difference between the dry weights of the swards from the three seed sizes. It is concluded that a t a leaf area index of about 4, interception of incident light energy is complete.

Competition between two varieites of subterranean clover (Trifolium subterraneum L.) as related to the proportions of seed sown

1961 ◽  
Vol 12 (5) ◽  
pp. 810 ◽  
Author(s):  
JN Black
Keyword(s):  
Vegetative Growth ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Light Energy ◽  
Sampling Occasion ◽  
Large Seed ◽  
Light Intensities ◽  
Petiole Elongation

The Yarloop and Tallaroolr varieties of subterranean clover (Trifolium subterraneum L.) xvere grown in swards in six mixtures, varying from 100% Yarloop/0%, Tallarook to 0% Yarloop/100% Tallarook, to find out whether the suppression of Tallarook by Yarloop consequent upon the greater petiole elongation of yarloop would still occur when only a few Yarloop plants were present. The swards were grown in large seed boxes and were sampled on four occasions during vegetative growth. Leaf areas for each 2 cm layer of the swards were determined separately for the two strains, and light intensities at each layer were measured at each sampling occasion. It was shown that Yarloop plants suppressed Tallarook in all mixtures. The relative amounts of light energy available to the two strains in the mixed swards left no doubt that the suppression of Tallarook was the result of shading by the taller-growing Yarloop plants.

scholarly journals The effect of continuous grazing on the seed production of Subterranean clover (Trifolium subterraneum).

2003 ◽  
Vol 11 ◽  
pp. 155-160
Author(s):  
M.L. Smetham ◽  
B.S. Dear
Keyword(s):  
Leaf Area ◽  
Seed Production ◽  
Seed Yield ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Area Ratio ◽  
Area Index ◽  
Plant Weight ◽  
Continuous Grazing ◽  
Intensive Sampling

Three pure swards of subterranean clover were either (a) left ungrazed with a leaf area index (LAI) of 4.6, or (b) continuously grazed leniently to leave 1 600 kg DM/ha herbage mass equivalent to an LAI of 1.0, or (c) hard grazed to leave 1 400 kg DM/ha herbage mass equivalent to an LAI of 0.6 throughout the flowering period. These swards yielded 1 250, 320 and 70 kg/ha of seed, respectively. One intensive sampling during the middle of flowering showed that seed yield was positively correlated with plant weight, leaf area per plant, and area per leaf, specific leaf area and leaf area ratio. Grazing reduced numbers of both inflorescences and burrs and hence seed yield. Whilst reduced leaf area and plant weight may have also been partly responsible, under hard grazing, only 58% of potential reproductive sites were occupied which suggests that grazing animals also reduced seed yield by consuming these. It is recommended that continuous grazing during flowering and seed maturation should be controlled to leave at least 1 600 kg DM/ha of residual herbage mass, equivalent to an LAI of 1.0, if adequate seed is to be produced to be ensure the establishment of a high producing sward in the following growing season. Key words: flowering, grazing, herbage mass, leaf area, seed production, Trifolium subterraneum

The influence of seed size and depth of sowing on pre-emergence and early vegetative growth of subterranean clover (Trifolium subterraneum L.)

1956 ◽  
Vol 7 (2) ◽  
pp. 98 ◽  
Author(s):  
JN Black
Keyword(s):  
Leaf Area ◽  
Seed Size ◽  
Vegetative Growth ◽  
Dry Matter ◽  
Relative Rate ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Total Leaf Area ◽  
Pot Culture

Changes in the pre-emergence distribution of dry matter in subterranean clover (Trifolium subterraneum L.) variety Bacchus Marsh were followed at 21°C, using three sizes of seed and three depths of sowing, ½, 1¼, and 2 in. Decreasing seed size and increasing depth of sowing both reduce the weight of the cotyledons a t emergence. Seed of the three sizes were sown a t three depths in pot culture a t staggered intervals so that emergence was simultaneous. Dry weight in the early vegetative stage was proportional to seed size, and total leaf area and leaf numbers showed similar trends. Plants of each seed size grew at the same relative rate. No effect of depth of sowing could be detected, and this was shown to be due to the cotyledon area a t emergence being constant for any given seed size, regardless of varying depth of sowing and hence of cotyledon weight. It was concluded that seed size in a plant having epigeal germination and without endosperm is of importance: firstly, in limiting the maximum hypocotyl elongation and hence depth of sowing, and secondly, in determining cotyledon area. Cotyledon area in turn influences seedling growth, which is not affected by cotyledon weight. Once emergence has taken place, cotyledonary reserves are of no further significance in the growth of the plants.

