Abstract
Abstract Due to climate change, crop production will increasingly be affected by water limitation, causing remarkable decreases in grain yields of cereals. Plant growth regulators such as paclobutrazol (PAC) have been shown to protect plants from detrimental impacts of drought stress, and improvement of root growth and antioxidant activity were identified as main reasons for their positive effect. A container experiment was conducted with two maize ( Zea mays L.) cultivars, Galactus and Fabregas, to investigate how PAC application affects root growth and grain yield under stress conditions. At growth stage V8, the plants were treated once with PAC (0, 2, or 3 mg PAC per plant), and concomitantly reduction in soil water content commenced until 30–35% of the maximum water‐holding capacity (WHC) was achieved. The plants were exposed to this drought condition for three weeks during flowering as the critical period for kernel setting. Both factors, PAC application and drought stress, caused decreases in plant height, whereas total leaf area was unchanged and transpiration rate was significantly reduced by water limitation only. Flowering was almost unaffected by PAC treatment; yet, drought stress significantly delayed start of silking. The straw yield was decreased due to PAC and drought stress, and an improvement of the harvest index was obtained for drought‐stressed Galactus plants with PAC application. Grain yield was unaffected by PAC application, whereas drought stress caused significant decreases by 15% on average of both cultivars. The kernel number of drought‐stressed Galactus plants was increased after PAC treatment, but concurrently smaller kernels were produced. Water limitation generally decreased kernel number. Drought‐stressed Fabregas plants consumed less water after PAC treatment, resulting in significant improvements of water‐use efficiency (WUE grain ) during silking and thus most likely alleviating stress intensity. For both cultivars, PAC treatment and water limitation showed almost no significant impact on root dry matter, root length density, and root surface area, either determined for different soil layers down to 80 cm or on a per‐plant basis. It is concluded that grain yield performance of maize plants, exposed to water limitation during flowering, was not source‐limited but sink‐limited. Consequently, even if PAC can cause improvement of antioxidant activity and photosynthesis, due to sufficient availability of assimilates in the maize kernels a positive effect on grain yield is improbable. Considering source–sink relationships during flowering and kernel set, enhanced root growth due to PAC treatment did apparently not occur.
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Claims 20
Claim · model-written summary
PAC application decreased plant height.
Not reportedTaxonComparator
Verbatim
e0“Both factors, PAC application and drought stress, caused decreases in plant height”
t0“maize”
Claim · model-written summary
Drought stress decreased plant height.
Not reportedTaxonComparator
Verbatim
e0“Both factors, PAC application and drought stress, caused decreases in plant height”
t0“maize”
Claim · model-written summary
Total leaf area was unchanged under PAC and drought factors.
Not reportedTaxon
Verbatim
e0“total leaf area was unchanged”
t0“maize”
Claim · model-written summary
Water limitation significantly reduced transpiration.
Not reportedTaxonComparator
Verbatim
e0“transpiration rate was significantly reduced by water limitation only”
t0“maize”
Claim · model-written summary
PAC almost did not affect flowering.
Not reportedTaxonComparator
Verbatim
e0“Flowering was almost unaffected by PAC treatment”
t0“maize”
Claim · model-written summary
Drought significantly delayed silking.
Not reportedTaxonComparator
Verbatim
e0“drought stress significantly delayed start of silking”
t0“maize”
Claim · model-written summary
PAC decreased straw yield.
Not reportedTaxonComparator
Verbatim
e0“The straw yield was decreased due to PAC and drought stress”
t0“maize”
Claim · model-written summary
Drought decreased straw yield.
Not reportedTaxonComparator
Verbatim
e0“The straw yield was decreased due to PAC and drought stress”
t0“maize”
Claim · model-written summary
PAC improved harvest index in drought-stressed Galactus.
Not reportedTaxonComparator
Verbatim
e0“an improvement of the harvest index was obtained for drought‐stressed Galactus plants with PAC application”
t0“maize”
Claim · model-written summary
PAC did not affect grain yield.
Not reportedTaxonComparator
Verbatim
e0“Grain yield was unaffected by PAC application”
t0“maize”
Claim · model-written summary
Drought reduced grain yield by 15% on average.
Not reportedTaxonComparatorOutcome
Verbatim
e0“drought stress caused significant decreases by 15% on average of both cultivars”
t0“maize”
Claim · model-written summary
PAC increased kernel number in drought-stressed Galactus.
Not reportedTaxonComparator
Verbatim
e0“The kernel number of drought‐stressed Galactus plants was increased after PAC treatment”
t0“maize”
Claim · model-written summary
PAC produced smaller kernels in drought-stressed Galactus.
Not reportedTaxonComparator
Verbatim
e0“but concurrently smaller kernels were produced”
t0“maize”
e1“The kernel number of drought‐stressed Galactus plants was increased after PAC treatment”
Claim · model-written summary
Water limitation reduced kernel number.
Not reportedTaxonComparator
Verbatim
e0“Water limitation generally decreased kernel number”
t0“maize”
Claim · model-written summary
PAC reduced water consumption in drought-stressed Fabregas.
Not reportedTaxonComparator
Verbatim
e0“Drought‐stressed Fabregas plants consumed less water after PAC treatment”
t0“maize”
Claim · model-written summary
PAC improved grain water-use efficiency during silking in drought-stressed Fabregas.
Not reportedTaxonComparator
Verbatim
e0“significant improvements of water‐use efficiency (WUE grain ) during silking”
t0“maize”
e1“Drought‐stressed Fabregas plants consumed less water after PAC treatment”
Claim · model-written summary
PAC and water limitation had almost no significant effect on root dry matter, length density, or surface area.
- Treatment
- PAC treatment and water limitatione0
- Outcome
- root dry matter, root length density, and root surface areae0
- Direction
- almost no significant impacte0
Not reportedTaxonComparator
Verbatim
e0“PAC treatment and water limitation showed almost no significant impact on root dry matter, root length density, and root surface area”
t0“maize”
Claim · model-written summary
Yield performance under flowering water limitation was interpreted as sink limited.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grain yield performance of maize plants, exposed to water limitation during flowering, was not source‐limited but sink‐limited”
Claim · model-written summary
The authors judged a PAC yield benefit improbable under sufficient assimilate supply.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“due to sufficient availability of assimilates in the maize kernels a positive effect on grain yield is improbable”
Claim · model-written summary
PAC apparently did not enhance root growth.
Not reportedTaxonComparator
Verbatim
e0“enhanced root growth due to PAC treatment did apparently not occur”
t0“maize”
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