Abstract
Absorption or screening of ultraviolet‐B (UV‐B) radiation by the epidermis may be an important protective method by which plants avoid damage upon exposure to potentially harmful UV‐B radiation. In the present study we examined the relationships among epidermal screening effectiveness, concentration of UV‐absorbing compounds, epidermal anatomy and growth responses in seedlings of loblolly pine ( Pinus taeda L.) and sweetgum ( Liquidambar styraciflua L.). Seedlings of each species were grown in a greenhouse at the University of Maryland under either no UV‐B radiation or daily supplemental UV‐B radiation levels of 4, 8 or 11 kJ m −2 of biologically effective UV‐B (UV‐B BE ) radiation. Loblolly pine seedlings were subsequently grown in the field under either ambient or supplemental levels of UV‐B radiation. At the conclusion of the growing season, measurements of epidermal UV‐B screening effectiveness were made with a fiber‐optic microprobe. In loblolly pine, less than 0.5% of incident UV‐B radiation was transmitted through the epidermis of fascicle needles and about 1% was transmitted in primary needles. In contrast, epidermal transmittance in sweetgum ranged from about 20% in leaves not preconditioned to UV‐B exposure, to about 10% in leaves grown under UV‐B radiation. The concentration of UV‐absorbing compounds was unaffected by UV‐B exposure, but generally increased with leaf age. Increases in epidermal thickness were observed in response to UV‐B treatment in loblolly pine, and this accounted for over half of the variability in UV‐B screening effectiveness. In spite of the low levels of UV‐B penetration into the mesophyll, delays in leaf development (both species) and final needle size (loblolly pine) were observed. Seedling biomass was reduced by supplemental UV‐B radiation in loblolly pine. We hypothesize that the UV‐induced growth reductions were manifested by changes in either epidermal anatomy or epidermal secondary chemistry that might negatively impact cell elongation.
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Claims 11
Claim · model-written summary
Less than 0.5% of UV-B passed through pine fascicle needle epidermis.
- Taxon
- loblolly pine
Pinus taedae0 - Organ / stage
- fascicle needlese0
- Outcome
- incident UV‐B radiation was transmittede0
- Value
- less than 0.5%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In loblolly pine, less than 0.5% of incident UV‐B radiation was transmitted through the epidermis of fascicle needles”
Claim · model-written summary
About 1% of UV-B passed through pine primary needle epidermis.
- Taxon
- Pinus taedaPinus taedat0
- Organ / stage
- primary needlese0
- Outcome
- transmitted in primary needlese0
- Value
- about 1%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“and about 1% was transmitted in primary needles.”
t0“Pinus taeda”
Claim · model-written summary
Sweetgum leaf transmittance was about 20% without UV-B preconditioning.
- Taxon
- sweetgum
Liquidambar styracifluae0 - Outcome
- epidermal transmittancee0
- Value
- about 20%e0
- Qualifier
- leaves not preconditioned to UV‐B exposuree0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“epidermal transmittance in sweetgum ranged from about 20% in leaves not preconditioned to UV‐B exposure, to about 10% in leaves grown under UV‐B radiation.”
Claim · model-written summary
Sweetgum leaf transmittance was about 10% after UV-B growth.
- Taxon
- sweetgumLiquidambar styracifluae0
- Outcome
- epidermal transmittancee0
- Value
- about 10%e0
- Qualifier
- leaves grown under UV‐B radiatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“epidermal transmittance in sweetgum ranged from about 20% in leaves not preconditioned to UV‐B exposure, to about 10% in leaves grown under UV‐B radiation.”
Claim · model-written summary
UV-B exposure did not affect UV-absorbing compound concentration.
- Taxon
- Pinus taedaPinus taedat0
- Treatment
- UV‐B exposuree0
- Outcome
- concentration of UV‐absorbing compoundse0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The concentration of UV‐absorbing compounds was unaffected by UV‐B exposure, but generally increased with leaf age.”
t0“Pinus taeda”
Claim · model-written summary
UV-absorbing compounds generally increased with leaf age.
- Taxon
- Pinus taedaPinus taedat0
- Organ / stage
- leaf agee0
- Outcome
- concentration of UV‐absorbing compoundse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The concentration of UV‐absorbing compounds was unaffected by UV‐B exposure, but generally increased with leaf age.”
t0“Pinus taeda”
Claim · model-written summary
UV-B treatment increased pine epidermal thickness.
- Taxon
- loblolly pinePinus taedae0
- Treatment
- UV‐B treatmente0
- Outcome
- epidermal thicknesse0
- Direction
- Increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increases in epidermal thickness were observed in response to UV‐B treatment in loblolly pine”
Claim · model-written summary
Pine epidermal thickness explained over half of screening variability.
- Taxon
- loblolly pinePinus taedae0
- Organ / stage
- epidermal thicknesse0
- Outcome
- variability in UV‐B screening effectivenesse0
- Value
- over halfe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increases in epidermal thickness were observed in response to UV‐B treatment in loblolly pine, and this accounted for over half of the variability in UV‐B screening effectiveness.”
Claim · model-written summary
UV-B delayed leaf development in both species.
- Taxon
- Pinus taedaPinus taedat0
- Treatment
- UV‐B radiationt0
- Outcome
- leaf developmente0
- Direction
- delayse0
- Qualifier
- both speciese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In spite of the low levels of UV‐B penetration into the mesophyll, delays in leaf development (both species) and final needle size (loblolly pine) were observed.”
t0“Pinus taeda in response to UV‐B radiation”
Claim · model-written summary
UV-B delayed final needle size in pine.
- Taxon
- loblolly pinePinus taedae0
- Treatment
- UV‐B radiationt0
- Outcome
- final needle sizee0
- Direction
- delayse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“delays in leaf development (both species) and final needle size (loblolly pine) were observed.”
t0“UV‐B radiation”
Claim · model-written summary
Supplemental UV-B reduced pine seedling biomass.
- Taxon
- loblolly pinePinus taedae0
- Treatment
- supplemental UV‐B radiatione0
- Outcome
- Seedling biomasse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedling biomass was reduced by supplemental UV‐B radiation in loblolly pine.”
The same questions in other papers
uv · molecular: metabolites · Pinus taeda (loblolly pine)Positive and negative results
1 in the opposite direction
- positive
uv · growth · Pinus taeda (loblolly pine)Results agree
6 papers in the same direction as this paper
- negative
- negative
- negative
3 papers more in this group
See all 7 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.