scholarly journals A Plant Process Economic Model for Weed Management Decisions in Irrigated Onion

1999 ◽  
Vol 124 (1) ◽  
pp. 99-105 ◽  
Author(s):  
Claudio M. Dunan ◽  
Philip Westra ◽  
Frank D. Moore
Keyword(s):  
Leaf Area ◽  
Plant Density ◽  
Light Extinction ◽  
Species Number ◽  
Yield Reduction ◽  
Weed Species ◽  
Early Application ◽  
Area Index ◽  
Variable Approach ◽  
Number Of Leaves

A simulation model was built as a decision aid for management of five weed species in direct seeded irrigated onion (Allium cepa L.). The model uses the state variable approach and simulations are driven by temperature and sunlight as photosynthetically active radiation (PAR). It predicts yield reduction caused by competition for PAR according to the ratio of crop leaf area index (LAI) to weed LAI and respective light extinction coefficients (k). Input variables are plant density by species and average number of leaves by species. Number of leaves per plant is used by the model to provide an estimate of initial leaf area per plant. The model calculates initial species LAIs by multiplying species density times average leaf area per plant. The model accurately describes competitive interactions, taking into account respective plant densities, time of emergence, and time of weed removal. It permits economic evaluation of management factors such as handweeding, chemical weed control, herbicide phytotoxicity due to early application, and control of weed flushes during the season. The model is also used to evaluate mechanisms of plant competition for sunlight. In a sensitivity analysis, onion yield loss was more sensitive to weed PAR interception than to PAR use efficiency, the latter a species-dependent constant in the model.

Defoliation as a factor in the growth of varieties of subterranean clover (Trifolium subterraneum L) when grown in pure and mixed swards

1963 ◽  
Vol 14 (2) ◽  
pp. 206 ◽  
Author(s):  
JN Black
Keyword(s):  
Agricultural Research ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Light Energy ◽  
Weight Changes ◽  
Agricultural Research Institute ◽  
Large Seed ◽  
Waite Agricultural Research Institute ◽  
High Yielding Varieties

This paper describes two experiments analysing the recovery from defoliation of subterranean clover varieties grown in swards in large seed boxes at the Waite Agricultural Research Institute, Adelaide. The first experiment examined the way in which the six common commercial varieties recovered from a single severe defoliation, and showed that under these conditions they can be placed in three groups: Yarloop and Clare are tall, high-yielding varieties with few, large leaves, recovering slowly from defoliation; Tallarook and Dwalganup are prostrate varieties, lower-yielding, with many small leaves, recovering rapidly after defoliation; Bacchus Marsh and Mount Barker are intermediate in all respects. In the second experiment mixed swards of equal numbers of Yarloop and Tallarook plants were grown under three treatments: A, no defoliation; B, defoliated twice at a height which removed the higher Yarloop canopy but left the lower Tallarook plants untouched; C, defoliated twice at a height which removed the canopies of both varieties. Measurement of dry weight on four occasions after each defoliation showed that in the undefoliated treatment, all Tallarook plants died by the end of the experiment. In the defoliated treatments, the removal of the Yarloop canopy resulted in only a temporary improvement in the illuniination in which the Tallarook plants grew, and their dry weight and plant numbers progressively declined. Dry weight changes in the Tallarook component were shown to be dependent on the light energy available to it, which was in turn determined by the light-absorbing capacity of the superior Yarloop canopy. In mixed swards, the ability of Yarloop to re-establish quickly a leaf canopy above that of Tallarook appeared to explain its success when defoliated.

