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.

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.

Canopy Dynamics of Eucalyptus Maculata Hook. I. Distribution and Dynamics of Leaf Populations

1984 ◽  
Vol 32 (4) ◽  
pp. 387 ◽  
Author(s):  
EW Pook
Keyword(s):  
Water Supply ◽  
Leaf Area ◽  
Shoot Growth ◽  
Temperature Limit ◽  
Leaf Fall ◽  
Leaf Production ◽  
Area Index ◽  
Average Size ◽  
Non Destructive

The canopy dynamics of a regenerated 16-year-old stand of pole and sapling E. maculata were studied for 2½ years by repetitive non-destructive measurements in tree crowns accessed from a 20 m high scaffold tower. Average canopy leaf area density over a sample plot of 36 m2 was 0.23 m2 m-3 at a leaf area index of 4.3. Some 75% of leaf area was held in the canopies of overstorey eucalypts above 10 m in height. Average size of leaves increased gradually from top to bottom of tree canopies. Foliage production was usually concentrated in the upper crowns of trees where there was a higher proportion of active shoots, more frequent growth flushes and more rapid turnover of leaves than in lower canopy layers. Leaf area in the upper canopy fluctuated widely but increased in the long term, in mid canopy was more or less maintained and in lowest canopy declined. Crops of developing flower buds present on uppermost branches delayed and/or reduced shoot growth. Foliage production occurred in all months of the year. There was a unimodal annual rhythm of growth rate reaching a maximum in summer and a minimum in winter. Variable water supply, however, influenced production to peak in spring, summer or autumn. No shoot growth occurs in E. maculata at Kioloa when daily mean temperature (averaged for weekly intervals) falls below c. 10½C in winter. An upper temperature limit for growth could not be defined. The species apparently lacks dormancy mechanisms. Shoot growth is 'opportunistic' and occurs whenever environmental conditions are favourable. Patterns of leaf production and leaf fall were variable but peaks showed a general synchrony. Leaf fall, however, tended to lag behind leaf production. Leaves of all ages were shed but main losses were from older cohorts. Some 49% (s.d.±18%) of new leaves were lost while still small or immature, mainly during periods of vigorous shoot growth or low water supply. Browse of immature foliage was light. Normal senescence and leaf fall accounted for almost the entire loss of mature foliage.

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.

Effects of root temperature on growth of four lines of subterranean clover

1972 ◽  
Vol 23 (1) ◽  
pp. 9 ◽  
Author(s):  
JD Williams
Keyword(s):  
Leaf Area ◽  
Dry Matter ◽  
Shoot Growth ◽  
Subterranean Clover ◽  
Root Temperature

One line of subterranean clover (CPI 14196) produced significantly more dry matter than three other lines (CPI 12621 — Israel, Dwalganup, and Mount Barker) at root temperatures suboptimal for shoot growth (10 and 15°C). These differences were associated with leaf area per plant and the size of individual leaves, and the greater growth was associated with partitioning of a greater part of the dry matter to leaves. The significance of the results is discussed in terms of limits to winter production of pastures based on subterranean clover.

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.

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.

Effects of soil salinity and mineral nitrogen on the acetylene reduction activity of Trifolium subterraneum

1984 ◽  
Vol 35 (1) ◽  
pp. 9 ◽  
Author(s):  
P Hopmans ◽  
LA Douglas ◽  
PM Chalk
Keyword(s):  
Linear Relationship ◽  
Soil Salinity ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Mineral Nitrogen ◽  
Acetylene Reduction Activity ◽  
Soil Mineral Nitrogen ◽  
Total N ◽  
Reduction Activity ◽  
C2h2 Reduction

Subterranean clover (Trifolium subrerraneum L.) was grown under controlled environmental conditions in pots containing a variety of soils. Non-destructive assays were used to measure rates of acetylene (C2H2) reduction by the plants. Soil mineral nitrogen (N) status and, to a lesser extent, soil salinity were found to be the most important soil properties relating to the development of C2H2reduction activity in subterranean clover. Application of KNO3 to pots resulted in an immediate decrease in the rate of C2H2reduction. A linear relationship was found between the loss in C,H, reduction activity and the amount of N applied up to 40 mg N kg-1 soil. Addition of salt (NaCl) to pots caused an immediate decrease in C2H2 reduction activity, followed by a gradual recovery. A linear relationship was found between the loss in C2H2 reduction activity and the level of soil salinity induced by salt addition. The loss in C2H2reduction \vas reflected in the lower total N content of the plants when soil salinity levels exceeded 4 mS cm-1.

