Abstract
Specific leaf area (SLA), the ratio of leaf area to leaf weight, is an important plant characteristic that affects the rate of dry matter production of crop canopies. It is affected by the conditions of growth of both isolated plants and crop communities, but the extent to which various environmental factors impact on SLA under field conditions is not clearly understood. This study was conducted to study the variability in SLA of leaves on the main culm, and in the leaf canopy as an entity, under different conditions of photoperiod, nitrogen and temperature for a number of wheat genotypes grown under field conditions. Five plantings at approximately bimonthly intervals on 12 May, 5 July and 22 September 1993; and on 9 June and 10 August 1994 were made under both natural photoperiod and an extended photoperiod of 20 h. A split plot design with two levels of nitrogen (0 kg N ha −1 and 150 kg N ha −1 ) as main plots and four genotypes of wheat comprising two spring types (Norseman and Roblin) and two winter types (Ruby and Harus) as subplots was used.SLA of individual leaves varied among leaf positions, but the pattern of variation was dependent on sowing date and genotype. For May and June sowing dates, SLA increased with leaf number up to leaf 5 and then declined with subsequent leaf numbers for the spring genotypes, but increased to leaf 5 and changed little thereafter for the winter types. For July or August sowing and for both spring and winter genotypes, the change in SLA with leaf position was less clear. The results further showed that some of this variability in SLA with leaf position could be accounted for by the mean air temperatures over which the leaves developed. As temperatures increased from 8 °C to 26 °C, SLA increased to a maximum value achieved at 18–20 °C and then declined. However, there was a large scatter of SLA values around 18–20 °C, due partly to some lower SLA values for the July and August sowing dates. This suggests the impact of other factors such as radiation and the degree of mutual shading within the canopy on SLA. Mean canopy SLA reflected the individual leaf values during the period of leaf production, and varied with sowing date and genotype, although the pattern of genotypic variability was inconsistent over sowing dates; it decreased rapidly after spike emergence presumably reflecting leaf aging. Neither nitrogen nor photoperiod had significant effects on SLA on both individual leaf and canopy bases.The results suggest that temperature is one factor affecting SLA under field conditions, but that further work to identify other factors impacting on SLA in the field will be necessary. For application of simulation models to situations in which temperatures are likely to vary, an accounting for the impact of temperature on the SLA of individual leaves would be desirable. Key words: Specific leaf area (SLA), sowing date, temperature, simulation, wheat
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Claims 18
Claim · model-written summary
SLA of individual wheat leaves varied among leaf positions, with the pattern dependent on sowing date and genotype.
- Taxon
- wheat
Triticum aestivumt0 - Outcome
- SLA of individual leavese1
- Qualifier
- dependent on sowing date and genotypee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“SLA of individual leaves varied among leaf positions, but the pattern of variation was dependent on sowing date and genotype”
Claim · model-written summary
For May and June sowing dates, SLA increased with leaf number up to leaf 5 in spring genotypes.
- Taxon
- wheatTriticum aestivumt0
- Material
- spring genotypese2
- Treatment
- May and June sowing datese2
- Outcome
- SLAe2
- Direction
- increasede2
- Qualifier
- with leaf number up to leaf 5e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e2“For May and June sowing dates, SLA increased with leaf number up to leaf 5 and then declined with subsequent leaf numbers for the spring genotypes”
Claim · model-written summary
For May and June sowing dates, SLA declined with subsequent leaf numbers in spring genotypes.
- Taxon
- wheatTriticum aestivumt0
- Material
- spring genotypese2
- Treatment
- May and June sowing datese2
- Outcome
- SLAe2
- Direction
- declinede2
- Qualifier
- with subsequent leaf numberse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e2“For May and June sowing dates, SLA increased with leaf number up to leaf 5 and then declined with subsequent leaf numbers for the spring genotypes”
Claim · model-written summary
In winter wheat types, SLA increased up to leaf 5.
- Taxon
- wheatTriticum aestivumt0
- Material
- winter typese3
- Outcome
- SLAe1
- Direction
- increasede3
- Qualifier
- to leaf 5e3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“SLA of individual leaves varied among leaf positions, but the pattern of variation was dependent on sowing date and genotype”
e3“but increased to leaf 5 and changed little thereafter for the winter types”
Claim · model-written summary
In winter wheat types, SLA changed little after leaf 5.