The significance of petiole length, leaf area, and light interception in competition between strains of subterrranean clover (Trifolium subterraneum L.) grown in swards

1960 ◽  
Vol 11 (3) ◽  
pp. 277 ◽  
Author(s):  
JN Black
Keyword(s):  
Leaf Area ◽  
Leaf Development ◽  
Plant Competition ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Sampling Period ◽  
Dry Weight ◽  
Petiole Length ◽  
Petiole Elongation ◽  
Light Profiles

Three strains of subterranean clover differing in leaf development were grown in pure swards and in all combinations in mixtures. The strain Yarloop has relatively few large leaves held on long petioles; Tallarook has many small leaves and short petioles; Bacchus Marsh is intermediate in all these respects. The swards were grown in boxes and were sampled on four occasions during the period of vegetative growth. Leaf area in each 2 cm layer of the sward was determined separately, and for both strains in the mixed swards, and measurements of the light intensity reaching each layer were obtained. Root weights were determined for all swards and separately for each component of the mixed swards. Examination of the dry weights showed that the growth of the strain having the lesser petiole elongation was suppressed. In the extreme instance Tallarook was so suppressed when grown with Yarloop that in the final inter-sampling period it grew completely in the dark, and lost about half its dry weight. Bacchus Marsh also suppressed Tallarook, but to a lesser extent, while Bacchus Marsh was itself suppressed in competition with Yarloop. The amount of light energy intercepted by the two components of the mixed swards was calculated from the leaf area and light profiles, and confirmed the importance of the spatial distribution of leaves in plant competition. It was concluded that, in the absence of defoliation, the success of a strain under competition was associated with its potential petiole elongation.

Growth of skeleton weed (Chondrilla juncea L.) as affected by growth of subterranean clover (Trifolium subterraneum L.) and infection by Puccinea chondrillina Bubak and Syd

1975 ◽  
Vol 26 (6) ◽  
pp. 975 ◽  
Author(s):  
RH Groves ◽  
JD Williams
Keyword(s):  
Leaf Area ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Root Competition ◽  
Leaf Number ◽  
Root Weight ◽  
Large Reduction ◽  
Plant Parts ◽  
Chondrilla Juncea

Growth of skeleton weed (Chondrilla juncea, form A) and subterranean clover (Trifolium subterraneum) was studied in a glasshouse experiment in which the species were grown alone or together and the resultant effects of shoot and root competition assessed. The leaf number and weight of plant parts of C. juncea were reduced by competition vith subterranean clover, especially when shoots of the two species were competing. The leaf area of C. juncea was reduced, especially when roots of the two species were growing together. Puccinia chondrillina on C. juncea rosettes reduced leaf number, leaf area, and weight of plant parts. Subterranean clover grown with C. juncea infected with P. chondrillina further reduced the size and weight of the weed. The large reduction in leaf area and root weight of C. juncea (form A) plants in the presence of both subterranean clover and P. chondrillina suggests that growth of this form of C. juncea in Australia will be greatly reduced in pastures containing these species. In the long term, densities of this form may possibly be so lowered that a significant level of control will be reached in a cereal cropping-pasture system.

Effects of early defoliation on the seedling growth of subterranean clover

1992 ◽  
Vol 43 (3) ◽  
pp. 717
Author(s):  
RC Rossiter
Keyword(s):  
Linear Relationship ◽  
Leaf Area ◽  
Seedling Growth ◽  
Shoot Growth ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Relative Reduction ◽  
Insect Damage ◽  
Leaf Production ◽  
Plant Densities

Two experiments were conducted in an open-sided glass shelter at Perth during winter. Subterranean clover (Trifolium subterraneum, L.) seedlings were grown in shallow seed boxes at low plant densities, 2 4 and 2 0 plants/dm2. The effects of a single defoliation involving mainly the removal of cotyledons only, on shoot growth and leaf production were measured at harvest, c. 5 weeks after sowing. Total shoot dry weights were reduced by 15-30% when 40-60% of the leaf area was removed by single defoliations from days 7 to 19 after planting. However, the growth was reduced by almost 70% when both cotyledons were removed (days 7 to 9) before emergence of the unifoliate leaf, i.e. when all of the leaf area was removed. In general, the relative reduction in growth largely depended on the percentage of leaf area removed, rather than on time of removal. Defoliation also reduced the size of trifoliate leaves, and total numbers of trifoliate leaves at harvest. There was a linear relationship between total leaf numbers and shoot dry weights. In the field, these findings are probably of more relevance in terms of insect damage, especially from redlegged earth mites, than for grazing by sheep.

Sign in / Sign up

Export Citation Format

Share Document