Distribution of magnesium in subterranean clover (Trifolium subterraneum L.) in relation to supply

1990 ◽  
Vol 41 (3) ◽  
pp. 499 ◽  
Author(s):  
BJ Scott ◽  
AD Robson
Keyword(s):  
Plant Growth ◽  
Shoot Growth ◽  
Leaf Tissue ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Solution Culture ◽  
Tissue Concentrations ◽  
Deficiency Symptoms ◽  
Young Leaves ◽  
Supply Current

The objectives of this study were to examine Mg distribution in subterranean clover (Trifolium subterraneum L.), to identify an appropriate tissue for diagnosis of deficiency and to establish minimum tissue concentrations associated with maximum plant growth. Plants were grown in solution culture with both discontinued (40 8M and 160 8M reduced to nil) and constant supply (0, 5, 10, 20, 40, 80, 160 8M Mg). Magnesium was depleted from old leaves when Mg supply to the roots was interrupted. However, deficiency symptoms occurred first on the young tissue under these conditions. Under constant but inadequate supply, initial deficiency symptoms occurred in old tissue. Symptoms in leaves were associated with Mg concentrations in the leaf of < 1046 8g g-1 with constant root supply and 586 8g g-1 when supply was interrupted. At luxury constant supply, concentrations of Mg tended to be higher in the older leaves than in the young leaves; the reverse occurred with inadequate supply. Tissue choice for diagnosis was not critical, but the minimum Mg concentration in tissue commensurate with maximum shoot growth varied from 740 8g g-1 for the unifoliate leaf to 1310 8g g-1 in the youngest open leaf (YOL), when plants were grown under constant Mg supply. Current supply of Mg to roots was reflected more rapidly in the concentrations in young leaf than in old leaf tissue.

Root distribution in space and time in Trifolium subterraneum

1985 ◽  
Vol 36 (4) ◽  
pp. 601 ◽  
Author(s):  
CJ Pearson ◽  
BC Jacobs
Keyword(s):  
Leaf Area ◽  
Root Length ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Coarse Sand ◽  
Horizontal Distribution ◽  
Dry Matter Partitioning ◽  
Rooting Zone ◽  
Root Death ◽  
Vertical And Horizontal Distribution

Distribution of length and weight of roots of subterranean clover cultivars Northarn and Nungarin were measured in the field throughout a growing season. Plants were grown at seven populations from 2 to 1510 plants per m2 in coarse sand which had a bulk density of 1.4 g cm-3. Root growth was described by its vertical and horizontal distribution as functions of population and time after emergence. Differences in growth between cultivars were small. Root depth, which reached a maximum (plateau) at about 90 days, did not vary with plant population. Root density (length per volume of soil) increased faster at high population due to a higher density of' roots beneath the mainstream and an attenuation with distance away from the mainstem which did not appear to be affected by population. Root densities were 10 cm cm-3 in the uppermost core (0-10 cm depth) and 1.6 -3.5 cm cm-3 throughout the rooting zone (0-50 cm) at 119 days after emergence. Root death, estimated from dichlorotrianzinyl staining, was negligible. Leaf area per plant declined with population above 16 plants per m2; leaf area per unit root length (in cores beneath the mainstream) declined 90-fold with increase in population. Top weight and burr yield per plant at final harvest also declined with increasing population; burr yield per m2 also fell significantly at the highest population. It is concluded that the amount of root per unit area increases with population and that plants appear to adjust conservatively in some respects (to much lower leaf area per root length) while being unable to sustain dry matter partitioning (reducing burr/top yields) at the highest population studied.

The influence of seed size and seeding rate on the growth of two strains of subterranean clover (Trifolium subterraneum L.)

1958 ◽  
Vol 9 (3) ◽  
pp. 286 ◽  
Author(s):  
EH Lawson ◽  
RC Rossiter
Keyword(s):  
Seed Size ◽  
Unit Area ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Early Spring ◽  
Root Production ◽  
Root Weight ◽  
Seeding Rate ◽  
Leaf Production ◽  
Net Assimilation

The results of a field experiment are presented in which large and small seeds of two strains of subterranean clover, Dwalganup and Mt. Barker, were sown at equal weights of viable seed per unit area. Two seeding rates were examined, and four harvests made during the winter-early spring period. The general conclusion is drawn that seed size has no effect on the growth rate of a subterranean clover sward, provided that sowing rate is held constant. It was found that the earlier strain Dwalganup outyielded the mid-season Mt. Barker strain in terms of total tops weight per unit area, although leaf production was higher in the mid-season strain. Root production, however, was consistently greater in Mt. Barker than in Dwalganup, and in fact total yields (of both tops and roots) were very slightly higher in the Mt. Barker strain. Growth rates are discussed in relation to net assimilation rates and leaf weights, and it is suggested that differences in root weight ratios between subterranean clover strains have not received adequate attention in the past.

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