Abstract Within the North American boreal forest, a widespread outbreak of the epidermal leaf miner Phyllocnistis populiella has damaged quaking aspen (Populus tremuloides) for nearly 20 years. In a series of experiments, we tested the effects of feeding damage by P. populiella on leaf water relations and gas exchange. Relative to insecticide-treated trees, the leaves of naturally-mined trees had lower photosynthesis, stomatal conductance to water vapor, transpiration, water use efficiency, predawn water potential, and water content, as well as more enriched foliar δ13C. The magnitude of the difference between naturally-mined and insecticide-treated trees did not change significantly throughout the growing season, suggesting the effect is not caused by accumulation of incidental damage to mined portions of the epidermis over time. The contributions of mining-related stomatal malfunction and cuticular transpiration to these overall effects were investigated by restricting mining damage to stomatous abaxial and astomatous adaxial leaf surfaces. Mining of the abaxial epidermis decreased photosynthesis and enriched leaf δ13C, while increasing leaf water potential and water content relative to unmined leaves; effects consistent with stomatal closure due to disfunction of mined guard cells. Mining of the adaxial epidermis also reduced photosynthesis but had different effects on water relations, reducing midday leaf water potential and water content relative to unmined leaves, and did not affect δ13C. In the laboratory, extent of mining damage to the adaxial surface was positively related to the rate of water loss by leaves treated to prevent water loss through stomata. We conclude that overall, despite water savings due to closure of mined stomata, natural levels of damage by P. populiella negatively impact water relations due to increased cuticular permeability to water vapor across the mined portions of the epidermis. Leaf mining by P. populiella could exacerbate the negative effects of climate warming and water deficit in interior Alaska.
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Characterizing the acoustic response of Thalassia testudinum leaves using resonator measurements and finite element modeling
Seagrasses play an important role in coastal ecosystems and serve as important marine carbon stores. Acoustic monitoring techniques exploit the sensitivity of underwater sound to bubbles, which are produced as a byproduct of photosynthesis and present within the seagrass tissue. To make accurate assessments of seagrass biomass and productivity, a model is needed to describe acoustic propagation through the seagrass meadow that includes the effects of gas contained within the seagrass leaves. For this purpose, a new seagrass leaf model is described for Thalassia testudinum that consists of a comparatively rigid epidermis that composes the outer shell of the leaf and comparatively compliant aerenchyma that surrounds the gas channels on the interior of the leaf. With the bulk modulus and density of the seagrass tissue determined by previous work, this study focused on characterizing the shear moduli of the epidermis and aerenchyma. These properties were determined through a combination of dynamic mechanical analysis and acoustic resonator measurements coupled with microscopic imagery and finite element modeling. The shear moduli varied as a function of length along the leaves with values of 100 and 1.8 MPa at the basal end and 900 and 3.7 MPa at the apical end for the epidermis and aerenchyma, respectively.
more » « less- Award ID(s):
- 2023211
- NSF-PAR ID:
- 10440211
- Publisher / Repository:
- Acoustical Society of America (ASA)
- Date Published:
- Journal Name:
- The Journal of the Acoustical Society of America
- Volume:
- 153
- Issue:
- 1
- ISSN:
- 0001-4966
- Page Range / eLocation ID:
- p. 678-688
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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