A Test of a Model for Light Interception by Mixtures

1985 ◽  
Vol 12 (6) ◽  
pp. 681 ◽  
Author(s):  
GM Rimmington
Keyword(s):  
Optical Properties ◽  
Dry Matter ◽  
Light Interception ◽  
Light Energy ◽  
Dry Matter Production ◽  
Additional Test ◽  
Matter Production ◽  
Competition For Light

Predicted and observed data for the amount of light energy intercepted by mixtures of clover and ryegrass are compared, in an additional test of a model which relates competition for light to crop dry matter production. The closeness of predicted and observed values for light interception implies that the optical properties of the component species do not change significantly when they are grown in mixtures. If this is true, then it should be possible to predict the growth of mixtures using information about their optical properties when they are grown in monocultures.

A Model of the Effect of Interspecies Competition for Light on Dry-Matter Production

1984 ◽  
Vol 11 (4) ◽  
pp. 277 ◽  
Author(s):  
GM Rimmington
Keyword(s):  
Dry Matter ◽  
Incident Light ◽  
Light Energy ◽  
Dry Matter Production ◽  
Interspecies Competition ◽  
Area Index ◽  
Unit Leaf ◽  
Matter Production ◽  
Absorption Of Light ◽  
Competition For Light

A model of the effect of interspecies competition for light on the daily dry-matter production of competing species is developed. It describes the absorption of light by the component species, accounting for their different optical properties. Absorption equations are formulated from the principle of conservation of light energy within a unit-leaf-area-index of canopy, and the integral of absorbed light energy is then used to calculate the rate of dry-matter production of each component species. This model proved useful for the analysis of data from experiments in which New Zealand white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) were grown in mixtures. Application of the model enabled the proportion of incident light energy absorbed by each component to be estimated and unambiguous differentiation between the amount of light energy absorbed and the efficiency of use of the absorbed light energy.

Analysis of the regrowth of a tropical grass/legume sward subjected to different frequencies and intensities of defoliation

1980 ◽  
Vol 31 (4) ◽  
pp. 673 ◽  
Author(s):  
MM Ludlow ◽  
DA Charles-Edwards
Keyword(s):  
Leaf Area ◽  
Dry Matter ◽  
Dry Weight ◽  
Light Interception ◽  
Photosynthetic Characteristics ◽  
Dry Matter Production ◽  
Canopy Photosynthesis ◽  
Area Index ◽  
Matter Production ◽  
Cutting Height

Dry weight, leaf area, light interception and canopy photosynthesis were measured during 3- or 5-week regrowth periods of Setaria anceps/Desmodium intortum swards cut to 7.5 or 15 cm. Dry matter production during the experiment and over the growing season increased with cutting height and with interval between defoliations, but the proportion of grass to legume was unaffected. These effects of defoliation on dry matter production were similar to those estimated for integrated canopy photosynthesis from measured light interception and calculated leaf photosynthetic characteristics. Height and frequency of defoliation had no effect on canopy extinction coefficient for light, nor on the leaf photosynthetic characteristics, except for the first 1-2 weeks after defoliation when leaf photosynthetic rates appeared to be depressed. The main effects of height and frequency of defoliation on dry matter production were through their effects on leaf area index and light interception.

Comparison of the Growth and Development of Two Selections of Guar, Cyamopsis tetragonoloba (L.) Taub., With Contrasting Branching Patterns

1984 ◽  
Vol 11 (5) ◽  
pp. 385 ◽  
Author(s):  
DF Beech ◽  
DA Charles-Edwards
Keyword(s):  
Growth And Development ◽  
Dry Matter ◽  
Light Energy ◽  
Dry Matter Production ◽  
Cyamopsis Tetragonoloba ◽  
Matter Production ◽  
Branching Patterns ◽  
Plant Densities ◽  
The Mean

Two selections of guar, C. tetragonoloba, with contrasting branching patterns were grown at two times of year at each of three plant densities. Although the efficiency with which they used intercepted light energy in the production of new dry matter did not differ between the two selections, or between the treatments, it did appear to increase during the ontogeny of the crops. The gross partitioning of new dry matter between leaves, stems and roots was similar between selections and across treatments, but there were large differences in the mean weights of stem associated with each internode, mean leaf weights and specific leaf areas of the two selections. The results of the analysis of dry matter production and partitioning are discussed in relation to the field performances of the two selections.

scholarly journals Responses of Young Tea (Camellia sinensis) Clones to Drought and Temperature. II. Dry Matter Production and Partitioning