- Taxon
- wheatTriticum aestivumt0
- Material
- winter typese3
- Outcome
- SLAe1
- Direction
- no_changeinferrede3
- Qualifier
- changed little thereaftere3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“SLA of individual leaves varied among leaf positions, but the pattern of variation was dependent on sowing date and genotype”
e3“but increased to leaf 5 and changed little thereafter for the winter types”
Claim · model-written summary
For July or August sowing, the change in SLA with leaf position was less clear.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- July or August sowinge4
- Outcome
- change in SLA with leaf positione4
- Qualifier
- less cleare4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e4“For July or August sowing and for both spring and winter genotypes, the change in SLA with leaf position was less clear”
Claim · model-written summary
SLA increased with temperature from 8 °C to a maximum at 18–20 °C.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- temperatures increased from 8 °C to 26 °Ce6
- Outcome
- SLAe6
- Direction
- increasede6
- Value
- 18–20 °Ce6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e6“As temperatures increased from 8 °C to 26 °C, SLA increased to a maximum value achieved at 18–20 °C and then declined”
Claim · model-written summary
SLA declined after reaching its maximum at 18–20 °C as temperature rose further.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- temperatures increased from 8 °C to 26 °Ce6
- Outcome
- SLAe6
- Direction
- declinede6
- Qualifier
- maximum value achieved at 18–20 °Ce6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e6“As temperatures increased from 8 °C to 26 °C, SLA increased to a maximum value achieved at 18–20 °C and then declined”
Claim · model-written summary
Mean air temperature could partly account for variability in SLA with leaf position.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- mean air temperaturese5
- Outcome
- variability in SLA with leaf positione5
- Qualifier
- could be accounted fore5
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e5“some of this variability in SLA with leaf position could be accounted for by the mean air temperatures over which the leaves developed”
Claim · model-written summary
SLA values were widely scattered around 18–20 °C.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- scatter of SLA values around 18–20 °Ce7
- Qualifier
- largee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e7“there was a large scatter of SLA values around 18–20 °C, due partly to some lower SLA values for the July and August sowing dates”
Claim · model-written summary
Some SLA values were lower for July and August sowing dates.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- July and August sowing datese7
- Outcome
- SLA valuese7
- Direction
- lowere7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e7“there was a large scatter of SLA values around 18–20 °C, due partly to some lower SLA values for the July and August sowing dates”
Claim · model-written summary
Factors such as radiation and mutual shading within the canopy may affect SLA beyond temperature.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- SLAe7
- Qualifier
- radiation and the degree of mutual shading within the canopye7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e7“This suggests the impact of other factors such as radiation and the degree of mutual shading within the canopy on SLA”
Claim · model-written summary
Mean canopy SLA reflected the individual leaf values during leaf production.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- Mean canopy SLAe1
- Qualifier
- reflected the individual leaf valuese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“Mean canopy SLA reflected the individual leaf values during the period of leaf production”
Claim · model-written summary
Canopy SLA varied with sowing date and genotype.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- Mean canopy SLAe1
- Qualifier
- varied with sowing date and genotypee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“Mean canopy SLA reflected the individual leaf values during the period of leaf production”
e2“varied with sowing date and genotype, although the pattern of genotypic variability was inconsistent over sowing dates”
Claim · model-written summary
The pattern of genotypic variability in canopy SLA was inconsistent over sowing dates.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- pattern of genotypic variabilitye1
- Qualifier
- inconsistent over sowing datese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“varied with sowing date and genotype, although the pattern of genotypic variability was inconsistent over sowing dates”
Claim · model-written summary
Canopy SLA decreased rapidly after spike emergence, presumably reflecting leaf aging.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- after spike emergencee2
- Outcome
- Mean canopy SLAe1
- Direction
- decreasede2
- Qualifier
- presumably reflecting leaf aginge2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“Mean canopy SLA reflected the individual leaf values during the period of leaf production”
e2“it decreased rapidly after spike emergence presumably reflecting leaf aging”
Claim · model-written summary
Nitrogen (150 kg N ha −1 against 0 kg N ha −1) had no significant effect on SLA.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- nitrogene1
- Outcome
- SLAe1
- Direction
- no_changeinferrede1
- Comparator
- 0 kg N ha −1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“Neither nitrogen nor photoperiod had significant effects on SLA on both individual leaf and canopy bases”
e2“two levels of nitrogen (0 kg N ha −1 and 150 kg N ha −1 ) as main plots”
Claim · model-written summary
Extended photoperiod of 20 h had no significant effect on SLA compared with natural photoperiod.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- extended photoperiod of 20 he2
- Outcome
- SLAe1
- Direction
- no_changeinferrede1
- Comparator
- natural photoperiode2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“field-grown wheat”
e1“Neither nitrogen nor photoperiod had significant effects on SLA on both individual leaf and canopy bases”
e2“both natural photoperiod and an extended photoperiod of 20 h”
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