Abstract
Variations in size and shape of multicellular organs depend on spatio-temporal regulation of cell division and expansion. Here, cell division and expansion rates were quantified relative to the three spatial axes in the first leaf pair of Arabidopsis thaliana. The results show striking differences in expansion rates: the expansion rate in the petiole is higher than in the leaf blade; expansion rates in the lateral direction are higher than longitudinal rates between 5 and 10 days after stratification, but become equal at later stages of leaf blade development; and anticlinal expansion co-occurs with, but is an order of magnitude slower than periclinal expansion. Anticlinal expansion rates also differed greatly between tissues: the highest rates occurred in the spongy mesophyll and the lowest in the epidermis. Cell division rates were higher and continued for longer in the epidermis compared with the palisade mesophyll, causing a larger increase of palisade than epidermal cell area over the course of leaf development. The cellular dynamics underlying the effect of shading on petiole length and leaf thickness were then investigated. Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase. Inversely, shading enhanced expansion rates in the petiole, so that the blade to petiole ratio was reduced by 50%. Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates. This effect on cell expansion was preceded by an effect on cell division, leading to one less layer of palisade cells. The two effects could be uncoupled by shifting plants to contrasting light conditions immediately after germination. This extended kinematic analysis maps the spatial and temporal heterogeneity of cell division and expansion, providing a framework for further research to understand the molecular regulatory mechanisms involved.
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Claims 15
Claim · model-written summary
Petiole expansion was faster than blade expansion.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Organ / stage
- petiolee0
- Outcome
- expansion ratee0
- Direction
- highere0
- Comparator
- leaf bladee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the expansion rate in the petiole is higher than in the leaf blade”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Lateral expansion exceeded longitudinal expansion at days 5 to 10.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- expansion ratese0
- Direction
- highere0
- Qualifier
- between 5 and 10 days after stratificatione0
- Comparator
- longitudinal ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“expansion rates in the lateral direction are higher than longitudinal rates between 5 and 10 days after stratification”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Lateral and longitudinal blade expansion later became equal.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- leaf bladee0
- Outcome
- equale0
- Direction
- equale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but become equal at later stages of leaf blade development”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Anticlinal expansion co-occurred with periclinal expansion but was an order of magnitude slower.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- anticlinal expansione0
- Direction
- slowere0
- Value
- an order of magnitudee0
- Comparator
- periclinal expansione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“anticlinal expansion co-occurs with, but is an order of magnitude slower than periclinal expansion”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Anticlinal expansion was highest in spongy mesophyll and lowest in epidermis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- spongy mesophylle0
- Outcome
- highest ratese0
- Direction
- higheste0
- Comparator
- epidermise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the highest rates occurred in the spongy mesophyll and the lowest in the epidermis”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Epidermal cell division was faster and lasted longer than palisade mesophyll division.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- epidermise0
- Outcome
- Cell division ratese0
- Direction
- highere0
- Comparator
- palisade mesophylle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cell division rates were higher and continued for longer in the epidermis compared with the palisade mesophyll”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Palisade cell area increased more than epidermal cell area over development.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- palisadee0
- Outcome
- cell areae0
- Direction
- larger increasee0
- Comparator
- epidermale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“causing a larger increase of palisade than epidermal cell area over the course of leaf development”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Low light reduced leaf expansion rates.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Low lighte0
- Outcome
- leaf expansion ratese0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase.”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Low light lengthened the growth phase, partly compensating for lower expansion rates.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Low lighte0
- Outcome
- duration of the growth phasee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase.”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Shading enhanced petiole expansion rates.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- petiolee0
- Treatment
- shadinge0
- Outcome
- expansion ratese0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“shading enhanced expansion rates in the petiole”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Shading reduced blade-to-petiole ratio by 50%.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- shadinge2
- Outcome
- blade to petiole ratioe0
- Direction
- reducede0
- Value
- 50%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the blade to petiole ratio was reduced by 50%”
t0“Arabidopsis thaliana leaves”
e2“shading enhanced expansion rates in the petiole”
Claim · model-written summary
Low light reduced leaf thickness through inhibition of anticlinal expansion.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Low lighte0
- Outcome
- leaf thicknesse0
- Direction
- reducede0
- Qualifier
- by inhibiting anticlinal cell expansion ratese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates.”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
Low light inhibited anticlinal cell expansion rates.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Low lighte0
- Outcome
- anticlinal cell expansion ratese0
- Direction
- inhibitinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates.”
t0“Arabidopsis thaliana leaves”
Claim · model-written summary
The cell division response preceded expansion and led to one fewer palisade layer.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Low lighte2
- Outcome
- one less layer of palisade cellse0
- Direction
- lesse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect on cell expansion was preceded by an effect on cell division, leading to one less layer of palisade cells.”
t0“Arabidopsis thaliana leaves”
e2“Low light reduced leaf expansion rates”
Claim · model-written summary
Contrasting light shifts after germination uncoupled division and expansion effects.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- shifting plants to contrasting light conditionse0
- Outcome
- two effects could be uncouplede0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The two effects could be uncoupled by shifting plants to contrasting light conditions immediately after germination.”
t0“Arabidopsis thaliana leaves”
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