Abstract
Seeds of a spring wheat (Triticum aestivum L. cv. ‘Condor’) were vernalized and then grown at 19°C in two naturally–lit environments, one with a moderate (12 h) and the other with long (18 h) photoperiod. Treatments consisted of transfers of plants from the moderate to the long photoperiod chamber on different occasions, or for periods of different durations. The main objectives were to determine whether wheat development responds to current and previous photoperiodic environments and whether there is a juvenile phase when the plants are insensitive to photoperiod. Plants under constant 18 h photoperiod had fewer leaves which appeared faster than those under constant 12 h photoperiod (i.e. phyllochron was increased from 4.4 to 5.1 d leaf−1). Plants transferred from 12 h to 18 h photoperiod at terminal spikelet appearance (TSA) reached anthesis 4 d earlier than plants retained at 12 h, while plants under continuous long photoperiod (18 h) completed this phase most rapidly. Thus, there was some evidence for a historic effect of photoperiod on development. Exposure to long photoperiod during the first 5 d after plant emergence accelerated the rate of development towards anthesis, suggesting that there was no juvenile period of photoperiodic insensitivity. There were, however, changes during ontogeny in the degree of sensitivity to long photoperiod, increasing from seedling emergence to a maximum c. 15 d later, and then decreasing again. Although all treatments were imposed before TSA, the response was not limited to the pre-TSA phase, suggesting that well before the terminal spikelet appeared, the plant was already committed to the initiation of this spikelet. Spikelet number decreased with delayed transfer to long photoperiod with a minimum for plants transferred to long days from 16‐20 d after seedling emergence. Additionally, there was a trend for an increase in the rate of leaf appearance (decrease in phyllochron) when the plants were exposed to long days between 10 and 35 d after seedling emergence. Although the differences were small, when considered in conjunction with the effects on final leaf number they become important in explaining differences in time to anthesis.
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Claims 8
Claim · model-written summary
Continuous 18 h photoperiod yielded fewer leaves than continuous 12 h.
- Taxon
- wheat
Triticum aestivumt0 - Treatment
- constant 18 h photoperiode0
- Outcome
- leavese0
- Direction
- fewere0
- Comparator
- constant 12 h photoperiode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants under constant 18 h photoperiod had fewer leaves which appeared faster than those under constant 12 h photoperiod”
t0“wheat”
Claim · model-written summary
Leaves appeared faster under continuous 18 h than 12 h photoperiod.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- constant 18 h photoperiode0
- Outcome
- leaves which appeared fastere0
- Direction
- fastere0
- Value
- 4.4 to 5.1 d leaf−1e0
- Comparator
- constant 12 h photoperiode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants under constant 18 h photoperiod had fewer leaves which appeared faster than those under constant 12 h photoperiod (i.e. phyllochron was increased from 4.4 to 5.1 d leaf−1)”
t0“wheat”
Claim · model-written summary
Transfer from 12 h to 18 h at terminal spikelet appearance advanced anthesis by 4 d relative to continued 12 h.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- transferred from 12 h to 18 h photoperiod at terminal spikelet appearancee0
- Outcome
- anthesise0
- Direction
- earliere0
- Value
- 4 de0
- Comparator
- plants retained at 12 he0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants transferred from 12 h to 18 h photoperiod at terminal spikelet appearance (TSA) reached anthesis 4 d earlier than plants retained at 12 h”
t0“wheat”
Claim · model-written summary
Continuous 18 h photoperiod completed the phase to anthesis most rapidly.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- continuous long photoperiod (18 h)e0
- Outcome
- completed this phase most rapidlye0
- Direction
- most rapidlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants under continuous long photoperiod (18 h) completed this phase most rapidly”
t0“wheat”
Claim · model-written summary
Long photoperiod in the first five days after emergence accelerated development toward anthesis.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- long photoperiod during the first 5 d after plant emergencee0
- Outcome
- rate of development towards anthesise0
- Direction
- acceleratede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exposure to long photoperiod during the first 5 d after plant emergence accelerated the rate of development towards anthesis”
t0“wheat”
Claim · model-written summary
Photoperiod sensitivity peaked around 15 days after emergence then declined.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- sensitivity to long photoperiode0
- Direction
- increasinge0
- Value
- c. 15 de0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sensitivity to long photoperiod, increasing from seedling emergence to a maximum c. 15 d later, and then decreasing again”
t0“wheat”
Claim · model-written summary
Spikelet number declined with delayed transfer to long days and reached a minimum with transfer 16–20 d after emergence.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- delayed transfer to long photoperiode0
- Outcome
- Spikelet numbere0
- Direction
- decreasede0
- Qualifier
- 16‐20 d after seedling emergencee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Spikelet number decreased with delayed transfer to long photoperiod with a minimum for plants transferred to long days from 16‐20 d after seedling emergence”
t0“wheat”
Claim · model-written summary
Exposure to long days between 10 and 35 d after emergence tended to increase leaf appearance rate.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- exposed to long days between 10 and 35 d after seedling emergencee0
- Outcome
- rate of leaf appearancee0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was a trend for an increase in the rate of leaf appearance (decrease in phyllochron) when the plants were exposed to long days between 10 and 35 d after seedling emergence”
t0“wheat”
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