Abstract
Post-anthesis drought and heat shock have been implicated in previous studies as factors contributing to ‘haying-off’ in wheat, but their relative importance has not been investigated. To separate the effects, wheat plants were grown at 2 levels of nitrogen (N) and then exposed to different levels of post-anthesis water deficit in factorial combination with the presence or absence of heat shock. The growth, yield, leaf carbon exchange, water use, and the contents of protein and soluble carbohydrate were measured and compared with the field results reported in Papers I and II of this series. The experiment consisted of wheat plants (cv. Janz) grown in 1·2-m-long tubes outdoors through winter and spring in Canberra, with either nil or 240 kg N/ha applied. The tubes were supported in a refrigerated box to maintain temperatures representative of those of soil in the field, and arranged to form mini-canopies with a density of 29 plants/m2. After anthesis, half of the plants at both levels of N were watered according to their transpiration demand and the other half at 75% of demand to reduce gradually the store of soil water so that water deficit could be initiated at the same time as heat shock. Fifteen days after anthesis, different temperatures were imposed by moving half of the plants into an adjacent glasshouse where heat shock was imposed by raising the air temperature to maxima of ~35ºC for 3 days, to simulate the pattern of temperatures experienced in the field during a heat wave. During this time, the control plants experienced daily maxima of ~25ºC. Following the heat shock, all plants were placed outside and rewatered to enable the assessment of treatment effects on potential leaf function. Both water deficit and high temperature reduced assimilation. After these measurements were taken, well-watered control plants were irrigated according to transpiration demand and the plants with imposed water deficit were watered at 50% of this amount. Yields increased in response to N at both levels of water status and both levels of temperature. That is, there was no evidence of the haying-off reported in Papers I and II of this series. Two factors are proposed to account for the difference between the field crops and the plants grown in the mini-canopy here. Firstly, the pattern of soil-water use differed from the field studies reported in Paper I, with the high-N plants using more soil water than low-N plants during grain filling. Secondly, the level of water-soluble carbohydrates (WSC) in the tube-grown plants of high-N status was greater than that for plants of low-N status, which was opposite to the pattern for field-grown plants reported in Paper II. In addition, the concentrations of WSC in the tube-grown plants were higher than those in the field-grown plants, apparently because lower spike density allowed better penetration of light into the mini-canopies and led to greater assimilate storage than by the denser field crops. The results confirm the conclusion of Paper I that high temperature is not necessary for haying-off, although it is likely that it would worsen the haying-off caused by post-anthesis drought and low WSC reserves in the field. The absence of the haying-off response in this experiment was mostly because the supply of WSC from the sparse canopy was adequate to ofiset the reduction of assimilation due to water deficit and heat shock. A contributing factor to haying-off in the field may therefore be dense canopies resulting in low levels of WSC
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Claims 13
Claim · model-written summary
Water deficit reduced assimilation.
- Taxon
- wheat
Triticum aestivumt0 - Treatment
- water deficite0
- Outcome
- assimilatione0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both water deficit and high temperature reduced assimilation”
t0“wheat”
Claim · model-written summary
High temperature reduced assimilation.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- high temperaturee0
- Outcome
- assimilatione0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both water deficit and high temperature reduced assimilation”
t0“wheat”
Claim · model-written summary
Nitrogen raised yields at both water levels and both temperatures.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Ne0
- Outcome
- Yieldse0
- Direction
- increasede0
- Qualifier
- at both levels of water status and both levels of temperaturee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yields increased in response to N at both levels of water status and both levels of temperature”
t0“wheat”
Claim · model-written summary
Haying-off was not observed in the experiment.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- no evidence of the haying-offe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no evidence of the haying-off reported in Papers I and II of this series”
t0“wheat”
Claim · model-written summary
High nitrogen plants used more soil water during grain filling than low nitrogen plants.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- grain fillinge0
- Treatment
- high-Ne0
- Outcome
- soil watere0
- Direction
- moree0
- Comparator
- low-N plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the high-N plants using more soil water than low-N plants during grain filling”
t0“wheat”
Claim · model-written summary
Tube-grown high nitrogen plants had greater water-soluble carbohydrates than low nitrogen plants.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- high-N statuse0
- Outcome
- water-soluble carbohydrates (WSC)e0
- Direction
- greatere0
- Comparator
- low-N statuse0
- Setting
- tube-grown plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of water-soluble carbohydrates (WSC) in the tube-grown plants of high-N status was greater than that for plants of low-N status”
t0“wheat”
Claim · model-written summary
The high-versus-low nitrogen WSC pattern was opposite to that in field plants.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- opposite to the pattern for field-grown plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which was opposite to the pattern for field-grown plants reported in Paper II”
t0“wheat”
Claim · model-written summary
Tube-grown plants had higher WSC concentrations than field-grown plants.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- concentrations of WSCe0
- Direction
- highere0
- Comparator
- field-grown plantse0
- Setting
- tube-grown plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the concentrations of WSC in the tube-grown plants were higher than those in the field-grown plants”
t0“wheat”
Claim · model-written summary
Authors attributed greater carbohydrate storage to improved light penetration from lower spike density.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- greater assimilate storagee0
- Qualifier
- lower spike density allowed better penetration of light into the mini-canopiese0
- Comparator
- denser field cropse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower spike density allowed better penetration of light into the mini-canopies and led to greater assimilate storage than by the denser field crops”
t0“wheat”
Claim · model-written summary
Authors concluded that high temperature is not necessary for haying-off.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- high temperaturee0
- Outcome
- haying-offe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high temperature is not necessary for haying-off”
t0“wheat”
Claim · model-written summary
Authors considered high temperature likely to worsen drought-associated haying-off with low WSC reserves.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- post-anthesis droughte0
- Outcome
- haying-offe0
- Qualifier
- low WSC reserves in the fielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it is likely that it would worsen the haying-off caused by post-anthesis drought and low WSC reserves in the field”
t0“wheat”
Claim · model-written summary
Adequate carbohydrate supply from a sparse canopy was proposed to explain the absence of haying-off.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- absence of the haying-off responsee0
- Qualifier
- supply of WSC from the sparse canopy was adequatee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The absence of the haying-off response in this experiment was mostly because the supply of WSC from the sparse canopy was adequate to ofiset the reduction of assimilation due to water deficit and heat shock”
t0“wheat”
Claim · model-written summary
Dense canopies with low WSC were proposed as a possible contributor to field haying-off.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- haying-off in the fielde0
- Qualifier
- dense canopies resulting in low levels of WSCe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A contributing factor to haying-off in the field may therefore be dense canopies resulting in low levels of WSC”
t0“wheat”
The same questions in other papers
nitrogen · yield · Triticum aestivum (wheat)Positive and negative results
1,736 papers in the same direction as this paper · 285 in the opposite direction · 39 reporting no difference from an alternative
- negative
- no effect
- negative
2,057 papers more in this group
See all 2,061 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.