Abstract
Controlling vegetative vigour is a key part of modern high-density apple orchards that use semi-dwarf rootstocks like M7. Genetic dwarfing is widely employed; however, additional management through chemical growth retardants or physical constraints is frequently necessary to preserve optimal canopy architecture. It is still not clear if these two different approaches stop growth by using the same metabolic pathways or different stress-mediated mechanisms. The objective of this study was to elucidate the physiological, metabolic, and hormonal profiles in three-year-old M7 apple trees exposed to three different treatments: mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ), and untreated controls. Even though the two treatments used different methods, they both worked to keep shoot elongation to less than 12% of the control. Hormonal regulation was the main cause of PBZ-induced dwarfing. This was shown by a marked decline in gibberellin A3 (GA3; 63% drop) and a rise in zeatin. This change in hormones was significant starch accumulation and better absorption of macronutrients with few signs of stress. In contrast, dwarfing through bonsai techniques caused a systemic stress response, as shown by a 284% rise in the stress osmolyte sorbitol and a 190% rise in abscisic acid (ABA). This group also had low nutrient levels, a sharp drop in the GA/ABA ratio, and clear signs of physiological stress, like lower photosynthetic efficiency and higher oxidative markers. Our results show that PBZ acts as a precise biochemical regulator that produces a sink-limited state without imposing substantial physiological stress on the plant, whereas bonsai techniques control growth by causing a resource-limited, stress-driven physiology. These contrasting signatures highlight paclobutrazol as a more controlled dwarfing tool and provide a physiological framework for developing stress-resilient dwarfing rootstocks.
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Claims 13
Claim · model-written summary
Mechanical dwarfing kept shoot elongation below 12% of control.
- Taxon
- apple
Malus domesticat0 - Treatment
- mechanical dwarfinge1
- Outcome
- shoot elongatione0
- Direction
- less thane0
- Value
- less than 12%e0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“they both worked to keep shoot elongation to less than 12% of the control”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
Paclobutrazol kept shoot elongation below 12% of control.
- Taxon
- appleMalus domesticat0
- Treatment
- paclobutrazole1
- Outcome
- shoot elongatione0
- Direction
- less thane0
- Value
- less than 12%e0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“they both worked to keep shoot elongation to less than 12% of the control”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
PBZ dwarfing was accompanied by a 63% decline in GA3.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“a marked decline in gibberellin A3 (GA3; 63% drop)”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
PBZ dwarfing was accompanied by a rise in zeatin.
- Taxon
- appleMalus domesticat0
- Treatment
- PBZe1
- Outcome
- zeatine0
- Direction
- risee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“a rise in zeatin”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
PBZ treatment was associated with starch accumulation.
- Taxon
- appleMalus domesticat0
- Treatment
- PBZe1
- Outcome
- starch accumulatione0
- Direction
- accumulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“This change in hormones was significant starch accumulation and better absorption of macronutrients with few signs of stress.”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
PBZ treatment improved macronutrient absorption.
- Taxon
- appleMalus domesticat0
- Treatment
- PBZe1
- Outcome
- absorption of macronutrientse0
- Direction
- bettere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“better absorption of macronutrients with few signs of stress”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
PBZ treatment showed few signs of stress.
- Taxon
- appleMalus domesticat0
- Outcome
- few signs of stresse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“few signs of stress”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
Bonsai dwarfing raised sorbitol by 284%.
- Taxon
- appleMalus domesticat0
- Treatment
- bonsai techniquese1
- Outcome
- stress osmolyte sorbitole0
- Direction
- risee0
- Value
- 284%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“a 284% rise in the stress osmolyte sorbitol”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
Bonsai dwarfing raised ABA by 190%.
- Taxon
- appleMalus domesticat0
- Treatment
- bonsai techniquese1
- Outcome
- abscisic acide0
- Direction
- risee0
- Value
- 190%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“a 190% rise in abscisic acid (ABA)”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
The bonsai group had low nutrient levels.
- Taxon
- appleMalus domesticat0
- Treatment
- bonsai techniquese1
- Outcome
- nutrient levelse0
- Direction
- lowe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“This group also had low nutrient levels”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
The bonsai group had a sharp decline in GA/ABA ratio.
- Taxon
- appleMalus domesticat0
- Treatment
- bonsai techniquese1
- Outcome
- GA/ABA ratioe0
- Direction
- drope0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“a sharp drop in the GA/ABA ratio”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
The bonsai group had lower photosynthetic efficiency.
- Taxon
- appleMalus domesticat0
- Treatment
- bonsai techniquese1
- Outcome
- photosynthetic efficiencye0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“lower photosynthetic efficiency”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
Claim · model-written summary
The bonsai group had higher oxidative markers.
- Taxon
- appleMalus domesticat0
- Treatment
- bonsai techniquese1
- Outcome
- oxidative markerse0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“M7 apple rootstock”
e0“higher oxidative markers”
e1“mechanical dwarfing (bonsai techniques), chemical dwarfing (paclobutrazol/PBZ)”
The same questions in other papers
paclobutrazol · growth · Malus domestica (apple)Results differ
12 papers in the same direction as this paper · 8 in the opposite direction
- negative
- no effect
- no effect
17 papers more in this group
See all 21 papers →paclobutrazol · nutrient: content · Malus domestica (apple)Positive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
- positive
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.