1996 ◽  
Vol 32 (4) ◽  
pp. 377-394 ◽  
Author(s):  
P. J. Burgess ◽  
M. K. V. Carr
Keyword(s):  
Dry Matter ◽  
Light Interception ◽  
Radiation Use Efficiency ◽  
Dry Matter Production ◽  
Wave Radiation ◽  
Physiological Basis ◽  
Matter Production ◽  
Use Efficiency ◽  
The Mean ◽  
Radiation Use

SUMMARYThe physiological basis for differences in yields from well-watered and draughted plants of four contrasting clones of tea was studied in terms of light interception, dry matter production and partitioning at a high altitude site in Southern Tanzania where there are marked seasonal variations in rainfall and temperature. The plant dry weights, including roots, were measured eight months after field planting and subsequently at intervals of three to four months, corresponding to the different seasons, during the following two years. Fully irrigated plants of one clone (S15/10) were also harvested after four years in the field. Clones differed in the rates of canopy spread and hence in their capacity to intercept solar radiation. The ‘radiation use efficiency’ (the net total dry matter production per unit of intercepted short-wave radiation) was similar for the four well-watered clones and ranged from 0.40 to 0.66 g MJ−1, which corresponds closely to values reported for other woody tropical plants. A 16-week drought treatment imposed two years after planting reduced the mean light interception of the four clones by about 25% and the mean radiation use efficiency by 78% to 0.09 g MJ−1. Clone S15/10, a cultivar from Kenya which produces large yields, partitioned a greater proportion of dry matter to leaves and harvested shoots than the other clones, and correspondingly less to large structural roots. This resulted in a maximum harvest index of 24%, substantially greater than other values reported in the literature. There were seasonal differences in partitioning, with more dry matter being diverted to roots and less to shoots during the cool season. Although the drought treatments had no significant effect on root growth, the amount of dry matter partitioned to leaves, stems and harvested shoots declined by 80–95%. The roots of all four clones extended in depth at similar rates (about 2 mm d−1), those of Clone S15/10 reaching 2.8m after four years. The results are discussed in terms of appropriate field cultural practices and possible selection criteria for high yielding clones.

Density and row spacing effects on irrigated short wheats at low latitude

1976 ◽  
Vol 87 (1) ◽  
pp. 137-147 ◽  
Author(s):  
R. A. Fischer ◽  
I. Aguilar M. ◽  
R. Maurer O. ◽  
S. Rivas A.
Keyword(s):  
Grain Yield ◽  
Dry Matter ◽  
Light Interception ◽  
Dry Matter Production ◽  
Seeding Density ◽  
High Fertility ◽  
Dry Matter Accumulation ◽  
Area Index ◽  
Matter Production ◽  
Very High

SummaryDuring four winter seasons eight spacing and density experiments were made under irrigated high fertility conditions in north-west Mexico (latitude 27° N). Experiments included various Triticum aestivum and T. durum genotypes of spring habit, short stature derived from Norin 10 genes, and contrasting plant type. Measurements included dry-matter production, photosynthetic area index, and light interception during one experiment, total dry matter at maturity in most others and grain yield and its numerical components in all experiments.Grain yield and most other crop characters were unaffected by row spacings within the range 10–45 cm interrow width. The optimal seeding density for maximum grain yield was 40–100 kg/ha (80–200 plants/m2). Yield reductions at lower densities (20, 25 kg/ha) were slight and accompanied by reduced total dry-matter production. Yield reductions at higher densities (160–300 kg/ha) were also slight and were associated with more spikes/m2 but fewer grains/m2 and reduced harvest index. It is suggested that lower than normal preanthesis solar radiation or weather conditions leading to lodging can magnify these yield depressions at higher densities.Measurements showed rapid approach of crops to 95% light interception, reached even at a density of 50 kg/ha within 50 days of seeding. It is suggested that provided this occurs before the beginning of substantial dry-matter accumulation in the growing spikes (60 days after seeding) there will be no loss of grain yield with reduced seeding density. Results point to a ceiling photosynthetic area index for maximum crop growth rate although there was a tendency for rates to fall at very high indices (> 9). This tendency was associated with very high density, high maximum numbers of shoots, poor survival of shoots to give spikes (< 30%) and reduced number of grains/m3;. The relatively low optimal densities seen here may be characteristic of genotypes derived from Norin 10.Genotype × spacing, genotype × density and spacing × density interactions were generally non-significant and always small. There was a tendency for the presence of non-erect leaves or branched spikes to reduce the optimal density, but large differences in tillering capacity had no influence. Differences in lodging susceptibility can however lead to substantial genotype x density interactions.

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